? Difference between walbro 255 and Ed Peter's Viper Pump

[Reaper1]

On my '88 Shelby Z I had to upgrade to 5/16" return line. I couldn't get my pressure below something like 60#'s even with a vac source to the reg.

I'm running a 255HP pump, +40 injectors, Accfab reg, FWD S5 cal.

[wheming]

Thanks for all the input.
I was leaning towards just replacing it with a stock unit. I'd like to keep the set-up how Gus designed it, and you helped me make up my mind.

I've had a new pump to replace the secondary in the engine bay also, just need to get the right fittings to install.

[DblTrbl]

Nice to see you keeping Slug stuff going.

I personally like the two pump setup. I believe 2 stock pumps will outflow a Wallbro 255 (no testing, just gut feel). Having said that, the only drawback is that there is now an extra point of failure.

BTW, I use two very large pumps in my Neon because I was dropping fuel pressure at 22 psi.

[Reaper1]

^^do you run them in parrallel or series?

Also, so you know the +'s and -'s of each of those set-ups. This is something I've been pondering about for a while now...

[DblTrbl]

Quote:

Originally Posted by Reaper1 ^^do you run them in parrallel or series? Also, so you know the +'s and -'s of each of those set-ups. This is something I've been pondering about for a while now...

Series. These pumps have a hard time with high volume at high pressure. The series configuration helps them maintain the volume at the higher pressure. 55 base + 30 psi of boost = 85psi. Very few single pumps can maintain high flow when you need it most.

With paralell, both pumps are pushing against each other. Both working very hard.
With series, they help each other, both under less load.

[Reaper1]

Thank you very much! That solved a problem I was wondering about for a long time!

[wheming]

Didn't see this in time, but yes, Slug's pumps are in series. The secondary is only activated under higher boost via pressure switch to power an auxiliary relay. The same relay also powers a light on the boost gage to indicate secondary pump is running.
I may add a second indicating light to light the in cowl fuel pressure gage, during the day it is clearly visable, however may be handy to see at night.

It is very effective, and lower buck than one of those super pumps. The secondary pump in Slug i think was a junkyard or take off when someone else went to a big pump. It is still working. Although occasionally it sounds like it is pumping marbles...

[DblTrbl]

Quote:

Originally Posted by DblTrbl Series. These pumps have a hard time with high volume at high pressure. The series configuration helps them maintain the volume at the higher pressure. 55 base + 30 psi of boost = 85psi. Very few single pumps can maintain high flow when you need it most. With paralell, both pumps are pushing against each other. Both working very hard. With series, they help each other, both under less load.

Sorry guys, I may have mislead you.

I was running out of fuel with the two bosch pumps I had in series. So I installed two Wallbro externals in parallel. Although there may have been a wiring issue with one of the series pumps, I have way, way more fuel now with the two Wallbros in paralell. So much fuel that I could only log a few blips over 10:1 on an entire 1/4 mile run using the same cal as the two series pumps. It ran like crap needless to say..

Theory is some value, but testing is better. I have not had any full power (high boost/high fuel pressure) runs yet because my AEM was acting up, but early tests show more fuel in paralell. Yes the pumps are working harder, but this is racing after all.

[BAKES]

i put the holley pump in the omni #12-904 255ltr universal mopar when i pulled the pump out of the box it was igraved holley pump by walbro on the side of it
sorry for late post to line 15