Car Tech 101: Variable valve timing explained
ฝัง
- เผยแพร่เมื่อ 27 เม.ย. 2014
- Few innovations under the hood have become as ubiquitous as variable valve timing. Automakers brag about it all the time, but seldom explain it. So Brian Cooley's here to do just that.
Never miss a deal again! See CNET’s browser extension 👉 bit.ly/3lO7sOU
Subscribe to CNET: / cnettv - บันเทิง
![ความรักของยักษ์เขียว (ทศกัณฐ์) - เดี่ยว ไออุ่น [OFFICIAL MUSICVIDEO 4K]](http://i.ytimg.com/vi/yCCy-QVHqK8/mqdefault.jpg)
0:36 four valves per cylinder common these days (more area to let the engine breathe in and out)
0:40 problem: a strictly mechanical system operates the same at all RPMs and all engine loads; that is not ideal for mpg, horsepower or emissions ; you want to vary behavior at different points of the engine's rev range ; that's why we have variable valve timing
3:40 solution: variable valve timing dramatically improves how engines raise MPG, increases horsepower, and lowers emissions ; one of the great revolutions in car engineering
1:00 changes three parameters (varies three valve events):
valve timing - at what point in the engine's rotation do the valves open and close
valve duration - how long the valve stays open,
valve lift - how far a valve moves off its seat when the valve opens
1:30 if you leave exhaust valve open longer on one stroke, you blow all the exhaust out, leaving a fully open and clean cylinder to take in the maximum gas and air on the next gulp, giving maximum power
1:44 if you close the exhaust valve a little sooner on one stroke, you leave some exhaust in the cylinder and therefore you take in less air and fuel the next time ; that kind of creates a virtually smaller engine for a moment, and that could give you better MPG
1:58 mechanisms that allow valves to change their behavior 3:28 every carmaker has their own brand of variable valve timing (is this bc patent law makes it too expensive to use a few best practices, or are there good reasons for such variation?) e.g.
2:06 multiple sets of lobes on the camshaft; different lobes of different shapes are used at different points in the engine's operation -- how are the lobes switched?
2:16 change the relationship between the rotation of the crank and the rotation of the camshaft so they're not always locked 1:1
2:25 eccentric cam drives: the engines turning at a certain RPM but eccentric drives on the ends of the cams allow them to accelerate and decelerate their rotation; that gives you a degree of control
2:40 invention - Fiat is credited with first mainstream production-ready system dating to 1969; known today as multiair, seen in the new Jeep Cherokee, now owned by Fiat
2:57 their version of changing valve events using hydraulic pressure out of the oil system (?)
3:05 the most famous form of valve timing is Honda's VTEC
THANKYOUU
This guy does an excellent job of explaining VVT in this video.
yea its called knowing your shit & being able to teach it RIGHT .... unlike most that KNOW their shit but can't teach for shit ...
Like when i 1st got hired on to the company i work for today, i rode with a tech that really knew his job well, but could not teach me for shit and when i asked questions he would just get pissed off ...
After riding with a 2nd tech that was not as good as the 1st, he was able to teach me very well and i learned more from the junior tech in 1 day than i didn't learn in one week with the senior tech ..
Except that the engine in the video can't vary lift, or duration, it can only vary timing. Only a few VVT systems can vary lift and duration (VTEC is the most well known), most only vary timing.
anybody knows the background song at the beginning ?
@@PistonAvatarGuy doesn't new Ford 5.0 Coyotes have VVT and VCT (variable valve timing and variable camshaft timing) which basically allows controlling lift, timing, and duration? And a few other engines, not just Honda. I'm pretty sure 99% of cars in America today have the equivalent of VTEC plus cylinder deactivation and all kinds of dynamic engine systems.
@@beezyj3227 No, VVT (variable valve timing) and VCT (variable cam timing) are usually used as two different names for the same thing, both of which only vary cam timing. VVT sometimes meant variable valve train, so that it could also describe systems like VTEC, but no one seems to use it that way anymore. The vast majority of engines manufactured today only have VVT, with no ability to vary lift or duration. Even Honda is slowly eliminating VTEC from their engine lineup, as turbochargers eliminate the shortcomings which VTEC had been designed to address.
-
Other than Honda's VTEC system (and those like it) cylinder deactivation technologies don't provide any means to vary the cam profile, they're either operating the valves, or not operating the valves.
This is exactly what I was looking for. No complex explanations or assumptions of what I know and what I don't - just very simple, conceptual and visual explanation. Thank you!
I like when someone explains it. especially as good as the man in the video
basically, at higher RPMs, there is some overlap between the time the intake valve opens and the time the exhaust valve opens. This leads to a slight loss of power at high speeds, because the engine should be compressing when it loses some intake air during the overlap with the exhaust cycle. So VVT switches the camshaft lobes with ones with a narrower slope angle, so that it changes the amount of time the valves are open (reduces the time). Then when the speed drops again, the actuator slides the camshaft back so that the other, larger lobe can take over at the lower speeds.
Nobody is better qualified to explain this topic than the designers of the 5th. generation Honda Civic powertrain.
And that's why it's extremely important to keep your oil clean.
damn. don't normally expect to learn that much from cnet. but having this explanation & visual made concepts i've heard about for years make complete sense. thanks!
anybody knows the background song at the beginning ?
Mr. Cooley, I have watched many of your videos, and I would have to say that you are one of the best individuals at explaining complicated technology in simple terms. Thank you!
This is hands down the best explanation ive seen yet. thank you. Ive seen fancy ass 3D videos with excellent graphics and presentation. but i was still left with about as much knowledge as i had before hand
Really enjoy how Brian explains things. Porsche was one of the first to take this to all of its engines with Variocam back in 1992 with the 968. And it works great.
One of the best mechanical explanations ive ever seen. Bravo Bravo...well done
Damn that was informative as hell! Thank you
Very clear explanation. Straight to the point no BS! Appreciated
Wow! You really explain things well. Crystal clear! Thanks.
Very informative. These car tech 101 videos are great!
This was exactly the level of detail I was looking for. Thank you!
My complements to you Brian..... you are a good and clear presenter..... that was great!
Thank you that was very informative. Didn't take long to explain and I totally understood.
Short, coincise and informative! Great video
This gentleman is very enthusiastic about explaining the idea! Thanks mister! I've learned something new!
Fantastic presentation. I own a 95 Lexus LS400 and noticed that a few years later they started adding these to their engines which apparently made the vehicle go up 30 HP. After hearing the term i had to look up what it is and how it works
I can not express how thankful I am for this video. When I got my 1GR FE no one could explain how it worked. The only detailed videos were in Russian so I was completely lost but wanting to understand.
@John Ross fj cruiser
@John Ross 270k in on my 2011. Some of the oil seals aren't too healthy but it's done alot of mud
@John Ross they probably weren't ran as hard. Entire body is covered in body damage. Redlined the coolant gauge (268° Incase you're curious what the red indicates) after a deer impact put a hole in the radiator. But she still stars and drives fine.
Marvellous explanation....great teacher of mechanics and tech
Quality! Well done! Bravo! Succinctly informative and comedic too. Brilliant. Simply brilliant! Today I learned what in hell v-tech is.
excellent presentation
10/10 for that meme in the end
These videos are really helpful - thanks!
That was extremely helpful I don't even know that word I want to use thank you very informative
excellent presentation , even better voice command control .. Well done!
Who is here because of your love for vtec?? 😂
Very interesting ! .. Thank you Brian !
I really appreciated this. :) Thank you.
I wasn't expecting this guy to do such a good job. Even if he was reading from a script, his delivery had me convinced that he's an expert.
Nice Explanation of Great Technology. 👍
Great video, very informative!
Thanks, that was informative.
Loved this video.. should be more of these.
Just by the name i knew what vvt was but i wanted to look up exactly how they change the timing bc im just weird like that. And this guy did a great job explaing it. Wanna see one of the engines with multiple lobes thay shift over work.
Great explanation! Thanks.
2019 and I am just getting a clue... nicely done. BUT ... I am still building an 331 stroker for my 65 Mustang though. Modular is just too complex for this old dude to tinker with and maintain. Plus - You can't beat the nostalgia of an old school exhaust sound!
Great video!! Non technical/mechanical so it's easy to understand. Thanks SO much!
Great video explaining VTC but you misleading called the high and low cam part of the VTC system. The high and low cam where it had three lobes was Variable Valve Lift. VVL has two cam profiles that allow the valve to switch from high to low lift came phasing. Low lift keeps the valves open less to allow for a tumble effect with the air and opens up to allow more flow. VTC helps make the VVL transition smooth and efficient along with everything else mentioned in the video.
Perfect way of explaining ..
Nice explanation. Very clear. 👌
Thank you for this informative video
Thanks for teaching me!!!
I learned so much !
Great explanation 🎉
The only downside of systems that dynamically change valve behavior is added complexity. All the extra mechanisms, sensors, actuators and control electronics are additional points where failures can occur. And they frequently do. Just having the camshaft(s) rigidly connected to the crankshaft, the way its been done for almost 100 years, does have its advantages.
Great explanation
I remember the 1st time i drove a honda prelude and when the V-Tech kicked in at ~5500 rpm, it felt like a 50 shot of dry nitrous ...
VTEC**
nice explanation thanks
Well explained. 👌👏
THIS VIDEO WAS GREAT
Good explanation bro
Excellent video,
the vtech is the most popular cause you hear it kick in so people like it
Great presentation. All the more importance of fresh oil in the crankcase. These systems need clean oil.
Old school guys say small turbo engines will not last long. Here it is 5 years later and my 2016 F150 2.7 twin turbo v6 is still running strong.
good narration
This guy is OG
In gt6 the 2011 mini apparently has one called "Variable Valves" or as I like to say it "Variable Valves kicked in yo".
Toyota also has a very catchy name: VVT/L-i.
He only talked about how exhaust VVT makes more power but not mentioned anything about how intake VVT makes more power, though it's still a nice explanation video!
Dam i know alot about cars but that was very informative and understandable
Very nice video and nice job it's my best job
This video is.. Awesome 🏆🥇👍
Variable cam/valve timing affects the power/ torque band. If the cam timing is early, there’s more low end power/torque. Later cam timing produces more power/torque at higher rpms. Drag racers used to file the camshaft key to change slightly adjust this. I’ve watched my dad do this along with the explanation for this.
It's like slowly turning the distributor on the old v8's back in the day,
Really useful
Variable Valve timing (and or lift) is so old I'm surprised so many people don't know what it is. It's been around for a long time
not everyone is a car guy. but then again nowadays a quick search online always help.
mrhiguy yes Alfa Romeo was the first company to put it in production they built their own system. But they never advertised it like companies do today.
@@jimmygrant3212 then they sold it to Honda and VTEC became well known.
My understanding it was Cadillac that concept and made first development in the 60's along with FORD. Ford got it to work, but it had very serious mechanical failures. The knowledge I learned was Honda had gained access to FORD's design, or FORD gave it to Honda to perfect. Honda actually got it to work, started really indepth track endurance testing in the 70's, and it made its way to the F1 Formula cars, thanks to interest by Lotus and McClaren. both who ran big engines. Lotus I believe was the biggest sponser because their cars are smaller, they wanted a smaller engine with lots of output. McClaren was interested, and shared suspension designs with Honda to make the F1 Cars, which won nearly every F1 race in the 80's. Then the VTEC came to commerical consumers market as far back as 1986 from what I heard. Those are overseas sold cars. mostly SOHC engines. The DOHC came up in 1988, as the b16a which was only found in the Overseas CRX, and DA/DB 2nd Gen Integra. VTEC made USDM market in the 1991 NSX, in a V6 3.0 engine, but Honda had their NSX on a 2.8 v6, which was limited to 280hp under a so called gentlemans agreement. The 4 cylinder DOHC VTEC made USDM market in the 1992/93 DB2 Integra Chassi known as the GSR. It ran the rarest of of DOHC VTEC engines ever made and VERY VERY HIGHLY sought after crank which was a 1.7l engine. It produced supposively 160hp, but I heard numbers of 170hp. The Compression on the b17a1, are 9.5:1, versus the b16a I believe range from 10:1 to as high as 11.5:1 giving the B16 Type-R engine the highest HP to liter Ratio at 1.6 liters for 180hp. But do not fully quote me on those numbers, there is a HUGE selection of B16 DOHC VTEC engines, where as the b17a1 there is only one model. I have had the chance to run the b16, nice engine, lacks torque, the B17a1, lil more torque, both rev really high. I have had 9200rpm on a stock b17a1 that ran a b18c5 type-r fuel map. The b16 I had was a JDM engine with a J1 super short transmission, lots of fun in the street, PURE MISERY on the freeway, as I recall running 4500rpm for 60mph in 5th gear, where as the b17a1 YS1 transmission ran 3500 rpm for 60 mph in 5th. Typical LS/GS manuals ran 2800 to 3000 rpms for 60 mph in 5th. All nice stuff, but you have remember the overseas run KPH, not MPH, ...
I now have a 2005 volvo v50 t5, and that is a super nice engine. All low end, idle to 3k is 70% power limited, then after 3k, the turbo kicks in, at 4500 the VVT is engaging and the car is a rocket. I have never rev-hard on 3rd,4th,5th ... 2nd takes me to 60mph really fast, and the car cruises 2200rpm at 60mph... very very clean engine, I would pick that engine over most Honda/Acura Engines, even those I have special like for the 1990-1993 sedan, and am working on building a b18c1 with a turbo kit, and I am aiming to get the power of a S60R for that engine and do similar to my v50, and see how these handle/compare. Obviously the lighter Integra SHOULD win .. but will lack the torque (maybe) that the volvo has.
I like this video, I am going to look into the history of FIAT, I am really interested in that knowledge from this video. Thanks for making this.
I love these
Very informative. Fiat might not be the best manufacturer out there but their engines always offer innovative technologies. They are also credited with the development of common rail diesel technology.
i love this guy
Spot on
Thank you
I dont always like cnet' video
But when I do I like brian'
Keep it up
great vid
It's really good
This video was good
For those interested:
Check out the UniAir-System by Schaeffler. It gets rid of inlet camshaft by using hydraulic actuators.
@Mathew Antony
You are correct. Fiat was always on the forefront of innovation, while others waited till the come up with something and then see if they can use it. Same goes for Alfa Romeo. I wish I'd see Lancia come back
Luv it. Thanx
Raff Needlman. He's a electronics tech reviewer, I didn't expect to see him in a car engine video.
Vvt first used in road vehicle by Alfa.
Alfa fiat also brought common rail tdi to the world.
Furst v6 by Lancia.
Multivalve tech alfa jtdm
The Multiair System is the Uni-Air System from Schaeffler. Schaeffler bought the original Patent from Fiat.
Valve timing is most valuable thing which effects on engine performance !
VTEC is life
Great film! want more.... !
Whats the downside of this system?
Expensive repair, small bits, yes, nothing else?
I like this guy
Tom Ogle invented a carburetor that gets 375 mpg on a 4-barrell. these manufactures know how to do it- BIG oil holds them in check
I must dwell some more on this subject.
You try to give the video more brightness it will be great if you do
The idea is over 100 years old, I have seen a Deutz stationary engine that used variable exhaust opening depending on speed of the engine
Timing and duration of the exhaust valve opening & closing also determines how much residual carbon is left behind in the cylinder which subsequently leads to soot build up in the cylinder. And in the case of unburnt fuel and air mixture precipitate, the life of the cylinder walls takes a beating too since the fuel's chemical constitution is transformed when it is mixed with air and set ablaze. This changed chemical composition then reacts with the material which the inside of the cylinders' walls are made of and may result in corrosion thus leading to involuntary and haphazard grooving of the bore thus further affecting the cylinders' volumetric efficiency over the longer term continued usage of the engine.
Mechanical engineering is indeed a fascinating and utterly pragmatic field of study.
Anyone interested in the future of variable valve timing, search "Inside Koenigsegg The Future of the Internal Combustion Engine" and enjoy
Drew Quinton The only useful comment. All this stuff is the same basically. That free air system is worlds better.
yeah d first to make d camless valve operation
It's not like to ever go into production, it's too difficult to implement.
thanks
1:26 where can I found the hour version of this?
Watch it 20 times.
xXUnoriginalNameXx33 you should win a Nobel prize
xXUnoriginalNameXx33
In a apprenticeship
find*
Nice
vtec just kicked in, yo!
Can you hear variable valve timing in operation like a faint knocking-mechanical sound for a couple of seconds on initial acceleration? Wondering if that's normal for my 2007 Yaris.
What if I unplug it? My cam lift might be to much for my Nissan vq35 when the vvt adj it's self. Until I get it tuned could i just unplug it so I have no chance of valves hitting pistons?