VVT

this question is above our pay grade. go ask a real forum

>>17026572
VVT is a way to "cheat" performance out of an economy engine. So are most modern turbos (looking at you Ford). There's no reason not to combine the two.

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Wtf? Variable valve timing isn't about "bouncing air waves" into the combustion chamber you fuckhead what does that even mean.
Vvti is used to adjust cam profile to allow for to come in sooner in the cycle, allowing faster combustion. Variable valve tech isn't even hard to understand. Get your autism checked.

>>17026572
VVT is used for:
1. improve VE over wider range (that translates to higher torque figures down low)
2. allow EGR action by running a lot of overlap to help with emissions (that's not needed and most of NA tunes eliminate that, along with making AFR slightly leaner especially at WOT)

FI engine works like NA engine, as it also has intake plenum that's handles intake "pulses" (nothing is ruined).

>>17026572

It is indeed complex problem and cam timings require more than one book... I will try to give you some simplistic points ELI5 style


Think of an engine as a vacum pump. Once the piston goes down during intake phase, it creates empty space with 0 pressure. Outside of the engine is 1bar of pressure (our atmosphere) and that difference in pressure means your engine suck the air in because nature kinda does not like voids.

That remains true for forced induction engines except now on the outside of the engine imagine more than 1bar - whatever that turbo/compressor is pushing at the moment. That's it.

There are some other things to consider like valve crossover (lobe separation angle) where intake valves open while exhaust valves are not closed yet - that gives you better overall flow if you have exhaust well configured with it and intake pulse can sync up with exhaust pulses and so on..

In general same principles are valid for both NA and charged engines, however their volumetric efficiency, adiabatic cycle and other shit differs slighty. The main purpose of VVT is to widen usable torqueband and make torque curve rise up outside of peak rpm, which indeed rises overall power...

>>17026647
cam profile / ram rate isn't changed, that's not a VTEC.

What is changed is overlap, and timing with regard to TDC/BDC if there are VVT gears on both EX an IN cams.

Adjusting cam overlap moves peak VE efficiency point across PRM range.

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>>17026669
This is a 10/10 explanation but can somebody translate what ever the fuck OP was trying to communicate? Lomgitudinal air pressure waves? Huh?

>>17026700
Basically he was talking about intake charge pulses.

https://mechanics.stackexchange.com/questions/25236/how-does-intake-manifold-runner-length-effect-the-power-curve-of-a-car

>>17026700
>Lomgitudinal air pressure waves?
Air has inertia. Thus cutting it off and not cutting it off causes longitudinal pulses in air pressure. I myself enjoyed making air pulses in a long underground tunnel under one of my employer's factory buildings. It's almost 3/4 of a city block long and fans are on one side to pull in fresh air if any other doors are opened elsewhere. At the far end, I can see the dot of light of the other wide doors. I open the doors at my end for a bit and then let them shut. The inertia of the air pulls the double wide doors shut on me. Now, there is an optimum rate of opening speed to open the doors quickly, an optimum length of time to leave the doors open, and of course the doors are shut fast as possible without slamming them (because damaging property is not allowed).

Done properly AND spaced properly, those pulses of air can speed up and be compressed by the time they reach the other end. If done improperly with the wrong timing because you didn't anticipate the inertial of the air, there are only gentle differences in the breeze. But when done right, the pulses are strong and distinct on anyone walking thru the tunnels from the far end where the suction fans are.

>>17026669
>>17026700
OP is referencing the shape a current of air likes to take.

This guy is correct >>17026603

vvt isn't about charge pulse. thats what variable runners are for.

it's about things which are too complicated for 4chan.

>>17026572
>I can see why VVT is useful

Does variable valve timing increase the amount of carbon deposits on intake valves of direct injection engines?

>>17026645
But turbos run the engine harder while VVT is more about optimizing what is already there. So for people who don't want to run the engine harder, VVT is preferred to turbos even though the power gain is less.

>>17029674
i dunno lol

>>17026572
Variable valve timing is used to adjust valve overlap you dingus. Less for low rpm torque and more for high rpm horsepower

>>17030907
m8 it's used to maximize torque at every RPM. More torque gives you more power.

P = τω