I am replacing the factory fuel pump mine is shot, I have the ati boost pump inline, should I replace the fact FP with an Ac delco or an aftermarket HIPO brand?

 

There are many options you can do here but if i were you I would replace your factory intank pump with a walboro 255 LPH (liter per hour) GSS340 Model Pump. Racetronics sell this pump with a hard wiring kit. If you buy this kit and pump for around 200 bucks or so you can get rid of your inline pump. I you just want to replace the pump itself, then just ge the Walboro 255 LPH pump without the harness, most places sell them for under 140 bucks.

do a search for Walboro pump or racetronics and you will find out more.

 

The 340 will let me eliminate the boost pump? Are you running one? If so any problems? Direct fit, any mods? Fuel pressure ok under boost?

 

I am running one with no inline pump. I have not put the blower on the car yet but the Walboro Flows 255 LPH and the ATI inline pump flows 243 LPH or so (according to ATI) I was told it would not be needed. I got my pump from Modern Muscle sports (i think) and got my hard wiring harness from racetronics. Do yourself a favor and send an email to racetronics and buy thier pump and wiring harness together. I think they sell it or around 210 bucks or so. If you go this route you will have enough fuel volume and pressure with the GSS340 model, that you will not need to use the loud inline pump from ati. I was also told that the ATI pump will also choke the Walboro since the ati pump flows less than the walboro.

Do a search on this Forced induction board as it will give you a better understanding, this topic has been discussed many times before.

Hope that helps.

 

I think there's some misunderstanding about in-line pumps. Let's take the simplest example. You have two identical pumps, each rated at 70gph @ 50ppsi. A single pump or both in series will flow approximately 70gph @ 50psi (it's more complicated than that, see the link below). But raise the pressure, and the dual pumps in line will flow more than the single pump. That ability to maintain flow as pressure is increased is why in-line boosters are so often used with an FMU. The FMU will significantly raise pressure as boost rises. Example: a 4:1 FMU will give 80psi @ 10lbs of boost when the base pressure is 40psi. An FMU is most often used when continuing to use "small" injectors after a SC install. When using an FMU, it is usually necessary to use an in-line booster. If you are using relatively large injectors, and therefore not using an FMU, you may not need an in-line pump. FWIW, the stock LT1 regulator is best thought of as a 1:1 FMU.

Here's some math on the subject. http://www.eng.fiu.edu/evrglads/cwr3...r8/lectur8.htm If you think about, predicting flow is really imposible with the information the pump manufacturers make generally available. Worst is a hp rating, but "x GPH @ y psi" is not a whole lot more useful. What we really need are curves of flow v. pressure at various voltages. If anyone has such info, it'd be great if they would post it.

Rich Krause

 

Rich,
Thanks for breaking it down, kinda makes sense now.
Thanks for your explaination.
So when using a fmu 2 pumps are better than one in this type smaller injectors i have accell 24 lb with a fmu.
Man thanks alot.

 

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Yep, for your combo a stock intank and in-line should do fine. I used a similar setup up to ~450rwhp.

Rich Krause