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sloberwacky

Question about vct and aftermarket cams/gears

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Hey all. Might be a noobish question but ill ask it any ways cause I cant seem to get a straight answer. I have and S15 JDM and it looses power on the dyno graph between 4500-5500 rpm. My tuner tells me this could be because the vct is on it's way out. It happens at the vct crossover range at 4500 rpm.

 

dyno graph.jpg

 

 

I have heard that adjustable cam gears will disable the vct unit as well as performance cams like tomei poncams, greddy easy cams HKS etc etc.

My question is if you were to install these cams and cam gears would it actually disable the vct making it in-operational? If so this is a $600 vct repair fixed by simply adding new cams/gears which would help boost that power curve from 4500 rpm onwards?

 

If this is correct why pay $600 to get the vct fixed when you can buy new cams/gears for approx $800 whilst also boosting power? Is this correct or am I reading into it all wrong?

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OK, the VCT unit is built into the factory cam gear on the front of the inlet cam, and it's actuated by a solenoid on the side of the head. We all know they get noisy with age, but I think there's a bit of a question mark over whether this causes a drop in performance??? Anyone???

 

You can replace with aftermarket cam gears, but the trade off is a loss of mid range performance for a gain in top end (something to consider if it's a streeter). You can run aftermarket cams like easy cams with the factory VCT cam gear, but I'm not sure with more aggressive cam profiles.

 

So the question re: cost, really comes down to how you want your charriot to drive. Maybe take a non-VCT SR for a spin if you can and compare the way the two drive. Some say the difference isn't that noticable, whereas others make a big deal about it. I can't comment as I've never driven a non-VCT SR.

 

 

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piss the vct off and get the stock s13 cam

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VCT was added when they reduced the size of the throttle body, played with the head, and generally reduced flow. It was there to maintain power whilst reducing emissions. If you're going for super power and big turbo and cams, then there's no need for it.

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Dont get rid of VCT there is always a positive for it IMO

The gains in midrange are massive, regardless of what power you are chasing. Only reason you would remove it is the cams your using dont support it..

 

Noisy or not it will not affect the performance of the VCT in any way.

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you havent told us enough details, when is the cam switching on and off ? are you sure the cam is switching on ie try doing a run or a drive with it disconnected will tell you.

 

15psi ? aftermarket ecu ?

 

4500rpm VCT cross over you mean this is where u are turning it off, its to early keep it on till mid 5000ish think factory is 5700

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Definitely keep the VTC it's basically what makes the s14/s15 motor better than the s13, and yes you'll loose power without it and no you can't make up for it with cams/gears

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do you have any other printouts?

 

You need the one that plots your boost togther with the injector cycle as well as power. What is your cat like?

 

Your power seems low and your injector rate is high, I think there are other issues other than VCT

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Running these items;

Pod

3" cat back with Hi-flow cat

3" dump pipe

EBC

FMIC

BOV

Apexi power FC

walbro pump

Z32 afm

 

with 1 bar with 98 pump fuel

Something has to give. Compression is fine no leaks etc. Thought it must be vct.

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