Originally Posted by
Kevin@JPCRacing
You're out of pump. A lot of these cars are hit or miss because they are on the ragged edge of the pumps capacity. Your pump might be getting tired or a dirty sock/filter is affecting it. If you put a brand new stock pump in the car you might get lucky and gain 10-15psi, but, that is still not what the desired pressure should be. All the stock fuel system cars drop pressure with a power adder. I've seen lots of low boost cars drop to the 45-50psig range, subtract the boost from that and you would be in the 30-35psi delta range. The only thing keeping these cars alive are the oversized injectors. If your pressure is dropping to 34(I'll assume you are running around 10psi boost and quoting gauge pressure), your actual fuel injector pressure delta is around 24psi. You are probably pegging the injectors or the fuel trims are maxed out. One thing I highly recommend on the "pressure droppers" that aren't near as bad as yours, is to model the Inferred Rail Pressure vs Fuel Flow table to match what the car is doing. If you do not have it correct, you will end up with the maf curve jacked up higher than actual and it will throw everything off(airflow and load calculations).
One last thing, don't worry about the alternator settings. The BAP acts like a step up regulator. If you have it set to 17 volts, it don't matter if the input voltage is 12 or 14, you will still have 17 coming out of it. It isolates the pump from the rest of the car and the alternator settings will not make a bit of difference as far as the pump is concerned.
Kev