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i guess its different with my car... vtec can engage in any rpm i want W.O.T. or N.O.T.

i guess its only because i have a head swap and everything else was bypassed...

but to add even more fire... we borrowed and used a datalogger on my friends 01ex and this is what happened.. i agree with some of the results riceburnrex got on his car

VTEC solenoid kicks in only with wide open throttle
Oil Pressure was at 65psi


but here is where the icing hit the cake.................
RPM's were at 3500.

 
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Thank you for the info everyone. Now we know for sure.

 
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yea.. it goes to show rpms can always be different

 
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So then it does engage at 3500 like what was originally posted.

 
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His datalogger said 3500, mine said 5100, and the service manual published by Honda said at least 4500.

Who knows what is going on. I know when mine kicked in, and it was around 5k according to the dyno and datalogs, and the other car I tested activated the vtec solenoid at 5100.

Maybe there is some kind of variation that the ECM does according to other outside factors, but the service manual says it doesn't... who knows.

There isn't a right or wrong on this thread. At least not right now.

 
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I guess I have to ask... Honda advertizes this thing so much, but I think almost nobody will ever use vtec. If you have to floor the car and even then it's only active past 5k rpms, what's the point?

 
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If you have a light wired up to the vtec signal on the ecu then you will notice that vtec kicks at two stages(unless you floor it all the way through).....once at 2500+ rpms/wot and once at 5500+/wot, I have done a lot of work on these cars and spoke to a lot of representatives from various places. The type s and si work in a very similar fashion but with the advantage of two cams. The signal from the ecu is the best way to tell and it is very easy to wire.

Brandon

 
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i thought that the whole point of v-tec was to change the timing of the cams so that you can still get power at "higher" rpms. 2500-3500 rpm is not really high so what is the point of v-tech kicking in that low? i think the honda guy is right. It HAS to kick in above 4000 in our cars or you would probably actually lose power. They used to have animations on honda or acura site (i dunno if they still do) that demonstrated v-tec engagement. It has something to do with air not being able to flow as well at higher rpms so the timing changes to compensate.

Edit: OK I found some more info:

If the engine is running at 4,000 rpm, the valves are opening and closing 2,000 times every minute, or thirty to fourty times every second. When the intake valve opens right at the top of the intake stroke, it turns out that the piston has a lot of trouble getting the air moving into the cylinder in the short time available (a fraction of a second). Therefore, at higher rpm ranges you want the intake valve to open prior to the intake stroke -- actually back in the exhaust stroke -- so that by the time the piston starts moving downward in the intake stroke, the valve is open and air moves freely into the cylinder during the entire intake stroke.


At high RPMs the high RPM lobe path is followed. The high RPM lobe's profile is designed to open the valves open wider, and for a longer duration of time, thus allowing more fuel/air mixture to enter the cylinder. The improved breathing allows the engine to sustain its torque output as RPM rises, thus resulting in higher power output.

So, there is no reason for v-tec to engage as low as 2500 or even 3500. The whole point is to sustain power at higher rpms.

All this info can be found on:

http://auto.howstuffworks.com/question229.htm

and

http://auto.howstuffworks.com/framed...tec/index.html

 
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Well there's a noticable sound change right as the rpms pass 4k. That's why when I first got the car I thought it was changing around 4500 rpms.

 
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what a website says and what is actually in peoples faces when it happens is 2 different things... look at riceburnrex and me... i have used a data logger on a stock ex and he did the same... i got vtec kicking in at 3500 while his was around 5000 or so.... but all the other factors are all the same... WOT.. oil pressure at 65psi.... and look at the niumerous others here that have different opinions on that too... i think that the reason why they say our ecus are smart is because it learns the way we drive and adjusts accordingly

 
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Isn't yours lower because you set it at the lower rpm with vafcII? Maybe that's why yours feels different. When the shop tuned mine and set the vtec to 2800, it felt alot stronger. I put it back to stock tho so it doesn't ruin anything.

 
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hey gearbox.. dont mean to burst ur bubble on ur theory of me using my vafc2 .. but


kool??

 
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oh hehe, didn't see the stock part.

 
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haha.. i figured...

 
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Yeah, mine kicks in at 3200rpm, and I don't need a computer to tell me that. I would like one though! I also have a honda that kicks in at 7000rpm. Yes, that is correct 7000. If you haven't guessed what motor it is, it is a '02 Honda VFR 800 Interceptor. The first motorcycle to have Vtec. I love it. It hauls mad wheelies.

 
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Im late posting but I do have to say aznboysrfr's answer adds up with my vtec indicator. 2200 for hard throttle, ~3400 or so on very light throttle.