I'm just over 400rwhp on a factory style Walbro 255. Important part as the Racetronix style upgrade for the power wire feeding the pump from the fuse block.

-Brian

 

I'm just over 400rwhp on a factory style Walbro 255. Important part as the Racetronix style upgrade for the power wire feeding the pump from the fuse block.

-Brian

Brian,
I am not at a point of needing to upgrade or replace my fuel pump. Do you know if there is a wiring upgrade kit for the factory pump. Assuming my car still has a factory pump, no telling what previous owners may have done. If so do you know if upgrading the harness to the existing pump may help extend the life? I have no desire to drop the fuel tank if I don’t need to for a pump replacement.
-Dan

 

At one point I did some calculating and the stock pump was around 125 lph, if I remember correctly. I just tried searching on ISSF and didn't find it. You can pretty easily calculate how much fuel you need based on a BSFC of 0.35. I just remember being shocked at how much overkill the 255 pump everybody loves to "upgrade" their relatively stock cars with, given that we have a return-style fuel system; overpumping just heats the fuel up.

If I could build my own fuel system, I'd use a return-less variable pressure fuel system with PWM and variable voltage control on the fuel pump, allowing the injectors enough dynamic range to fuel reliably down to 400rpm and then all the way out to redline at max airflow. But.. that's not how these cars were setup. So I upgrade the wiring to the stock pump on my relatively stock cars and call it good.

 

Yes it's probably overkill. Part of me bought into the hype, but it's reported reliability is better than the parts store brands available and I wasn't putting my 270k factory back to use on a brand new engine and risk it dying during break-in and wrecking something else.

-Brian

 

Dan, lots of people like the kit from Racetronix. I was re-wiring alot of my engine harness anyway as part of my swap to the LS computer so kinda did my own mods using an additional relay and spliced in the trigger at the fuse box. The Racetronix kit is plug and play. I haven't looked in a while but Innovative Wiring is the other place I would Google to see if he has a plug and play kit. I have their headlight and battery harness upgrades in my car.

-Brian

 

Some random musings here.
Remember pump ratings are typically at pump, no pressure, optimal voltage.
Horsepower used in calculations is non power adder crankshaft HP

That said the only stock GM pump info I have personally is
330 rwhp , stock pump at 10 volts would not lean out . LIKELY no leeway though.

Yes a variable output PWM pump with no return would be the end all, with some caveats

Thing about non return systems ( yes every fi street car I own has one)
Any gulp, burp, bubble ,the only way out is though an injector.
Any hot soak of the rails that causes vapor, that vapor has to go out the injector.
If you built a PWM returnless system that was variable presure and ran super low pressure at idle and low load you might be inviting boiling fuel in the rails.
My LS7 is returnless, 58 psi.
It in a narrow band of outside temp,engine temp, time parked, will be soggy for a couple seconds on restart.
It uses a Kinsler high flow flapper door style, check valve and does not hold pressure for ever.
I surmize it is "eating"fuel vapor.
If designing from scratch with a PWM pump controlling pressure, I would be tempted to keep the pressure up to reduce possibly of vaporising fuel and better atomisation from nozzles.
Also a return regulator off the rails set at a higher pressure than set in the pump.
This for two reasons.
You could set the pump to run full blast on key on, this to purge hot fuel and any air on start up.
Also as a fail safe if the pump had a runaway.
Just my thoughts.

 

To add , in my case , my walbro 255 runs at zero pressue,so it,pumps at about 200-210 liters per hour.
My "044" at 58 psi is about 210 liters per hour
This more or less falls into the 600 ish hp range I am likely in.

 

Does anyone know what the current draw is on the factory pump?

 

Stick your multimeter probes in the fuse box ?

 

30Amp Amp meter for fuses. Weirdly enough I was testing a fuel pump with it last.

All my other meters max out at 10Amps.

 

I would but my multimeter has been MIA for a few months and I haven't talked myself into spending the money to replace it.

 

In the name of science.

Stock regulator no reference, so 47 psi ish.
I did use meth , no need to burn the garage down to answer a question.
I tried my fluke first but was seeing a voltage drop as it is only rated to 10amps so I brought out the cheapo inductive, which has shown to be quite accurate.

 

Awesome - Thanks for doing that. Seven amps is more than I would have thought! Guess that explains why the wiring is so important on these. If someone upgrades to a higher flow pump, I'm guessing it will draw more current (assuming same fuel pressure and same pump efficiency) which would make the wiring even more critical.

 

Lots of good info in here

I'm currently trying to set up a drop-in ready fuel sending unit with pump.

Currently on the stock LT1 - stock cam, heads, etc, with the bolt ons - cold air intake, full 2.5" exhaust with long tube headers, but the car sees a lot of extended high rpm use on the road course AND will eventually be refreshed to LE heads/cam road race style build - aiming for the 350-400whp mark.

Looks like 400ish whp is the mark where a lot of folks talk about upgrading the fuel system?

Curious to hear thoughts or links to threads where this has been discussed with currently available pumps.

Thanks!

FWIW I think you'd be fine with a Walbro 255 with pretty much any N/A Lt1 setup you could dream up except for the most extreme setups. At 400whp I think you'd be fine, but if you wanted a bit more wiggle room you could look into an Aeromotive Stealth 340 pump. Pretty sure you could make one work either drop in or with very little modification to the bucket/hanger. Knowing with how you push your car and the type of racing you do, I would upgrade the pump and harness regardless of whether or not the stock pump could handle the power levels. Reason I say this is because your car probably spends a significantly higher amount of time at higher RPM's than the average street/strip car and the pump is seeing higher pressure/load more frequently and for longer sustained periods of time. I'd rather be ripping around a track with a walbro 255 working only half as hard as it could be than having a stock pump going max effort to maintain fuel pressure under load.

With the 255 drawing more amps and the fact that your car sees such frequent race track use with sustained/frequent high RPM's could mean more heat in the harness than the average street car would see running that same setup. Heat, like length, also has an effect on particular wire diameter's ability to handle current. May be overkill, but if it were my car running say a 400-450whp N/A stroker being frequently raced, I'd do the following.

Walbro 255
10 gauge power
10 gauge chassis ground
Stock fuel lines should be fine.
Regulator of your choice

I doubt you really need 10 gauge, but can't hurt to upsize.

Only other thing I'd think about is fuel control, but if you aren't having any starvation issues now out on the track I assume you only run it with a decent amount of fuel in the tank? Wouldn't want to be leaning your new motor out.

 

Lots of good info in here



FWIW I think you'd be fine with a Walbro 255 with pretty much any N/A Lt1 setup you could dream up except for the most extreme setups. At 400whp I think you'd be fine, but if you wanted a bit more wiggle room you could look into an Aeromotive Stealth 340 pump. Pretty sure you could make one work either drop in or with very little modification to the bucket/hanger. Knowing with how you push your car and the type of racing you do, I would upgrade the pump and harness regardless of whether or not the stock pump could handle the power levels. Reason I say this is because your car probably spends a significantly higher amount of time at higher RPM's than the average street/strip car and the pump is seeing higher pressure/load more frequently and for longer sustained periods of time. I'd rather be ripping around a track with a walbro 255 working only half as hard as it could be than having a stock pump going max effort to maintain fuel pressure under load.

With the 255 drawing more amps and the fact that your car sees such frequent race track use with sustained/frequent high RPM's could mean more heat in the harness than the average street car would see running that same setup. Heat, like length, also has an effect on particular wire diameter's ability to handle current. May be overkill, but if it were my car running say a 400-450whp N/A stroker being frequently raced, I'd do the following.

Walbro 255
10 gauge power
10 gauge chassis ground
Stock fuel lines should be fine.
Regulator of your choice

I doubt you really need 10 gauge, but can't hurt to upsize.

Only other thing I'd think about is fuel control, but if you aren't having any starvation issues now out on the track I assume you only run it with a decent amount of fuel in the tank? Wouldn't want to be leaning your new motor out.

Good notes on the wiring upgrades. I'll definitely look into that.

Does the 255 Walbro drop right into the stock sending unit otherwise?

Fuel control is somewhere on the list as well. May do a smaller custom tank in the stock location, as I don't particularly like the high CG of a trunk mounted fuel cell, nor do I want to give up the trunk space - as funny as that may sound for a "race car" - I still load it up full every time I drive to the track.
Currently, I run the tank FULL up as much as possible, as it prevents fuel starvation, reduces slosh, and hopefully helps keep the pump and wiring a bit cooler. It does also help with rearward ballast/balance, but it would be nice to be able to lose some fuel weight and then try to get similar weight out of the front of the car....

 

I THINK the racetronix plug and play harness kit uses 10 gauge wire from what I remember installing it on another B body I had but I never actually measured it. It would probably be the easiest way of doing it.

 

If our fuel pump is the same as the LT4 fuel pump when / where it matters, it should be able to handle 345-360 horsepower @ 43psi with little concern.
Wiring upgrades on our cars are seldom a bad idea.
(eats popcorn in hopes of learning more …)

 

More trivia.

LT1 pump , free flow with about a foot of 3/8 hose , 4.52 amps
Peak amps on start up with no pressure head 4.64 amps
Again methanol, not gasoline
PCM current draw at rest, both batt and ign circuit 0.47 amps

96 lt4 295-305 ish at the wheels

 

More trivia.

LT1 pump , free flow with about a foot of 3/8 hose , 4.52 amps
Peak amps on start up with no pressure head 4.64 amps
Again methanol, not gasoline
PCM current draw at rest, both batt and ign circuit 0.47 amps

96 lt4 295-305 ish at the wheels

Awesome - Thanks for sharing this! Was the pump in Post 12 a stock LT1 pump?

 

Yessir,
Stock used factory pump

 

One thing about the relay and oversize fuel pump wire kits.
They work well and I get why they are built with the relay at the rear .
This so they are completely bolt in- plug in.

I would submit , if a guy is a do it yourselfer, I would have the relay at the front of the car near the fuse box
This so the large feed wire running front to rear is only energized when the pump is running, not live all the time.
Now if you have a rear mounted battery, rear relays such as I have make more sense.

 

That is what I did. My new FP relay and fuse lives right next to my fuse box and I ran a new 10ga wire back to the tank, down the pass side frame rail.

Brian

 

The disadvantages of more pump than the motor needs are they demand/consume more amperage ,and tend to have shorter lives. All that additional fuel just goes back to the tank ,warming up that fuel. I've had my Impala for 25 years ,and 170k miles. Replaced one fuel pump over 10 years ago. Once you have something that deliver enough fuel. The ability to deliver more is of no real advantage ,and likely come with built in drawbacks of their own.

 

If i remember correctly the racetronix upgrade harness powers direct off the alternator giving the pump a voltage boost as well