Power Loss? All Standard R33 Gtr

[GD51LA]

After some research i believe my s3 r33 gtr is making less power than it should, 162 AWKW.

Long story..Stock standard gtr, i removed the original exhaust and put a 3.5 stainless turbo back, everything was good...for a few hours. i put my foot down and i felt a hesitation in power, at that very moment i looked at the standard boost gauge, the boost was down and the engine immediately felt weaker. and still feels weaker. On a cold night the car some time gets very lazy, the boost on the standard gauge goes down and the car take ages to rev?? i have taken it to three different mechanics two of them gtr owners/tuners.

There is a small hiss coming from under the plenum, we covered the area in water but it still didn’t go away. One mechanic said that it cause that much of a power loss??

Anyway, we checked the following

Coils...Ok

Volt sensors on the exhaust..Fine

Air flow metres..Fine

Turbo... working fine

When on the dyno the boost level was fine?? (Even though my standard gauge is still down...how could my gauge fail at the same time i lost the power???)

vacuum leaks... none

Air/fuel...ok

Looked inside the cat..Ok

Compression...All 6 at 175

Removed the rubber hose and the spring is in the right place

Did a smoke test..Ok

Here i am few hundred dollars poorer, and still have the same problem??

Any input is greatly appreciated

What else should i check?

[Trozzle]

reset ECU by disconnecting battery for like 15 minutes. Also check vacuum line going to boost gauge, as if it is reading low perhaps there's a split/leak in it.

Jammed actuator(s) for turbos, or wastegate(s) stuck open. Give that a shot, as if they're open a little bit it will cause boost to build very slowly/the car will feel like a slug...what boost was it making and when did it make it?

[GD51LA]

standard boost+exhaust, the dyno was showing 11 to 13psi

how do i check the actuators?

[MrR33666]

hissing sound from plenum and boost guage not working sounds like vac leak in boost guage line.

[-_-StRyDeR-_-]

  MrR33666 said:

hissing sound from plenum and boost guage not working sounds like vac leak in boost guage line.

+1

[STATUS]

BOV vac line.

[GD51LA]

I haven't worked on a Gtr before so excersise some patients boys

Ok, where do I find this hose?

[TUF250]

would a vac leak cause those symptoms? i have no idea im just curious myself.

[Scradly]

Vaccum leak going to the BOVS will cause them to open under full load as there wont be enough pressure in the vac line to keep them closed , causing your power loss.

[MrR33666]

  Scradly said:

Vaccum leak going to the BOVS will cause them to open under full load as there wont be enough pressure in the vac line to keep them closed , causing your power loss.

doesnt explain the boost guage inop

[gotRICE?]

  MrR33666 said:

doesnt explain the boost guage inop

Are you sure? I would have thought if the BOV's were being pushed open then all the boost would be blowing straight out.. Thus the Bov not reading properly as the air is not reaching the plenum.

[TUF250]

what about a normal vac leak, say near the manifold, would this cause an issue?

[Moodles2]

  MrR33666 said:

doesnt explain the boost guage inop

Have a feel behind the back of the balance tube, the hose may of popped off or split in half that supplies the factory boost gauge's MAP sensor.

[3LGODZILA]

id be replacing all the standard vac/boost lines with silicone ones. they're old and brittle

ur symptoms point towards that too - hissing noise, loss of power & incorrect boost pressure reading

i had a similar prob with mine, when i installed my boost gauge a few days later it started doing the same things, obviously when i installed the T piece, the standard hose was brittle and split

[-GTR-]

I know you said hissing was comming from plenum, however i had exact symptoms and slight hissing sound, it was the turbo to front pipe gasket had blown a chunk out. try finding the hiss with a silicon pipe/tube in your ear. worked for me.

[GD51LA]

Could I have a lazy fuel pump?

[t_revz]

lazy fuel pump will cause detonation and will pop miss and break pistons all the way to redline but doesnt fit your symptoms.

[GD51LA]

what about lazy coilpacks? when its cold it pops & missfires

there is 10 to 20kw missing, i paid allot for this car, this is realy giving me the sh ts

what else could it be??

here is the plug, they reckon its about right

[WRRR]

Instead of using water to trace the "hiss" trying using aerostart or similar.

If you have a vac leak (thinking gaskets?) your revs will rise at idle if you hit the spot with the spray. ie more fuel.

Gasket leak will also bleed boost at higher rpm.

Might be worth a try.

Cheers

[GD51LA]

the plenum gaskets look like they have been changed

its only a 60k car, are the plenum gasket a common problem?