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Chasing 350-400rwhp, But With Much Less Lag. Advice Please?

SoFreshSoClean

By SoFreshSoClean,
in Engines & Forced Induction

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wolverine Grand Master

wolverine

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For a GT-RS on a RB25 it seems to be coming on fairly late at 3600rpm.

The peak looks about right so there is still room for more power earlier when that is sorted. I'd expect it to be all in about 500rpm or so earlier.

SoFreshSoClean Proficient

SoFreshSoClean

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I think he is concerned that excessive blowby will develop if I go any further HP wise.

Apparently the standard exhaust manifold starts to become a restriction at this level too, ie excessive exhaust pressure/heat buildup. Correct me if I'm wrong.

usmair Mentor

usmair

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Posted (edited)

dont think so dude... i had my old car making 290rwkw on the standard manifolds and it was all good... no catch can either :D

he must want you to have it as a precaution rather than anything else...

Edited by usmair
SoFreshSoClean Proficient

SoFreshSoClean

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The manifold is not an issue at that power level.

I would have a look at the wastegate as a reason for the lazy-ish boost response.

So thats just a matter of fitting a tighter spring, right? Would the stock BOV have anything to do with this ie leaking?

dont think so dude... i had my old car making 290rwkw on the standard manifolds and it was all good... no catch can either :)

he must want you to have it as a precaution rather than anything else...

How long were you running that power level? How do you know you didnt have blowby if you didnt have a catch can?

Harey Veteran

Harey

Posted
Posted

I dont think you will get much more than 250rwkw out of a GTRS on a stock RB25. But it should have really good response.

If the stock bov was the issue you would have issues with high amounts of air not with response.

Granthem Mentor

Granthem

Posted
Posted (edited)

Mine GT-RS runs 256rwkw @ 14psi.

However, it has headwork, HKS cams, Plazaman plenum aswell.

Nice results! Bet you are happy. Gets boring quick tho :P

Edited by Granthem
The Mafia Grand Master

The Mafia

Posted
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Standard everything else, RB25, Powerfc, injectors, FMIC, exhaust, and GT3076 with 56trim, 0.6 comp cover, a 0.63 IW rear housing, 18psi of boost. Full boost at about 3100rpm.

314rwkw-2.jpg

3.jpg

Boost was on steady here to stop traction loss. Came on hard though, and at around 3000rpm as I said.

Set up the 3076 properly, and it will not be laggy.

SoFreshSoClean Proficient

SoFreshSoClean

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Standard everything else, RB25, Powerfc, injectors, FMIC, exhaust, and GT3076 with 56trim, 0.6 comp cover, a 0.63 IW rear housing, 18psi of boost. Full boost at about 3100rpm.

Boost was on steady here to stop traction loss. Came on hard though, and at around 3000rpm as I said.

Set up the 3076 properly, and it will not be laggy.

Er.. while thats annoying to see it spooling earlier than my smaller turbo, its not entirely relevant now that I have a GT-RS :P

I am pretty happy with the way it drives though, much smoother coming onto boost.

Unfortunately after 6 months of being f**ked around by yellow sticker, getting hail damage, and having it stuck at the workshop for 3 weeks getting tuned guess what.. its been raining all day yesterday and today, which means I can't really test the acceleration properly.

Simon-S14 Grand Master

Simon-S14

Posted
Posted

since we're posting set ups...

heres mine... stock neo motor, un opened except for poncams type b's, has AM performance stainless steel steam pipe manifold with custom collector, 3076, tial 44 gate, fmic, 3.5 inch exhaust, nistune, 600cc injectors and runs 50/50 ethanol/bp98

img0106rr.jpg

running 16 psi too... its crazy to drive and is very VERY responsive. torque chart was on the wrong read out when they printed it but it makes around 550 nm torque at the wheels.

SoFreshSoClean Proficient

SoFreshSoClean

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Check the wastegate preload SoFreshSoClean. If the actuator has some play in it, crack the 10mm nut and go a turn or two!

This wont need retuning because the AFM compensates for the extra air and adds fuel right?

Gonna have a look-see tomorrow. If its stopped raining. Which it hasnt. :)

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