mrfred

iTrader: (50)

I was right about the pressure drop in the stock fuel line. I measured a whopping 16 psi pressure difference between the pump housing outlet and the fuel rail at WOT 7800 rpm just before I let off. Its probably 1-2 psi worse at the pump outlet itself.

First set of pics below show the adapter I made up log fuel pressure. It just barely all fits in there. I had to tweak the 45 deg connector to get everything to line up. I would have loved to log outlet pressure using a pressure sensor, but it wasn't worth the cost of another sensor. I checked the accuracy of the gauge by starting the car, letting it warm up and then killing the motor. Fuel pressure holds high because the check valve in the pump outlet prevents pressure release. The gauge pressure matched the rail pressure of 43 psi pretty much exactly.

I ended up using my camera to make a video of the gauge during my WOT run. Worked like a charm and got good pressure data. The data plot shows pump outlet pressure sitting approximately 14 psi higher than fuel rail pressure for most of the run, and then as the motor revved out past 7500 rpm, the pressure difference increased to 16 psi with the pump housing outlet sitting at 84 psi just before I lifted. Fuel pressure directly at the pump outlet is probably 1-2 psi higher. During the run, I observed fuel pump voltage to be about 13 volts, so using the Walbro 400 data chart, I get an estimate pump flow rate of 250 lph at 85 psi and 13 volts. The FIC1100 injectors are at about 90% IDC (E85), so 90% * 4 injectors * 1.1 lpm *60 minutes = 237 lph. It all adds up pretty well, and basically what's happening at WOT is that my injectors are consuming all the available fuel that the pump can send with virtually none going down the return line. No eff'in wonder I can't maintain any margin of fuel pressure at the rail.

So there ya go. I think the bottom line is that anyone making more than 450 whp ought to considering running larger diameter fuel line from the pump housing to the rail. -6 AN is what most people run, and it should reduce the pressure drop to less than 5 psi at 500 whp of E85 fuel flow. Its either that or run a boost-a-pump, but that will likely drive pump outlet pressure up to 90+ psi where the pump flow begins to fall like a rock.

One other comment I'll make is that running -6 AN line will likely allow a Walbro 255 or DW300 to support significantly more power. My guess is that anyone who has been able to make more than 500 whp on either of these pumps with E85 was running upgraded fuel lines or a boost-a-pump. Either that or their fuel pressure was falling off without them knowing it.


Adapter assembly to allow monitoring fuel pump outlet housing using stock fuel feed lines. The adapter that attaches to the pump housing is Russell PN 644120 (I had previously incorrectly listed it as 670340). Its sweet. They also make one with a -8 AN outlet.



Here's the installed adapter assembly. It just barely fit.



Video of the gauge during the WOT run. I double-stick taped my point-and-shoot camera to the back of the console. Kinda cracks me up.
http://youtu.be/6oueiLW-5P0


Here's the data plot. Currently making at least 485 whp DJ. Might be closer to 500 whp.



Here is the Walbro 400 flow data. Pump was at 13 V and 84 psi at liftoff. Interpolating between 85-90 psi and 12-13.5 volts, I get about 250 lph of flow which is just barely enough for 500 whp.

way2qik

iTrader: (5)

Dude, this is AWESOME info and testing. Thanks for taking the time to do it and share your conclusions.

BTW, I maxed out Buscher's double pumper system (through the stock fuel lines) at about 760whp on a Mustang dyno on E-85.

I just switched everything over to a -8 feed and -6 return along with two new Walbro 400 s on the double-pumper. Will be shooting for 850-900 in a few weeks.

mrfred

iTrader: (50)

It certainly was an eye-opening experiment. My feeling at this point is that a fuel supply line upgrade can do more for fuel supply than a fuel pump rewire, and its not that hard to do.

I'll bet that pump pressure was 95-ish psi when you were running double-pumpers on the stock fuel line. Net fuel injector pressure was probably falling to about 20-35 psi depending on your boost level. You'll have massive amounts of flow with your new setup, probably 3x the flow capacity.

mxguy1286

iTrader: (11)

<mistake>

RSMike

iTrader: (1)

he's using E85, not normal pump fuel.

Awesome testing results, it's always a great feeling to prove yourself right with solid data. Well done

mxguy1286

iTrader: (11)

The male end all the way to the left that will allow the stock line to clip onto, have the P# for that? I need that

mrfred

iTrader: (50)

Russell PN 640940.

mrfred

iTrader: (50)

I've now got Earl's -6 AN braided stainless teflon hose installed from the pump to the rail. What a PITA... took me most of the day to get it installed reasonably cleanly. Below is a pic of the fittings I used to mate the hose to the fuel pump outlet. Total cost of fittings and hose was around $120. The hose is super tough and impervious to any fuel, but its super stiff. If I were to do it again, I'd be tempted to use Earl's high-end hose with the ultra flexible teflon and kevlar braid. Its 4x the cost though. At any rate, the -6 AN hose had virtually no flow restriction, and pressure at the pump outlet was only ~3 psi higher than pressure at the fuel rail. That's a 12-13 psi pressure reduction which is good for about another 50 lph of fuel. Net injector pressure now looks to be holding 44 psi across pretty much up to max fuel requirements.


Fittings at the fuel pump outlet



Log showing only ~3 psi difference between pump outlet pressure and fuel rail pressure

n2oiroc

iTrader: (33)

excellent! im glad more and more people are doing things the smart/correct way instead of tuning around pressure drop. there is zero downside to larger fuel lines. any added volume between the pump and regulator can only do good.

n2oiroc

iTrader: (33)

btw, russell also makes the same fitting in a direct push on model.

http://www.summitracing.com/parts/RUS-640853/

EmeryatSTM

iTrader: (79)

With the 400 pump we were able to make about 510 whp on E-85 with the stock wiring. Once we added a rewire kit the car was able to make 586. This happen on both Evo's and DSM's for us.


-Em

mrfred

iTrader: (50)

Yeah, I've seen that one. I think the one I'm using is a little more compact which is helpful for the tight space.

Factory fuel supply line?

ZeroGravity

mfred, in post #16 you're listing the adapter that attaches to the pump housing as a Russell PN 670340.

But when I check on the Summit Racing website, it shows a Russell Fuel Pressure Take-Off :

http://www.summitracing.com/parts/RUS-670340/

Would be great if you could list the part number of the adapter to the pump housing in -6AN and or -8 AN.

Thanks for your help and testing!

mrfred

iTrader: (50)

Oops. Correct PN for the quick connect that attaches to the pump carrier outlet is (3/8"): blue = 644120, and black = 644123

Also, if anyone wants to connect to the metal hardline, that is a different size (5/16"): blue = 644110, and black = 644113

getsideways

iTrader: (18)

Any updates on this?