My turbo is a T3/To4e from a rev hard kit and its a/r is .50. At the track the other day when I went from 14 to 17 pounds all the car did was pick up 2 mph and lost a tenth of a second. both times were run with similiar 60 foots. I am just wondering if I could have maxed out my turbo all ready. These passes were made on a stock block and head so i figure if it was leaning out it would have blown up. Could it be possible that the boost was not allowing the vlaves to close and causing it to not run up to par at higher boost levels. thanks for the help. I really would like to figure this out becuase i am looking at building this car into a big hp set up.

 

Yes, you could concievably be getting out of the efficiency band of the turbo. Your ECU may also not be mapped well up to 17 PSI so it may be delivering too much or too little fuel.

I recently kicked my new turbo setup up from 5 psi to 8 psi and felt NO improvement. Sure enough, I put it on a wideband and at 5 psi I was at 11.5:1 AF and at 8 psi I was at 9.5:1 AF. Trimmed the fuel down and power picked up instantly!