Fuel Pumps

Joe Boruch

Joe Boruch

Member
In addition to SCCA sprint racing, I am on a ChampCar team that races a 5 liter Mustang in endurance races, ranging from 8 to 12 hours. We are having problems with pumps not holding up due to high fuel temperatures and occasionally running dry. We have measured gasoline temps up to 150 deg F. We are taking steps to route fuel lines away from exhaust and differential heat, but we will likely still have temps above 110 deg. We run 43 psi to the fuel injectors and about 12 gph. We use a lift pump into a surge tank and then a high pressure pump from the surge tank. Return is to the surge tank.

Does anyone have a suggestion of pumps that will hold up? Any idea what teams that run big races like the Daytona 24 run for pumps?
 
couple thoughts..
Are there other ways you can reduce fuel temps? i.e. better send/return line routing was mentioned, but what about insulating the fuel tank from exhaust heat and forcing air around it to help keep the tank cooler, etc?

No idea what the fuel temps were in my 240SX, but I ran that sucker 8 hours a day for yeeeears on a Walbro 255lph pump in Texas summers.
 
The Ranger super truck uses 2 facet pumps into a sump and inline ford HP truck pump. The pressure lines are run through the cheap insulation stuff and the return is snugged to the frame rails as a heat sink . You can use a Ford PS cooler as a fuel cooler on the return.
 
I am a firm believer in the Bosch 044. Its what BMW & Porsche Motorsport use(d) for a long time. I don't know if they have since moved on but it was as common as BBS wheels on those two German marques.
I have them on two cars and they are as reliable and robust as sunrise.

As suggested above I also have a fuel cooler in my system as well.
Was not my idea, when I bought my ex-Prodrive campaigned BTCC car they integrated one into the fuel system, Prodrive were the BMW works team in the BTCC back in the day this car raced, so I figured it had to have some benefit or they wouldnt have added it.
 
Thanks for all the suggestions. We have been looking into insulating the cell and getting air flow into the compartment where the cell is. Had the exhaust pipes wrapped near the cell. We will also look to see if we can incorporate a cooler into the return line.

The Bosch 044 pump was replaced by a FP200-7. One of the team members just did some heated fuel pump testing (ignoring our requests not to, but they survived unscathed). At least they did it outside. The FP200-7 flow went to zero at 110 degF. When cooled off it flowed at factory spec. Must have been cavitating above 110deg.
 
a couple more thoughts...

Where is surge tank/HP pump located? under hood? Perhaps you should run the return/bypass back to tank, so always working with newest/coolest fluid at surge tank. Relocate the HP pump if in hot spot...with a lift pump sounds like possible under hood? Do you really need the lift? Could you put HP pump back by tank? Of course in-tank pumps usually stay cooler, but personally, like external ones that you can "get to".....change.

Could use some finned tubing for supply/return... HVAC places should have some in 3/8" dia., might be copper or alum....don't know how/where you're measuring the temp....

Those Bosch 044 pumps are pretty bullet proof... however, many sold on ebay are Chinese knockoffs with all the good markings and box... They are limited to 5 bar (72-75psi) out put...if you want more, then Walbro makes one that goes higher at decent price...using the Walbro on Lucas mech injection on the SV engine.....running it above 100 psig @ fuel distributor.


Okie
Is your HP pump "pumping" faster than you lift pump? Might be starvation, not cavitation.
 
HP pump is in the "trunk" (its a hatchback) near the cell and the surge tank. Concerned that if we don't use a surge tank that the HP pump will suck air with a few gallons left in the cell in high G corners. Can't have engine cutting out due to fuel starvation.
 
The return line should return to the sump. The top of the sump drains back to the tank. Air and extra fuel leaves the sump tank at the same time.
This makes sure that the HP pump stays wet.
 
I didn't have such problems "feeding" a 100 horse Sprite engine, but suspect what others have hinted at: Your high-pressure pump is adding heat -all pumps do. The excess returns to the small surge tank and is picked up again and heated more in a short loop... Round and round, getting more heat. Get the return back to the tank where it can mix/cool with the fuel there. For example, Detroit Diesels had a similar two-pump system but the return went back to the tank. Any coolers in the lines will certainly help, as will insulation from the heat sources but that short loop is likely the problem. Joel
 
Too much pressure, and especially volume are not good. You want enough to run the motor at full power with a 20% safety margin. More than that it is like running an air compressor. The fuel is aerated and heated going through the system for nothing. If you have more than 20% run return to tank so it has time to cool. Run return from sump to tank as well. If the lift pump in tank will not keep up without return from motor feeding it that is a separate issue. Wrap your exhaust all the way up as heat is traveling back towards cell from the entire system, not just radiant heat next to cell. May not be as big a problem as we have on a rotary.
 
I'm running the 2nd pump (044 style) in a surge tank, with the return dumping there, but also a passive return path to the tank from this reservoir.

For heat management, the surge tank is behind the passenger footwell with feed/return lines (steel - I used 3/8" steel brake line, with AN tube nuts) routed through the car - to get it away from the exhaust. The surge tank IS adjacent to the last 18" of tailpipe, so I installed a heat shield on the pipe, and one off the surge tank mount.

The single best way to manage heat is with a head shield that has an air gap. This has a great impact on radiant heat transfer between the hot components and not-hot components.
 
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