Is there an advantage or disadvantage to use a controller to have vtec KICK in at 4500rpm as oposed to 5500????
What other factors will come into place???
Will timing have to be altered?? ( ignition and cam)
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Is there an advantage or disadvantage to use a controller to have vtec KICK in at 4500rpm as oposed to 5500????
What other factors will come into place???
Will timing have to be altered?? ( ignition and cam)
If the engine is stock, there's no need to adjust VTEC crossover point.
From what I understand, the VTEC crossover point is set at a value stock where the amount of power being made by the engine, the amount of air and exhaust to go into and come out of the engine is increasing, and therefore the valves have to say open for longer. Now, when the valves are open for longer, you get what's called valve overlap.
The point is, that when VTEC crosses over to the higher profile, is when the motor requires longer duration and lift. Therefore, if you do it too early, it's making it too difficult for the motor to get the air that it requires in, and out.
E.G. If you have a straw, if it's small, it takes smaller effort to inhale / exhale, but the volume is diminished. That's great, but you can't really drink your big cup of coke through a tiny tiny straw. So, when your motor is in NON VTEC mode, it's being economical, and creating a bit of power, but once you need to get more air IN and out of the engine, you need to have longer duration.
Now for overlap, this is my understanding, and I might be wrong.
When you have really bumpy camshafts geared towards making more power N/A - they tend to have high lift and long duration. With the long duration you have long overlap. Long overlap makes the motor lose some compression seeing that the exhaust valves are open when the piston begins its compression stroke,you know, when it moves towards the head for the big bang!
So when you put in like TODA VTEC KILLER CAMS, you're better off upping your compression ratio in the engine to make the best possible power.
You DONT need a VTEC controller unless you have got NEW cams or you've upped your compression. And this is something that YOU HAVE TO do on the dyno, with a knowledgable tuner, like Adrian from Toda, or Dyno Dave, or other well known and published tuners (Adrian is in EVERY autosalon and Hot4's magazine somewhere).
Why doesn't it work setting VTEC to crossover lower? cuz you've got a lobe thats designed to work at higher rpm's running when it isnt needed. if you were to adjust it higher, you'd be choking the engine of the air it needs to burn, and when it did kick in, it'd be like a kick in the face.
As for cam timing etc, there's no point in adjusting cam timing unless you have aftermarket cams, and there's no point in adjusting the ignition unless you have built up your engine & installed cams.
Yes it's that simple ;) . The only room to further optimise the stock setup would possibly be with fuel mixtures, so therefore an aftermarket ecu and a dyno tune will be in order.Quote:
You DONT need a VTEC controller unless you have got NEW cams.................
changing ur vtec crossover point to 4500rpm on a stock motor will effect the perfomance marginally.i.e loss in power.
Just leave it at 5800 rpm or whatever stock is.
This has been dyno'ed proven. NO gains were made.
my guess would be that in a stock R everything is pretty much optimized....so theres no real need to adust much...honda realised the R to be as fast as they could make it...if changing the vtec kick in point by 500 rpm or whatever made it faster i would think they would have done so...IMO anyway...or you could just look at the other 3 above responses there more techinical
Read this for what overlap is. Also good help for choosing a cam.Quote:
Originally Posted by yourfather