33gtr : Decrease In Power After Tune

[humble]

Hi All

Ill give you the story:

Good mate of mine has a 33GTR with twin N1 turbo’s, cams exhaust, full rebuild etc…. got approx 260RWKW’s on a very reputable workshops dyno. This is with a standard computer on 14psi

He has just gotten his car back after having the head reco’d due to a cracked gallery?? And also got a PowerFC installed and turned. All other components are the same.

He got 203AWKW @ 12psi with this tune. This again was from a reputable workshop although not the same one as mentioned previously?

We understand that having dyno’d in 4WD compared to RWD will show loss of KW on a graph.

The question is: why would it drop approx 60KW after the head was fixed and a PowerPC has been added to the mix and tuned??

Poor tuning??

Dodgy Job??

From what my mate said the workshop owner advised that the Head was also decompressed??

[a20089]

Loss of power directly from these two items

2 psi less

AWKW

General differences

Different Dyno

Different weather conditions, different adjustments for the weather conditions

Yes it could also be a doggy head job, bad tune. Without back to back testing it's very hard to say but the first two things I listed probably contribute the most.

Hi All

Ill give you the story:

Good mate of mine has a 33GTR with twin N1 turbo’s, cams exhaust, full rebuild etc…. got approx 260RWKW’s on a very reputable workshops dyno. This is with a standard computer on 14psi

He has just gotten his car back after having the head reco’d due to a cracked gallery?? And also got a PowerFC installed and turned. All other components are the same.

He got 203AWKW @ 12psi with this tune. This again was from a reputable workshop although not the same one as mentioned previously?

We understand that having dyno’d in 4WD compared to RWD will show loss of KW on a graph.

The question is: why would it drop approx 60KW after the head was fixed and a PowerPC has been added to the mix and tuned??

Poor tuning??

Dodgy Job??

From what my mate said the workshop owner advised that the Head was also decompressed??

[SLIPPERY]

maybe it was running out of fuel and the tuner backed it off a little earlier in the rev range, or took a lot of timing out cause it was detonating.

There are too many factors

The questions is.....how does it feel to drive now, compared to before?

If it feels just as good or better then theres no problem

[R31Nismoid]

Does the car feel a lot slower or not?

Have you spoken to the workshop in question?

I mean, without an idea from them on the situation... you really cant do a lot

[humble]

well personally it seems to be less "break ya neck" than prior then again i havent been in the car for approx 2 months and its been off the road for about 1 month.

the current dyno run with the tune was done 2 days ago at about 7pm..... nice a cool (freezing) night

the previous run was done about november 2006 from what he said the day was nice but not cold

100% agree with 2psi less and 4wd compared to rwd dyno but you would think that which a tune and fixed head it would have compensated for that??

i just confirmed with him that the tuner told him that the head had been cracked for a while and should have been picked up whilst the previous workshop had it.

November was the time cams, turbos and rebuild was done then dyno'd.

this afternoon i strongly suggested that he take it back to the shop and have them take a look but on the way there his tyre blew due to random screw.

well see what the shop says tomorrow

[ferni]

Power seems a little low, stock turbos you can get about 250rwkw on 14psi, N1's i'd expect a bit more with a bit more boost.... my old setup had 258rwkw and about 240awkw to give you some idea..

something isn't right.

[humble]

hopefully the issues will be sorted today when the car goes back to the shop.

I advised that he also take it to another shop to get opinions after a dyno run.

any recommended shops?