sup,
i've been researching (noob) and foound this qoute from another user

"VTEC is a simple engine function that allows the engine to select one of two separate cam profiles: one tuned for low rpm use, the other for high rpm use. VTEC engagement depends upon the ECU you are using and/or any piggybacks also in use."

i know wat vtec is.... but why would you want to tune it for high rpm use and low rpm.....Thanks

 

Because one single cam profile can't be real good over a really wide range of rpms.

One profile is good at lower rpms. It idles OK & works well, but starts to lose power at high rpms.

The other cam profile makes more power at high rpms, but it sucks at low rpms & maybe doesn't idle so good.

 

do you need low rpm profiles or high rpm profiles? thanks

 

yes... there are 2 seperate profiles... each with different lift and duration specs.

The smaller profile performs well idling and at lower rpm. The larger profile takes advantage of the engine's rpm and is designed to produce bigger Hp numbers.

If you ran the vtec cam profile below the vtec engagement point... the car would idle horribly (if it is able to idle) and low rpm performance would suffer tremendously as the cam profile for the vtec lobe keeps the valve open too long at low rpm to be effective.

 

when you race you want high cam profiles....so why would you adjust it to low? thanks

 

larger cam profiles, as said, do not perform well at low rpm (700 to 4 or 5k) they actually will make LESS power than the smaller profile at that rpm range.

VTEC actually has 2 seperate cam lobe profiles on the cam. The engine runs the low profile up to the VTEC engagement point (4500-5500 depending on what car)... after which, the big profile comes into play. The intention is to have the crossover and power production to seem transparent.

 

so u can only have either low cam profiles or large cam profiles? thanks

 

You've got to be kidding me right? I think this guy is playing around cause its been explained over and over in this post! Next topic plese!