Up to what hp can I run a single 255lph Racetronix fuel pump? (with bigger injectors, of course)

I want to run a T76 gts turbo on a 383 LT1 and need to know if my feul delivery system will suffice. Thanks

 

It won't be up to snuff. You'll need a dual pump setup for that blown 383 setup. Factory lines and filter should be fine though.

Ken R.

 

255lph pump is good to 800 hp at 43.5psi

Now depending on how much boost you want to go you may need a second pump.

 

I only want to run up to 15psi on a 383 LT1 with a D1SC procharger. That's in the 600-650rwhp range. Are you saying one Racetronix 255lph fuel pump will do the job? I'll probably need a boost-sensitive adj. fuel pressure regulator or boost-a-pump though, right?

 

A boost referenced regulator, which will up your pressure with boost, therefore requiring more fuel. I run the Aeromotive boost referenced LT1 reg. I started leaning out pretty quick past 11psi or so and couldn't get much more out of it no matter how high i took my tune, so i upgraded to dual in tank pumps. I had to take a bunch of fuel out of my tune after that and my a/f was flat lined through my dyno runs up to 14psi too.

Ken R.

 

You can't calculate the engine's fuel requirements from rear wheel HP. The fuel demand is deteremined by flywheel HP. A blower engine also has a much higher brake specific fuel comsumption (BSFC) than a normally aspirated engine, so you need to take that into consideration as well.

You also have to know what fuel pressure you will be running, and at what fuel pressure the Walbro pump is capable of flowing 255LPH. As fuel pressure goes up, the pump's flow capacity goes down. Can the Walbro flow 255LPH at 43.5psi?

I'd also question the ability of a 255LPH pump to support 800 flywheel HP. That would represent 800HP at a BSFC of 0.50 #/HR/HP and would not provide for any return to the tank, which is required for the pressure regulator to maintain the pressure. A blower engine will have a BSFC higher than 0.50 meaning its very unlikely you can do what you want to do with a single pump.

I make 800 flywheel HP on a dry nitrous setup (all the fuel through the injecotrs) and I run dual Bosch 205LPH pumps at 58psi.

 

Does anyone know what the psi at which the Racetronix 255lph fuel pump flows?

Actually, according to Procharger's site, a D1 or D1SC would give 75% hp increase(12-20psi) on a 350. Assuming i start with 430-440rwhp(stroker+cam), 75% gain would put me at around 750rwhp ON A 350. I assume I'd get more power with psi on a 383. So, I want to be able to run up to 15psi(maybe in the low 800rwhp range). Rich said he used a single 255lph in-tank pump and a KB for 700rwhp on a 383(?) So, I could get to the 700 range with that fuel set up, but if I want past 10-12 psi, I'll have to spend around $2000-$3000 on a new fuel system.

 

IMO, you're not gonna get 750rwhp, 20 psi from a D1SC on your combo for a number of reasons. Besides, looks like you've got an
A4 so that ='s more drivetrain losses. I think your previous estimate is more accurate.

 

So you don't think my a4 will make 750rwhp even at 20psi with a D1SC?! I must respectfully disagree. The D1SC is rated much higher than 750rwhp on a 350. I'll be putting it on a fully modded 383(with a custom blower cam) with an LT4 top end. A4 or not, 750rwhp is very attainable at even 15psi in my application.

but the proof is in the pudding: you have a stroker LT1 with a D1SC and a custom BRE cam. What rwhp do you make and at what psi?

 

20psi will not make 750rwhp on a car with LT1 heads and intake.

Rich

 

If it was so easy to just make 750 h.p. like that then everybody would be doing it



I don't see you making it with that combo....maybe 550

 

FWIW, I don't happen to think extremely high fuel pressures (which torture the pump) are required to make power. What IS required is sufficient fuel volume at the injector tip... and for boosted applications that means fuel pressure has to rise with boost. The solution is lower static fuel pressure with higher volume, so the pump isn't trying to provide high volume at the same time it provides high pressure.

As far as "What will the racetronix pump do..." Someone take the time to read the name on the pump itself, not the outside of the box. I doubt seriously Racetronix suddenly went into the fuel pump manufacturing business. [It's a Walbro pump]Flow charts for the pump are available online, showing what volume the pump is capable of at what pressure... and given a specific voltage. Short form is this: a given pump, provided with 12.2 volts at the pump, may well be able to flow 255 LPH at 45 psi, but might only flow 105 LPH at 70 psi.

Injuneer's totally correct about the BSFC issue, and fuel requirements will therefore be (significantly) higher than you might think if you ignore BSFC.

there's a couple factors to look at:
Efficiency, viewed as worst case BSFC
Worst case voltage to the pump
Age and condition of the pump, since it's not gonna get better with wear
Desired/expected HP output
Resistance to flow, determined by... pretty much by fuel line size.
Last but far from least: SAFETY MARGIN

I'd like to tell you the single 255 will be fine, but I'd be inclined to say the safety margin is far too thin, and you probably would need to increase the size of feed lines, put a relay on the pump and a very large gauge power supply wire to provide full battery voltage to the rear of the car, and add a bit of prayer to have it work.

Oh yeah... how to get lower static pressure with higher volume: Big injectors and fuel lines. Replace the feed line with bigger braided, and use the factory feed line for a return. Recalculate injector 'size' at the new lower static pressure, tune accordingly. Don't go too low, some injectors get really non-linear at lower pressures (but probably not as badly as they would at excessively HIGH pressures). Run 'less' pump than you would otherwise need, but overall still get what you are aiming for, correct fuel VOLUME into the cylinder for whatever your airflow calls for.

Yes, this requires a bit more math and likely more tuning effort than a simple, yeah, throw a really good (expensive) pump, or more than one pump, at the problem to meet the volume need at some insanely high pressure... but ultimately it'll get the job done, and very likely pump life and overall cost will be significantly better as well. This will make the lower pressure setup more reliable as well.

 

I'll just ask John at futral. They'll be doing the install.

Oh, Rich its an LT 4 top end. Sorry, didn't explain. Induction mods are in sig. LT4 intake, Holley 58mm tb, GTP LT4 stage 2 ported heads, replacing cam with blower cam and adding 383 Lunati stroker and D1SC.

 

Trust me, you'll want to do dual 255's in the tank now if your gonna be putting a pump anyway. Like stated above, which is a very good point, its about volume and not so much pressure. You can jack the pressure up as much as you want, but if the volume isn't there, it's not gonna make a difference. Twin's on a boost referenced regulator will give you plenty of volume at 15psi and well above that. You would already be pushing the limit with a single, if it would even be able to keep up in the first place.

Ken R.

 

I am making low 700's with 14# boost on stock LT1 intake and Not so stock Victor jr heads modified for reverse cooling....that is on a mustang dyno also! We still have tuning to do also, so its not yet maxed out.

Def. need the dual 255 pumps and a boost ref regulator. I tried it w/o and no luck!!