Question about fuel pressure

[TheShit]

When looking at data logs, while at WOT and high rpms, what is the min fuel pressure for a stock fuel pump with bap?
Is there a point where you don't have enough fuel pressure to do the job? And is it a simple PSI number?
And if you upgrade the fuel systems, does the PSI go up while at WOT and high RPMS, or does it stay around a set or desired PSI?

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[NGOT8R]

Here’s a little info. from a nitrous data log that I recorded with my DW400 pump and JMS BAP. If you look at the numerical columns to the right, you‘ll see the rpm and fuel pressure range.

 

[NGOT8R]

Here’s a short video that I just recorded in an attempt to determine where I want to set the high and low fuel pressure limits in my progressive nitrous controller. I went WOT just to see what the max. and min. pressures were. The sweep is very fast, so I recommend dragging the video frame by frame and looking at the rpm and fuel pressure to see actual values.

 

[NGOT8R]

@TheShit what high and low fuel pressures are you seeing with the stock pump and BAP on your car?

 

[TheShit]

@TheShit what high and low fuel pressures are you seeing with the stock pump and BAP on your car?

It was dipping into the low 30s, but only in 4th gear (6 speed)
at 6k RPM at WOT I had 70PSI, then at 7k RPM it drops to 31psi.
After 7k RPM it would go between 30psi and 35psi until we let off at 7800rpm.

 

[NGOT8R]

It was dipping into the low 30s, but only in 4th gear (6 speed)
at 6k RPM at WOT I had 70PSI, then at 7k RPM it drops to 31psi.
After 7k RPM it would go between 30psi and 35psi until we let off at 7800rpm.

Oh okay. Have you been experiencing hard starts when your engine is warm? If so, it’s a good chance that your fuel pump could be dying.

 

[NGOT8R]

Here’s some more food for thought.

https://www.mustang6g.com/forums/threads/suspected-bad-fuel-pump-2019-bullitt-on-e85.189945/

 

[LOL WUT]

It was dipping into the low 30s, but only in 4th gear (6 speed)
at 6k RPM at WOT I had 70PSI, then at 7k RPM it drops to 31psi.
After 7k RPM it would go between 30psi and 35psi until we let off at 7800rpm.

Any signs of the car leaning out as the pressure drops via the AFR/Lambda readings? 30psi at WOT seems a little sketchy.

 

[TheShit]

Oh okay. Have you been experiencing hard starts when your engine is warm? If so, it’s a good chance that your fuel pump could be dying.

After the Dyno run where I ran into that fuel issue, I replaced the fuel pump with a DW400 and a BAP. I guess I'm trying to figure out what to look for as warning signs, or what the limits are of the fuel system.

 

[LOL WUT]

After the Dyno run where I ran into that fuel issue, I replaced the fuel pump with a DW400 and a BAP. I guess I'm trying to figure out what to look for as warning signs, or what the limits are of the fuel system.

You should be looking at injector duty cycle (IDC) to help determine if the pump is maxing out. A reading of 49.9 IDC equates to the pump being at 100% capacity.

Also, as you have been doing, monitor fuel pressure accordingly. I no longer have the factory system but I believe you’d want to maintain 50 psi or higher throughout a WOT pull. A dip to 30PSI at WOT would be enough for me to not go WOT until changes are made.

In conjunction with monitoring your PSI, watch your AFR/Lambda to see if the car is starting to lean out at WOT as PSI drops. When this happens, things go boom.

 

[NGOT8R]

After the Dyno run where I ran into that fuel issue, I replaced the fuel pump with a DW400 and a BAP. I guess I'm trying to figure out what to look for as warning signs, or what the limits are of the fuel system.

Oh okay, well that leads me to believe it could also be related to the DW400 pump. Do you know if yours has a check valve in it? When I bought my DW400, it came without a check valve. I think I got one of the older versions of the pump that had been sitting on the vender’s shelf. My car was always hard to start afterward. It would start, die, start, die and finally start. I ended up installing a DW check valve in the factory fuel line which fixed that problem.

 

[HKusp]

The stock fuel rails on the Gen 3 are suspect much north of 700whp. Also on the gen3's the DI pump should be doing a lot of the work. Who tunes your car?

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