VTEC engagement

[spetz]

If VTEC kicks in at 5500 rpm
And then there is an upshift, and the car is floored but the revs drop to about 5200 rpm, will the engine go back into primary cam or stay in secondary cam lobe?

[FR33K]

obviously it will drop out of vtec..

[SKREMN]

well thats what you would think but id have to say no
in my old motor b18 I noticed it did stay in vtec when i did do not do full rpm shifts
unless the stock tacho is out it would drop to about 5300 and stay in vtec i allways wonderd why that was
mine was set to 5500 aswell

[Felix]

maybe cause B18C's vtec engages at about 4500 RPM. Thats for VTIR anyway.
Or did you have some other b18 vtec?

[SKREMN]

i had b18b block with b16a head running and obd1 ecu no piggy back

[revNhevN]

VTEC disengages at a lower RPM than engagement. Not sure by how many hundread rpm though.

[SKREMN]

that would make sence then

[redliner]

diff model has diff vtec kick in
dunno which car u r specifying
but i would assume that if vtec kicks in at 5500rpm and rev drop to 5200rpm when shifting, then its out of vtec.

[ProECU]

The FACT is this:

Vtec has both an engagement point and a disengagement point.
The disengagement point is usually a few hundred rpm below engagement.

Honda intended this by design.

[FR33K]

i tried this this morning in my car
and vtec disengaged at the same point both when upshifting and dropping the revs to about 4700 and driving in vtec and letting go of the accelerator..

[saleeb]

think about it, if u keep ur revs at 5500 going slightly up, slightly down if the engagement point and disengagement point were the same it'd constantly switch on and off.

as long as ur revs when u change stay above the disengagement point u'll stay in vtec

[FR33K]

think about it, if u keep ur revs at 5500 going slightly up, slightly down if the engagement point and disengagement point were the same it'd constantly switch on and off.

as long as ur revs when u change stay above the disengagement point u'll stay in vtec

well that just depends how hard u got your foot down on the accelerator
my vtec engages at 4800 but i can get it up to about 6200 without it engaging.. u just have to accelerate slowly

so if your cruising up and down around ur vtec point then vtec will not engage anyway

but if u got ur foot down and let go.. yes vtec will engage and disengage

[saleeb]

yeah there are other checks the ecu does before engaging it, like wot (i believe) and engine temp, etc

[dark8]

maybe cause B18C's vtec engages at about 4500 RPM. Thats for VTIR anyway.
Or did you have some other b18 vtec?

i thought all VTEC's kick in at 5500rpm, r u sure thats not the different length intake runners opening up full ball in your B18 to make that different sound to give u wrong impression?

[KB]

yeh 4500 is the IAB engaging on the Teg. ACtual VTEC is like 5600 or 5800.

[ProECU]

well that just depends how hard u got your foot down on the accelerator
my vtec engages at 4800 but i can get it up to about 6200 without it engaging.. u just have to accelerate slowly

so if your cruising up and down around ur vtec point then vtec will not engage anyway

but if u got ur foot down and let go.. yes vtec will engage and disengage

OMG!!
NOT TRUE!!

Vtec will always activate.
The ECU has a low load and high load engagement point. They usually differ by approx 300rpm.
Low load will engage vtec LATER
High load will engage vtec EARLIER.

Depending on Load, the ECU will monitor the actual RPM, and compare it to the Target VTEC Engagement RPM, and activate it accordingly.
No If's, No But's!

[ProECU]

i tried this this morning in my car
and vtec disengaged at the same point both when upshifting and dropping the revs to about 4700 and driving in vtec and letting go of the accelerator..

I would love to know how you determined vtec disengaged !

[KB]

must be a warning light on his laptop next to the "danger to manifold" one :)

Just make your self a cheap VTEC light. Need a LED led or a 12v globe(samll). THen positive goes to VTEC solenoid wire/VTEC ecu pinout and negative goes to any ground on the car. Then you can see for a fact where VTEC is on and off.

[ProECU]

That works in theory, however there is the tacho accuracy to account for.

The easier option is to believe me. I've read the code. I know for fact what i described is indeed the case.

[tinkerbell]

I would love to know how you determined vtec disengaged !

http://www.ozhonda.com/forum/showthread.php?t=35505&highlight=vtec+light

[ProECU]

http://www.ozhonda.com/forum/showthread.php?t=35505&highlight=vtec+light


That works in theory, however there is the tacho accuracy to account for.

I'll for give your lack of understanding and attention to detaill, so i'll ask again, how can you determine vtec disengaged?
If you dont have an oscilloscope, dont expect to be accurate, unless you spend time decompiling the code and reading thousands of lines of code.

[FR33K]

thanks dave !!!

ProECU what do you mean by tacho accuracy ??
My tacho is not out by 1400rpm
would you like me to go make a video for you ??

EDIT: here u go i made one http://www.users.on.net/~majic/Movie_0001.wmv (http://www.users.on.net/%7Emajic/Movie_0001.wmv)

[FR33K]

must be a warning light on his laptop next to the "danger to manifold" one :)

Just make your self a cheap VTEC light. Need a LED led or a 12v globe(samll). THen positive goes to VTEC solenoid wire/VTEC ecu pinout and negative goes to any ground on the car. Then you can see for a fact where VTEC is on and off.

Yes i do have a warning light on my laptop :rolleyes: loser

[ProECU]

hows that motec system exhaust treating you? lol

[FR33K]

what are yoin goin on about now ?

[FR33K]

bump.. curious about the truth behind this !!