What would cause me to lose HP?
I would first adjust your clutch pedal so first and reverse goes in good. Just back it out until it goes in easily when car is warmed up. It might be a bit touchy when cold.
Too far out is not great either, you don't want it to engage way too far from floor. A badly adjusted clutch can make it slip and kill it fast. My cartech died at only 450 engine hp in like a 1000 miles and didn't realize it was the clutch until pulled it out and looked at it. Figured something else was wrong with the car. Put in new tex and car gained like 200 hp back! And the mph came back as well.
And you can do some simple things. Take out the driverfs side plugs..front three or so and mabye couple on other side. Take a pic or show us them. I would not do leakdown right now. You could do compression on the ones you take out .The engine might need some more miles to seat properly. And it might put a bit of oil out the back again until the rings seat properly. Its new motor and you can't have that many miles on it yet do you??
Then if you can get a scanner to check timing and knock retard while driving around that will tell us a lot. Wideband would also tell us more.
The GTO use the same turbos don't they and think the base c5 kit? Have to check the site. And don't think problems with the turbos is very common. Not to say it can't happen but again the 20g mits are normally super super reliable.And they are rebuildable.
The easiest thing to do is a leak down right now, plug out, tester in, ta-da results! 5-12% is around the norm, any more and i would ask a few questions.
Where was RPM picked up on the dyno? Plug wire? Balancer? Rollspeed?
The only reason why im pushing to leak it down is, if you were on the edge of detonation and you rattled it really good with the timing advance, this can and WILL break a piston. 60hp doesnt just vanish, 200hp is a huge amount to loose.
When you dynoed you would have heard the clutch slip, and or smelled it. The textrailas die all at once from what i have seen, either that or they weld up.
Also if he took out anything major in the motor isn't it going to be doing the 007 thing out the back? I might be old fashioned but usually only do leakdown if compression looks low and want to know whats up more precisely but seems to me from what I have seen with blown up turbo cars the ringlands let go but that is on the non forged pistons. And those cars put out massive blue smoke. Blown head gasket of course puts out lots of white smoke. Coolant in the oil ,overheating and all that stuff. His engine is forged at least so thats a good thing.
Also if he took out anything major in the motor isn't it going to be doing the 007 thing out the back? I might be old fashioned but usually only do leakdown if compression looks low and want to know whats up more precisely but seems to me from what I have seen with blown up turbo cars the ringlands let go but that is on the non forged pistons. And those cars put out massive blue smoke. Blown head gasket of course puts out lots of white smoke. Coolant in the oil ,overheating and all that stuff. His engine is forged at least so thats a good thing.
The boost graph should look like a normal graph up untill it sucks shut.
We had it happen with a car around the same HP, when it did the boost went up to about 8psi (normal boost), then soon after it laid over beacouse of the inlet duct, and the boost cut in half. One turbo will NOT make 700hp plain and simple.
The inlet duct is a HUGE issue on these, once they get heat cycles they get gummy and are more flexible. This IS a flaw and should be taken care of.
I would say to just be safe, check motor, then pull ducts and make a run.
I have been down this road before as far as chasing the ducts, it was a pain!
The only thing that might 007, is the front shaft seal sucking out, seen this as well! Not pretty, it does 007 for real.


