Gtr Down On Power

[arsnic_apple]

Hi guys,

Recently had my 32 Gtr on the dyno to fix an unrelated boost controller issue which has now been solved. However the problem is my car has lost roughly 150hp since it was first tuned.

Specs of my setup

Stock 26 motor

Type B Poncams

3582R

All supporting mods, Exhaust, Fuel etc.

It was tuned on a hub dyno originally and made 510hp at the rear. Just recently my tuner has bought his own roller dyno which is what my car has recently been on. Obviously you expect some power loss because of the different dyno (he has a few other cars which have been on the same hub dyno as mine and they have experience about a 10% drop in figures). So now im trying to figure out how my car has gone from 510 all the way down to 365.

I have checked the following things;

-Ive removed each piece of the exhaust and checked for blockages and there is none (no cat)

-Ive done a compression test, 152-158 across all cylinders

-Ive taken the timing cover off and rotated the engine until the timing marks on the cam gears lined up with those on the head. Not sure if there is a way of me getting the motor to TDC without being able to see the gear at the bottom to ensure i have checked that the belt has not skipped a tooth? The belt and tensioners etc. were changed prior to the car first getting tuned.

When the car was on the dyno there were no obvious reasons as to why the car had lost power. It held boost fine, AFR stayed constant...Tuner said between 7 and 8k rpm it started to break down a little which may be because of the stock coil packs, but couldnt cause 150hp difference.

I've run out of ideas and its doing my head in, so any suggestions would be great.

Thanks

[GTSBoy]

I'd suggest, unless it feels significantly slower than it used to, that it hasn't lost any real power.

Trust conversion/comparisons between dynos at your peril. If the ignition timing is the same, the boost is the same and the AFRs are the same, and there are no blockages or boost leaks, then the power shouldn't be much different.

One thing you didn't say you'd looked for properly was boost leaks.

[rondofj]

I recently lost a lot of power on my car and did all i could to get it back. Timing was bit retarded and advancing it got a lot of it back.

BUT then I did my service which was overdue - plugs, oil flush/ new oil, oil filter, new air filter - BAM a completely different car!

Service - a simple overlooked thing. Do it if you havent/

Edited November 13, 2014 by rondofj

[Stixbnr32]

Yeah boost leaks? Clutch slip? Wheel spin on dyno due to bad rubber on the roller since you said you are not using 4wd (you said rear's)?

[arsnic_apple]

I can see what your saying with comparing dynos, I'm just concerned because the variance is so large. In terms of boost leaks, couldn't hear anything when it was on the dyno and held boost fine. I'll have a closer look at the intercoooler pipes and stuff anyway. Car was serviced probably less than 2k ago. Good tyres and good clutch. He has just had another gtr on there, had - 5's, similar cams and 17psi...made 370? Does this sound about right or should it be more also?

[XGTRX]

you sure not comparing hp to kws?

[arsnic_apple]

Haha maybe we he computer is getting mixed up between HP and kW. But screen was definitely saying hp

[XGTRX]

What does your arse dyno say because if it has dropped that much it would be a totally different car to drive.