[parish8]

let say the low side fuel pressure is at 45psi and I run out of hpfp at 600hp on e85. would getting that low side fuel pressure up to 60 or even 70psi help the hpfp go any farther?

I am looking for someone that has tried this in the real world and either saw an improvement or didn't see an improvement.

[Hyper SS]

I will let you know. My JMS is going in. 2 weeks

[Hyper SS]

From what I have studied. I am in the same boat with you. Except I run 93. The high side is looking for fuel from the line. Which is the low sides task to maintain. I am hoping it will support the 3.9 pulley. It's a crap shoot. I know how you feel

[Hyper SS]

No meth for me this time around. Although I ran it on my twin turbo LS1, with no issues.

[Hyper SS]

How bad was your high side tanking? Mine was at least 40%....Scary.

[JoeAyalaM]

Originally Posted by parish8

let say the low side fuel pressure is at 45psi and I run out of hpfp at 600hp on e85. would getting that low side fuel pressure up to 60 or even 70psi help the hpfp go any farther?

I am looking for someone that has tried this in the real world and either saw an improvement or didn't see an improvement.

The LP is an Electric centrifugal pump and the HP is a mechanical positive displacement (piston) pump. So unless the LP side is tanking, the HP output will be the same. Because the HP speed and flow per stroke remain the same.

[parish8]

Originally Posted by JoeAyalaM

The LP is an Electric centrifugal pump and the HP is a mechanical positive displacement (piston) pump. So unless the LP side is tanking, the HP output will be the same. Because the HP speed and flow per stroke remain the same.

That seems reasonable but is that how it works in the real world?

Anyone have some real world experience?

[jwdominick]

My bmw was DI, had a "lpfp" and a "hpfp". Car made 600awhp out of 3.0l on e85.
Had to upgrade the LPFP with a higher output in tank one, many used an inline too with similar results. the stock HPFP could then keep up.

dropping in a higher output lpfp here would also cure most of the issues many are seeing.

[Perdieu]

Originally Posted by parish8

That seems reasonable but is that how it works in the real world?

Anyone have some real world experience?

I was just told today the high side needs fuel supplied to it at a certain pressure when that pressure drops it will eventually drop too.

What they are seeing isn't good. Some low sides will drop early and other won't. They are very inconsistent from fuel pump to fuel pump

Other then that good luck finding anyone to share info on the fuel systems...

[Perdieu]

Originally Posted by JoeAyalaM

The LP is an Electric centrifugal pump and the HP is a mechanical positive displacement (piston) pump. So unless the LP side is tanking, the HP output will be the same. Because the HP speed and flow per stroke remain the same.

feed it a little it won't have the fuel to "flow the same"

[JoeAyalaM]

Originally Posted by Perdieu

feed it a little it won't have the fuel to "flow the same"

Agreed, if feed is insufficient, output will fall.

But since gasoline is a liquid and can not be compressed going into a piston type pump, feed it a lot, and it will still flow the same as feeding it just enough. The HPFP is not a centrifugal pump that may spin faster if there is less pressure delta to overcome.

[jessrayo]

I have a pressure gauge in my fuel line but I don't remember exactly what it is running at. I know I am running a lot more low side pressure than stock. I kind of feel you would get a gain from even more low side pressure but I honestly don't know how much further it can go. I realize the fuel is not compressible and what Joe says in the post above me is logical but I feel there are some other intangibles because the low side pump changes made a lot more difference in total power than the high side in my car and that really does not make sense from the above explanation. If you do see more overall power with say 70 psi low-side, I don't think it would be much. 600whp on e85 is a lot of fuel through a stock high side pump. I have the upgraded high side pump and injectors with stock cam configuration. In my car there was not much gain with the high side changes without including a cam upgrade. These 1LT motors are going to take some significant mods to push over 800. I figured that right off and just decided to leave my car as it is now.

I don't know how committed you are to E85, but if fuel is at the limit you will make more power on race gas with more air. I kind of think the best idea is to get one of the MSD manifolds with the injector bung and add another port injector. I really don't fully understand how you fuel map that with the current computer but others have told me it can be done...... I'm still waiting to see what you come up with.

Edit** I just looked up the specifications on my pump and it is rated at 60psi. I guess that fits with my other comments above.

[parish8]

I was speaking more generally but just to be clear I am running an zl1 lpfp and lt4 pump and injectors. I think on a dynojet that would get me to around 640rwhp but I haven't confirmed that. I have no intrest in race gas but could thin down the ratio a little.

Tuning for port injection seems like it would be the easy part of tuning this engine. Just flatline the maf at some point and phase in the port injection. You could even input the same maf into the stand alone and tune it via maf so things should phase in nicely. I am going to save his project for winter.

[cmitchell17]

How is the low side pump controlled? I tried looking at HP tuners tune, but didn't see anything specific for the low side duty cycle or anything? I'm wondering if there is any way in the tune we can boost output on the low side with a max duty cycle change or something?