So all cars w/ DOHC vtec have an rpm where the vtec engages as your revs climb but there's also a certain rpm set lower than the engage point where its set to disengage (for instance when you're at 7000rpm and coasting/slowing down and the revs are dropping but the car is still in gear) right? I swear I remember reading on hondatech or somewhere that when someone was moving the engagement rpm down they also had to move the disengage rpm down so it didnt engage and then disengage right afterwards.

Anyway, if this makes any sense, what's the vtec disengagement point for the s2000?

 

Edited my unrelated comment... I misread your first statement.

Second, if you're using a VAFC or something to set the VTEC crossover, it won't allow you to set the disengagement point higher than the engagement point. It may actually force you to set it 100RPMs lower... I can't recall.

With the stock ECU, the VTEC engagement point (and also disengagement point, I believe) are set to 5950 RPMs IIRC (or it may be 5850, I forget). I don't know that anyone has actually tested this, but I doubt Honda was concerned that some fool will sit there bouncing from 5949 to 5951 RPMs over and over, just to engage/disengage VTEC.

 

WOT vtec engagement I believe is 6200, and disengagement point is 5900

 

I always thought vtec was like an on-off switch activated by a certain RPM given certain conditions are met, almost like a Boolean variable in programming. Unless i know even less about cars and computers than I thought, switch can only be turned on or off but not both at the same time, right? I don't see how honda could program the ecu to engage vtec at a certain rpm (say 5950) but also tell it to disengage vtec at 5950rpm and still have vtec 'work'... It would either turn on for a hair of a split second and then off again immediately after and it would never engage or it would turn off and then turn on, but never disengage because as you coasted from 6500 down to 3000 say you would hit 5950 and the computer would get the disengage message and then the engage message immediately afterwards and it would stay engaged until you turned the car off.

Maybe they set the engage for 5950 and the disengage for 5949?


Just from looking at dynos on comptech's site it seems like all the s2000s they test get a big jump in hp and tq between 5900 and 6000rpm (it helps that they actually have the hp and tq #s written on the sidebar at 100 or 200rpm increments).

 

I don't think so.. I have numerous dynos with stock ECUs showing VTEC engagement before 6000. The 5950 is a believable number.

 

Holy crap... don't overanalyze.

I simply meant 5950 was the "cutover point". In other words, if RPMs are greater than 5950, then the high cam is engaged. If RPMs are less than 5950, then the low cam is engaged.

If your RPMs are increasing, then 5950 becomes the "engagement point". If your RPMs are decreasing, then 5950 becomes the "disengagement point".

Here, I reverse-engineered the code in my ECU and this is what I found:
[CODE]if (RPM >= 5950) {

 

[QUOTE=mxt_77,Mar 20 2005, 08:14 PM]
I simply meant 5950 was the "cutover point".

 

oil pressure is related to rpm... the more rpm the higher pressure, the lower the rpm the lower the pressure.

Vtec works on oil pressure. when the revs climb the oil pressure increases. once a certain point is reached (dont know what pressure) Vtec engages.
(rpm at this point is 6000 (ish))

vtec dissengages when the oil pressure drops below (dont know the number)
(rpm at this point is about 6000 (ish))

it is NOT the ecu calculating the revs, its the oil pressure sensor tells the ecu.
the ecu has pre programmed points where to engage and dissengage Vtec
with a VAFC you can by pass the stock ecu settings and set them to the a different rpm.

 

the oil pressure sensor only tells the ECU if there is enough oil pressure to engage the hi cam followers. the oil pressure alone does NOT determine when the hi cam engages. the ECU does this at a specific pre-set rpm.

there seems to be a fair amount of misinformation kinda jumping around this thread.

I do know that in stock form, the vtec disengagement point is LOWER than the engagement point.

 

i stand corrected

thanks for the information, i will now know for future reference.