Another FPR question, 300+hp
 

Yep, another one. All references I found are f ing old and never talk about MOAR than 300 hp.

Basics of my set up
NA /vvt
EFR 6258- allofit boost
Walbro 190hp
Id1000's

Does the stock FPR keep 3 bar over boost always? Or as I approach 25 psi boost, am I now down to just 18 psi Fuel pressure over boost? As understand, if would be hard to see in TS because injector duty cycle will look fine. In my world, the only way to know anything, would be to just throw fuel until it no longer changes the AFR. But that's a random shitty water to know IMO, or maybe that IS how you find out.

Would my setup benefit from more pressure?

Stock NA regulator is boost referenced, so it's always 43psi DFP (differential fuel pressure). Stock NB regulator is atmosphere referenced, so it's 60psi DFP at 0psi, 50psi at 10psi boost, etc.

If you don't have a fuel pressure gauge, then you find out you're out of pressure because additional injector DC% doesn't richen AFRs.

Depending on what the actual boost level is, your setup might benefit from an aftermarket FPR. It would almost certainly benefit from more fuel pump.

You will 100% need moar pump

Pefect, I understand now.

Well I don't. NA body and fuel system, VVT engine, 750cc injectors, EFR 6758 running 19 psi of boost. Walbro 190HP fuel pump as well. Why would I be needing a higher flowing pump?

Stable 11.5 AFR under WOT.

if it's holding 11.5 afr in all gears, all rpm, all loads, all fuel blends and all temps, then you're likely ok.

chances are it's not, but you just haven't really experienced "the perfect storm".

We usually recommend for people to have more than they need, just in case.

My data on the 190 says it moves 170lph at 60psi (you're at 43+19=62psi). 170lph is 2833cc/min. IOW, you don't have enough fuel pump to max out your injectors at your current boost level. I assume you're running somewhere around 300-320whp, at maybe 75-80% injector DC. So you're fine, but your pump is working as hard as it can. 750s are good for maybe 350whp on gas, 250whp on E85. If you had 1000cc injectors, like the OP, and you wanted to make 300whp on an NA FPR on E85, a Walbro 190lph will not do that. A DW200 and a 255HP wouldn't get there either, in fact.

For your setup, a DW200 would be plenty of pump to max out your injectors, even with some more boost on top, and it will be quieter than the 190lph you have.

At 60psi of rail pressure, this is the max injector size that these fuel pumps will support:

DW100: 500cc
Walbro 190: 709cc
DW200: 937cc
Walbro 255HP: 962cc
DW300: 1145cc
DW300 (2014 update): 1270cc
Walbro 455: 1587cc

thank you guys, I really appreciate you sharing your knowledge. Funny enough, I looked up in my datalogs when I did my WOT Virtual Dyno pulls (car weighed right before doing the pulls). Under WOT I had stable 11.5 AFR right up to the rev limiter, while my injector duty cycle would never exceed 64%. The pulls would yield 322 WHP running 102 RON pump fuel with spark going from 13° to 16° once full boost (230 kpa) is reached. So my peasant knowledge of forced induction leads me to believe my current 190 HP is doing a-ok and pump+injectors not nearly maxed out?

750cc/min x 60 min x 4 injectors x 64% duty cycle is 115.2 liters per hour, innit?

My lame question harvested some awesome information! Thanks everyone.

I made 350whp on an NA8 fpr, walbro 190Lph, ID1000 on the 6758, and that was on a Dyno Dynamics unless there was some black magic going on.
​​​​​​
​​​​It wasn't until I upgraded pumps for E85 that I needed a fuel pressure regulator that would play nice with the dw300

And it made me want to understand how FPR witchcraft works:

http://injectordynamics.com/articles/fuel-pressure-explained/

255lph seems to be "the line". Most are at their limit, some fail or get overwhelmed. The na vac referenced ones tend to do better than the nb junk.

Oh goodness, I'm sorry I read Savingtons comment incorrectly. He was saying on e85 that pump won't deliver. I can see that.

My bad, carry on