Nistune Forums

seems the z32 boys like to adjust this to get a better curve, by doing 2 runs one with it on permantly and 1 with it off completely then looking where the graphs cross and set the off point at that rpm

has anyone done this on a sr20det with noticable gains? i live 90miles from the nearest decent dyno so it'll be expensive round trip

I have heard mixed stories regarding that..some have switched it off at 4800 and said that it benifited the top end.. and others said it does very little.. I guess when it is talking about overlap.. if it is advancing he intake cam and not the exhaust cam it should decrease the overlap.. and should you switch it off and then retard the intake cam and increase the overlap.. you could help the exhaust get out.. you could loose boost by blowing through the overlap.. or if the exhaust manifold pressure is high enough.. exhaust may come back in the engine.. If that makes sense..

the other week i tuned an sr20det on hks 264 step 2's with td05 18g..

there was a noticeable difference in engine rpm rate of rise with the vtc set to switch off at 5300rpm not the usual 5700rpm..

it is to reduce overlap as mentioned to stop the exhaust reversion at high rpm.. (exhaust PR is always higher than MAP)

This was one we are meaning to try out on my R34 to see what the differences in the power curve are like. More to follow. I'm doing some more updates to the software and need to get the innovate WB installed prior to that and then testing will commence

Matt wrote:This was one we are meaning to try out on my R34 to see what the differences in the power curve are like. More to follow. I'm doing some more updates to the software and need to get the innovate WB installed prior to that and then testing will commence

so far ive found the factory r33 and r34 switching points pretty much spot on @ up to around 300rwkw.

nothing to do then

I pretty much do this with every vct vehicle I tune

9 / 10 the facctory settings are very close

But quite often with very very good gains - a lot of cars surprisingly end up with good gains by leaving vct on until around 6000 - 6100

Some are weird and actuly go best with it turned off mid 4000s

Trick is to do it at the very end as your optimal switch point will be different for all different boost pressures generally

But well well worth the time spent in a few extra ramps at the end of a session

I've tried changing VCT switch point many times on SR20's and I've gone back to factory every time.

Apparently it's one of the first things the Z32 boys play with but I'm yet to see gains on SR's. That won't stop me trying though. As the other guys said, the more radical the engine, the more likely it'll need adjusting.

PL

the majority of ones we see gains with are the usual

poncams
740cc inj
z32
2871r
14-18 psi boost

type combos