Whats the largest injectors a stock PCM can run?
05-09-2013, 07:46 AM
#21
You should have a boost referenced regulator. If that one isn't, get one that is.
If you have a fuel pressure gauge, then you should know if you're loosing fuel pressure. Only reason to be loosing fuel pressure is not enough volume. You can connect a light (like a shift light or something) to your secondary pump, so you can see when it's being energized, or if it isn't at all. This won't tell you if the pump is actually running, but it will tell you if it's being energized.
The best way to tell if the pump is running is with an inductive amp probe, but I would assume you don't have one.
If you have a fuel pressure gauge, then you should know if you're loosing fuel pressure. Only reason to be loosing fuel pressure is not enough volume. You can connect a light (like a shift light or something) to your secondary pump, so you can see when it's being energized, or if it isn't at all. This won't tell you if the pump is actually running, but it will tell you if it's being energized.
The best way to tell if the pump is running is with an inductive amp probe, but I would assume you don't have one.
05-09-2013, 02:27 PM
#24
Ok, done with work, so hopefully typing this out it makes sense. I saw this once before on a car (also using an Aeromotive FP regulator) where the return was not large enough and whenever you would start to get on it the fuel pressure would drop because the engine was actually USING enough gas to where the regulator was able to start regulating and not backing up causing the fuel pressure to go too high. So cruising along it would be steady and then as soon as we went into boost it would start dropping and then come back up after that. At first tuning it, it was throwing me for a mega loop. I could not figure out why no matter how much fuel I threw at the thing it would have a steep drop off and go lean right as we went into boost. Hooked up a fuel pressure gauge and saw what was happening.
To combat this, we just had to adjust the fuel pressure UP until at idle it actually started rising above 55 psi. This was also on a dual pump set up using twin 340's in the tank with one being boost activated. This is one reason when you use a very high volume fuel pump on a street car, it pays to get a larger return line and a regulator that will take at least a -8 or -10 return.
Hopefully this helps and solves the problem. It is worth a shot anyways!
To combat this, we just had to adjust the fuel pressure UP until at idle it actually started rising above 55 psi. This was also on a dual pump set up using twin 340's in the tank with one being boost activated. This is one reason when you use a very high volume fuel pump on a street car, it pays to get a larger return line and a regulator that will take at least a -8 or -10 return.
Hopefully this helps and solves the problem. It is worth a shot anyways!
07-06-2013, 05:06 AM
#25
So let me get this straight. I should not put too much credence into the IDC that HPtuners calculates based on injector pulse width? The reason I ask is I'm at ~82-85% IDC with 60lb injectors, but I'm also on the stock factory fuel pressure regulator, so at max IDC, the injectors are still seeing ~60psi rail pressure, but the pressure differential is only ~45psi. I'm sure I could gain some more room with the injectors if I went with a boost referenced regulator in the engine bay.
