There's still a lot of confusion about engine braking. All good, perhaps more content on it! In the meantime, a few clarifications. How does engine braking work in diesels? Here you go! th-cam.com/video/o8Cta2cC2Co/w-d-xo.html Also confusion about downshifting. It is 100% fine to downshift, and yes, downshifting will provide greater engine braking because your engine will be spinning at a higher rate, thus the energy lost through pumping losses (as a result of the closed throttle) will increase. More energy lost = slows your car down more. Rev-matching your downshifts means no clutch wear, so it's no big deal at all. If you're into Snapchat, I have no way to please you. But if you're on the Instagrams feel free to follow! instagram.com/engineeringexplained/
Does engine braking by downshifting without the rev matching really do significant damage to the clutch? In driving schools here we're taught to break on the engine by downshifting, but we're not taught to do rev matching.
Normal engine braking (ie leaving it in gear while coming to a stop, or holding a gear during a long downgrade) is perfectly fine. The potential problem arises because of the the helical cut gears in the transmission. All modern gearboxes use these for forward gears because they're quieter. Problem is, they also create an axial load. So there's a thrust bearing there to take up the load in the normal direction. When loaded in reverse, however, the thrust is in the opposite direction. There is a tiny little thrust bearing in most transmissions for this opposite load, but there are two things to remember. 1. It is design for normal opposite loads... not inertial loads (ie when downshifting without rev matching) and 2. whenever you're going from a negative load to a positive load, you're "passing the zero".. ie you're going from one thrust washer to the other via a gap. The axial acceleration in this clearance causes an impact to the washer. It can take it... but only for so long and so many times. Basically, under normal deceleration, you're fine if you rev match. But do it wrong, and you're looking at a costly transmission rebuild instead of a simple brake job.
What is the meaning of life? How much wood could a woodchuck chuck? What is the mechanism of engine braking? All very important questions that need answering.
You're probably right. I am American and I did fail both Thermodynamics I and Thermodynamics II in school. That may also explain why I have a hard time justifying all of the explanations about engine braking.
Ridiculous. Deliberate engine braking offers the capable driver a remarkable amount of additional control over the vehicle, and is also one of the most enjoyable features a "manual" car comes with.
Agreed, mate...after my father died 7 years ago (he'd always sworn that the day he purchased a car with an 'auto' transmission would be the day that he died & unfortunately, those words proved to be 100% prophetic!), my mother purchased a new V6 Accord - her first ever automatic - & ever since then, she's forever offering to wash my 'manual' Civic Type R or to fill it with petrol, as she so misses driving a 'manual' & having so much control over the car...as well as her enjoyment of the exhaust sound upon my car vs hers!!
There's a 2.5 km downhill section near where I live. If I go just the right speed at the top of the hill, I coast down the entire section exactly at the speed limit (70 km/h) and without having to touch the throttle. Love it every time.
When I think about it, I usually apply a combination of engine braking and foot brake. Depends on the rate of deceleration. I prefer engine braking exactly for one of the reasons mentioned: fuel economy. One physics lesson I remembered and applied early on is the fact that regardless of how braking is applied, it's converting kinetic energy to heat which is essentially a waste of energy. So anticipating the road conditions ahead, for instance a yellow light about to turn red should trigger the reaction to ease off the accelerator. I always challenge myself to drive as smoothly as possible without having to brake. When fuel prices are as high as they are in the NL driving economically is a must. And of course the added effect of lowering emissions that way isn't a bad thing either.
hahaha you drive the exact same way as me, exept that traffic in morocco is crazy enough that its hard to anticipate but i try most of the time... also im not really good with thermodynamics but i assume that it will consume less during engine braking than when putting in neutral and leaving the car to coast in idle.... also may i ask how much are oil prices in netherlands ? here its about 80 cents for diesel.. and nearly 1 euro for petrol, so i'm planning to switch my high consuming petrol for a tdi
I too do that on my bike, but I pull in the clutch, so that I can reach the desired distance and then apply break Instead of applying engine braking why not just stop accelerating and pull in the clutch ( do not shift it to neutral in case some emergency arrives and u need to stop or accelerate quickly) Btw fuel price in India are approx INR 100 ( 1.21 USD ) per liter For both petrol and diesel
@@warbot2544 if I understand you correctly you are pulling your clutch but not shifting into neutral. What that does is, you wont get the benefit of 0 fuel consumption or slowing you down because the engine will have to burn fuel in order to stay on (because you detatch it from the gearbox). And the thing with emergency brakes is: when you have to stop very quickly and you then Release the clutch so that the engine slows you down as well thats actually affecting your breaking Performance negatively. You see, the engine has its own rate of slowing down because of its own moment of spinning weight. If you then want to slow down quickly, its actually bad for your breaking Performance because you will need to slow the engine down faster than it would normally do as well... Hope I could explain that understandably.
Have you seen the signs going down mountain roads that say "Heavy Trucks Gear Down"? Most heavy trucks (20 tones +) would overheat their wheel brakes very quickly going down long mountain roads. They have to engine brake and use J-brakes (another form of engine brake) in order to go down the mountain at a controlled pace. Yet, these trucks have engines that last millions of miles. If engine braking was bad then how could these truck engines last so long?
Just go light on both, brakes and engine braking. They work less hard together. Another advantage is if you downshift while braking, you are then ready to accelerate if you have to, such as approaching a red light but then it turns green.
ArneBergsch I believe this is taught anywhere with manual cars. I don't understand why so many people in the comments sounds so stressed about it. This is a everyday thing for me.
Here in the USA, driving is a "right" so they hand out drivers licences to anyone that can breath. The "tests" are a complete joke, you could pass one blindfolded! Oh wait, they say "driving is a privilege " but really, everyone feels entitled to be crappy drivers here. People here take zero pride in car care, tire pressure checks, tire choices, alignment choices, etc. THEN, they will follow you at the same distance regardless if you're moving at 5 mph or 85mph. This is best demonstrated when you take off from a red light to a green light, everyone WAITS til they have that 2 car length space BEFORE they even begin to start to move. So half the number of cars actually get through each light, and yet, once you're moving from 5mph up to around 45 mph, they still have the same exact following distance. I love seeing just HOW fast I need to go to get someone to not tail gate. It's fun when you get them up to around 90mph and they have that sudden realization that the speed limit is 55, and then they freak out and brake abruptly. People here believe the rear view mirror is for checking themselves out/taking "selfies" rather than watching what is occurring behind them, then the same morons: "the cop just came out of nowhere" when they are crying about their speeding ticket. Duh! We need more hot blond attractive German women who were not raised on a diet of processed and preserved foods in the USA to teach these people how to freakin drive here!
All new drivers in the UK learn to drive manual and are taught to engine break as a 'proper' way to drive a car. If you didn't do it you wouldn't pass your test.
Harry Brookman I don't know how different The test was back then, but the only time you are taught (and this is only as part of your theory) to engine break is when travelling down hill to help avoid brake fade. You would not be marked down on your driving test to be in 5th gear even when travelling down hill.
Now there is a difference between engine braking and excessive engine braking. If you just driving normally but you are downshifting so many gears causing the rpm to get near redline, that's excessive.
When trucks and buses with manuel transmission were still around it was common to brake with the engine. Either with a dedicated engine break system that slows down the engine even more, or with downshifting. To reduce wear from downshifting you can go into neutral, rev up the engine to get to get it to spin more closely to what it would in the lower gear at your speed and then put in the lower gear. This way the clutch doesn't have to work so hard.
Excellent! Many years ago I had a 1964 flat windshield Chevy van DIY camper conversion. I put in a 1957 Chevy OD transmission to lower highway RPM, darn thing just snapped into place. The OD transmission had a freewheeling clutch, a planetary gear high/low range --6 gears! Sorta -- and a cable controlled freewheeling lockout. Loved it, clutchless shifting, gear choices when negotiating New England snow, and a little better fuel economy. But, there is a certain risk with a freewheeling clutch in the mountains. All was fine if you remembered to lockout the clutch, and the cable wasn't seized. Had some exciting moments on the edge of total brake fade.
This was in the owner's manual of the last manual transmission car my family owned. In my current automatic, it seems to automatically engine brake (high RPM down a hill if I'm off both pedals) good to know it isn't dangerous to the engine and actually saves fuel!
The main problem with downshift engine braking (assuming that you rev match) is that it increases wear on the upper main bearings in the engine. This is fine and won't be a problem - but it will be a problem if you are trying to use downshift engine braking during everyday driving traffic. It's fine let the car slow down in gear, but shifting to a lower gear to rev up the engine will cause that wear - but again this is only a problem if it's a driving habit. If it's a downhill only practice it works great.
nerdyengineer yeah.. but what do I do when I want to practice heel and toe downshifting I have to do it often how am I gonna get good at it if I do it occasionally? I have to practice at almost every opportunity once good I can do it less
I have a 6-speed manual FRS. I use the engine to break all the time. The result was that I did my first brake job on it replacing only the pads and the original pads still had about 1/16 of an inch left on them. this was at 142,000 miles.
@@dnawrapsatl I'm or of those guys that thinks the FR-S has all the power it needs. :) I'm more into handling. I use the gears to manage the power curve, and engine longivity is paramount.
I always give these guys proper following distance as they are going to kick up rocks and they typically need to change lanes unexpectedly (prius drivers), so I keep out of the blind spot and pass with a vengeance or just stay way back. I feel sorry for truckers that have to navigate around all these people that are for the most part indecisive on the road.
Is it that simple then , just drop a cog or two and that will save you , brakes are there to slow you down and lower gears are used to maintain that slower safe speed .
In Malaysia, not at all, they aint even teach you when to shift, some of the tutor says 3k, some say 2k, and they cant explain why. now i learned how to drive by daily driving, i shift whenever i like, like learn to handle the redline, so i won't get nervous when i need it. no mom spaghetti or if i feel like to cruise & chill, shift before 2.5 (or 2, depending on vehicle, my car has the best torque in 1.7k and 4k, on paper, so) In short, they only teach me how to ignite a car, not drive, no engine brake, no skipping gear shift, nothing at all, i gained more knowledge from youtube tbh.
Most cars today will go up a hill in top gear. I can overtake going up hill in top gear in mine. Top gear will not keep the car from accelerating down the same hill. Neither will 5th. You need to go down to at least 4th to hold speed and 3rd to decelerate.
I think it will be beneficial also after the engine break-in period as it gives the piston rings "some action" if the engine is operated normally only at low rpm.
Another thing to metnion - if you have AC turned on, while engine braking on descend it will actually run the compressor for AC without burning any fuel. So you recycle part of the kinetic energy to do useful work insetad of buring fuel.
@@ScripturaSola777 Yes and you also recover some of the energy from already burnt fuel back to usefull stuff like: - Turning alternator to power electrical systems and charge the battery - Running AC compressor to cool the cabin - Running power steering system - Running Water pump to cool the engine So you get the double gain. Since all of those utitliy systems are connected to engine, you actually brake by letting all those systems take the load of the gravity pulling you down. And of course no additionl fuel being burend on descend. + your brakes are cool and not wearing down pointlessly. You just apply brakes every now an then when needed before a turn or if speed goes too high.
Engine breaking can save the need to replace your breaks by up to 3 times the need. Down shifting is better for your car than shifting up in gears. It is also safer to use engine breaking.
With the injectors off it's the wheels that are transferring power back into the engine to overcome it's inertia and friction to keep it turning and that is how the kinetic energy is dissipated. Secondly with the throttle closed, little air is coming into the engine and since there is no fuel added it is just taking the heat out of the cylinders and out the exhaust. Love your channel by the way and great video!
Thanks, I’ve always used engine braking in my 5.0 Litre Mustang, I love the sound and now I’m assured that this method has no adverse effect on the mechanical components of my drivetrain
One thing to note is that if you are going downhill in the Rokies or whatever and have the heater on, it is totaly normal for your coolant tempretature to go down. Lots of cold air hits your engine and you are asking for heat yourself to warm the cabin. Heat from engine braking really is miniscule. I am commenting on this because many thermostats have been changed for no reason. In cold environment going downhill with no throttle, engine temps can only go down no matter what, and this is normal.
Engine breaking and down shifting is a skill every driver needs. Everyone should be taught how to slow a car down from 70mph to 3mph without using brakes, useful for at least 2 situations. Icy roads or brake failure.
Love your videos, Jason!😍👌 Very interesting... I was putting engine braking to the test yesterday in the western NC mountains. Had a blast! Have a great day, buddy!🙋
Engineering Explained Awesome, man. Your S2000 would be right at home there. Yesterday, I was on 226A that goes into Little Switzerland. They call that stretch the Diamondback. Check it out when you get back home.😆 Cheers!
Your Slowbro I was in my 2014 Q50S Hybrid RWD. I was trying out my new Michelin Pilot Sports and 14" Stoptech slotted rotors. It's no S2000, but the car handles great, especially for its size. Great stretch of road... give it a go when you get a chance.
From watching these engineering videos, I was told that the vacuum created on the intake was the key to engine braking, but a simple experiment on my motorcycle led to the opposite conclusion. I was coming down a hill in gear. I hit my engine killswitch and fully opened the throttle with my hand. There was no difference in the amount of braking with an open or closed throttle. What gives?
sac speed The rotational energy lost compressing the piston is simply regained once the piston decompresses. The friction and vacuum explanations make more sense. I'm most inclined to believe EE as he is (was) a well studied engineer who designs car engines for a living. Though, OP's experiment throws the vacuum theory out so I'm still curious for any further insight.
I think when people say engine breaking they are referring to that slight shock of downshifting when you ONLY let go of the clutch slowly (as opposed to rev matching)
@@robr430 rev matching means you press the accelerator while downshifting, so the engine reaches optimal RPMs. In racing it keeps the car balanced, while in regular driving it reduces wear on the drivetrain
When you use engine braking all the pressure on transmission gear faces and engine bearings is reversed allowing a slightly thicker oil film between metal parts and overall reducing engine and transmission wear.
Another detail you didn’t mention, particularly with the BMW you are driving, when you engine brake on those cars, the instant MPG gauge goes to what looks like battery charging. My Audi does it. It’s not a hybrid either. Was wondering if you could do a video on how it all works and why some cars do it, if you haven’t done that already.
In order to save fuel, modern cars try to use the alternator more sparsely, as it's quite significant load to the engine - during the engine braking, they'll use it to recharge the battery, acting sorta like low power regen braking.
I had a car with a stuck open thermostat, and the only way to get the heat to work during the winter was to let it sit and idle. as soon as you started to move, the heat instantly got colder and colder, to the point where it was just blowing cold air. engine cooling systems are extremely effective, and engine braking, as explained, will only cool off your engine, even though it is loaded.
@@hojnikb That depends. If the oil gets injected into the air intake (just past the throttle body) it would still lack the airflow to reach the piston. I don't actually know if there's engines with oil injection directly into the crankcase or onto the bottom of the piston.
Yes I was just querying this. How does the charge get stored...via the alternator back into the battery? We didn't get around to discussing this in my electrical course.
@@southernkatrina8161 With an BEV? - The Engine is then used as Generator and stores the generated "Power" into the Battery. Combustion engine: It rotates powered by kinetic energy from the car and also the 12V Generator rotates to load the lead battery. If rotating faster (and regulation can increase generation level) it generates more Watts in the same time. Additionally the AC-Compressor works at higher rpm and cools faster.
I just hit 120k miles on my 2013 Mustang Gt with a manual 6 speed and still have not changed the pads or rotors, though I will soon as they're about 25% with a little grab on light braking. My automatic friends are amazed. (I'm still on the same clutch as well).
Breaks are way better than they use to be 20 years ago and in a manual transmission. I rather replace breaks than a clutch, so I will always use breaks to slow the car down than engine breaking or the clutch. It’s way cheaper! You are awesome, I love your videos Thank You
The dual clutch gearbox does a good job of using the engine for braking..it doesn’t always know which way to change gear but most of the time I’m happy with mine.
It's not only brakes you are saving. It's entire suspension system. It's not much of a consideration in new vehicle but in older ones it's definitely something to keep in mind.
I have 20 year old Toyota Corolla w/ 5 speed manual trany. I engine break all the time by down shifting up and down hills, around sharp corners and to slow the vehicle when coming to a stop. I always rest my hand on the shifter when I feel I might need to change gears for whatever reason. I still have the original clutch and have only had a single brake repair. The front pads required replacing 3 years ago, the rear pads still had 50% wear left. I never ride my clutch - never. I also pull a smaller trailer with my Toyota all the time. Saved me having to purchase a pickup truck for hauling things! I also put my car in neutral when going down longer hills when there doesn't appear to be any reason to slow down and I let gravity do its thing! There are some hills that allowed the car to go close to 100 mph in neutral.
Look It's That Boy i owned a lot of cars in my life and trust me the clutch is not gona wear off unless when u downahift u go over 4 k rpm in gasoline engine and around 2.5 k rpm on most diesel engines (not by trucks)
what about all the Extra stress on the piston and wrist pin? Instead of the piston being pushed down, its being pulled down by the con rod and worse the intake is closed causing more resistance.
The piston has to get pulled down anyhow, the rods, etc have to deal with so much more force from the power stroke that they will always EASILY handle this load
So you think thats worse than an engine under load? The piston is built to handle thousands of explosions a minute... No engine braking will have no significant wear on anything...
chainsaw2010 But don't the rods pull the pistons down when it's under load too? In a 4 stroke engine during the power stroke the piston pushes the rod down, but during the intake stroke the connecting rod is pulling the piston down. When one cylinder fires that power gets transferred through the crank and through the connecting rods to the other pistons. It seems to me that the connecting rods are designed to pull the pistons down
And in Germany in some of the standard questions for your theory exam for a drivers license its specifically stated that on long downhill rides you are supposed to disengage the clutch often and use your breaks. Because it will be bad for your clutch.
I was told "engine braking" in driving school. 🤷♀ It's good to save gas, spares the brakepads & its saver on long downhills. Never thought that there might be a discussion about it.
If your brakes fail completely, downshift (or lockout, in an automatic) as soon as possible and start using your handbrake/emergency brake firmly but carefully, so you don't lock the rear wheels. If that doesn't work, call 911 (or your country's equivalent) before you pick up too much speed, then start weaving the car back and forth. The resistance from the tires will help slow you down. If necessary, drive up onto the dirt banking for a similar effect. Choose them wisely, though, and don't drive too far up them, because it could cause you to lose control. Then, look for any runaway ramps, or some kind of place that you can turn off to shed speed. It's not great to drive into one of those ramps, but it's a hell of a lot better than the alternative.
I have a question: I have noticed that under braking, downshifting using the clutch only results in a smooth enough transition that rev matching is not necessary. As an engineer my guess would be that the synchros are sufficient in low speeds and braking itself would help match the revs of the transmission to the engine. What's your opinion?
This only applies when your revs are low, as downshifting at 1500 rpm will make you jump to 2000, not a big change in numbers. However if you downshift at 4000 rpm, you will go to 5400, the % is the same but the actual figure is higher, so you will feel the jerk much more. That’s when you need to rev match.
You thirdly get better traction in a turn dropping it into second and your revs are already higher so it's easy to accelerate out of the turn and have much more control coming out of the corners. Corners are often blind and you won't be able to stop or slow enough to turn sharp enough to avoid an obstacle at the very last second.
its not smooth or fast though, car probably doesnt like it either. and trying doing that at high revs in a car thats not brand new. good way to upset the car
could u please explain throttling delay in new cars, which i face "engine is seconds slow to react if i press acceleration paddle". is it a good thing or not? should i tune it at service center?
Some new cars stop there engine if your at a dead stop. Or maybe if u press to hard in automatic car it might try to downshift b4 you move which takes time
I lived for a while near a steep enough 200 m (650 ft) of altitude descent. It was steep enough that I could engine break in third gear almost the whole way down. The engine didn’t really warm up very much before the downhill section started. In winter, even with a functioning thermostat, going down the engine cooled down enough that even though I had some heating at the top, at the bottom there was no heat anymore. Essentially the heat to warm up the passenger compartment I was extracting from the engine was more than engine braking put back into the engine.
@@TheBoxingNinja the cluch is what connects the engine shaft to the gearbox so as long as you don't rev your engine while braking it shouldn't do damage
the 4th benefit is where overbraking may lock the wheels (non abs), whereupon you lose steering, adding engine breaking to braking maximises braking effectiveness while maintaining wheel rotation and not losing steering.
You can downshift if you heel/toe it to keep the rpms up. What you don’t want to do is push on shifter until it will easily go into a lower gear. This kills the synchros.
Yeah, throttle response is pretty abysmal and I assumed that because of the smaller rev-range of diesels and more torque the jerks when poorly rev-matching are more intense then in a low-torque petrol cars.
I would say it isn't just you. I drive CMV, and being able to rev match is a necessity to downshift any gear since there isn't a sycronizer. My last truck seemed way more forgiving in all gears, but the truck I currently drive seems to have narrower margins for error. In other words you are going to have to take time to adapt to the vehicle rather.
I rev match into a lower gear when I slow down at lower RPM's when I'm coming to a slow turn or something similar, but at lights and stop signs I just shift into neutral and stop. Thoughts?
Depends on the amount of traffic I'm in, and whether I have time. But generally prefer slowing down less, but earlier, increasing the chance I don't have to come to a stop before lights go green and traffic in front starts moving again. Then yeah, might as well save the brakes while I'm at it, as well as having a bit of fun rev-matching. :)
@@brrrt7623 because it's dangerous. Both go to neutral or clutch fully kick in when rolling down the road is dangerous. When the road is straight, maybe not that bad, but when the road have some turns you don't have any load on the wheel and you can lost control to your car. If you drive motorcycle, even worst. Honestly i don't really know how to explain this correctly in scientific way. I used to do it once and then i almost fcked up. Little bit more and maybe i'm not here right now haha
@@Nick-ko1tw I was just curious as to why its irritating as a French. The only time I shift into nuetral whilst rolling is when I am coming up to a stop light that I know I'm gunna be at for awhile
@@brrrt7623 That not a problem, the problem is when Americans shift in neutral at 110km/h as I saw in many videos.. They didn't learnt how to drive it properly so they do anything..
Thx man! I always used engine braking, but more as a reflex. Was worried, I would damage the engine. Good to know, that it's a recommended technique :) Have a great day bud!
It is bad not to engine brake - with any car. Especially if on a long descent. Not using engine brakes is so dangerous that on some roads in the Alps, roadsigns tell you to use engine brakes. One example: the N85 near Vizille, France. On more than one occasion, buses have had their brakes overheated there, with a lot of casualties as a result. One other thing: it is also a good idea to have both hands on the steering wheel.
It also saves gas. If you think coasting, like I used to do, is gas-saving with the car in neutral, it is not. The engine has to muster up unnecessary power to maintain the idle when it is coasting in neutral. But if you are in-gear you create a lower, natural demand with the engaged transmission. Plus you are in better control with the car in-gear.
Fun anecdote: every time I brought in my Jetta 2.0TDI 6 speed manual for the scheduled maintenance, they kept telling me "hey, the brakes are still in very good shape." To which I often replied "well, I never use them." They thought it was joke, but with a manual transmission, and a little foresight, you coast in high gear, downshift appropriately, and really use the brakes only when you get to second gear before coming to a full stop. In addition to a seemingly little to no break wear I was making 44-46 mpg on average. Boy, I loved that diesel. Then the emission scandal broke and I went for the buyback. I drive a Prius C now, have to hit the brakes all the time but I get an average MPG of 50... hard to beat.
Engine braking and changing down the gears was all the rage in the UK in the past and you were expected to do this when doing the test to gain a driving licence. I never continued doing this though. I'd rather wear the brake pads out rather than my clutch. Steep descents or when driving a truck, fair enough but for a car - no.
Very helpful video! I've always downshifted to engine brake, but I've had some friends say it's saving the brakes at the expense of wearing the clutch more, and brakes are cheap and clutches aren't. That being said, the car my dad and i drove that we always engine braked on went 300k miles on the original clutch. I've also heard people say the clutch wear is mostly irrelevant because it's resisting spin in the opposite direction it usually does. Was just interested in your thoughts. Thanks!
My moto mechanic gave me two appointments for brake replacement but he was surprised each time at how little brakes I use and didn't need to change the brakes. Engine braking saves money in parts and it's also a smoother ride.
On long downhills engine braking keeps engine in higher rpm's which means your water pump runs faster effectively making coolant running faster through the system and cooling it down better rather than idling od downhills and brake, which makes water pump running relatively slow.
I once drove a very experienced driver and after minutes he told me never put your car out of gear (in europe we drive mostly manuals). From that point on i engine brake all the time even in the city
If you are in a gear too low, engine braking can cause the engine to rev beyond the rev limiter, possibly causing damages. Hybrids and all electrics use engine braking to help charge the big battery.
No it is actually very important it helps keep the ring lands clean in the Pistons. This comes from a 35-year-old mechanic who’s built many small blocks and big blocks
Engines with high compression actually do have a LOT more engine breaking... I had a 1,9L Ascona B with 90hp and it had a high compression engine and a 4 speed manual, in winter you could do hand bread turns by gearing down one gear and dump the clutch, also if the engine stopped and you tried to roll start it was really hard to do that and you had to put it in 4rth gear in winter to roll start.
Jason you are so beyond awesome there is no formula to state it.!!! Thanks for all the best videos unlike so many others. I have to purchase some swag to support you!
There's still a lot of confusion about engine braking. All good, perhaps more content on it! In the meantime, a few clarifications. How does engine braking work in diesels? Here you go! th-cam.com/video/o8Cta2cC2Co/w-d-xo.html Also confusion about downshifting. It is 100% fine to downshift, and yes, downshifting will provide greater engine braking because your engine will be spinning at a higher rate, thus the energy lost through pumping losses (as a result of the closed throttle) will increase. More energy lost = slows your car down more. Rev-matching your downshifts means no clutch wear, so it's no big deal at all. If you're into Snapchat, I have no way to please you. But if you're on the Instagrams feel free to follow! instagram.com/engineeringexplained/
Does engine braking by downshifting without the rev matching really do significant damage to the clutch? In driving schools here we're taught to break on the engine by downshifting, but we're not taught to do rev matching.
Normal engine braking (ie leaving it in gear while coming to a stop, or holding a gear during a long downgrade) is perfectly fine. The potential problem arises because of the the helical cut gears in the transmission. All modern gearboxes use these for forward gears because they're quieter. Problem is, they also create an axial load. So there's a thrust bearing there to take up the load in the normal direction. When loaded in reverse, however, the thrust is in the opposite direction. There is a tiny little thrust bearing in most transmissions for this opposite load, but there are two things to remember.
1. It is design for normal opposite loads... not inertial loads (ie when downshifting without rev matching) and
2. whenever you're going from a negative load to a positive load, you're "passing the zero".. ie you're going from one thrust washer to the other via a gap. The axial acceleration in this clearance causes an impact to the washer. It can take it... but only for so long and so many times.
Basically, under normal deceleration, you're fine if you rev match. But do it wrong, and you're looking at a costly transmission rebuild instead of a simple brake job.
arh .. thanks for this explanation, again. hopefully i didn't learned anything. but still appreciate the work ! keep going in ;)
What is the meaning of life? How much wood could a woodchuck chuck? What is the mechanism of engine braking? All very important questions that need answering.
You're probably right. I am American and I did fail both Thermodynamics I and Thermodynamics II in school. That may also explain why I have a hard time justifying all of the explanations about engine braking.
And is it bad for a BMW to use the turning signal lights?
Diesel+engine brake, that`s common sense.
BMW+turn signal... thats a tough one!
Engineering Explained, please help!
I dare you to find a more useless job than the guy that mounts turning signs on a BMW
Didn't realise that they had turning signal lights
You know how expensive those bulbs are?
They think we are in awe of their stature. We are actually just fearful of their trajectory.
Engine braking is only bad from the perspective of the person tailgating you.
BMW drivers...
Lmaoo
R.S. in my experience it’s mostly VAG drivers 🤔
VAG?
As in... you know, that wonderful slippery thing?
Matrix Mirage no, as in Volkswagen Aktiengesellschaft
Ridiculous. Deliberate engine braking offers the capable driver a remarkable amount of additional control over the vehicle, and is also one of the most enjoyable features a "manual" car comes with.
Thomas Raywood idk bout most enjoyable feature
I agree, the pulling feeling you get from it is pretty satisfying, especially if my DD has no pull going forward.
Agreed, mate...after my father died 7 years ago (he'd always sworn that the day he purchased a car with an 'auto' transmission would be the day that he died & unfortunately, those words proved to be 100% prophetic!), my mother purchased a new V6 Accord - her first ever automatic - & ever since then, she's forever offering to wash my 'manual' Civic Type R or to fill it with petrol, as she so misses driving a 'manual' & having so much control over the car...as well as her enjoyment of the exhaust sound upon my car vs hers!!
What's an engine braking??
@@TheeDevilWearsPrada down shifting while stoping...
There's a 2.5 km downhill section near where I live. If I go just the right speed at the top of the hill, I coast down the entire section exactly at the speed limit (70 km/h) and without having to touch the throttle.
Love it every time.
Just put your gear in Neutral then turn off engine for saving fuel and clutches and voila. ENTER DIRECTLY IN YOUR GARAGE 😊
@@ironpatriot6053 And when you have to suddenly brake or turn, because of a deer crossing the road, enjoy having no servo and no brake pressure.
@@ironpatriot6053 Turn off the engine?Hope you're kidding
@@EliteNoob22 😂
@@ironpatriot6053 Alright 😂
I love it when i hit the perfect gear and i descent at constant speed. Satisfying things
Those are quite steep descents you have, I've only been on a couple where even my top gear wouldn't slow me down
@J. Coal exactly, if it slows down on the top gear, it would be slowing down on lower gears
@J. Coal if even the top gear slows you, it's not a very steep hill, that's all xD
And with a loud ass car it’s so loud
I took a trip to Colorado and did this constantly haha. Love it
When I think about it, I usually apply a combination of engine braking and foot brake. Depends on the rate of deceleration. I prefer engine braking exactly for one of the reasons mentioned: fuel economy. One physics lesson I remembered and applied early on is the fact that regardless of how braking is applied, it's converting kinetic energy to heat which is essentially a waste of energy. So anticipating the road conditions ahead, for instance a yellow light about to turn red should trigger the reaction to ease off the accelerator. I always challenge myself to drive as smoothly as possible without having to brake. When fuel prices are as high as they are in the NL driving economically is a must. And of course the added effect of lowering emissions that way isn't a bad thing either.
hahaha you drive the exact same way as me, exept that traffic in morocco is crazy enough that its hard to anticipate but i try most of the time... also im not really good with thermodynamics but i assume that it will consume less during engine braking than when putting in neutral and leaving the car to coast in idle.... also may i ask how much are oil prices in netherlands ? here its about 80 cents for diesel.. and nearly 1 euro for petrol, so i'm planning to switch my high consuming petrol for a tdi
@@العقيدمعمرالقذافي-ح4ف Today it's €1,47 for regular gas. Diesel is €1,14. Stay safe!👍
@@robbievangeenenNL thank you
I too do that on my bike, but I pull in the clutch, so that I can reach the desired distance and then apply break
Instead of applying engine braking why not just stop accelerating and pull in the clutch ( do not shift it to neutral in case some emergency arrives and u need to stop or accelerate quickly)
Btw fuel price in India are approx INR 100 ( 1.21 USD ) per liter
For both petrol and diesel
@@warbot2544 if I understand you correctly you are pulling your clutch but not shifting into neutral. What that does is, you wont get the benefit of 0 fuel consumption or slowing you down because the engine will have to burn fuel in order to stay on (because you detatch it from the gearbox). And the thing with emergency brakes is: when you have to stop very quickly and you then Release the clutch so that the engine slows you down as well thats actually affecting your breaking Performance negatively. You see, the engine has its own rate of slowing down because of its own moment of spinning weight. If you then want to slow down quickly, its actually bad for your breaking Performance because you will need to slow the engine down faster than it would normally do as well... Hope I could explain that understandably.
The answer to the question can be summarized with one simple word... NO.
Turbo Diesel Why no? Every race car always stay at gear... :D
Jacek Lewandowski : What?! Watch the damned video if you need a long explanation. Good grief!
Turbo Diesel: Agreed.
The channel is called “engineering explained” for a reason... people don’t come here for one word answers
Have you seen the signs going down mountain roads that say "Heavy Trucks Gear Down"? Most heavy trucks (20 tones +) would overheat their wheel brakes very quickly going down long mountain roads. They have to engine brake and use J-brakes (another form of engine brake) in order to go down the mountain at a controlled pace. Yet, these trucks have engines that last millions of miles. If engine braking was bad then how could these truck engines last so long?
Just go light on both, brakes and engine braking. They work less hard together. Another advantage is if you downshift while braking, you are then ready to accelerate if you have to, such as approaching a red light but then it turns green.
In Germany, these are things we learn in driving school.
ArneBergsch Also in spain
ArneBergsch I believe this is taught anywhere with manual cars. I don't understand why so many people in the comments sounds so stressed about it. This is a everyday thing for me.
ArneBergsch in UAE we learn how to wheelie and drift in driver school
Same here!
Here in the USA, driving is a "right" so they hand out drivers licences to anyone that can breath. The "tests" are a complete joke, you could pass one blindfolded! Oh wait, they say "driving is a privilege " but really, everyone feels entitled to be crappy drivers here. People here take zero pride in car care, tire pressure checks, tire choices, alignment choices, etc. THEN, they will follow you at the same distance regardless if you're moving at 5 mph or 85mph. This is best demonstrated when you take off from a red light to a green light, everyone WAITS til they have that 2 car length space BEFORE they even begin to start to move. So half the number of cars actually get through each light, and yet, once you're moving from 5mph up to around 45 mph, they still have the same exact following distance.
I love seeing just HOW fast I need to go to get someone to not tail gate. It's fun when you get them up to around 90mph and they have that sudden realization that the speed limit is 55, and then they freak out and brake abruptly.
People here believe the rear view mirror is for checking themselves out/taking "selfies" rather than watching what is occurring behind them, then the same morons: "the cop just came out of nowhere" when they are crying about their speeding ticket. Duh!
We need more hot blond attractive German women who were not raised on a diet of processed and preserved foods in the USA to teach these people how to freakin drive here!
Can you do a video explaining "engineering explained" ?
Gears and Gasoline already did! :) th-cam.com/video/d2dFjum7O0Y/w-d-xo.html
That's so meta.
Gears and gasoline already did that
In Poland, on driving license exam.. you MUST braking by engine, by lowering your gears, if you dont do this- its fail.
damn that's hardcore, here in Canada, I've never met a woman who knows what engine braking is, even most guys don't even know what it is.
@@LeViIain Yep.. it is a little bit hardcore... stig from top gear tried our test.. and he fail :D
Thats why i pass test in UK - waaaaay easier.
@@LeViIain i didn't even know what it was, I just did it because it works.
@@Ulthion Somehow, I doubt The Stig knows Poland's road laws that well. Give him a few days to study, and he'd have passed with flying colors.
@@chrisseger2346 Law is same, just the diference is how examiners and police is looking at it. Im polish guy in UK, trust me.. its huge diference.
All new drivers in the UK learn to drive manual and are taught to engine break as a 'proper' way to drive a car. If you didn't do it you wouldn't pass your test.
M B we have to engine brake her in the US if we drive a manual while learning to drive also
M B this is completely false.
Jamie Lingard not really. I passed 6 years ago and engine braking was a thing back then that you had to demonstrate some knowledge in..
Harry Brookman I don't know how different The test was back then, but the only time you are taught (and this is only as part of your theory) to engine break is when travelling down hill to help avoid brake fade. You would not be marked down on your driving test to be in 5th gear even when travelling down hill.
Jamie Lingard Will you be marked down on your test for not rev matching?
Now there is a difference between engine braking and excessive engine braking. If you just driving normally but you are downshifting so many gears causing the rpm to get near redline, that's excessive.
i always engine break when i coast downhill. your engine will sound so good as well, i always listen to the sound of my full exhaust and smile
When trucks and buses with manuel transmission were still around it was common to brake with the engine. Either with a dedicated engine break system that slows down the engine even more, or with downshifting. To reduce wear from downshifting you can go into neutral, rev up the engine to get to get it to spin more closely to what it would in the lower gear at your speed and then put in the lower gear. This way the clutch doesn't have to work so hard.
SHORT ANSWER:
No, it's not bad to engine brake, so long as you revmatch correctly
Engine braking != downshifting
Excellent! Many years ago I had a 1964 flat windshield Chevy van DIY camper conversion. I put in a 1957 Chevy OD transmission to lower highway RPM, darn thing just snapped into place. The OD transmission had a freewheeling clutch, a planetary gear high/low range --6 gears! Sorta -- and a cable controlled freewheeling lockout. Loved it, clutchless shifting, gear choices when negotiating New England snow, and a little better fuel economy. But, there is a certain risk with a freewheeling clutch in the mountains. All was fine if you remembered to lockout the clutch, and the cable wasn't seized. Had some exciting moments on the edge of total brake fade.
This was in the owner's manual of the last manual transmission car my family owned. In my current automatic, it seems to automatically engine brake (high RPM down a hill if I'm off both pedals) good to know it isn't dangerous to the engine and actually saves fuel!
The main problem with downshift engine braking (assuming that you rev match) is that it increases wear on the upper main bearings in the engine. This is fine and won't be a problem - but it will be a problem if you are trying to use downshift engine braking during everyday driving traffic. It's fine let the car slow down in gear, but shifting to a lower gear to rev up the engine will cause that wear - but again this is only a problem if it's a driving habit. If it's a downhill only practice it works great.
nerdyengineer yeah.. but what do I do when I want to practice heel and toe downshifting I have to do it often how am I gonna get good at it if I do it occasionally? I have to practice at almost every opportunity once good I can do it less
Next video: "Is it bad to turn on a vehicle?"
Yes. If you never drive it, it will last forever.
Sounds about right
@@yudax5057 No, not really. Actually, aircraft engines that are flown everyday are more reliable and last longer than those that sit for long periods.
Total LOL in the OP's favor.
@@garyvanremortel5218 Airplane engines are serviced like every week tho
Always us gears to slow down approaching a hazasd (corner,Roundabout etc ) so I am in the correct gear to pull away.
I have a 6-speed manual FRS. I use the engine to break all the time. The result was that I did my first brake job on it replacing only the pads and the original pads still had about 1/16 of an inch left on them. this was at 142,000 miles.
Nice. Gonna boost that frs?
@@dnawrapsatl I'm or of those guys that thinks the FR-S has all the power it needs. :)
I'm more into handling. I use the gears to manage the power curve, and engine longivity is paramount.
@rob wells - still on the original clutch too?
@@ghostwrench2292 The throw out bearing went out at 150k so I replaced it all. I did my first brake job at 142k. Brakes are for chickens.😉
@@ReasonablySaneHow many miles are you at right now?
Mack truck= drop a gear and hit the jake babyy 🤘🏻
Jake brakes are sweet! Made a video discussing how they work. :) th-cam.com/video/o8Cta2cC2Co/w-d-xo.html
I always give these guys proper following distance as they are going to kick up rocks and they typically need to change lanes unexpectedly (prius drivers), so I keep out of the blind spot and pass with a vengeance or just stay way back. I feel sorry for truckers that have to navigate around all these people that are for the most part indecisive on the road.
mack engines don't use Jake brakes technically, they have their own system
Mack trucks have what they refer to as a Dynatard system. Same concept but slightly different system and name.
Sound Hound I work on Mack trucks. Love the jakes!👍
Much
Dont they teach this in driving schools?... Engine breaking is good and is actually suggested especially on slippery and wet road.
Dominik No I dont know....I used engine braking on ice once....bad idea haha.
Dominik No when i tried engine breaking the police charged me for vandalism
Is it that simple then , just drop a cog or two and that will save you , brakes are there to slow you down and lower gears are used to maintain that slower safe speed .
Engine breaking is the worst, but engine braking is great.
In Malaysia, not at all, they aint even teach you when to shift, some of the tutor says 3k, some say 2k, and they cant explain why.
now i learned how to drive by daily driving, i shift whenever i like, like learn to handle the redline, so i won't get nervous when i need it. no mom spaghetti
or if i feel like to cruise & chill, shift before 2.5 (or 2, depending on vehicle, my car has the best torque in 1.7k and 4k, on paper, so)
In short, they only teach me how to ignite a car, not drive, no engine brake, no skipping gear shift, nothing at all, i gained more knowledge from youtube tbh.
Protip:
In the mountains, go down in the same gear as you went up.
Most cars today will go up a hill in top gear. I can overtake going up hill in top gear in mine.
Top gear will not keep the car from accelerating down the same hill. Neither will 5th. You need to go down to at least 4th to hold speed and 3rd to decelerate.
@@calvinnickel9995 Correct.
It's also beneficial for setting your piston rings during break in, an acceleration followed by deceleration.
I think it will be beneficial also after the engine break-in period as it gives the piston rings "some action" if the engine is operated normally only at low rpm.
Another thing to metnion - if you have AC turned on, while engine braking on descend it will actually run the compressor for AC without burning any fuel. So you recycle part of the kinetic energy to do useful work insetad of buring fuel.
You maybe mean no additional burning of fuel. Because the engine continiously run during an engine breaking.
@@ScripturaSola777 Yes and you also recover some of the energy from already burnt fuel back to usefull stuff like:
- Turning alternator to power electrical systems and charge the battery
- Running AC compressor to cool the cabin
- Running power steering system
- Running Water pump to cool the engine
So you get the double gain. Since all of those utitliy systems are connected to engine, you actually brake by letting all those systems take the load of the gravity pulling you down.
And of course no additionl fuel being burend on descend. + your brakes are cool and not wearing down pointlessly. You just apply brakes every now an then when needed before a turn or if speed goes too high.
Engine breaking can save the need to replace your breaks by up to 3 times the need. Down shifting is better for your car than shifting up in gears. It is also safer to use engine breaking.
With the injectors off it's the wheels that are transferring power back into the engine to overcome it's inertia and friction to keep it turning and that is how the kinetic energy is dissipated. Secondly with the throttle closed, little air is coming into the engine and since there is no fuel added it is just taking the heat out of the cylinders and out the exhaust. Love your channel by the way and great video!
Thanks, I’ve always used engine braking in my 5.0 Litre Mustang, I love the sound and now I’m assured that this method has no adverse effect on the mechanical components of my drivetrain
One thing to note is that if you are going downhill in the Rokies or whatever and have the heater on, it is totaly normal for your coolant tempretature to go down. Lots of cold air hits your engine and you are asking for heat yourself to warm the cabin. Heat from engine braking really is miniscule. I am commenting on this because many thermostats have been changed for no reason. In cold environment going downhill with no throttle, engine temps can only go down no matter what, and this is normal.
So basically if you drive a manual like a normal human being than have been doing engine braking just never realized it
Boostang S.I.C You'd be suprised how many people are actually aliens.
Not necessarily, Boot. A lot of normal humans driving manuals _do_ realize it.
Engine breaking and down shifting is a skill every driver needs. Everyone should be taught how to slow a car down from 70mph to 3mph without using brakes, useful for at least 2 situations. Icy roads or brake failure.
Part of my driver training involved engine breaking. Done properly saves maintenance on brakes.
Love your videos, Jason!😍👌 Very interesting... I was putting engine braking to the test yesterday in the western NC mountains. Had a blast! Have a great day, buddy!🙋
Grew up in NC, love the Appalachians!
Engineering Explained Awesome, man. Your S2000 would be right at home there. Yesterday, I was on 226A that goes into Little Switzerland. They call that stretch the Diamondback. Check it out when you get back home.😆 Cheers!
TheMick26 Love those mountains! I've been meaning to drive that stretch of road. What kind of car were you in?
Your Slowbro I was in my 2014 Q50S Hybrid RWD. I was trying out my new Michelin Pilot Sports and 14" Stoptech slotted rotors. It's no S2000, but the car handles great, especially for its size. Great stretch of road... give it a go when you get a chance.
TheMick26 Alright I Will! Also, I have been using those MPSS. They are phenomenal.
From watching these engineering videos, I was told that the vacuum created on the intake was the key to engine braking, but a simple experiment on my motorcycle led to the opposite conclusion.
I was coming down a hill in gear. I hit my engine killswitch and fully opened the throttle with my hand. There was no difference in the amount of braking with an open or closed throttle.
What gives?
Pedro Silva reality kicked in and broke the TH-cam pseudoscience machine
[Commenting b/c I want to know the answer too.]
Its just the friction of the components and overcoming reciprocating motion of pistons etc
You are correct
What gives? the vacuum explanation is a nonsense, its not the reciprocating motion of the pistons or friction either, its the force of compression.
sac speed The rotational energy lost compressing the piston is simply regained once the piston decompresses. The friction and vacuum explanations make more sense. I'm most inclined to believe EE as he is (was) a well studied engineer who designs car engines for a living. Though, OP's experiment throws the vacuum theory out so I'm still curious for any further insight.
I think when people say engine breaking they are referring to that slight shock of downshifting when you ONLY let go of the clutch slowly (as opposed to rev matching)
yep. and im still unclear about that although i just makes sense to me that it probably isnt good.
If you rev match and slow down that way as you slow down is that fine and safe??
@@robr430 rev matching means you press the accelerator while downshifting, so the engine reaches optimal RPMs. In racing it keeps the car balanced, while in regular driving it reduces wear on the drivetrain
When you use engine braking all the pressure on transmission gear faces and engine bearings is reversed allowing a slightly thicker oil film between metal parts and overall reducing engine and transmission wear.
but what if i LOVE that pow pow pow sound?
da tin goes skrrrrrrrrrrrat POP POP POP POP POP
Another detail you didn’t mention, particularly with the BMW you are driving, when you engine brake on those cars, the instant MPG gauge goes to what looks like battery charging. My Audi does it. It’s not a hybrid either. Was wondering if you could do a video on how it all works and why some cars do it, if you haven’t done that already.
In order to save fuel, modern cars try to use the alternator more sparsely, as it's quite significant load to the engine - during the engine braking, they'll use it to recharge the battery, acting sorta like low power regen braking.
@@Papinak2 thank you! I was wondering why my non hybrid car would show charging while letting go of the gas
I had a car with a stuck open thermostat, and the only way to get the heat to work during the winter was to let it sit and idle. as soon as you started to move, the heat instantly got colder and colder, to the point where it was just blowing cold air. engine cooling systems are extremely effective, and engine braking, as explained, will only cool off your engine, even though it is loaded.
TLDR: Engine braking is perfectly fine as long the engine is not two-stroke.
its fine on 2 strokes as well, as long as the engine is oil injected and not oil premixed with gas.
@@hojnikb That depends. If the oil gets injected into the air intake (just past the throttle body) it would still lack the airflow to reach the piston. I don't actually know if there's engines with oil injection directly into the crankcase or onto the bottom of the piston.
This is what they taught me during CDL-training: Shift down, jake and brake.
also its free AC and battery charge :D
Yes I was just querying this. How does the charge get stored...via the alternator back into the battery? We didn't get around to discussing this in my electrical course.
@@southernkatrina8161 I believe so
@@southernkatrina8161 With an BEV? - The Engine is then used as Generator and stores the generated "Power" into the Battery.
Combustion engine: It rotates powered by kinetic energy from the car and also the 12V Generator rotates to load the lead battery. If rotating faster (and regulation can increase generation level) it generates more Watts in the same time. Additionally the AC-Compressor works at higher rpm and cools faster.
I just hit 120k miles on my 2013 Mustang Gt with a manual 6 speed and still have not changed the pads or rotors, though I will soon as they're about 25% with a little grab on light braking. My automatic friends are amazed. (I'm still on the same clutch as well).
does that BMW come with turn signals as standard?
Don’t be silly, that’s obviously an extra.
Theres a special m-training for turn signals
Yea but it's a switch and it's weird to use.
Yes! BMW even designed a new Type of Blinkerfluid. It is less harmful to the blinkergaskets. So the turnsignals should work longer.
Breaks are way better than they use to be 20 years ago and in a manual transmission. I rather replace breaks than a clutch, so I will always use breaks to slow the car down than engine breaking or the clutch. It’s way cheaper! You are awesome, I love your videos Thank You
The dual clutch gearbox does a good job of using the engine for braking..it doesn’t always know which way to change gear but most of the time I’m happy with mine.
It's not only brakes you are saving. It's entire suspension system. It's not much of a consideration in new vehicle but in older ones it's definitely something to keep in mind.
I have 20 year old Toyota Corolla w/ 5 speed manual trany. I engine break all the time by down shifting up and down hills, around sharp corners and to slow the vehicle when coming to a stop. I always rest my hand on the shifter when I feel I might need to change gears for whatever reason. I still have the original clutch and have only had a single brake repair. The front pads required replacing 3 years ago, the rear pads still had 50% wear left. I never ride my clutch - never. I also pull a smaller trailer with my Toyota all the time. Saved me having to purchase a pickup truck for hauling things! I also put my car in neutral when going down longer hills when there doesn't appear to be any reason to slow down and I let gravity do its thing! There are some hills that allowed the car to go close to 100 mph in neutral.
What about an Auto with slap shift?
I use a balance of Brakes and Engine Braking
K9 JSB thats right! the right balance is the best technique! brake + down shift !!!
marian mar constantly downshifting wears out your clutch faster than it would otherwise wear. Brakes are cheaper than clutches.
Look It's That Boy i owned a lot of cars in my life and trust me the clutch is not gona wear off unless when u downahift u go over 4 k rpm in gasoline engine and around 2.5 k rpm on most diesel engines (not by trucks)
best technique - brake + revmatch/heel&toe + downshift
@@jordanlazarus7345 Did you know there is something called rev matching?
what about all the Extra stress on the piston and wrist pin? Instead of the piston being pushed down, its being pulled down by the con rod and worse the intake is closed causing more resistance.
chainsaw2010
That's like saying too much boost on a stock turbo charged engine isn't good at WOT
The piston has to get pulled down anyhow, the rods, etc have to deal with so much more force from the power stroke that they will always EASILY handle this load
So you think thats worse than an engine under load? The piston is built to handle thousands of explosions a minute... No engine braking will have no significant wear on anything...
Combustion not explosion... engines don't explode, they are called internal combustion, not explosion, engines.
chainsaw2010
But don't the rods pull the pistons down when it's under load too?
In a 4 stroke engine during the power stroke the piston pushes the rod down, but during the intake stroke the connecting rod is pulling the piston down.
When one cylinder fires that power gets transferred through the crank and through the connecting rods to the other pistons. It seems to me that the connecting rods are designed to pull the pistons down
And in Germany in some of the standard questions for your theory exam for a drivers license its specifically stated that on long downhill rides you are supposed to disengage the clutch often and use your breaks. Because it will be bad for your clutch.
I love this channel.
Thanks! 🙏
@@EngineeringExplained I still do.
I was told "engine braking" in driving school. 🤷♀ It's good to save gas, spares the brakepads & its saver on long downhills. Never thought that there might be a discussion about it.
What should you do when the brakes fail while driving?
downshift + E brake
If your brakes fail completely, downshift (or lockout, in an automatic) as soon as possible and start using your handbrake/emergency brake firmly but carefully, so you don't lock the rear wheels. If that doesn't work, call 911 (or your country's equivalent) before you pick up too much speed, then start weaving the car back and forth. The resistance from the tires will help slow you down. If necessary, drive up onto the dirt banking for a similar effect. Choose them wisely, though, and don't drive too far up them, because it could cause you to lose control. Then, look for any runaway ramps, or some kind of place that you can turn off to shed speed. It's not great to drive into one of those ramps, but it's a hell of a lot better than the alternative.
Bavarian Banshee so informative! Thank you ❤
Put it in neutral and turn the key off. Obviously.
Conspirazy turning off the key won't lock the steering wheel?
I have a question: I have noticed that under braking, downshifting using the clutch only results in a smooth enough transition that rev matching is not necessary. As an engineer my guess would be that the synchros are sufficient in low speeds and braking itself would help match the revs of the transmission to the engine. What's your opinion?
Just double clutch in that case so that you won’t wear your synchros, thats it.
This only applies when your revs are low, as downshifting at 1500 rpm will make you jump to 2000, not a big change in numbers. However if you downshift at 4000 rpm, you will go to 5400, the % is the same but the actual figure is higher, so you will feel the jerk much more. That’s when you need to rev match.
You thirdly get better traction in a turn dropping it into second and your revs are already higher so it's easy to accelerate out of the turn and have much more control coming out of the corners. Corners are often blind and you won't be able to stop or slow enough to turn sharp enough to avoid an obstacle at the very last second.
Don't forget about the jakes lol
Been down shifting for many years without rev matching and everything is prefect.
its not smooth or fast though, car probably doesnt like it either. and trying doing that at high revs in a car thats not brand new. good way to upset the car
could u please explain throttling delay in new cars, which i face "engine is seconds slow to react if i press acceleration paddle". is it a good thing or not? should i tune it at service center?
Some new cars stop there engine if your at a dead stop. Or maybe if u press to hard in automatic car it might try to downshift b4 you move which takes time
just like Bart from science garage said
I lived for a while near a steep enough 200 m (650 ft) of altitude descent. It was steep enough that I could engine break in third gear almost the whole way down. The engine didn’t really warm up very much before the downhill section started. In winter, even with a functioning thermostat, going down the engine cooled down enough that even though I had some heating at the top, at the bottom there was no heat anymore.
Essentially the heat to warm up the passenger compartment I was extracting from the engine was more than engine braking put back into the engine.
Is it bad to push the clotch in when breaking.
No
@@low-qualityasmr2600 thank you.
@@TheBoxingNinja the cluch is what connects the engine shaft to the gearbox so as long as you don't rev your engine while braking it shouldn't do damage
the 4th benefit is where overbraking may lock the wheels (non abs), whereupon you lose steering, adding engine breaking to braking maximises braking effectiveness while maintaining wheel rotation and not losing steering.
What if i completely locked wheels for a second while engine braking hard? Is it really bad?
I always operate without a thermostat in my 260Z during summer months
Props for driving the least popular Z. Only ever seen a couple of them.
Your fuel economy must suck on short trips.
You can downshift if you heel/toe it to keep the rpms
up.
What you don’t want to do is push on shifter until it will easily go into a lower gear. This kills the synchros.
Seen many people strip the key way on their cranks from not rev matching or maybe went into the wrong gear
Why is it hard to precisely rev-match a diesel car when downshifting? Or do I just suck at it?
Yes, that will probably be it.
I'd say it's hard in every car, maybe in your particular diesel it's even harder because it has poor throttle response
it should be easy as diesel engine usually operate in a smaller rpm window, you just suck
Yeah, throttle response is pretty abysmal and I assumed that because of the smaller rev-range of diesels and more torque the jerks when poorly rev-matching are more intense then in a low-torque petrol cars.
I would say it isn't just you. I drive CMV, and being able to rev match is a necessity to downshift any gear since there isn't a sycronizer. My last truck seemed way more forgiving in all gears, but the truck I currently drive seems to have narrower margins for error. In other words you are going to have to take time to adapt to the vehicle rather.
I rev match into a lower gear when I slow down at lower RPM's when I'm coming to a slow turn or something similar, but at lights and stop signs I just shift into neutral and stop. Thoughts?
Are you me?
Depends on the amount of traffic I'm in, and whether I have time. But generally prefer slowing down less, but earlier, increasing the chance I don't have to come to a stop before lights go green and traffic in front starts moving again. Then yeah, might as well save the brakes while I'm at it, as well as having a bit of fun rev-matching. :)
As a French, the thing that turn me mad is when American people shift in neutral while rolling.. 🤦🏼♂️
Why
@@brrrt7623 because it's dangerous. Both go to neutral or clutch fully kick in when rolling down the road is dangerous.
When the road is straight, maybe not that bad, but when the road have some turns you don't have any load on the wheel and you can lost control to your car. If you drive motorcycle, even worst. Honestly i don't really know how to explain this correctly in scientific way.
I used to do it once and then i almost fcked up. Little bit more and maybe i'm not here right now haha
@@Nick-ko1tw I was just curious as to why its irritating as a French. The only time I shift into nuetral whilst rolling is when I am coming up to a stop light that I know I'm gunna be at for awhile
@@brrrt7623 lol sorry then
@@brrrt7623 That not a problem, the problem is when Americans shift in neutral at 110km/h as I saw in many videos..
They didn't learnt how to drive it properly so they do anything..
Thx man! I always used engine braking, but more as a reflex. Was worried, I would damage the engine. Good to know, that it's a recommended technique :)
Have a great day bud!
Clutch wear can be avoided by reving the engine up to the level, which will be awaited in the lower gear - also the shock disappears.
Rev matching
@@toad3222 Right.
It is bad not to engine brake - with any car. Especially if on a long descent. Not using engine brakes is so dangerous that on some roads in the Alps, roadsigns tell you to use engine brakes. One example: the N85 near Vizille, France. On more than one occasion, buses have had their brakes overheated there, with a lot of casualties as a result.
One other thing: it is also a good idea to have both hands on the steering wheel.
Fun fact: here in germany, if you don't engine-brake when reaching a roundabout or a red-light twice in driving test, you're 100% gonna fail
Sounds like a failure by the test to me.
In the US, 90+% of people have never driven a manual car
It also saves gas. If you think coasting, like I used to do, is gas-saving with the car in neutral, it is not. The engine has to muster up unnecessary power to maintain the idle when it is coasting in neutral. But if you are in-gear you create a lower, natural demand with the engaged transmission. Plus you are in better control with the car in-gear.
With all the modern trickery in the engine, it would be fun to have the option to disable the exhaust cam and have even more engine brake.
This comment section looks more like Pakistan vs India. Lol.
Usman Ali why
Fun anecdote: every time I brought in my Jetta 2.0TDI 6 speed manual for the scheduled maintenance, they kept telling me "hey, the brakes are still in very good shape." To which I often replied "well, I never use them." They thought it was joke, but with a manual transmission, and a little foresight, you coast in high gear, downshift appropriately, and really use the brakes only when you get to second gear before coming to a full stop. In addition to a seemingly little to no break wear I was making 44-46 mpg on average.
Boy, I loved that diesel.
Then the emission scandal broke and I went for the buyback. I drive a Prius C now, have to hit the brakes all the time but I get an average MPG of 50... hard to beat.
Engine braking also reverses the normal wear pattern on the bores and assists lubrication of them too.
U should have 1st explained how to engine brake..
Engine braking and changing down the gears was all the rage in the UK in the past and you were expected to do this when doing the test to gain a driving licence. I never continued doing this though. I'd rather wear the brake pads out rather than my clutch. Steep descents or when driving a truck, fair enough but for a car - no.
Why is this guy driving a different upper middle class car each time I see him in a video?
Very helpful video! I've always downshifted to engine brake, but I've had some friends say it's saving the brakes at the expense of wearing the clutch more, and brakes are cheap and clutches aren't. That being said, the car my dad and i drove that we always engine braked on went 300k miles on the original clutch. I've also heard people say the clutch wear is mostly irrelevant because it's resisting spin in the opposite direction it usually does. Was just interested in your thoughts. Thanks!
My moto mechanic gave me two appointments for brake replacement but he was surprised each time at how little brakes I use and didn't need to change the brakes. Engine braking saves money in parts and it's also a smoother ride.
On long downhills engine braking keeps engine in higher rpm's which means your water pump runs faster effectively making coolant running faster through the system and cooling it down better rather than idling od downhills and brake, which makes water pump running relatively slow.
Pulling a vaccum or de-compressing air also lowers the temperature of the air. That can help the engine cool evern further.
Driving cross country, I Definitely noticed my car getting hot going uphill and cool going down.
I once drove a very experienced driver and after minutes he told me never put your car out of gear (in europe we drive mostly manuals). From that point on i engine brake all the time even in the city
I use oil on downhills in gear, I use no oil coasting or on slow descents that require engine to maintain high enough speed.
In Belgium where actually thought to engine brake by downshifting. Sometimes even from 4th to second
If you are in a gear too low, engine braking can cause the engine to rev beyond the rev limiter, possibly causing damages. Hybrids and all electrics use engine braking to help charge the big battery.
Trucks often have special systems to improve engine braking to prevent overheating the brakes.
No it is actually very important it helps keep the ring lands clean in the Pistons. This comes from a 35-year-old mechanic who’s built many small blocks and big blocks
Engines with high compression actually do have a LOT more engine breaking... I had a 1,9L Ascona B with 90hp and it had a high compression engine and a 4 speed manual, in winter you could do hand bread turns by gearing down one gear and dump the clutch, also if the engine stopped and you tried to roll start it was really hard to do that and you had to put it in 4rth gear in winter to roll start.
Jason you are so beyond awesome there is no formula to state it.!!! Thanks for all the best videos unlike so many others. I have to purchase some swag to support you!