As a pro ECU tuner, I see this problem all the time in the newer LT Chevy engines with DI. Especially with aftermarket superchargers. Gotta be very careful tuning these new engines. Great video!
Rhett Castillo have any of your customers considered a water/methanol system to reduce chances of this problem from what I've read it seems to work well for forced induction.
Dude, I'm from Brazil and really like seeing your videos, not only for the great explanations themselves, but to get familiarized with mechanical terms in English. The content presented is always rich, yet in a simple and clear didactics!
@@pedrodossantos5890 E o que tem de errado em alguém que já conhece os termos em português, como no meu caso, querer aprendê-los em inglês? Cada comentário...
O canal dele é excelente. O bom é que o inglês dele é bem tranquilo de entender. Alguns canais europeus, com inglês britânico, são bem mais difíceis de entender.
@Ungregistered User aren't flat tappet cams/valves used in pretty much every car engine unless u go with a roller setup which is for higher performance?
Never go full throttle at low revs in an MPS. My tune alleviates most of this by pushing the torque curve towards 4000 to 6000rpm to avoid bending rods
@Ungregistered User Nope, it doesn't apply to modern engines, it applies to all. It's just that modern engines usually run hotter. And they usually have direct injection which causes deposits. Btw, *here is how to cause preignition and the super duper knock:* (1) Machine your engine parts with a dull endmill, machine as roughly as possible and DON'T deburr. (2) Cause as much carbon deposits as you can; to do that mix oil into your fuel and reduce the pressure of your injection system or use work out injectors to get a crapy fuel mist. (3) Hook up an EGT gauge and tune your engine to run hot. After that your engine should go boom. (unless you blow your headgasket first, XD) Burrs and carbon deposits kinda work like a glow plug: they do get warm by the combustion but they don't get cooled by the cylinder walls. Just think about it: a burr sticking to the side of a block of metal has a relatively high surface area that's contacting with the air around it, but it's connected to the rest of block of metal by a small surface area. Carbon deposits that get on the valves can have the same effect. But with carbon deposits it depends on how porous they are, how smooth they are, etc; not all carbon deposits are equal. The smooth carbon deposits that almost seem to be brushed on won't cause knock as quickly as the rough ones.
@@huntergman8338 Reminds me of water hammer also ie the problem that occurs when you try to close a valve on a rapidly flowing pipeline full of fluid in effect trying to arrest it's momentum too suddenly. This can similarly result in failure of the valve and/or the pipeline especially if you try this on a long distance pipeline where you can have literally tons of water in motion suddenly being forced to stop violently the pressure spikes can reach levels that are in the realms of an actual explosive device going off right next to the valve.
@@huntergman8338 Indeed, exceeding the rated pressure limits of a vessel is a bad idea however it happens. There is a reason why such limits exist after all once you pass them you are eating through your margin of safety and probably permanently reducing that margin through added metal fatigue too even if you remain short of causing outright catastrophic failure.
Its funny that people dont like light knock when that is basically what mazda's sky active engine is designed to do. Spark Controlled Compression Ignition is just using the spark to start ignition and then the increase in pressure causes compression ignition every where else. the only difference I can see between the two is that light engine knock is not consistent and happens in only one location and then propogates instead of being a controlled universal compression ignition. Such a small change can take it from being engine knock, to a super advanced engine technology that you WANT.
You know that the skyactive X is capable of both compression ignition (like diesels do) and spark ignition as it has spark plugs too. I wonder how reliable and long lasting they will be.
How about using a higher octane gasoline??? How about to get the coldest air through the intake that you possibly can set up for??, How about, because it is a turbo engine and direct injection, will assume, by delaying closing the exhaust valve during the intake stroke and also delaying the fuel injection you can evacuate the burned gasses with forced fresh air and lower your chamber temperature???. How about upgrading your intercooler to a better quality that can give you more cooling and a correct amount of flow by the engine set up????.. remember that the manufacturers go the cheapest they can get. I am a great fan, really like your channel but those are questions that I will like to be answered. Keep up the good work. Thanks for being educating us.
@Ungregistered User its actually P*C*V it stands for pollution control valve. Its emissions equipment that recycles oil vapor instead of letting it make a mess under the hood or making oil slicks on the streets. Its important but its advised to install a oil catch can between it and the intake system to prevent octane dilution.
@Ungregistered User It stands for Positive Crankcase Ventilation. With old cars they just let the crankcase vent with a tube or basically an open hole. That allowed all the gasses and some oil to escape which made a mess and was bad for the environment. So, modern cars put the crankcase gasses and everything back into the intake. That way everything gets burned and emissions are better. It also means the vacuum of the intake helps pull everything out of the crankcase so it's more efficient.
Gamma Light I think you are getting confused with the EGR valve (exhaust gas recirculation) which can have a similar effect in the engine regarding knock and superknock because of hot and uncombusted gases entering into the combustion chamber. PCVs are used to avoid high pressure concentrations in the crankcase which will lead to blowing gaskets and as you said cause oil dilution, but also make sure the unburnt toxic gasses passing through the piston rings (blow-by) aren't freed to the atmosphere.
So if your car is tuned for a higher octane, let’s say 91-93 and you run 87 to be cheap, that would cause light knock or potentially both? Awesome video!
I honestly never seen any report of early engine breakdowns due to "super knock". LSPI is also not the problem of the modern engines like it was mentioned. this type of abnormal combustion is not new, and it can also occure in NA engines with high compression ratios. it is a preignition caused by a hot surface accompanied with knock. cause of knock: a very advanced spark timing(usually spark timing should not be that advanced at low rpm) if you read the reference given below, there are at least 6 types of abnormal combustions, knock can be directly regulated using spark retardation, but for preignition u need to cool the engine temperature down. john B heywood - internal combustion engine fundamentals chapter 9- part 6: Abnormal combustion
@Ungregistered User no, knock is a secondary ignition point somewhere else in the cylinder that results from the pressure increase after the spark plug fires. You end up with completing flame fronts that accelerate the burn and increase cylinder pressure at an undesirable rate. Pre Ignition is an ignition event prior to the spark plug firing.
I have an engine susceptible to LSPI. It's a 2016 Vauxhall Astra 1.4 turbo (140ps) - same engine as some Chevy Cruze models. My solutions so far : 1. Use 98 octane fuel (widely available in the UK) 2. Never drive uphill in 4th/5th/6th gear with high throttle load at
I switched to a very expensive motor oil about 6 years ago and it keeps LSPI from happening or does a great job of keeping it at a very low percentage of happening with the low octane fuel by keeping the pistons from over heating ....
Quite clear explanation and short accurate video!! You've got one more subscriber. I really appreciate that you take your time and draw on the board like that, that makes the videos even more understandable.
Knock and pre-ignition are two totally different things. "Super knock" is pre-ignition and has been an issue with engines for years. Knock is the noise of two flame fronts hitting each other.
I think Engineering Explained should start a petition for the Department of Energy and the Department of Weights and Measures for the United States to raise pump gas octane levels to 95 octane. He'd know exactly what to say and I'm positive we'd all back it up
Most cars have no need for increased octane. The burden falls on the manufacturers for pushing the limits of what their engines can do. It has already become extreme.
@@flagmichael as emission requirements increase so does the need for higher octane. Hotter IAT, EGR and excess PCV use dramatically reduce octane levels. Every car I've worked on would see huge benefits from an increase of octane when fully loaded with passengers or when driven in a manner above economy purposes. But hey, if everyone's happy driving with extremely retarded ignition timing then let's not change a thing. I honestly can't think of one car that wouldn't benefit from higher octane, please enlighten me
LSPI is probably what caused my 2016 Subaru Forester XT to develop a hole in the engine block around 45,000 miles. Subaru covered a new block, then new heads. I had a brand new 50th Anniversary NA Forester for over 12 weeks. As soon as I got the car back, I sold it to Carmax. I now drive a 2019 RAM 1500 Limited. No more worrying about LSPI. And I can pull my Jeep on a trailer.
So even engines have a "normal" size, going much below it brings unwanted consequences. Just like making cars too small has detrimental effect on a lot of things (usability, stability, safety etc)
It's not quite "the size" of the engine that increases risk of this; it's the cylinder pressure when/as the piston reaches the top of the compression stroke.....it's just that smaller engines typically have higher compression ratios or use forced induction.
hi jayson. may i ask the pros and cons of deleting an egr system in diesel engine, theres plenty of vids out there but your explanations is the only one i trust. thank you
Super interesting video! We covered some of this (or something similar) in our Internal Combustion Engines class (the name wasn't Super Knock though 😂) but there was still stuff to be learned, very interesting to see oil manufacturers testing for LSPI. We didn't cover that, or at least I can't recall it right now. To the people reading the comments, this isn't some super dumbed down content by the way, in uni we cover this in a similar way. Amazing to see this type of content on TH-cam!
I had a rod knock. No smoke, good acceleration. Turns out bearings are fine. Piece of piston in the sump. 0.7L turbo charged 80kW engine. Now my second engine is developing the same symptoms - knock originating from wall of middle cylinder (3cyl engine)...
As per one of your previous videos, especially for those of us with MT, Don't Lug the Engine! Based on my experience in my wife's new traditional 8 sp AT vehicle in normal or eco mode it's always trying to upshift asap (gas savings) at the expense of higher load at lower RPMs. We live in a mountainous area and the AT obviously can't predict the numerous approaching inclines and is often "confused". Though she typically isn't using it for "speed", we've noticed that setting it to sport mode has worked the best for us in our normal daily driving (less lugging and fewer shifts). Thanks for your informative videos.
Hello, nice video, thx. I have few questions/notes. 1. Why this occurs in low speed/revs and NOT in high ones?? What is actually meaning of "low"? 1500-1800 rpm? This is something that no one technically describes - pitty. 2. The chart in top-right corner is not correct/accurate - why should superknock pressure be that higher than light knock/normal combustion situation. I would say, that the main problem is timing and pressure increase speed, not the overall pressure. 3. Why the oil that has much higher ignition temperature than petrol is causing this?? 4. Why direct petrol injection is worse than indirect one? 5. Is superknocking detectable? "Normal" knocking is and when it is detected engine control system can deal with it. Why is that knocking worse?
7:10 taking away power from the user willy-nilly is a bad solution because it can be fatal. If I'm in the middle of an overtaking maneuver or need just a bit more power to move away from something and the engine decides that right now I should not get the power I am used to - that is deadly. They allow manufacturers to do that? What a world we live in ... Safety should be a much higher concern than efficiency.
@Engineering Explained If oil in the cylinder is bad for knock then shouldn't rotaries and two stroke piston motors have uncontrolled knock or super knock? Do they?
@@OtisFlint just fine, yes. But few handle it perfectly. Mix E85 into a sample of oil and observe it's ability to polarize the fuel. In my findings I'd seen more bad results then good.
Another factor that doesn't get enough attention is differing fuel quality between markets in North America. ACN (Arizona, California, Nevada) 91 octane fuels are far more knock prone than 91 octane fuels in other states. Same problem in Western Canada where 91/94 behave poorly compared to similar 91/94 in the East. This probably comes down to refinery feedstock, heavy grade oil probably nets a poorer quality gasoline. Our AKI system is prone to refiners juicing RON numbers and leaving MON lower than similar fuels in Europe. AKI is RON+MON/2. Anyone running off the shelf tunes for cars need to ensure the fuel they have in their market is appropriate, not all 91/93s are created equal.
I'm certain GM's 2.0T LTG engine suffers from this condition. Several 2014+ Buick Regal, 2013+ Cadillac ATS, etc owners have reported failures (cracks) at the top of the pistons, exactly where this condition would cause a fatal issue. It seems to happen regardless of driving style or whether the engine is tuned/modded, and at varying times from 500 miles to 50,000 miles.
Hi, Your graph shows super knock happening AFTER spark, but earlier you explained it as occurring before spark (pre-ignition), on the compression stroke.
There are after market solutions to this but the manufacture is not going to introduce them because it is a high maintenance solution most owners would not want to deal with. Water/methanol injection seems to work really well at cooling intake temps and actually raising the equivalent of the octane of the fuel your burning especially in forced induction and high compression engines.Another benefit for DI engines is it cleans the intake valves.
There are a lot of racers in the Porsche world who use outboard 2 stroke oil in their sumps because supposedly the octane rating is nearly the same as 87 octane gasoline. I do not have an online reference for this, but since they rebuild their engines frequently, this works.
LSPI has recently been attributed to oil additives; specifically high calcium and sodium. The method isn't well understood, but the right oil makes all the difference apparently. See the latest DEXOS 1 Gen 2 oil analysis. TLDR is basically Calcium + Sodium = bad, Molybdenum and Zinc (ZDDP) = good, more alcohol in the fuel (and/or cooler distillation curve) are good.
Thank you for explaining this. I would never have imagined that motor oil could be a potential source. Now I understand more about the SN Plus designation. Previously, I always thought the electrode of the spark plug, being long and thin, would not have been able to get rid of heat fast enough and would be the likely source of pre-ignition knock in higher compression engines.
Now that I think more about the compounds in the oil, it seems the calcium is a catalyst for lower temperature ignition compared to the other metals mentioned such as magnesium?
I wonder if super knock is why the Oldsmobile Jetfire used fluid injection? Would make sense. The methanol further increases octane level alongside the tetraethyl lead that was in gas at the time, and then the corrosion inhibitor did what it says on the tin, the distilled water cools the turbo and dilutes the methanol.
Can you please explain why LSPI is most likely to occur at low RPM and high engine loads? I guess at HIGH RPM and high engine loads you also have high pressure and high temperatures?
I think part of the reason pressures are much higher is this: the combustion happens too early and the air-fuel mixture heats up, increasing pressure in the cylinder, which is still compressing. Because of this the cylinder must put much more work into compressing it, raising the temperature, and because of this also pressure, much more than would happen if the ignition was timed correctly. That can destroy an engine in short order.
Hiii what do you think of 2 or 3 spark plugs per cylinder. Does it reduce the probability of super knock _ (DSTI Engine in Bajajs motorcycles engines )
Super knock occurs before any spark, so you can have a dozen plugs in there and it wouldn't make any difference. Watch the video all the way through. Jason discusses this.
@@SoulTouchMusic93 No he doesn't sleep. He owns and operates a chain of three stores in my area with a skeleton staff and does all his own stock pick up and deliver. The man runs on a mixture of coffee and cheeseburgers.
You didn't mention the new standard coming out from the API. ILSAC GF-6. It will be the new standard for oils that includes testing for LSPI. SN Plus was just a temporary band-aid because it was taking too long for everyone to agree to the new standard. It looks like the standard has been agreed upon and oil manufacturers can start getting certified for ILSAC GF-6 starting early 2020. SN Plus will stick around as a supplemental certification though. Also ILSAC GF-6 includes two standards. GF-6A which is what will be backwards compatible with previous gen and GF-6B which is ONLY for the new implementation of oil type 0W-16 (yup an even thinner oil that the Japanese have been using in Japan for a while now) for fuel efficiency.
This reminds me of why you don't try to attempt to suddenly close a valve on a long pipeline trying to suddenly arrest the momentum of a fluid with a lot of energy behind it doesn't end well. Very easy to create a pressure spike that exceeds the failure strength of the material attempting to contain it this way and well RIP part if you do this.
Is a solution to destructive knock a gateway to treating gasoline like diesel for combustion? Could even a small amount of diesel mixed in gasoline create the same effect?
hey got a question for you i got 1990 blazer 5.7 tbi had engine rebuild about month ago got a few up grades bigger cam so i had to get my computer chip tune to raise fuel and timing on the chip i change pressure regulator and adjust that the cam i have in there is xe 262 h comp cam the block was 30 over.and i still have the factory swirl port heads i should had put some vortec heads on there...but for some reason cant get it to run right just dont have no power and im getting a ping sound from engine and #6 had oil on spark plug threads only the rest of plugs are fine i dont no where im getting the ping sound dont no if the oil on the spark plug have anything to do with it or something with the fuel and timing is not right..
my car runs low rpm so as soon as you need to accelerate a bit it starts to shake slightly, obviously designed to work in the high load/low rpm region for better economy. But I drive it in sport mode and it bumps a bit the rpm and runs perfectly smooth.
But real question, I have a twin turbo v12 2004 but lately my intake temps been high since I have recalibrate my intercooler system my car been throwing codes of random misfire, how bad is that.
Hi Jason, hopefully you scrolled far enough to see my question: Would adding a catch tank/can to the engine potentially reduce engine knock or super knock, due to the fact that it removes part of the oil/fuel mixture that can make its way into the cylinder? Thanks -Adam
This video made me think about Smokey Yunick and his patented flame ignition. Is enough known about how it works mechanically that a video could be made of it?
So how does the incresed likelihood of knock and superknock affect engine longevity in modern vehicles. Also on an unrelated note a video discussing the engine oil acidity and its effects over time and what oil companies do to help resist this would be nice.
It maybe due to different languages (I'm from Germany), but to me "knock" was always referred to as happening during compression before top dead center. Didn't know there was a difference in knocks that one happens during power cycle.
A combination of intake manifold injection with a mixture that is too lean to ignite itself and additional direct injection just before the ignition solves this problem, also the engine is more efficient in partial load.
Good to know about API SN Plus. My parents just bought an Edge with a 2.0T so I'll make sure to recommend it to them. But I guess my Mustang's Coyote engine isn't considered "modern" since it's big, NA, and based on my current tank's MPG of 12, not efficient
There is a lot of truth to the oil being a culprit for knocking. While my experience relates to the light knocking/pinging, I can see how it could develop into a super knock with a forced induction engine. I used Amsoil (which at the time didn't meet SN+ standards) and my normally aspirated car would ping all the time under light load. Switching to Mobil 1 which was SN+ certified, the pinging went away.
(5spd driver) sometimes when i am going downhill or using engine braking, and after a few seconds when i press the gas to start accelerating there is a lurch. Is this LSPI? This occurs if engine brakign was holding around 2.5k RPM. Yes, this is a GDI engine
I always thought the V6 ecoboost had worse gas milage when towing than N.A. engines was because they injected more fuel to cool the turbos under load. Maybe its a case of sending much more fuel to prevent super knock. Mixture is too rich to allow super knock.
Cool! Jason, do you have a link by any chance, that talks about the Ca-related LSPI in oils that you mentioned? Would be huge help. Or was it "personal communication"? Thanks!
As a pro ECU tuner, I see this problem all the time in the newer LT Chevy engines with DI. Especially with aftermarket superchargers. Gotta be very careful tuning these new engines. Great video!
Ouch, one of the engines I hoped it wouldn't happen to
do you rempap these engines or do you use tuning chips ?
@@karimnasser6710 Tuning chips? Is it 1990?
@@OtisFlint it's 1999dec31
Rhett Castillo have any of your customers considered a water/methanol system to reduce chances of this problem from what I've read it seems to work well for forced induction.
it's not a problem, it's a feature - free crank inspection windows for everyone!
This made my day lol
knock knock.......who there?? rod bearing 1 2 3 4.....
Rod bearing 1 2 3 & 4 who?
@@jGRite who who you got a blown engine....
@@jGRite Rod Bearing moving out from your block.
Hyundai.....lol
Thank you. i had a bad day, and now it's good again.
Dude, I'm from Brazil and really like seeing your videos, not only for the great explanations themselves, but to get familiarized with mechanical terms in English.
The content presented is always rich, yet in a simple and clear didactics!
Grande erro, porque eu mesmo já num sei os termos mecânicos em português
@@pedrodossantos5890 E o que tem de errado em alguém que já conhece os termos em português, como no meu caso, querer aprendê-los em inglês?
Cada comentário...
O canal dele é excelente. O bom é que o inglês dele é bem tranquilo de entender. Alguns canais europeus, com inglês britânico, são bem mais difíceis de entender.
@@ianferreiraian Sim, a pronúncia dele é clara, não é aquela tipo "cachorro roendo osso", emendando palavras.
E a didática também é muito simples!
raindrop, rod knock, there's a hole in your engine block.
Knockin on your pistons go pop pop *BANG*
My superknock is bad and boujee, eating up pistons like smoothie
Valvedrop, rodknock would be better lol
Mazda speed 3 people call this “zoom zoom boom”
@Ungregistered User aren't flat tappet cams/valves used in pretty much every car engine unless u go with a roller setup which is for higher performance?
Never go full throttle at low revs in an MPS. My tune alleviates most of this by pushing the torque curve towards 4000 to 6000rpm to avoid bending rods
So do the ecoboost crowd now too.
Facts ive blown 2 motors already
It'd be cool if Project Farm can induce super knock with his see through head engine and slomo guys capture it using high speed camera.
It would need to be a gasoline direct injection engine
Ungregistered User wrong, older engines with larger compression ratios are way more likely to knock
@Ungregistered User Nope, it doesn't apply to modern engines, it applies to all. It's just that modern engines usually run hotter. And they usually have direct injection which causes deposits.
Btw, *here is how to cause preignition and the super duper knock:* (1) Machine your engine parts with a dull endmill, machine as roughly as possible and DON'T deburr.
(2) Cause as much carbon deposits as you can; to do that mix oil into your fuel and reduce the pressure of your injection system or use work out injectors to get a crapy fuel mist.
(3) Hook up an EGT gauge and tune your engine to run hot.
After that your engine should go boom. (unless you blow your headgasket first, XD)
Burrs and carbon deposits kinda work like a glow plug: they do get warm by the combustion but they don't get cooled by the cylinder walls. Just think about it: a burr sticking to the side of a block of metal has a relatively high surface area that's contacting with the air around it, but it's connected to the rest of block of metal by a small surface area. Carbon deposits that get on the valves can have the same effect. But with carbon deposits it depends on how porous they are, how smooth they are, etc; not all carbon deposits are equal.
The smooth carbon deposits that almost seem to be brushed on won't cause knock as quickly as the rough ones.
If anybody can do it, he can! Love that guy.
I don’t always have knock, but when I do... I prefer *SUPERKNOCK*
@bbkangs lmao 😂😂
I'm dead 😂
Omg Im drying.
Predetonation = a condition where the engine is trying to compress an explosion.
Good luck with that.
Reminds me of hydrostatic shock.
@@huntergman8338 Reminds me of water hammer also ie the problem that occurs when you try to close a valve on a rapidly flowing pipeline full of fluid in effect trying to arrest it's momentum too suddenly. This can similarly result in failure of the valve and/or the pipeline especially if you try this on a long distance pipeline where you can have literally tons of water in motion suddenly being forced to stop violently the pressure spikes can reach levels that are in the realms of an actual explosive device going off right next to the valve.
@@seraphina985 Ether way, something will break and it will be expensive.
@@huntergman8338 Indeed, exceeding the rated pressure limits of a vessel is a bad idea however it happens. There is a reason why such limits exist after all once you pass them you are eating through your margin of safety and probably permanently reducing that margin through added metal fatigue too even if you remain short of causing outright catastrophic failure.
@@seraphina985 Like a fat man at a buffet. That belt gets weaker with every bite.
Engine: “This form is Light Knock!”
(Spools up)
“But this is to go..even further...beyond”.....
*Super Knock*
Que 5 straight episodes of screaming.
nick procive revving*
Look Vegeta it's a pokemon
Really informative video about a serious topic. Thanks for that 👍
Its funny that people dont like light knock when that is basically what mazda's sky active engine is designed to do. Spark Controlled Compression Ignition is just using the spark to start ignition and then the increase in pressure causes compression ignition every where else. the only difference I can see between the two is that light engine knock is not consistent and happens in only one location and then propogates instead of being a controlled universal compression ignition. Such a small change can take it from being engine knock, to a super advanced engine technology that you WANT.
You know that the skyactive X is capable of both compression ignition (like diesels do) and spark ignition as it has spark plugs too. I wonder how reliable and long lasting they will be.
The SPCCI engines are built to handle the high pressure and temperature that comes with this kind of operation. Kind of like a diesel.
How about using a higher octane gasoline??? How about to get the coldest air through the intake that you possibly can set up for??, How about, because it is a turbo engine and direct injection, will assume, by delaying closing the exhaust valve during the intake stroke and also delaying the fuel injection you can evacuate the burned gasses with forced fresh air and lower your chamber temperature???. How about upgrading your intercooler to a better quality that can give you more cooling and a correct amount of flow by the engine set up????.. remember that the manufacturers go the cheapest they can get. I am a great fan, really like your channel but those are questions that I will like to be answered. Keep up the good work. Thanks for being educating us.
Yeah, i was also wondering about running higher octane gasoline.
With direct injection motors, replacing the cams solves most of the problems
@Ungregistered User its actually P*C*V it stands for pollution control valve. Its emissions equipment that recycles oil vapor instead of letting it make a mess under the hood or making oil slicks on the streets.
Its important but its advised to install a oil catch can between it and the intake system to prevent octane dilution.
@Ungregistered User It stands for Positive Crankcase Ventilation. With old cars they just let the crankcase vent with a tube or basically an open hole. That allowed all the gasses and some oil to escape which made a mess and was bad for the environment. So, modern cars put the crankcase gasses and everything back into the intake. That way everything gets burned and emissions are better. It also means the vacuum of the intake helps pull everything out of the crankcase so it's more efficient.
Gamma Light I think you are getting confused with the EGR valve (exhaust gas recirculation) which can have a similar effect in the engine regarding knock and superknock because of hot and uncombusted gases entering into the combustion chamber. PCVs are used to avoid high pressure concentrations in the crankcase which will lead to blowing gaskets and as you said cause oil dilution, but also make sure the unburnt toxic gasses passing through the piston rings (blow-by) aren't freed to the atmosphere.
I miss the 70s engines that would run on after the ignition was switched off.
My 71 vw bug with a 2165cc dual 44mm carb would turn if a couple times if hot
@Addicus Taylor Detonation because of the new emission devices on cars. Also timing was advanced.
@Billy Bhanchode Carbon build up.
Please make a video on suspension Rebound, Compression and Preload.
@@E.Asinus hahaha, it took me a while to understand.
So if your car is tuned for a higher octane, let’s say 91-93 and you run 87 to be cheap, that would cause light knock or potentially both? Awesome video!
Great topic this week! Valuable information as always! Thanks for making such detailed videos!
I honestly never seen any report of early engine breakdowns due to "super knock".
LSPI is also not the problem of the modern engines like it was mentioned.
this type of abnormal combustion is not new, and it can also occure in NA engines with high compression ratios. it is a preignition caused by a hot surface accompanied with knock. cause of knock: a very advanced spark timing(usually spark timing should not be that advanced at low rpm)
if you read the reference given below, there are at least 6 types of abnormal combustions, knock can be directly regulated using spark retardation, but for preignition u need to cool the engine temperature down.
john B heywood - internal combustion engine fundamentals
chapter 9- part 6: Abnormal combustion
Hi octane fuel can help as well. Less likely to pre ignite.
Old comment but E85 solves a lot of issues
Knock = secondary ignition event after the spark plug fires Pre Ignition = uncontrolled ignition event pre spark plug.
Fin
@Ungregistered User no, knock is a secondary ignition point somewhere else in the cylinder that results from the pressure increase after the spark plug fires. You end up with completing flame fronts that accelerate the burn and increase cylinder pressure at an undesirable rate. Pre Ignition is an ignition event prior to the spark plug firing.
That is what I said, A secondary ignition event after the the spark plug or "Primary ignition" event occurs.
I have an engine susceptible to LSPI. It's a 2016 Vauxhall Astra 1.4 turbo (140ps) - same engine as some Chevy Cruze models.
My solutions so far :
1. Use 98 octane fuel (widely available in the UK)
2. Never drive uphill in 4th/5th/6th gear with high throttle load at
I switched to a very expensive motor oil about 6 years ago and it keeps LSPI from happening or does a great job of keeping it at a very low percentage of happening with the low octane fuel by keeping the pistons from over heating ....
Lesson - don't go below 3.5k RPM 😂.
Misterlikeseverythin. Lesson. Flog the crap out of it! 👍
Quite clear explanation and short accurate video!! You've got one more subscriber. I really appreciate that you take your time and draw on the board like that, that makes the videos even more understandable.
Knock and pre-ignition are two totally different things. "Super knock" is pre-ignition and has been an issue with engines for years. Knock is the noise of two flame fronts hitting each other.
I think Engineering Explained should start a petition for the Department of Energy and the Department of Weights and Measures for the United States to raise pump gas octane levels to 95 octane.
He'd know exactly what to say and I'm positive we'd all back it up
Most cars have no need for increased octane. The burden falls on the manufacturers for pushing the limits of what their engines can do. It has already become extreme.
@@flagmichael as emission requirements increase so does the need for higher octane. Hotter IAT, EGR and excess PCV use dramatically reduce octane levels.
Every car I've worked on would see huge benefits from an increase of octane when fully loaded with passengers or when driven in a manner above economy purposes.
But hey, if everyone's happy driving with extremely retarded ignition timing then let's not change a thing.
I honestly can't think of one car that wouldn't benefit from higher octane, please enlighten me
LSPI is probably what caused my 2016 Subaru Forester XT to develop a hole in the engine block around 45,000 miles. Subaru covered a new block, then new heads. I had a brand new 50th Anniversary NA Forester for over 12 weeks. As soon as I got the car back, I sold it to Carmax. I now drive a 2019 RAM 1500 Limited. No more worrying about LSPI. And I can pull my Jeep on a trailer.
Excellent explanation and I'll give a different motor oil a try.
So even engines have a "normal" size, going much below it brings unwanted consequences.
Just like making cars too small has detrimental effect on a lot of things (usability, stability, safety etc)
It's not quite "the size" of the engine that increases risk of this; it's the cylinder pressure when/as the piston reaches the top of the compression stroke.....it's just that smaller engines typically have higher compression ratios or use forced induction.
So this is just as possible in an older but freshly rebuilt engine right?
Wow, mega top quality content as always.
Can we have a video on Mitsubishi Super Select 4WD? It's kinda unique
Best channel on youtube handsdown
Thank God another EE video I really needed to learn something today
Does using a fuel more resistent to knock, like E85 or E100, help?
Yes.
You answered your own question in the question.
Holly molly, this kind of video is fascinating, i love when you cover this kind of topics
hi jayson. may i ask the pros and cons of deleting an egr system in diesel engine, theres plenty of vids out there but your explanations is the only one i trust. thank you
Super interesting video! We covered some of this (or something similar) in our Internal Combustion Engines class (the name wasn't Super Knock though 😂) but there was still stuff to be learned, very interesting to see oil manufacturers testing for LSPI. We didn't cover that, or at least I can't recall it right now. To the people reading the comments, this isn't some super dumbed down content by the way, in uni we cover this in a similar way. Amazing to see this type of content on TH-cam!
I had a rod knock. No smoke, good acceleration. Turns out bearings are fine. Piece of piston in the sump. 0.7L turbo charged 80kW engine.
Now my second engine is developing the same symptoms - knock originating from wall of middle cylinder (3cyl engine)...
Brb, gotta check my laundry detergent. Don’t want LSPI in my washer machine.
As per one of your previous videos, especially for those of us with MT, Don't Lug the Engine! Based on my experience in my wife's new traditional 8 sp AT vehicle in normal or eco mode it's always trying to upshift asap (gas savings) at the expense of higher load at lower RPMs. We live in a mountainous area and the AT obviously can't predict the numerous approaching inclines and is often "confused". Though she typically isn't using it for "speed", we've noticed that setting it to sport mode has worked the best for us in our normal daily driving (less lugging and fewer shifts). Thanks for your informative videos.
Hello, nice video, thx. I have few questions/notes.
1. Why this occurs in low speed/revs and NOT in high ones?? What is actually meaning of "low"? 1500-1800 rpm? This is something that no one technically describes - pitty.
2. The chart in top-right corner is not correct/accurate - why should superknock pressure be that higher than light knock/normal combustion situation. I would say, that the main problem is timing and pressure increase speed, not the overall pressure.
3. Why the oil that has much higher ignition temperature than petrol is causing this??
4. Why direct petrol injection is worse than indirect one?
5. Is superknocking detectable? "Normal" knocking is and when it is detected engine control system can deal with it. Why is that knocking worse?
7:10 taking away power from the user willy-nilly is a bad solution because it can be fatal. If I'm in the middle of an overtaking maneuver or need just a bit more power to move away from something and the engine decides that right now I should not get the power I am used to - that is deadly. They allow manufacturers to do that? What a world we live in ... Safety should be a much higher concern than efficiency.
@Engineering Explained
If oil in the cylinder is bad for knock then shouldn't rotaries and two stroke piston motors have uncontrolled knock or super knock? Do they?
The main problem is everyone drives away from stops under full throttle. Everyone thinks they are at the track.
If everyone did that then we would have a lot less traffic.
It doesnt happen in low gears.
"Low speed" is referring to the engine speed, not road speed. LSPI generally happens at 30+mph.
As someone who is a lab tech for a major oil company and spent 5 years doing nothing but octane(knock) testing I’ve never heard this term.
This is also why everyone needs to be running E85 and we need motor oil companies to make oil handle E85 better
Any good synthetic will hold up to E85 just fine. Running 5K mile intervals i can't tell any difference in my oil analysis running pump or E85.
@@OtisFlint just fine, yes. But few handle it perfectly. Mix E85 into a sample of oil and observe it's ability to polarize the fuel. In my findings I'd seen more bad results then good.
@@gammalight1312 Even Amsoil, the king of extended drain intervals recommends factory specified intervals when running E85.
Another factor that doesn't get enough attention is differing fuel quality between markets in North America. ACN (Arizona, California, Nevada) 91 octane fuels are far more knock prone than 91 octane fuels in other states. Same problem in Western Canada where 91/94 behave poorly compared to similar 91/94 in the East. This probably comes down to refinery feedstock, heavy grade oil probably nets a poorer quality gasoline. Our AKI system is prone to refiners juicing RON numbers and leaving MON lower than similar fuels in Europe. AKI is RON+MON/2. Anyone running off the shelf tunes for cars need to ensure the fuel they have in their market is appropriate, not all 91/93s are created equal.
Is there something to be said for the lack of humidity as to why the change seems more measurable between the regions?
@@pmdinaz I think it's mostly regulations, with crude quality being another potential component.
Piss poor quality of 91 + octane makes me dont want to tune my car.
Cool vid😁👍 Didn't know about superknock until i read about the sn plus api-spec.
I'm certain GM's 2.0T LTG engine suffers from this condition. Several 2014+ Buick Regal, 2013+ Cadillac ATS, etc owners have reported failures (cracks) at the top of the pistons, exactly where this condition would cause a fatal issue. It seems to happen regardless of driving style or whether the engine is tuned/modded, and at varying times from 500 miles to 50,000 miles.
Hi,
Your graph shows super knock happening AFTER spark, but earlier you explained it as occurring before spark (pre-ignition), on the compression stroke.
Exactly. Wanted to point it out, but you were quicker :)
Look at the
Look at the pressure rise before the spark timing line
This is why small turbo engines seem gutless at the low end. It's also why you then wind them up a few more rpm, get them into boost and they drink.
There are after market solutions to this but the manufacture is not going to introduce them because it is a high maintenance solution most owners would not want to deal with. Water/methanol injection seems to work really well at cooling intake temps and actually raising the equivalent of the octane of the fuel your burning especially in forced induction and high compression engines.Another benefit for DI engines is it cleans the intake valves.
There are a lot of racers in the Porsche world who use outboard 2 stroke oil in their sumps because supposedly the octane rating is nearly the same as 87 octane gasoline. I do not have an online reference for this, but since they rebuild their engines frequently, this works.
LSPI has recently been attributed to oil additives; specifically high calcium and sodium. The method isn't well understood, but the right oil makes all the difference apparently. See the latest DEXOS 1 Gen 2 oil analysis. TLDR is basically Calcium + Sodium = bad, Molybdenum and Zinc (ZDDP) = good, more alcohol in the fuel (and/or cooler distillation curve) are good.
Is there information on WHICH small turbocharged engines have this problem the most?
I would stay away from VW 3 cylinders and anything lower than 1.2L.
I've seen Peugeot 1.2 turbo and Opel 1.0 turbo engines having that problem
So the flammable metal decreases the early flames? Neat!
Thank you for explaining this. I would never have imagined that motor oil could be a potential source. Now I understand more about the SN Plus designation. Previously, I always thought the electrode of the spark plug, being long and thin, would not have been able to get rid of heat fast enough and would be the likely source of pre-ignition knock in higher compression engines.
Now that I think more about the compounds in the oil, it seems the calcium is a catalyst for lower temperature ignition compared to the other metals mentioned such as magnesium?
yup, all the ecoboost Ford fiesta ST's are blowing up over here.
That's just Ford for you
Mikey The new GM LTs are doing it too...
Ecoboost would be better named Ecoboom. They are god awful engines.
I have one and I have not heard anything about this.
Yet.
Great explanation as usual 💯
Good video as always!
API SN-Plus. The widely accepted assumption for the cause is oil intrusion.
a simple catcan can keep so much oil from entering via intake, it still blows my mind they aren't factory.
I wonder if super knock is why the Oldsmobile Jetfire used fluid injection? Would make sense. The methanol further increases octane level alongside the tetraethyl lead that was in gas at the time, and then the corrosion inhibitor did what it says on the tin, the distilled water cools the turbo and dilutes the methanol.
Thanks for the class!
Thanks for a great informative video!
Oh wow this makes a lot more sense! Thank you!!
Can you please explain why LSPI is most likely to occur at low RPM and high engine loads? I guess at HIGH RPM and high engine loads you also have high pressure and high temperatures?
I believe redlining once a day would keep this problem away 😂
Could help reduce carbon buildup in the cylinder... so really your not wrong... but I dont think the cop will buy it!
I think part of the reason pressures are much higher is this: the combustion happens too early and the air-fuel mixture heats up, increasing pressure in the cylinder, which is still compressing. Because of this the cylinder must put much more work into compressing it, raising the temperature, and because of this also pressure, much more than would happen if the ignition was timed correctly. That can destroy an engine in short order.
Hiii what do you think of 2 or 3 spark plugs per cylinder. Does it reduce the probability of super knock _ (DSTI Engine in Bajajs motorcycles engines )
Super knock occurs before any spark, so you can have a dozen plugs in there and it wouldn't make any difference. Watch the video all the way through. Jason discusses this.
Love your videos as usual..very informative...keep sharing x
have you ever considered dissolved and entrained air in the fuel itself and the resultant problems it creates?
Super knock make EcoBoost go ECOBOOM! That being said a friend of mine just turned over 500000kms on a 3.5L EcoBoost.
How? Does he even sleeps?
@@SoulTouchMusic93 No he doesn't sleep. He owns and operates a chain of three stores in my area with a skeleton staff and does all his own stock pick up and deliver. The man runs on a mixture of coffee and cheeseburgers.
@@huntsbychainsaw5986 damn. I hope he's healthy.
@@SoulTouchMusic93 Healthy ish... lol! He doing well.
You didn't mention the new standard coming out from the API. ILSAC GF-6. It will be the new standard for oils that includes testing for LSPI. SN Plus was just a temporary band-aid because it was taking too long for everyone to agree to the new standard. It looks like the standard has been agreed upon and oil manufacturers can start getting certified for ILSAC GF-6 starting early 2020. SN Plus will stick around as a supplemental certification though. Also ILSAC GF-6 includes two standards. GF-6A which is what will be backwards compatible with previous gen and GF-6B which is ONLY for the new implementation of oil type 0W-16 (yup an even thinner oil that the Japanese have been using in Japan for a while now) for fuel efficiency.
This reminds me of why you don't try to attempt to suddenly close a valve on a long pipeline trying to suddenly arrest the momentum of a fluid with a lot of energy behind it doesn't end well. Very easy to create a pressure spike that exceeds the failure strength of the material attempting to contain it this way and well RIP part if you do this.
Is a solution to destructive knock a gateway to treating gasoline like diesel for combustion? Could even a small amount of diesel mixed in gasoline create the same effect?
hey got a question for you i got 1990 blazer 5.7 tbi had engine rebuild about month ago got a few up grades bigger cam so i had to get my computer chip tune to raise fuel and timing on the chip i change pressure regulator and adjust that the cam i have in there is xe 262 h comp cam the block was 30 over.and i still have the factory swirl port heads i should had put some vortec heads on there...but for some reason cant get it to run right just dont have no power and im getting a ping sound from engine and #6 had oil on spark plug threads only the rest of plugs are fine i dont no where im getting the ping sound dont no if the oil on the spark plug have anything to do with it or something with the fuel and timing is not right..
my car runs low rpm so as soon as you need to accelerate a bit it starts to shake slightly, obviously designed to work in the high load/low rpm region for better economy. But I drive it in sport mode and it bumps a bit the rpm and runs perfectly smooth.
But real question, I have a twin turbo v12 2004 but lately my intake temps been high since I have recalibrate my intercooler system my car been throwing codes of random misfire, how bad is that.
very
Sweet bruh. Thanks for the very informative video.
Hi Jason, hopefully you scrolled far enough to see my question: Would adding a catch tank/can to the engine potentially reduce engine knock or super knock, due to the fact that it removes part of the oil/fuel mixture that can make its way into the cylinder? Thanks -Adam
Great Video champ
does using 87 or 91 or 93 octone make a difference in lspi issue ?
This video made me think about Smokey Yunick and his patented flame ignition. Is enough known about how it works mechanically that a video could be made of it?
So how does the incresed likelihood of knock and superknock affect engine longevity in modern vehicles. Also on an unrelated note a video discussing the engine oil acidity and its effects over time and what oil companies do to help resist this would be nice.
It maybe due to different languages (I'm from Germany), but to me "knock" was always referred to as happening during compression before top dead center. Didn't know there was a difference in knocks that one happens during power cycle.
A combination of intake manifold injection with a mixture that is too lean to ignite itself and additional direct injection just before the ignition solves this problem, also the engine is more efficient in partial load.
Good to know about API SN Plus. My parents just bought an Edge with a 2.0T so I'll make sure to recommend it to them. But I guess my Mustang's Coyote engine isn't considered "modern" since it's big, NA, and based on my current tank's MPG of 12, not efficient
would magnesium also fill in wear spots?
Hi Sir, is it okay to change the gears manually with the gas pedal pressed in an automated manual transmission car? Please advice
Can lspi happen at 4K rpms? My focus st is doing this intermittently, it sounds violent when downshifting to overtake.
There is a lot of truth to the oil being a culprit for knocking. While my experience relates to the light knocking/pinging, I can see how it could develop into a super knock with a forced induction engine. I used Amsoil (which at the time didn't meet SN+ standards) and my normally aspirated car would ping all the time under light load. Switching to Mobil 1 which was SN+ certified, the pinging went away.
Can we get a video about colder spark plugs to follow this video
Awesome videos! Could you please do a one explaining the mechanics behind head gaskets?
(5spd driver) sometimes when i am going downhill or using engine braking, and after a few seconds when i press the gas to start accelerating there is a lurch. Is this LSPI? This occurs if engine brakign was holding around 2.5k RPM. Yes, this is a GDI engine
Would it be wise to run a new style of engine on super unleaded only?
I always thought the V6 ecoboost had worse gas milage when towing than N.A. engines was because they injected more fuel to cool the turbos under load. Maybe its a case of sending much more fuel to prevent super knock. Mixture is too rich to allow super knock.
Cool! Jason, do you have a link by any chance, that talks about the Ca-related LSPI in oils that you mentioned? Would be huge help. Or was it "personal communication"? Thanks!
Would the new api rating be a must on high compression performance engines?