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Input On Possible Restrictions

Hanaldo

By Hanaldo,
in Engines & Forced Induction

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SargeRX8 Grand Master

SargeRX8

Posted
Posted

I'm missing about 60rwkw with my hypergear turbo. Stock bottom and top, power fc, full 3" dump to a 3" exhaust which expands up to a 3.5" or 4" not sure(HKS exhaust) same cat. No mufflers in the exhaust. The intake is a full 3" metal intake with an apexi on the end. Base timing was setup on the first tune, just couldn't get the expected number on the dyno.

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Hanaldo Grand Master

Hanaldo

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Posted (edited)

Well the last time it went on the dyno, the VCT was turning on at I think 1500rpm and off again at 7000rpm. That time it made 320rwhp. Lithium actually discovered that and we were both a bit puzzled as to why it would have been set that way, so Lith tried setting it to turn off at 5800rpm, but I couldn't feel much difference just driving. Hasn't been on the dyno since then.

I can post up the map when I get a chance.

Edited by Hanaldo
Ben C34 Grand Master

Ben C34

Posted
Posted

VCT should really be pulled back out before 5k rpm. It's something like 4700 in Nistune for the R34s.

I had 5400 in my head, but could be confused :) my understanding with vct is to do a pull with it off then one with it on all the way and where the graph crosses should be set as your switch point.

GTSBoy Grand Master

GTSBoy

Posted
Posted

That's possibly not entirely valid, because the way the engine is pulling before the actual switch point will likely influence the power it makes directly after the switch point when the engine is accelerating up through the switch point. If you know what I mean?

I'm proposing that;

  • if you tested the engine either in steady state a bunch of times (ie held at a given rpm with VCT either on or off) you'd get one set of engine behaviours that would tell you that at some rpm point it makes more power with the VCT switched over,
  • if you did two accelerating runs with the VCT in one state or the other you'd possibly get a different switch over point from the crossover of the curves,
  • if you did a number of accelerating runs with the VCT switched at 100 rpm increments you'd possibly find a completely different recommended switchover point. And I'd guess it might be earlier than any of the others.

The difference might not be much...but then again a 200rpm difference might make it feel a lot better. I haven't had a chance to test this theory. It's hard enough to get my car to the dyno as it is. It's been on once in 15 years, and my brother-in-law owns a dyno!

Hanaldo Grand Master

Hanaldo

Posted
  • Author
Posted

tried blocking of bov?

cheers

darren

Yes, it doesn't actually have a bov at the moment. Need to get it welded on again after putting the Plazmaman on.

That's possibly not entirely valid, because the way the engine is pulling before the actual switch point will likely influence the power it makes directly after the switch point when the engine is accelerating up through the switch point. If you know what I mean?

I'm proposing that;

  • if you tested the engine either in steady state a bunch of times (ie held at a given rpm with VCT either on or off) you'd get one set of engine behaviours that would tell you that at some rpm point it makes more power with the VCT switched over,
  • if you did two accelerating runs with the VCT in one state or the other you'd possibly get a different switch over point from the crossover of the curves,
  • if you did a number of accelerating runs with the VCT switched at 100 rpm increments you'd possibly find a completely different recommended switchover point. And I'd guess it might be earlier than any of the others.
The difference might not be much...but then again a 200rpm difference might make it feel a lot better. I haven't had a chance to test this theory. It's hard enough to get my car to the dyno as it is. It's been on once in 15 years, and my brother-in-law owns a dyno!

My tuner will set the VCT up on the dyno when it goes in for the flex fuel tune next week. I'm not sure what the old tuner was doing :/

Hanaldo Grand Master

Hanaldo

Posted
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Posted

i would look at removing the cams and putting the stock ones back in and testing it.

the symptoms have cam timing written all over it. more boost no more power. that is exactly what happens.

dont bother dropping the exhaust, just drill a hole and screw in a fitting, then connect it to the dynos boost pressure sensor and measure the pressure in the exhaust, it should not really exceed 7 or 8psi pressure in the exhaust.

Well, decided to try swapping back to stock cams but didn't solve the issue. Didn't get an exact power figure from my tuner, but he said it wasn't any better. So put the Tomei's back in and went ahead with the flex fuel tune. Car fell short of 400rwhp on E85. Didn't respond to boost at all, it made better power with more timing and less boost. Apparently the car loves timing but hates boost. Tuner isn't impressed with the turbo at all but stopped short of blaming it for the issues.

Will find out more details when I pick it up tomorrow.

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