Cut out point with Vtec

[Menzy]

This may sound like somthing stupid ... i have done my search but couldnt really find anything so here iam going to ask it ...


With Turbo cars, the turbo wont start spooling/kick-in till it hits over 3200+ depending on the setup... and they cut out at 7000 - 8000 depending on the setup as well...

now with vtec unless you have a vtec controler to control when vtec kicks in it will kick in at 5000+ most of the time for stock but ... does it keep up all the way till redline ... im not sure about this but s2k cuts vtec out so its not all the way until the redline ... which is 8300 but most s2k drivers might push it till 9000 ... the question is do vtec cut out at some stage of the rev range?

technical answers are welcome :)

[notorious_ahmie]

hmmm...with my car...vtec engages at 6k and all the way to redline at 9k and can still keep going..but thanks to fuel cut off cant go that far haha

[h22a accord]

This may sound like somthing stupid.......the question is do vtec cut out at some stage of the rev range?

technical answers are welcome :)

technically no.

[sivic]

uh... redline on S2000 is 9000rpm.
and vtec does not cut out.
can be sure of this because i've been putting round in one today as well as watching one on a dyno:)

[DynoDave]

This may sound like somthing stupid ... i have done my search but couldnt really find anything so here iam going to ask it ...


With Turbo cars, the turbo wont start spooling/kick-in till it hits over 3200+ depending on the setup... and they cut out at 7000 - 8000 depending on the setup as well...

now with vtec unless you have a vtec controler to control when vtec kicks in it will kick in at 5000+ most of the time for stock but ... does it keep up all the way till redline ... im not sure about this but s2k cuts vtec out so its not all the way until the redline ... which is 8300 but most s2k drivers might push it till 9000 ... the question is do vtec cut out at some stage of the rev range?

technical answers are welcome :)
First of all do you know what Vtec is and does in a engine because your question really is a bit strange.Its almost like you have been reading info from another brand of engine that uses some other kind of cam control.
Regards Dyno Dave

[2MPRSS]

vtec doesnt cut out after it is engaged unless you have low oil,i know from my experience that when i had low oil my vtec wouldnt work on first gear,then engage in 2nd gear at higher revs,on third gear it engaged normal time but kept cuting out and cuming back on.from my experience again i know for a fact that vtec turns of when you have low oil in your engine and will cause the engine light to come on meaning vtec wil not work(again from experience)so you goto top the oil up and you will be fine.
thats my experience with the vtec coming on and cuting off

[Lukezen27]

Someone let me know if I'm wrong but Hondas VTec works on oil pressure so if you drive in first all the way to redline but do it slowly ie not boot it you can redline without VTec kicking it in all

Rgith?

Cheer's Luke

[Lukezen27]

Dam it Omar beat me to the punch lol

to busy using spelll check :p

[2MPRSS]

vtec still kiks in luke bro you can hear it when it engages

[Lukezen27]

vtec still kiks in luke bro you can hear it when it engages

Well there ya go :)

I assumed that low oil, not booting it VTec wouldn’t kick in :rolleyes:

But hay guess not :o

[2MPRSS]

Well there ya go :)

I assumed that low oil, not booting it VTec wouldn’t kick in :rolleyes:

But hay guess not :o

ohh didnt know u ment low oil,no it doesnt kick in

[Lukezen27]

ohh didnt know u ment low oil,no it doesnt kick in

Yea

So you can drive to redline but do it slowly you won't raise the oil preesure and hance VTec won't kick in?

[aaronng]

I don't think it is because of low oil pressure that vtec does not engage when you rev it slowly. It's because that less load is detected by the ECU so VTEC does not engage.

[Lukezen27]

I don't think it is because of low oil pressure that vtec does not engage when you rev it slowly. It's because that less load is detected by the ECU so VTEC does not engage.

That doesn’t make any sense if VTec is controlled by oil pressure that what dose the ECU have to do with it?

[aaronng]

That doesn’t make any sense if VTec is controlled by oil pressure that what dose the ECU have to do with it?


You need oil pressure because oil pressure is what forces the engagement pin to lock in highcam. But between your engine oil pressure and the VTEC mechanism, there is a valve that is actuated by the VTEC solenoid. The solenoid gets its signal from the ECU. If the ECU is programmed such that at low loads-high rpm that VTEC should not be engaged, then it won't send a signal to the solenoid to open the valve, thus not allowing the pressurised oil to force the locking pin in.

If the ECU did not play a role with the engagement of VTEC, then how could the aftermarket programmable ECUs and piggybacks be able to alter the VTEC engagement rpm? :)

[Lukezen27]

You need oil pressure because oil pressure is what forces the engagement pin to lock in highcam. But between your engine oil pressure and the VTEC mechanism, there is a valve that is actuated by the VTEC solenoid. The solenoid gets its signal from the ECU. If the ECU is programmed such that at low loads-high rpm that VTEC should not be engaged, then it won't send a signal to the solenoid to open the valve, thus not allowing the pressurised oil to force the locking pin in.

If the ECU did not play a role with the engagement of VTEC, then how could the aftermarket programmable ECUs and piggybacks be able to alter the VTEC engagement rpm? :)

Cool

Thx for the into :thumbsup: :thumbsup:

[ProECU]

Someone let me know if I'm wrong but Hondas VTec works on oil pressure so if you drive in first all the way to redline but do it slowly ie not boot it you can redline without VTec kicking it in all

Rgith?

Cheer's Luke

Incorrect! as far as i can tell, vtec code will engage regardless of engine load, and my datalogs tend to agree.

[Lukezen27]

Incorrect! as far as i can tell, vtec code will engage regardless of engine load, and my datalogs tend to agree.


lol ok then

[aaronng]

Incorrect! as far as i can tell, vtec code will engage regardless of engine load, and my datalogs tend to agree.
Is it possible to via a programmable ECU to disengage VTEC under low loads?

[ProECU]

Generally yes, depends on the quality of the ECU

[Menzy]

First of all do you know what Vtec is and does in a engine because your question really is a bit strange.Its almost like you have been reading info from another brand of engine that uses some other kind of cam control.
Regards Dyno Dave

i sort of know what vtec does to the engin but its the think that people say these days that make you think twice and ask... i didnt want to assume so i asked on here :) but yea it doesnt make sence if it did cut out unless there is a problem with the engin ...

thanks for the info guys really does make sence but the thing about the oil pressure being raised ... no matter how hard your gonna punch it its gonna be the same rev ... so i would say it would kick in regardless and ill try it with my friends Type R (integra) and ill see if that helps hehehe maybe even record the engagment point :D

[giannetto]

cant beat the sound of vtec kicking in!

[crx_boy7]

Hmm mebe if i vtec in reverse all the oil will move forward causin vtec to disingage.




haaahaaaahaaa!!! u guys kill me. i havent laughed this much for quite sum time
and if u had any clu how oil pumps work and wat vtec is for u will kno exactly why im in tears

[crx_boy7]

i hav to teach u a little so that u dont make a fool of yourself again

vtec- designed to impove breathing for the engine at certain revs where it is needed and eliminate the bad driveability of having large cam profiles with forward timing. kicks in using pins pushed in by oil from the oil pump the stage of vtec is controlled by an electrical solenoid wrich is activated by the ecu at certain preset revs regardless of load on the engine and dose not disingage(unless u run out of oil)untill ur revs drop below the same level that it kicked in at

oil pump- suks oil from the sump it is located beneth ur waterpump and is like a small gear within a larger inverted gear. kind of hard to explain with no pic so look it up
yes ur revs are directly linked to oil pressure but this has nothing to do with what stage vtec u are in this is only controlled by ur ecu

sorry for laughing i know that people arent born knowing everything

[Limbo]

on the earlier models of VVT from Toyota their version of Vtec cuts in at about 4,400RMP and then cuts out at 6,800RPM. I think that is where your hearing this stuff from.

The reason for this is the design of the variable timing is different. The toyota version only adjusts ignition timing whilst the honda version actually changes the cam profile which adjusts amost all engine dynamics.

Honda's system is different. Also the system is designed to run on the high cam profile, just think of it like gears, if you chose 1st gear then got to sencond and almost redlined it you wouldn't be going back to first.

The High cam is designed to run at high rpm.

If you don't want vtec to engage you can run the car whislt cold (not recommended!) and vtec will not engage. I have noted that vtec under other conditions will still engage no matter how slow you rev it up cos the pressure & RPM switch it over. Once it gets to the correct RPM it uses the pressure to push the cam profile to the high cam.

The disengaging is due to lack of oil pressure and prob the ECU disengaging to protect the engine, as it does when the car is cold.

[Limbo]

btw if you disconnect your vtec solinoid or disable it then you won't have vtec but that's a dumb reason.

Also i have heard of people making a vtec light to show when vtec cuts in. That will also show you if it cuts out. It works off the vtec solinod if i rem rightly.

[Menzy]

well thanks all for the replies, i didnt expect vtec to cut out as its a different cams coming in at different rpm range, but assuming isnt always the best option so me ask here to make sure hehehe ... thanks again, if anyone else wants to add anything else pleaes do :) many thanks