ale76051

iTrader: (2)

I've had a walbro 255L in my car for some time now, but the new build is together and i plan to increase the nitrous. But before i run it all out, will a 255L support a 355 with 232/240 cam, 32lbs injectors, and a wet 200 shot? Thanks

Cajun ELESS-ONE

in for answers too

ale76051

iTrader: (2)

Bumpp

ACE1252

From some discussions I've seen, it's in the 550hp range.

ale76051

iTrader: (2)

So I assume it's kind of a trial and error process. Is it best to watch for a fuel pressure drop on the top end, then step up the pump? I just don't comprehend how a pump will support X amount of horsepower without knowing volume amounts

ACE1252

No, it's not a trial and error process. Most ratings I've seen selling this pump put the number at 500+. Why? I'm not certain.

To try and put some numbers to it......

255 LPH = 404.6 lb/hr

Dividing that by 8(injectors) = 50.575 lb/hr

Using this formula from one of Greg Banish's books....and assuming that this is a NA engine.

Corrected Injector flow = ((BSFC x Power)/(# of injectors x (100%-safety margin)))

We can now calculate Power assuming a BSFC of 0.45, a safety margin of 20%, and that this is an 8 cylinder engine.

50.575 = ((0.45 x Power)/6.4)

Rearrange the equation....

Power = ((50.575 x 6.4) / 0.45)
Power = 719.28hp

Throw the safety margin out the window(which makes the 6.4 an 8) and you get 899.11hp.

bowtienut

iTrader: (1)

I wouldn't argue with Eric's numbers. That could well be the case with a brand new, unworn pump; ideal voltage at the pump (when under load!); no pressure drop through the filter, through the lines, through the regulator (all of which cannot be ignored).
From experience, I can say the pump with about 10k miles on it supports over 650 hp with part of that being a 100 shot with an overall A/F ratio of 12:1. From this, I'd venture to say that 700 hp on an N/A 13:1 setup isn't unrealistic. With a boosted application, I wouldn't count on much over 600 hp.

SpeedJunkee

I've seen a single 255 LPH pump "salefy" do between 450 RWHP and 500 RWHP. There was a time I was at 600 RWHP and I'm telling you a single 255 LPH would not have even come close to getting me there. I run dual 255 LPH pumps and plan on taking them to their limit, which should be around 1,000-1100 RWHP.

bowtienut

iTrader: (1)

Of course not. That could be 750 crank hp. With a safe A/F for boost....no way.

ale76051

iTrader: (2)

That makes more sense. Thanks

ACE1252

For boosted apps, looks like the BSFC changes to 0.55-0.7. That would lower the rating of the pump.

Assuming 0.65 with the 20% safety margin lowers the rating to 497hp. I'm not sure where most boosted apps settle in at on BSFC, so the 0.65 may be on the high side. However, boosted apps for sure does make a difference in the rating.

voaitnient

I wouldn't count on much over 600 hp.