When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
History behind the question...I'm starting a turbo build on my 98 Camaro. I need some help understanding what others are doing for fuel pumps. I need 336lph to support 800fwhp on 93. For the sake of this discussion we will only reference 93 not E85. I will be doing a boost reference AFPR. So when looking at pump specs and flow charts a walbro 450 only flows 349 @50psi @12 volts and 298@70psi @12v see chart below straight from Walbros website. So my question is how do you figure out what size pump to use. My initial thought is I need to buy my pump/pumps according to what they flow at the fuel pressure I'll be seeing for my set up so between 55-70psi. When I originally started looking into it I was thinking a 340lph on a hot wire kit with a 255 on hobbs for future growth. But after looking at the flow chart for the 450lph I feel like a 450lph and 340lph would be needed to meet the goal. Am I off on what my interpretation of what I need?
Thanks
A pair of 255 Walbros will easily cover your needs and be cheap/reliable. There isnt really any need for more fuel than they could offer you unless you intend to shoot higher in the future.
I usually go overkill on the pumps. With a good regulator, there isn't much of a downside.
Pair of 340s would be my personal preference for in-tank pumps. A pair of 450s is hard to fit in most EFI tanks without some modifications.
255s will work, but don't leave much headroom and don't operate well at high fuel pressures. Under a few circumstances, they could be topped out at that power level.
I usually go overkill on the pumps. With a good regulator, there isn't much of a downside.
Pair of 340s would be my personal preference for in-tank pumps. A pair of 450s is hard to fit in most EFI tanks without some modifications.
255s will work, but don't leave much headroom and don't operate well at high fuel pressures. Under a few circumstances, they could be topped out at that power level.
Some guys in the US claim making in excess of 1000rwhp on a pair of 255's
I know a single 255 will do a genuine 500 proper HP regardless of how happy/sad the dyno is.
So his goals of 800 flywheel HP will be very easily and safely covered, and tried and tested with the 255's. So even 255's are overkill here. But also true, any of the Walbro style in-tank pumps start dropping off quiet a bit around 70-75psi.
But yes 340's would be another option, with upgraded wiring to suit the higher current they will pull. ( 255's will need suitable wiring too anyway )
Lots of 15% ethanol in gas around here, and I'd be very reluctant to believe 1000whp on a pair of 255s based on my testing with them.
You can get a single 525 pump for less than a pair of genuine 255s. They're OEM Hellcat pumps. That might be another option.
Lots of 15% ethanol in gas around here, and I'd be very reluctant to believe 1000whp on a pair of 255s based on my testing with them.
You can get a single 525 pump for less than a pair of genuine 255s. They're OEM Hellcat pumps. That might be another option.
As said, the 255's will do a genuine 500each. As to the wheel power claims....I'd disbelieve most of them too as likes of Dynojet would certainly be happy dynos even if others would dispute that
The OP is only asking for 800fwhp, not wheel power.
I'd assume that OEM Hellcat runs variable speed control and is perhaps even a brushless pump ? Is it a return style or dead end ?
A pair of 255 Walbros will easily cover your needs and be cheap/reliable. There isnt really any need for more fuel than they could offer you unless you intend to shoot higher in the future.
A 450 and 340 would be massive overkill.
Even a single 450 should cover you.
Originally Posted by JoeNova
I usually go overkill on the pumps. With a good regulator, there isn't much of a downside.
Pair of 340s would be my personal preference for in-tank pumps. A pair of 450s is hard to fit in most EFI tanks without some modifications.
255s will work, but don't leave much headroom and don't operate well at high fuel pressures. Under a few circumstances, they could be topped out at that power level.
I understand keep it simple and plan to do so but according to to my math one gallon of gas will support 9hp per hr if using .65 bsfc. If one gallon weights 5.994 lbs 5.994/.65=9.22 so I round down to 9. 800/9=88.88 so I round up to 89. 89gph is whats needed to support 800fwhp 89gph=337lph. So one 340 would support the 800fwhp if it truly flow 340lph@55-70psi but they don't. This is the reason for the post and why I'm semi confused about how to correctly size the pump. As mention in my original post the second pump would be for head room for future growth.While I don't disagree with steve that a 450 and 340 combo would be overkill I also don't understand how it would be if according to walbro a 450 only flows 323lph @60psi@12v. So are people running these @13.5v they still flow 355lph at 70psi then. Also my car is a 98 so there is no bucket that the pumps have to fit in.
As said, the 255's will do a genuine 500each. As to the wheel power claims....I'd disbelieve most of them too as likes of Dynojet would certainly be happy dynos even if others would dispute that
The OP is only asking for 800fwhp, not wheel power.
I'd assume that OEM Hellcat runs variable speed control and is perhaps even a brushless pump ? Is it a return style or dead end ?
The walbro hellcat pump flows 86.4gph @70psi@12v and is a brushed pump.
I understand keep it simple and plan to do so but according to to my math one gallon of gas will support 9hp per hr if using .65 bsfc. If one gallon weights 5.994 lbs 5.994/.65=9.22 so I round down to 9. 800/9=88.88 so I round up to 89. 89gph is whats needed to support 800fwhp 89gph=337lph. So one 340 would support the 800fwhp if it truly flow 340lph@55-70psi but they don't. This is the reason for the post and why I'm semi confused about how to correctly size the pump. As mention in my original post the second pump would be for head room for future growth.While I don't disagree with steve that a 450 and 340 combo would be overkill I also don't understand how it would be if according to walbro a 450 only flows 323lph @60psi@12v. So are people running these @13.5v they still flow 355lph at 70psi then. Also my car is a 98 so there is no bucket that the pumps have to fit in.
A 450+340 would be enough fuel for around 12-1300hp on 93....so yes for an 800hp engine it is overkill.
And when all cars run on a 14v system....if your pump is only getting 12v, you have a problem, your alternator has failed etc.
And you would only use 70psi, if you needed to use 70psi....for only 800hp, I'd expect it's a pretty low boost setup, so there is no need to be running the pump to 70psi unless you have undersized your injectors.
A 450+340 would be enough fuel for around 12-1300hp on 93....so yes for an 800hp engine it is overkill.
And when all cars run on a 14v system....if your pump is only getting 12v, you have a problem, your alternator has failed etc.
And you would only use 70psi, if you needed to use 70psi....for only 800hp, I'd expect it's a pretty low boost setup, so there is no need to be running the pump to 70psi unless you have undersized your injectors.
Just so I understand correctly your saying the reason for using a 1:1 boost ref AFPR is to increase the pressure because you don't have enough injector at a lower pressure?
Just so I understand correctly your saying the reason for using a 1:1 boost ref AFPR is to increase the pressure because you don't have enough injector at a lower pressure?
The reason it is common to use a 1:1 FPR is to maintain a constant pressure delta across the injector, which makes tuning easier and more consistent
You could choose to do many other things too....really, it is up to you.
But if you have less pressure across the injector, obviously it will flow less. If you have more, it can potentially flow more, assuming pumps etc can cope.
According to witchhunter fuel calculator I need 81lb/hr 853cc/min static flow rate injectors. I have 750cc/min or 71lb/hr @43.5psi injectors which according to witchhunter would be 873cc/min or 83lb/hr@58psi
750cc's will easily see a safe 800hp at 43.5psi if you so choose.
There would be no need to run them to 58psi base pressure, but you could also do that if you wanted, again factoring in the extra work the fuel pumps will be doing at the higher pressures.
750cc's will easily see a safe 800hp at 43.5psi if you so choose.
There would be no need to run them to 58psi base pressure, but you could also do that if you wanted, again factoring in the extra work the fuel pumps will be doing at the higher pressures.
Ok so since these cars don't want to start if they aren't seeing the 55psi range is that something that can be changed in the tune I guess? I understand I will be able to control what my base pressure is with the regulator but will I need to change something in the tune for the car to run on 43psi see how 58psi is what they run from the factory? I appreciate the help
10-20-2018, 10:38 AM
sizing fuel pump questions 
