well i was wondering what is the criteria for vtec to work...like over certain mph and certain engine temp and over....i know some just not everything i was wonderin bout the CEL and some other stuff ...so let me know if u guys got a link or if u know 100% sure and is it different for dohc..sohc...vtec-e....and so on thanx

 

It actually has nothing to do with vehicle speed or engine temp.Im pretty sure its activated buy oil pressure.

 

the solenoid is activated when the ECU tells it to due to the rpm. usually for dohc 5000 rpm

 

I know your car has to be warmed up, you have to be going over ten miles an hour, and have proper oil pressure or it will not activate. If it was just oil pressure then you could hit vtec while revving in neutral.

 

actually it has to do with many factors , off the top of my head it has to do with Engine speed, vehicle speed, water temp, oil pressure and throttle position. if any of these do not agree with the ecu then vtec will not corss over

 

"actually it has to do with many factors , off the top of my head it has to do with Engine speed, vehicle speed, water temp, oil pressure and throttle position. if any of these do not agree with the ecu then vtec will not corss over"
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i most definitely agree with this and also in cases with the computer throwing engine codes would cause v-tec not to ingage

 

Four things. Vehicle speed (car has to be moving). Oil pressure obviously. Water temp (Why dont my vtec kick in when I first start my car up in the mornin and race out of my driveway after it has been sitting out all night? ). If these three criteria are met then whatever pre determnined RPM point it is set at, it should engage at. Assuming everything is functional and no CEL's are present.

P.S. - Let's only give Tech advice if we are sure.

 

yes,, those 4 and throttle position , and engine speed, and assuming that your ecu isn't running in limp mode becasue of a CEL, though i have seen cars in the past where vtec still works even if there is a CEL not all codes put the ecu into limp mode

 

Obviously. I mean codes pertaining to the operation and engagement of VTEC. I am throwing 4 codes right now and VTEC still works like a champ.

 

well my CEL is on ...and im guessing VTEC works i just did a gsr swap so i haven't heard a gsr wit headers and IM and how deep it is i dunno if its vtec...im used to driving the b16...so hmm i dunno not in limp mode...im gonna buy a new harness asap then ecu and hopefully this will get rid of the prob of CEL and then maybe i can see if this is really vtec or not...if it is not holy **** im in for a treat

 

so what exactly is your setup, what motor and in what kind of car and what ecu. im kinda a space cadett today and couln't follow your post, also did you ever see what code the ecu is throwing. are you saying you can't hit vtec?.

 

em1 ....long block jdm gsr wit couple things from b16 switched over...skunk2 IM.....dc ss 4-1..greddy evo....cam gears...rest of the bolt ons...im on stock b16 tranny wit clutch anc short shifter...then i got stock si ecu.....wirez next to the ecu were hacked long time ago so i think its creating a bunch of shorts...car can bog in the middle of driving at 3K or 4K...i got CEL on...it was throwing o2 sensor..vtec solinoid..and the other vtec one...and knock sensor...well this all doesn't apply cuz its a screwed harness and should be shorting out so once i get the nect one install it and check the codes if ne then we will see...btw does ne body have a how to on installing the harness i heard its a bitch

 

yeah fist things first get that harness fixed, either just cut it all and resplice it all or just get a replace ment, but that could be expensive. post back after you fix that and see what codes your are throwing if any

oh yeah and your running a b18 with some bolt ons, and your using a stock si ecu, i think your gonna have a problem, not enough fuel, and that could be why your throwing the o2 sensor.

 

vtec only needs three things:

at least 19mph
at least 55psi oil pressure.
Correct rpm (activates solenoid)

 

ok you go start your car on a nice cold morning and floor your car and see if you hit vtec without being at the propper temp required to hit vtec, propper coolant temp is vitial for vtec

your right about the speed, the RPM and the oil pressure,

and also from driving my car i have noticed that if you are not a at a certian throttle position vtec will not engage, meaning that not everytime you go above 5000 (for prelude vtec) are you going to hit vtec, throttle position matters.

 

i heard hitting vtec when engine is cold is bad and can break the pin in the rockers

 

you can NOT hit vtec if you engine is cold the ecu will not let it, in my opinion you suldn't even reve past 4 grand when your car is cold, doing so can cause damage, vtec will not work unitl the propper temp is reached ( probably so no engine damage is done when engine is cold). the temp i think is some where around 150 to 180 degrees

 

well heres a story,

i installed a apex'i v-afc in a friends '01 type r and the engine was already warmed and everything.

we played around with the vtec cross over points and tryed flooring it in nautral and the vtec sign on the v-afc has indicated that vtec is activated.

meaning it crossed over to vtec in nautral?

anybody with a v-afc want to try it out and let me know im not the only one here.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mike1114 &raquo;</TD></TR><TR><TD CLASS="quote">vtec only needs three things:

at least 19mph
at least 55psi oil pressure.
Correct rpm (activates solenoid)</TD></TR></TABLE>
and water temprature, and over 20% throttle

 

depends what motor jdm or usdm. both have a set change over (rmp) set to engage the vtec programed into the computer. if your motor has just one plug of the vtec assm on the end of the head. the computer uses engine coolant temperature to determine when the motor is hot enough to engage vtec. usdm motor with 2 plugs use a seperate oil pressure switch mounted on the vtec assm, in addition to the engine coolant temp to tell the computer when the car is ready to engage vtec. the only thing different motor to motor is the change over point, what engine speed 4500, 5000, 5500 the motor engages vtec