Lack Of Power

[Muff]

Hay guys, had my gtr tuned a while back and it was lacking on power something fierce.... it running 350 hp at all four on 15psi.... it built and all the rest... ive changed the exhaust twice and seem to not change anything.... the only thing i can think is the exhaust is very quiet for a 3.5 inch hks..... it got a high flow cat. but i cant seem to find the problem.....maybe the turbo???? maybe the manifold?? maybe the exhorst????

any ideas would be great....

thanks

ps would like it to spool bout 1000rpm earlier, any ideas also would be great....

oh yeah the turbo comes on about 5200 rpm full boost... i think thats a little late but not to sure.....

[Morgs]

You might want to post a little more detail..... what sort of T04Z/manifold/gate/engine specs/fuel system/ECU/dyno sheet/etc

[PM-R33]

Ok first thing you gotta ask yourself, does it make much more power on much more boost. If the answer is no, you know you have a problem.

You said you changed the exhaust twice, as in the catback? That usually aint going to do shit as the exhaust restriction is usually due to a collapsing cat. What "high flow" cat is in there?

What does the power graph look like? What are the turbo specs? What ECU?

Also if it was tuned a while ago and made that power on 15psi, what did the tuner say? Why did he leave it like that and give it back to you.

Need more info man.

Edited April 20, 2010 by PM-R33

[R31Nismoid]

Full part list required, nowhere near enough detail to debug a 450rwkw setup with a couple of lines

[STATUS]

what happened when you dialed in 18-20psi?

[PM-R33]

Thats what I would like to know

[Muff]

sorry guys. its got- stock cams. garret t04z .70 and .84. jap manifold. tial copy 44 mm gate. 3 inch dump. 3.5 inch magna flow cat brand new. 3.5 inch Hks exhaust. 044 pump in tank. 780cc injectors . vipec comp. tuned by godzilla motor sport. made 280Hp on 11psi. 350Hp on 15psi. 380Hp on 17 psi. my exhaust is really quiet. my mate has same exhaust and can't even tell my car is on when he is sitting next 2 me at the lights. we tried swaping exhaust and taking cat Out no difference yet. but haven't checked on dyno.

[Adriano]

Does your mate have cams, they make an exhaust louder. TBH you arent much down on power, you are only running 15psi, and teh power does increase with boost. Do you have cam wheels?

[discopotato03]

A feller I know recently was playing with an RB26 in a VL , it had a 6Boost manifold with a 44mm TiAL and a GT3582R with the 1.06 AR turbine housing + questionable 3" exhaust .

He felt he made significant gains by having a 3.5" exhaust all the way through , just about everything I've seen indicates that the exhaust needs to be BIG right behind the turbo and if I was you I'd strongly consider having a 3.5" if not larger dump pipe .

That feller mentioned above also found that the 44mm waste gate wasn't coping and boost crept upwards , had a different fitting welded on for a 50mm Turbosmart gate and that solved the creep problem .

From memory he had a 100 CEL cat fitted , don't remember which brand .

For the record does the turbo and manifold use a T3 or the larger T4 sized mounting flange ?

A .

[Harey]

A feller I know recently was playing with an RB26 in a VL , it had a 6Boost manifold with a 44mm TiAL and a GT3582R with the 1.06 AR turbine housing + questionable 3" exhaust .

He felt he made significant gains by having a 3.5" exhaust all the way through , just about everything I've seen indicates that the exhaust needs to be BIG right behind the turbo and if I was you I'd strongly consider having a 3.5" if not larger dump pipe .

That feller mentioned above also found that the 44mm waste gate wasn't coping and boost crept upwards , had a different fitting welded on for a 50mm Turbosmart gate and that solved the creep problem .

From memory he had a 100 CEL cat fitted , don't remember which brand .

For the record does the turbo and manifold use a T3 or the larger T4 sized mounting flange ?

A .

+1 a 3" dump pipe behind a T04Z is criminal. 3.5" at an absolute minimum.

The other thing I would try is running it on the dyno without a cat, so just using the dump pipe.

[STATUS]

Power and response see about right for your combo, This GTR only made 369hp @ 15 psi and 461hp @ 17 psi the T04z is a cop on a std rb26 until 20-24psi (decnt manifolds do help a bit).

The same setup then made well over 500awhp @ 22psi. Your boost response seems about right too for your setup.

[STATUS]

Just for shits and giggles check out the gt2860-5 @15psi versus To4Z @15 psi, i wont post the -7's or -9's as it is even better again.

The T04z needs minimum 20psi to wake up and a redline of 9000rpm, not ideal for a stocker.

[discopotato03]

Yes I'd have thought a GT3582R/GT3540R (same) would have been better on a reasonably std and std capacity RB26 , particularly if the manifold has a T3 flange .

Cheers A .

[SimonR32]

Just for shits and giggles check out the gt2860-5 @15psi versus To4Z @15 psi, i wont post the -7's or -9's as it is even better again.

The T04z needs minimum 20psi to wake up and a redline of 9000rpm, not ideal for a stocker.

interesting... r32-gts t04z was making 520rwhp on 16psi and mine made over 500 on 17psi

both were also making loads more torque between 4000-5000rpm compared with the graph you posted... something wrong with the setup?

[Muff]

well im seeming to agree with you guys about the dump, but have seen the same turbo come on harder alot earlier with the same set up. and make more power at 18psi...... there is a gtr at godzilla motorsport that runs the same turbo and has made 540hp on 18psi , the only differance is a set of cams, and a sub zero manifold, and a 4" dump + cat back.....

i am not running cam gears yet.. the are sitting in a box under my bed atm...... as cams would be good also - any sugestions????

the engine is rather fresh and godzilla motor sport didnt want to push it to hard......

as for response id like to drop it buy about 1000 to 1500 rpm...... so im thinking :cams : cam gears: 3.75" dump: sub zero manifold : hpc coating:

any thing else would be great......

ps i ran a set of standard turbos with same engine and it ran 330 kw on 19 psi..... and came on at 2500 rpm... would it be cheaper putting some steel wheels on these and boosting them up????

[Muff]

would it be worth going to a .70 / .70 ???? so changing the rear from .84 to .70?????

your thoughts

[R31Nismoid]

330rwkw from factory turbos?

That aside... have you even spoken to Godzilla yet about this?

[Muff]

it is a t4 split pulse also....

[Muff]

Yeah, they said to put cam gears in it, change the exhorst ( remove the middle muffler ) change the intake pipe (pod set up) and maybe a cold air box...

out of that the exhaust has been change to a hks 3.75 inch, pod has been moved into the guard with a cold air box.....

the only thing im waiting for is cam gears to go on , i just dont want to put cam gears on it and them 6 months later put cams in... trying to figure what to get for it.,.....

sorry it was 330 hp.... was looking at the wrong sheet...

[Muff]

Say I was to go to a Gt3582r, Yes my manifold has a t3 flange, would that drop my response and produce the same sorta power??? im looking at about 500hp..