PROBLEM: Power dies off straight after 5600rpm and engine feels very constipated.

Does anyone have any experience with fitting an external gate to a turbo that has an internal and getting the little one welded up.... does the reduced gasflow going down the main exhaust reduce backpressure a lot and increase power? (assuming screamer pipe) or would it make little difference?

I was thinking that by fitting an external gate with screamer pipe and welding my turbos internal shut, that I could reduce backpressure in the top end by a fair margin where the engine feels really constricted and get maybe..20-30 extra hp all over or at least hold ~340hp till 7000/7500

Or would I get a better top end improvement with bigger cams? and leave my turbo as an internal gate...

Thanks for any advice.

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don't know for sure but could the turbo be a bit small? Specially for your 2.5.. Where does a GT25 usually die off?

I think the external gate could help I spose

how would an AVO400L go?

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K.E.R.S!!!1

GT25 isn't a huge turbo. Lots of Silvia's and 180's run them with good results.

I'd look at a bigger turbo.

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you mirin?

turbos very small for a 2.5.. i would look at getting a GT30R or GT35R.. but cams do die off in power around 5500-6000rpm...

Changing ur cams would be a good idea however u need a turbo to be able to flow alot of air in the high rpms..

I dont think an external gate would help much on a lil turbo...

Being a lazy motor a GT30R would work perfectly with the sti cams.

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www.racewars.com.au

I was going to go against the trend here and recomend a bigger turbo.

Seriously, id be looking at maybe a HKS 2835 pro ... awesome response and will go close to 400hp @ the wheels.

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or 3037

Evos seem to be getting good results with it

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M POWER

Seems like it comes on pretty late for a turbo that is potentially too small for the 2.5. I would want to be spooling up way quicker than that if the turbo was too small. Gonna be even peakier with a bigger huffer.

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Rotor of Fail
Ducati 998s
Ducati Streetfighter S
496 CI Injected Big Block. Carbon positive???

It might actually be a backpressure issue from being so small causing it? Ie its so choked it cant spool... how do i explain .. all this air from the 2.5 rushing to get into it but this tiny little things going "i cant accomodate all of you youll have to line up!"... but looking at the chart again I agree Blaise, way too late.

3037 is ok if your keen for outright figures, but if response is important (im not sure what the goal is for the car, track or getting chopped by simon on the freeway ) then 2835 be a better option

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I think its a bit of a dog hybrid ie. there is a HUGE diff between compressor wheel and turbine wheel. The turbo is rated to 44lb which is only 5lb less than the 500hp FPGREEN but the turbine is a fair bit smaller than the FPGReens.... so you sorta get a rush of boost and then a choke point after that. I think it spools slow because its about a 7 year old turbo....

So what turbo should I get then

GOAL is for streetable between 3500-7500 but still with some top end choppage to be had on the freeway... dont mind sacrificing 20hp up top for 20hp extra on the left side of the curve. .... Id like to run 20psi from 3600-7500cutoff and might as well be an external gate if I am going to the trouble. Do GT35R's spool any sooner than 4500 on a 2.5?

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