Which Walbro??

[Diverteh]

Was just looking on Ebag for the 393 and load of hits came up for the 392. The 392 seems to be slightly cheaper but with a higher flow of 255lph.

Why does everyone seem to go for the 393? Can the injection system not handle the increase in the flow rate of the 392, or is it something else?

I have just installed 360cc injectors.

[Charlie @ Evergreen]

Both will work fine the 393 less gpm and draw vs the 392 being the highr flowing 255 pump will be good with the HI injectors.

Just think about the Fuel Pressure Regulator controls the pressure. So you will have plenty of flow for the higher HP levels and bigger injectors.

[Betterthanfabio]

I wouldn't go for anything that draws more amps. The charging system already has enough to deal with & was beefed up slightly to handle the fuel injection anyway. The one we use has more than enough pressure on a modified engine. I suppose it has the advantage of a bigger flame front if the bike catches fire.

[Charlie @ Evergreen]

That is likely important but would say bet Walbro newer design pumps take less amps to run then the old 80s fuel pump designs?? Maybe someone has checked this out. No one has had any issues with over 10 installed including my own. So that is good information to have or would not recommend it. When I had all those extra electrical gauges added for FP, Boost, AFR, plus my Speed Hut gauges had a intermittent surge now and then. Went back analog on all except the Speedo and RPM removing everything it went away. So yes the amp draw must be important.

[DEATH_INC.]

In My case with the high boost and higher fuel pressure, the 392 on it's own will draw more than half the amps that the alternator puts out. I know that's only at full boost, but it also draws higher amps off boost too. Made worse by the fact I run a bumped up n/a alternator. I run the 'high pressure' 195lph pump.
Here's all the numbers;
https://www.autoperformanceengineering. ... specs.html

[Diverteh]

Thanks for the prompt reply guys.

I intend to run with 810, 360cc injectors, pcv with Autotune, fpr, bov, larger boost pipework and a gt2056 with ported spider, dyna 2.2's etc.

Electrics are witchcraft to me. I've had a look at the APE table and to be honest with you, I don't understand if the difference is significant. Which do you recommend??

Sorry for the dumbass question

[DEATH_INC.]

If you're chasing big HP/boost go with the one I did, a high pressure 195lph model (GSL394-max pressure 87psi). It was the best balance between amp draw and fuel flow at high boost. I was running up to 30psi boost with 45psi static fuel pressure.
Otherwise lower boost and fuel pressure will be safe with a standard 190lph model (GSL391- max pressure 50psi).

walbro.jpg (72.95 KiB) Viewed 4876 times

[nadrol]

You guys should look at the flow charts and use a fuel pump calculator. the listed max pressure is very misleading.
Calculator: https://deatschwerks.com/pages/fuel-pump-calculator
flow charts: https://walbrofuelpumps.com/walbro-gsl3 ... -pump.html
https://walbrofuelpumps.com/walbro-gsl3 ... -pump.html
https://walbrofuelpumps.com/walbro-gsl3 ... -pump.html
https://walbrofuelpumps.com/walbro-gsl3 ... -pump.html

the 391 flows a few more GPH under boost than the 393. The 394 flows a few more GPH than the 391. 392 flows 40% more than the 394.

At 65psi (20psi boost) and 12v:
393: 28 GPH, 7A
391: 32 GPH, 8A
394: 33 GPH, 8.5A
392: 48 GPH, 10A

75 psi (30psi boost) and 12v:
393: 26 GPH, 8A
391: 27 GPH, 9.5A
394: 31 GPH, 9.5A
392: 45 GPH, 11A

WHP required pump flows:
150: 16 GPH, 23 GPH E85
250: 27 GPH, 38 GPH E85

I'm using a return-less (low current ) boost referenced system on E85 and the 393 is plenty. shooting for 150 wheel.

391, maybe 394 is the most any of us should need.

[Würstchens-Turbo 810]

i use a 393 ,about 200 PS rwp ,about 20 psi boost

[Lorcan]

The 393 was recommended, by me, back in 2005 because it had the flow required but was a lower current draw than the more commonplace 392. I had previously had issues with flat batteries running a Weldon alcohol pump and a high power ignition on my dragbike, so went for a Walbro that was big enough but the lowest current draw on my petrol bike.

I'd still go for the smallest pump that does the job. No point running an oversize pump that wastes electrical energy circulating fuel around the system when the charging system is already marginal.