Fuel problem for s/c apex

[insane]

I ran 180 miles with no issues. Started popping when going from mid to w/o for a few miles then went from there to popping and the afr was way lean up near 18. I have a 2:1 regulator with a fuel pressure gauge on it and the pressure was dropping from 45 psi to 25 psi back and forth rapidly. When i adjusted the regulator to a higher pressure(70 psi) it smoothed out and the sled ran fine. I thought I had a bad fuel pump(inline walbro 393) so I replaced that with an in line walbro pump gsl 392. Went out for a ride and sled ran fine for about 5-10 miles then it started going lean again and got progressively worse, the fuel pressure seemed like it was holding steady this time though. Also, both times the fuel pumps made a high pitch squealing sound when they started at the turn of the key. I am running the stock fuel regulator with the 2:1 reg in series with the stock injectors. I plan on modifying my stock injectors and using only the stock regulator, hoping the regulators are the problem. I just don't get why it ran great for 180 miles.

 

[kinger]

Sounds too complex with your fuel system. My upgraded 255 lph pump supplies plenty of fuel for my maxed out stage 1, with the stock regulator. Can u just do that or no?

 

[insane]

Complex, as in too many regulators? That's the way I'm leaning. I am running about 13-14 psi so I think I am at the peak of what my injectors in stock form can handle.

 

[insane]

Has anyone run both regulators together? What is the ratio on the stock regulator?

 

[heath@mpi]

How much boost are you running and hwat is your elevation?

thanks

 

[kinger]

Yes complex as in too much stuff on the fuel line. If I rear right your running two regulators, two fuel pumps correct?

The factory is a fixed regulator holding the psi spec (40-45lbs somewhere in there) your aftermarket one is a rising rate and tied to boost as you know so it ramps up as the boost does.

I'm not a fan of uping the fuel pressure unless you really are forced to its hard on the injectors to open and close with 60+ psi on them and can shorten life.

If it were mine I think a big in tank pump 255 lph, then the stock or the rising rate regulator but not both. Preferably stock would be best.

What boost are you running?

 

[DC5]

The factory regulator is a rising rate 1:1.

 

[kinger]

Really I never heard of that thought a regulator was just that regulates a certain fuel pressure.

Cool guess I learn something new every day...

 

[insane]

I'm running 13 lbs of boost. I'm pretty sure that with the modified injectors the stock regulator will be sufficient for what I am running as there are guys running alot more boost with the stock regulator. I'm just concerned that there might be something else wrong. I just wanted to know if someone else ran tandem regulators and had the same problem. I am only running one fuel pump as I got rid of the stocker and the stock pick up and installed hurricane's fuel cell plate with a filtered pick-up off that. It is really a nice clean mod for improving your fuel system. Correct me if I'm wrong but I believe these pressure sensitive regulators do regulate fuel pressure based on barometric pressure so that a efi sled doesn't have to change jetting based on altitude (in stock form anyway) the stock regulator is set at a fixed pressure and gives 1 psi of fuel pressure to 1 psi of boost where the aftermarket is adjustable and gives 2 psi of fuel for 1 psi of boost. They actually should work together as long as I set my mapping to the right afr for the combo. I just would like a scientific explanation on why I am going lean after the sled warms up.

 

[heath@mpi]

There is no reason to install 2 fuel pressure regulators.

The single 1-1 is best. if thats not enough change injectors.

 

[insane]

There is no reason to install 2 fuel pressure regulators.

The single 1-1 is best. if thats not enough change injectors.

I agree, and that is my next step, but why doesn't the two work? I guess one could be choking off the other one, but why does it not do it until miles into the trip? I guess I'll try this next step and if it solves the problem then I'll analyze what changed. Just trying to wrap my brain around this. Thanks for your help guys.

 

[heath@mpi]

13 psi is probably pretty close to injectors limits at sea level.