Does anyone have an idea on why Toyota (and Honda I might add) decided to make the the high speed cam kick in at such a high RPM? Is the cam lobe engineered to provide increased performance only after 6000RPM and setting it lower would actually degrade overall performance? If anyone has an idea please share.

Also, do you think there will be a kit to increase the Celica's engine displacement to 2 liters in the future? I am new to the import scene so I don't know how the aftermarket usually works. Thanx for all the help!!

i think it may be because most 4bangers dont start making horsepower until they reach high rpm's. so if the vvt kicked in at lower reves it would be wasting energy...maybe even robing some power. i would emagine that if u had a larger displacement engine the vvt could kick in at lower rpm's. im not sure though, just a guess. maybe it would just be impractical for everyday driving if it kicked in everytime u hit 45k:cool:

Well the main reasons they have it set up that way is for flexability. The "big" cam that comes on at higher rpm's is good for making power, but would suffer in drivability (less low rpm torque) and slightly better gas mileage. So for driving around town the "standard" or "small" cam is more ideal and for more spirited driving the "big" cam kicks in for added power and better breathing. This allows the displaceent to stay relatively small while getting the most power out of it as possible. There is still no rea replacement for displacement, but it's definately a good idea. It's a surprisingly simple concept that's really catching on with lots of other manufacturers like BMW and MB even. I'd say nearly every manufacturer out there either has a type of "VTEC" system in their lineup or will eventually.

The more aggressive cam lobes kick in at high RPM because the cam profile was probably chosen to have VTEC/VVTLi stay engaged when you're racing. Like say if you have a 8000 RPM redline and a 1-2 shift brings you down to 6200, then if the VTEC cam is engaged at 6000 you stay in VTEC while you race, you don't need it lower. It's optimized for full throttle redlining operation. They don't stick a bigger cam in there not so much as drivability as much as emmissions reasons.

At what rpm does Toyota's VVTLi kick in?