Frustrated & Confused

[72nismo]

Originally dynoed stock Ka-T on datsun 510 came out with 250hp at 10 psi.Blew motor so i rebuilt with CP Pistons only.Went back to dyno and only hit 230 hp at 15psi. WTF!!! A couple frinds have said to check cam timing and ignition timing. I've already double checked and everything looks normal. Anybody else have any suggestions???

[eazye2000]

What is the compression ratio on the new pistons?

[s13rb25det]

did you use the same dyno? and what is the c/r on the new pistons? were you told it made 250hp or did you really see/dyno it.?

[72nismo]

C/R 9.1. Car was dynoed at the same place were I phisically saw what the car made on the dyno. The one thing that the dyno guy said was that I still needed to break in the motor.Aside from that he noticed a big lag at the beginning of take offs.Which I never had those issues with the stock motor.

[WDRacing]

Break it in hard, then re-dyno it. If it was a fresh build the rings weren't even seated.

[72nismo]

Ok but is that what would affect the lag on take offs?

[WDRacing]

What are the AFR's? Just cause you didn't change anything doesn't mean there isn't a problem. Lag could be a turbo going bad, could be really rich, which would account for the power loss.

Need more to go by other then "lag on take off" what does that mean exactly?

[72nismo]

AFR's were at 10.5 - 11. A little rich. In regards to turbo going bad i dont know but the car doesn't get driven much but on weekends sometimes so I can't see it going bad but you never know.

[WDRacing]

The turbo can go bad with just running a 10.5:1 AFR bro. At that afr you're allowing fuel into the oil...a quick check of my charts and it apears that oil and fuel aren't a good combination.

WD

[72nismo]

Ok. Any suggestions on how to check for that?

[480sx]

If your still making boost, chances are your turbos fine. Just check your oil to see if it smells like gas. If it smells like gas at all you need to change it.

You can check your turbo by trying to move the shaft side to side, and in and out. A little side to side play is normal. If you have ANY in and out play your turbo is toast.

10.5 is pretty rich, you can lean that out and make a good bit more power. Im leaning towards your tune being one of the reasons your not making as much power as you expected.

Yeaaaa you really just need to finish breaking in the motor dude.. Your rings wont be fully steated till 1500-2000 miles or more.

[72nismo]

Turbo is still boosting. I will check it anyways. I have a JWT Tune.