how does FI work with VVTL-i?

[ldpan]

I've always been thinking abt this.....

Say u hv the turbo/SC set at 3K.... does that mean the boost kick in at 3k and then VVTL-i kick in even more at 6k? Or would it be better to set the boost at 6k, so it kicks in at the same time as the VVTL-i to produce even greater push?

I know this might sound stupid, but it has always amazed me.... Would someone pls clarify the theory for me?

Thanks :chuckles:

[larryd]

you dont set the boost in a turbo or s/c.. there is power from when you turn the car on till when u turn it off.. bigger turbo's spool up slower so it may not hit full boost till a higher rpm but it will still be under boost.. S/Cs make more boost with the more throttle you give it.. the more throttle means it spins the pulley faster which makes more boost..

[ldpan]

Thanks.. makes more sense now :)

[Da Kine Guy]

yeah, you'll get two kicks with a turbo. First will be the turbo spooling up, second will probably be lift. I would imagine lift helping out quite a bit with the larger duration and valve lift allowing more of that jetted air to be pushed inside the cylinder.

Or would the wastegate bleed this all away? Anyone?

[larryd]

actually wether or not you feel lift or not is still up in the air.. the thing is the turbo will likely smoothen the power band and change alot of things around so its possible you wouldnt feel it anymore..

[ldpan]

I wonder how is it like for the VTEC w/ FI? Anyone knows?

[larryd]

i do believe they keep the 2nd cam engagement

[gts24]

Most bolt on's for vtec enabled engines retain the "lift"...


We should too, if the manufacturer decides to do it right. Like Larry said though, lift will probably not be as noticable, if not completely gone because of how the torque curve will be flattened out. This is actually a good thing, with proper setup for this car, a turbo/sc should help us with our low end "problems".

[Sublime]

GTS24 is correct. Torque is mostly a function of air velocity. In a NA engine you increase the velocity of the air by using low lift. With a limited valve opening the "sucking" force formed by the piston moving down is increased. The extra velocity causes a more thorough mixture of the fuel and air. When you add forced induction the SC or Turbo provides the velocity, so you can add much more lift down low, without suffering torque loss.
For the celica engine I'd say you'll want to either kick the high cam over a lot earlier or change the cam (or rockers) to have even more lift at all rpms, but leave the switch over where it it. You'll also want to control the cam timing. In a FI car you don't want a lot of duration as it'll cause blow-by. Thats when the air entering the cylinder not only helps push the exhaust out, but blows right on by and out your exhaust pipe... precious air/fuel lost.