Doesn't matter how big of a pump you put in the oem return less setup. You'll never avoid that pressure drop at the big end. Everyone will see it if they measure fuel pressure at the rail.

And like seb said, they're seeing it at 450hp, so pretty low flow.

This is interesting since phunk and I both made 500+ on E85 which we know requires even more flow.

didn't phunk have his return setup? I know the drop is there. Maybe just not bad enough to cause problems until you get up into the higher end, but you could see the pressure drop even at low boost

He was returnless. It may drop well over desired. But if afrs are in check .......

Not running E85 but I put a fuel pressure gauge in using Phunk's multi-adapter. I'm running aero340 fuel pump at about 9-9.5 lbs boost. I'm definitely seeing the pressure drop Seb is referring to. AFRs are solid and the venturi restriction at the pump is holding much higher fuel pressure than stock but I'm definitely dropping 10lbs under boost. Next time I drop the turbo I'll definitely be installing Phunk's S1 return system and drilling the venturi out to get pressure reading to expected 52 psi of a stock VQ.

So stock pump, stock setup with bigger injectors and e85 on a NA is ok or no?

I did make 586rwhp @9psi returnless with E85. I had a mild feed line upgrade, but I did not have the return portion. I do have the CJM S2SE return system now, but not when I was on the dyno. When I was running returnless, I did have pressure drop. I cannot remember now how much it was, but it was clearly there as indicated by the gauge in the engine bay, which we could see on the dyno. Since I watch my A/Fs like a hawk and have the ability to readjust my tune as required, pending changes in weather, etc... I just dealt with the pressure drop and accommodated it as required.

edit: I should stress/imply that it is not recommended to run it how i did. those of us in the industry are often willing to take greater risks with our personal cars. i will run my own car in a state that i would never give back to a customer.

My car runs more boost on the street than it does on the dyno... tuned at 9 psi. but more often than not, on the street, my boost is 10-10.5, sometimes even hits 11. once i hit 13! lol. Its funny how the boost sounds so low if you talk to guys with 4 cylinders running around with 30-40 psi to make our power!

So Im guessing you could get past 600whp running pump gas on this stock fuel system if were seeing it getting close on a fuel requiring 25% more flow.

There is no doubt that just injectors and pump could make over 600rwhp with gasoline. Its just not recommended as it wouldnt be considered "safe". But if you know what you are doing and watch what you need to watch, and dont mind constantly watching it... than it can certainly be done. Youll just never get anyone who is remotely responsible for that engines longevity to recommend it!

?

I have no information about the flow of the stock pump, so I dont know if its good enough for E85 NA or not.

Boost pressure fights fuel pressure -- so long as AFR's are maintained, the pressure may drop, but it would technically be sufficient.

If it skews lean under the right conditions, and there's no more bigger pump or injectors to use (or if there's driveability issues -- poor spray pattern/atmomization/cylinder wetting from the injectors or too much pressure from the pump for a smooth idle), I suppose you could try a rising rate/variable fuel pressure valve.

I thought switching to a return system brought with it a whole host of potential running and tuning issues (including possible vapor lock) under all circumstances except high load and high boost -- maybe I'm mistaken?

It all depends on how much more fuel you need to maintain the same torque levels. If you need, say, 20% more fuel, you need 20%+ more pump. Sounds like the OEM pump will be struggling with that.

Synolimit -- see what the infamous 250+ whp E85 Z is using. Sounds like that's what you would need. I think there's at least one other member on here who switched to an E85 safe set-up too.

Pressure drop is a sign of approaching the limit. The limit will shift around based on environmental conditions, system voltage, filter condition, etc. So if you find yourself at the limit of your fuel system, for the sake of consistency, its a good idea to upgrade and protect your engine.

There are generally no problems, if its built and installed correctly.


That is not exactly how it works. If you need 20% more fuel, but your pump is large enough to supply it already, than you dont need 20% more pump. There are just limited samples of anyone even bothering experimenting with the stock pump to get a solid idea of how much fuel its moving.