255lph rwhp
09-04-2009, 02:10 PM
#2
4th Gear Member
Join Date: Dec 2007
Location: Lafayette, LA
Posts: 1,700
dont really know....
I say call lethalperformance or another top notch company and ask them. They will more than likely be able to answere this one better than anyone on here.
just my .02
EDIT: but if i could guess, id say somewhere in the ballpark of 520rw or so...
I think you are going to be limited by the injector, not the pump.
I say call lethalperformance or another top notch company and ask them. They will more than likely be able to answere this one better than anyone on here.
just my .02
EDIT: but if i could guess, id say somewhere in the ballpark of 520rw or so...
I think you are going to be limited by the injector, not the pump.
09-04-2009, 02:46 PM
#3
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
Base assumptions:
B.S.F.C (Brake Specific Fuel Consumption) for f/i is 0.6 lb/h/HP--I.e. it takes 0.6 lbs of fuel per hour to make 1.0HP;
Premium fuel (93 octane) weighs 6.2lb/gal at STP (Standard Temperature and Pressure, 68°F, 14.696 psi barometric pressure);
So, 255 lph = 67.36 gal/h = 417.6 lb/h, therefore in theory the pump can support 417.6 / 0.6 = 696HP;
A 42lb/h injector, at 43psi (the standard rating pressure for injectors) and 80% duty cycle, can inject 33.6lb/h--obviously then, 8 can inject 33.6 * 8 = 268.8lb/h;
This is less than the pump's maximum, so so far, so good.
268.8lb/h of fuel can support 268.8 / 0.6 = 448HP...
Enough facts?
B.S.F.C (Brake Specific Fuel Consumption) for f/i is 0.6 lb/h/HP--I.e. it takes 0.6 lbs of fuel per hour to make 1.0HP;
Premium fuel (93 octane) weighs 6.2lb/gal at STP (Standard Temperature and Pressure, 68°F, 14.696 psi barometric pressure);
So, 255 lph = 67.36 gal/h = 417.6 lb/h, therefore in theory the pump can support 417.6 / 0.6 = 696HP;
A 42lb/h injector, at 43psi (the standard rating pressure for injectors) and 80% duty cycle, can inject 33.6lb/h--obviously then, 8 can inject 33.6 * 8 = 268.8lb/h;
This is less than the pump's maximum, so so far, so good.
268.8lb/h of fuel can support 268.8 / 0.6 = 448HP...
Enough facts?
Last edited by cliffyk; 09-04-2009 at 02:50 PM.
09-04-2009, 03:07 PM
#5
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
A couple of other considerations:
B.S.F.C. can be higher than 0.6lb/h/HP at higher boosts;
Fuel pressure for our engines, unless altered in the tune, is 40psi--this makes the actual injector capacity less then its rated capacity (at 43.5psi).
The formula is:
SquareRoot(rated pressure/new pressure) * old flow rating = new flow rate;
Injectors can be pushed to 85% to 90% duty cycle, though it's not recommended.
B.S.F.C. can be higher than 0.6lb/h/HP at higher boosts;
Fuel pressure for our engines, unless altered in the tune, is 40psi--this makes the actual injector capacity less then its rated capacity (at 43.5psi).
The formula is:
SquareRoot(rated pressure/new pressure) * old flow rating = new flow rate;
Injectors can be pushed to 85% to 90% duty cycle, though it's not recommended.
09-04-2009, 03:12 PM
#6
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
Not really, theory and practice are different animals, and there are a good number of other variables/considerations beyond fuel consumption...
Drop the B.S.F.C. to 0.55 (through better VE [Volumetric Efficiency]) and 268.8lb/h of fuel could support 488HP, getting close to your guesstimate.
Drop the B.S.F.C. to 0.55 (through better VE [Volumetric Efficiency]) and 268.8lb/h of fuel could support 488HP, getting close to your guesstimate.
09-04-2009, 03:32 PM
#7
4th Gear Member
Join Date: Jul 2008
Location: NC
Posts: 1,956
Yup, cliffy is the ****.....I asked him to marry me but he said no.
I remember him posting this a while back and I wrote down every single thing and I was gonna put all that but I was almost certain cliffy would take care of it and I was busy at the moment lizzy put the thread up :P
I need a pocket cliffy.....hmmm.......
I remember him posting this a while back and I wrote down every single thing and I was gonna put all that but I was almost certain cliffy would take care of it and I was busy at the moment lizzy put the thread up :P
I need a pocket cliffy.....hmmm.......
09-04-2009, 04:34 PM
#9
6th Gear Member
Join Date: Feb 2006
Location: Virginia
Posts: 11,786
with a single 255, I made 436rw with the pump at 10.9v and with 60# injectors and still had plenty of pump left. I'm 590's now with a single intank 255 and an inline 255 both wired at 12-13v.
If this setup is yours you can get away with less pump if you have more injector.
If this setup is yours you can get away with less pump if you have more injector.
