Fuel Pump Duty Cycle Problem

[Vette Killer]

Hi All,

Had the car on the dyno a couple of weeks ago and came across a challenging problem to understand. The numbers were good (618 RWHP on a Mustang dyno at 3500'...the dyno is notoriously stingy...lol) but we ran into something neither Matthew or I have come across yet. The fuel pump duty cycle pegged at 46% instead of 50% and fuel pressure started to dip at 5500 RPM +. The car never leaned out and we ran it up to 6500 RPM this time; I am going to go after cleaning up the sock first for the pressure...assuming I got bad gas somewhere as with less than 12,000 km on it there is no way it should need cleaned yet.

Has anyone run across this duty cycle issue before? Matthew has seen it once on a modded Ford GT that he is working with Ford on and even their engineers could not ID what the problem is; they replaced pumps, drivers, software etc and no change.

Would really appreciate some help with this one, hoping someone else has run across this one; I plan on going to the Fore triple hat as part of the next HP updates (alum beefed up block/bottom end, heads, cams etc.) and want to make sure this issue is out of the way before I move to the 1000+ crank HP range.

Thanks,

Rob

[Birdman]

Hi All,

Had the car on the dyno a couple of weeks ago and came across a challenging problem to understand. The numbers were good (618 RWHP on a Mustang dyno at 3500'...the dyno is notoriously stingy...lol) but we ran into something neither Matthew or I have come across yet. The fuel pump duty cycle pegged at 46% instead of 50% and fuel pressure started to dip at 5500 RPM +. The car never leaned out and we ran it up to 6500 RPM this time; I am going to go after cleaning up the sock first for the pressure...assuming I got bad gas somewhere as with less than 12,000 km on it there is no way it should need cleaned yet.

Has anyone run across this duty cycle issue before? Matthew has seen it once on a modded Ford GT that he is working with Ford on and even their engineers could not ID what the problem is; they replaced pumps, drivers, software etc and no change.

Would really appreciate some help with this one, hoping someone else has run across this one; I plan on going to the Fore triple hat as part of the next HP updates (alum beefed up block/bottom end, heads, cams etc.) and want to make sure this issue is out of the way before I move to the 1000+ crank HP range.

Thanks,

Rob

Rob,

@618 on an unaltered Mustang Dyno you are really making about 680rwhp on a Dynojet
The max fuel pump duty cycle setting in the tune should be changed from stock .46 setting to .50 to allow for you increased fuel needs.

If this has already been done and you saw more than a 2 lb drop in pressure then you need to upgrade to the dual FGT pump set up now which will take you to well over the 800rwhp level.

I had to do this upgrade on mine when mine was at about the same power level you are at now.

hope this helps.

George...

[Vette Killer]

Rob,

@618 on an unaltered Mustang Dyno you are really making about 680rwhp on a Dynojet
The max fuel pump duty cycle setting in the tune should be changed from stock .46 setting to .50 to allow for you increased fuel needs.

If this has already been done and you saw more than a 2 lb drop in pressure then you need to upgrade to the dual FGT pump set up now which will take you to well over the 800rwhp level.

I had to do this upgrade on mine when mine was at about the same power level you are at now.

hope this helps.

George...


Thanks George,

Appreciate the input, I am actually looking at the Fore triple hat rather than the dual FGT...figure if I need to go into the tank I might as well get it to the fuel delivery level it needs to be at for future mods rather than spend $ twice like I have been....lol

Rob

[Birdman]

Thanks George,

Appreciate the input, I am actually looking at the Fore triple hat rather than the dual FGT...figure if I need to go into the tank I might as well get it to the fuel delivery level it needs to be at for future mods rather than spend $ twice like I have been....lol

Rob

Given your long range goals that would be the prudent thing to do while your at it but a dual pump set up is plug and play while the triple pumps requires an expensive add on pump controler (another $800 or so) that isn't necessary for you right now. You could always install the triple pumps in the Fore holder but only connect the two pumps for now.