Is it just engine speed dependent, on at one RPM and off at another? Is there also a throttle position input? Is there a time delay on turning off VTEC? That is, does it say if engine speed drops below this point for more than so many seconds then turn off VTEC?

As a corollary, how do you modify the ECU to change the VTEC settings?

Thanks,

David

 

As far as I know of it's dependant on RPM and oil pressure...5600-5800 rpms & the right level of oil pressure. Which is why if your a tad bit low on oil you'll see VTEC hezitation, not to mention it being bad for your engine as well.

 

^ Its more then just that
VTEC change over occurs under the following conditions

-The engine must reach its target RPM value - in the S2000, 6k rpm
-Their must be sufficient oil pressure, which is determined by the VTEC Solenoid valve
-Throttle position must be at a certain % and higher
-ECU must pick up a speed signal from the transmission
-Coolant must reach a temperature level or higher.

 

This member knows their stuff!

 

Maybe I'm wrong on this, but I believe there is a traction factor too. If you break traction (powersliding a turn) I do not believe VTEC kicks in. This would make sense as the sudden burst of power would likely upset the balance of the car.

 

[QUOTE=scottrunsxc,May 7 2006, 11:35 AM]Maybe I'm wrong on this, but I believe there is a traction factor too.

 

Vtec will still function, when the wheels are moving, the speed sensor in the transmission picks up movement.

Where do you get your info from?

 

Your speed sensor has to detect 13mph or higher.

 

I have a RED LED light wired straight into the ECU harness to light up with vtec engagement. at a dead stop, the light comes on if I'm at full throttle past 6000 rpm.

normal?

 

Like I said, I may be wrong. I get my information from personal stupidity and nothing else. I was trying not to go into it b/c I know I'll get flamed for S2000 abuse. Anyway, I've gotten myself into a bind before the car was fully warmed up. It was either get in a wreck or get out of the way, I elected to get out of the way.

Here's what you do, go crank up the car, find a place with no traffic, make a u-turn slowly in 1st gear before fully warming up the car. Halfway through the turn floor the gas pedal, hang the rearend out, take the car above 6000rpms and see if you hit the rev limiter. In my experience, you will not hit the limiter. On this occasion I was around 7500rpms. This either means that traction is a limiting factor in VTEC changeover, or that VTEC can change over without reaching operating temperature. Since it is common knowledge on this site that VTEC will not operate below "3 bars" (in an AP1) I can only assume that traction is a limiting factor in VTEC changeover.

Sorry if I was relaying incorrect information. Just seemed to be a logical assumption to me. If someone can explain this to me, I'm all ears.