Variable Valve Lift vs Variable Valve Timing - VVL vs VVT

What is VVL? What is VVT? How does VVL/VVT work?

What is variable valve lift? What is variable valve timing? We're going to look at the valvtrain from a 2009 Audi 2.0L I4 Turbo engine to check out the differences. Variable valve lift is used to enhance performance depending on the RPM and load, while variable valve timing is typically used for emissions control (lowering combustion temperatures and thus reducing NOx), but also has performance and efficiency benefits as well.

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[HumbleMechanic]

Rock on man. Thanks for coming and hanging out. It's always a fun time collaborating with ya.

[CarterHansonlb]

Just recently got a job at a local car shop! They're enrolling me in an Auto Technician school! I'm super excited and grateful. Hopefully I obtain as much knowledge as you guys! Keep at it!

[TheGinger]

I was completely lost due to the lack of a white board and many many different coloured pens ;-)

[Leoine]

Go watch the beginning of his very first video from 5 years ago, then click over to this. Insane how far you've come man!

[kcwalkman]

Jason, once again you're raising the bar for automotive channels. And always a great deal of valuable information presented in an easy to understand manner. Thanks for sharing your talent and time with your subscribers.

[andrewpochettino]

Leaving the intake valve open longer can also increase power. Because air has mass, it also has momentum so as velocity gets near the speed of sound, assuming there's no turbo/supercharger, the air will continue to flow into the cylinder as the piston reaches BDC due to Newton's first law of motion. This means you can get more charge into the cylinder, and therefore increase power.

[calska]

I love all the clever little mechanisms engineers come up with to get tiny percentage increases in performance. It's just endlessly fascinating. There are some really gifted people out there.

[murdelabop]

Actually, all this valve timing stuff is only partially for emissions. It's also in large part for efficiency. If you close the intake valve late, but keep the exhaust valve open all the way from bottom dead center to top dead center then what you wind up with is an "Atkinson cycle" in which the effective power stroke is longer than the intake stroke. This is very efficient, but not very good at making high power.

Honda uses Atkinson cycle valve timing in their IMA hybrids, which is why a first generation IMA hybrid with a dead battery pack can still get 50mpg.

[StaufferGarage]

Bravo sir, very well explained and glad you had visuals instead of the board to explain.

[briansmobile]

VVL just kicked in doesn't sound the same as VTEC. Or Vee Vee TEE BABY! Good explanation guys!

[souravzzz]

I know it's not always possible but more videos where you show the actual parts would be awesome.

[thesparksplug]

Just had a discussion with a mechanic about these same two topics: VVL against VVT, now I have this video to my assistance.
Thank you guys so much.

[Laszek]

Jason I just wanna add that in turbocharged engines closing intake valves a pinch later allows to use the momentum of the compressed charge. While compression stroke begins piston is moving upward, intake cam is still opened and compressed air flowing into cyllinder meets moving piston and increases pressure. Valve should close just before air starts to flow out of cyllinder. That is called dynamic charging. Thank you for your videos man!

[Cypeq]

This is so cool, and when you run specific emissions test you can run it in a way that it always provides lowest NOx emission.

[fire]

Hands down this is the best video I have seen on VVL and VVt, thank you.

[tonystark]

I can't express my gratitude enough for you guys explaining this stuff so simply. Thanks a bunch! Now I know for a fact what VVTL-i is and how it differs from VVT-i.

[Camilla.A.K.A.Crucifix]

Great video, this really broke down every question on how variable timing worked, and even answered questions I hadn't even started asking about valve lift, I appreciate it very much

[barrysargent]

My old Toyota Corolla 1800 VVti has a banging low end because of this. The bloody thing hauls up most hills with gusto in fifth, first, third, fifth no worries and hauls my jet ski like a trooper! It's a great little engine.

[jackstrapp]

Rover's VVC is kinda interesting too. It doesn't changes the timing but it changes the opening duration of the intake valves like this vvl does but this vvl (explained in this video) is a binary feature ( just on and off / higher and lower profile ) just like a vtec or something else. The advantage of VVC is that it's an analog feature (short opening at low rpm and long duration at high rpm).

[Sixstringbassist]

This is cool, my Celica has VVTL-i, with timing and lift on both the intake and exhaust camshafts.