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Built Gtr Not Making Power

Shazz

By Shazz,
in Engines & Forced Induction

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GTRNUR Grand Master

GTRNUR

Posted
Posted

Smoke tests don't just find holes or split hoses. You may well find an over tightened clamp has pinched the hose somewhere....

I've been down this path so many times before that I don't even bother tuning a car anymore until the intake manifold can be pumped up to 20PSI with an air compressor with just the output pipe from the twin turbo pipe being blocked.

The last GTR I tuned the guy was taking back to the same tune shop time and time again... its making less power bla bla bla. Have you pressure tested the intake... (my mechanic said he checked it over...is the response. Most likely a visual inspection of all the hoses and clamps)...

Most leaks are that small you can only hear them when everything is very quiet. But for your power loss its got to be a decent leak.

The next biggest tell is if you are using MAF based tuning and a power fc. You can compare your old and new fuel maps. If the current map is using a heap less fuel for the same airf low measured, then you definatly have a leak.

Ants Grand Master

Ants

Posted
Posted

+1 for smoke test.

I think you have a leak somewhere. Whether due to over clamping or split pipe. That would explain why you are making less and less power, as more pressure is being vented into the atmosphere!

Shazz Collaborator

Shazz

Posted
  • Author
Posted

Alrighty.....

Carried out a pressure test today not 100% sure on exact pressure, however I found two leaks. First one is on the silicone joiner to the plenum, its quite substantial. Enough so that it relieved the pressure in about 8 secs or so.

The second leak. This one only appeared as te pressure was almost gone. Where the throttle linkage attaches to the throttle body has a minor leak, so hopefully a new spring washer should fix that. However it only leaks as the pressure drops, so obviously when under pressure it's sealing.

So I will sort these out tommorow and re pressure test it. I do believe that this may be the reason it's not making more than 15psi boost. However I don't think this could cause a 100hp power drop at 15psi.....

Now that I'm looking into it all, the tuner has retarded the timing with the cas as much as possible. Ehich seems odd, so I'm thinking the timing may be a tooth out...,,

Shazz Collaborator

Shazz

Posted
  • Author
Posted

Alrighty, so fixed the leak I had in the intercooler piping. I'm now able to dial in as much boost as I desire. However it still feels doey. Running 16psi and 26psi certainly doesn't feel like a 10psi difference in power....

I'm now leaning towards a timing issue. Am going to investigate it further

Shazz Collaborator

Shazz

Posted
  • Author
Posted

Problem solved!......well not solved but diagnosed. Turns out the front turbo has a shagged bearing, im thinking from possible oil starvation. explains why im now making boost but not as much power. Also why its shuffelling its ass off! so now comes decission time rebuild, replace, or go single........

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