Contour Enthusiasts Group Archives Forums Modifications Forced Induction Fuel pressure confusion. Whats the deal?

Well I don't think it is the fuel pump, it runs all the time at full tilt and is regulated by the FPR...which should be plugged into vacuum/boost as I said. That will take some error out.

You have several other heat related factors however:
- injectors themselves run at a lower duty cycle normally, in back to back runs they could be getting hot though this is a small possibility to me.
- oxygen sensors could be reading differently as the heat sets in.
- IAT sensor could be getting too hot and not cooling down on its own between runs if it is mounted before the intercooler but after the turbo.

More like the O2 sensor and or exhaust temp the cause:
If the O2 was read with a tailpipe sniffer then it could be affected as the turbine and exhaust components heat up. Hotter exhaust components can at the least help the exhaust gasses continue to combust for a longer period of time, maybe lowering the measurable air fuel ratio at the tailpipe.
On top of that, do you have a catalyst? If so then that may be more of the issues. The catalyst would be especially sensitive to the hot/cold exhaust factors in terms of 'light-off' time; as in if you did the first run cold without a warm cat, and then the others as the system progressively warmed up.
And even if you don't have a cat, if you did the first run cold (without a good 15min drive on the road shall we say) then the heat the exhaust system is leaching out of the exhaust stream will result in less complete burn.

If you did like I do, drive to the dyno 100miles on the highway, pull in and do a run while the car is still quite hot, then I don't know what to tell you other than look at your FPR and your O2 sensors.
On my runs, all of them where I didn't dyno at ADC were made by driving 60-100 miles to a dyno to meet an appointment and then doing the runs. I am impressed that my engine was able to set down 350+ HP at the settings it did, right off the street with a full catalyst exhaust. It also agrees with your system running about 14psi anbd with lower compression producing around the same numbers.
What I can't wait to see is what that setup you have will do on 18-20psi.

From what I saw in your dyno graphs I wouldn't worry too much about it as long as your fuel pressure isn't dropping, as long as your MAF voltage isn't near maximum during the run, and as long as your injector duty cycle isn't over 85%.
With those factors kept in check then you can just keep going up two-three psi at a time.