Stage 3 fuel and still dropping pressures

[shushikiary]

So I'm running the precision race works stage 3 LPFP setup with the CP-E PI (55# injectors) with N20 sensor on GC lite 2.0's, straight E85. Currently around 5000 or above RPM at 24 PSI of boost my LPFP pressures keep dropping into the 40's. It even does it if I run the pumps both straight at 100% output (wired straight to the battery). Full tank of gas as well.

The pressure always pops back up, but its annoying to see them drop like they do.

Here are a few logs:

https://datazap.me/u/shushikiary/gc...-no-boost-request-increase?log=0&data=3-13-23

https://datazap.me/u/shushikiary/1st-tune-change-gc-lite-20?log=0&data=3-13-23

https://datazap.me/u/shushikiary/gc-lites-20-3rd-gear-changed-recordings?log=0&data=3-13-23

I'm really thinking the restriction is somewhere else in the system, not the pumps, because they should be able to supply enough fuel. Is it in the fuel line from the tank to the engine bay? Is it in the stock FPR? (which PR sells an upgrade for): http://www.precisionraceworks.com/index.php?route=product/product&path=20_59&product_id=90

Anyone running these kinds of power levels who have experienced issues like this, I'd love to hear what you did to fix it. Thanks!

 

[Cruizinmax]

I got the same problem with a external fpr, it is bleeding out the pressure, but not to 0 in a few sec. Also here is some info from aeromotive fpr:

6.) I’ve installed my new Aeromotive bypass regulator. Fuel pressure seems to adjust fine and holds great when the engine is running, but when I shut the engine off, pressure drops quickly to zero. Shouldn’t the pressure hold like it did with a stock regulator?
No, Aeromotive EFI bypass regulators may not seal perfectly when the pump is off. They are engineered for the highest possible performance when the engine is running. OEM regulators must hold pressure for 30-minutes after shut-down to pass EPA emissions standards. At Aeromotive we know our customers priority is to have the best possible flow and pressure control when the engine is running and we don’t compromise this standard to force the regulator to seal when the engine is off. If extended crank or hard-start becomes a concern, first allow the pump to run and prime as long as possible after turning the key to the run position, then start cranking the engine, just before the pump shuts off. If the priming cycle is too short to allow the engine to start easily with this approach, extend the priming cycle in the ECU if programmable, or ad a timer board or momentary button to the fuel pump run circuit.

I have always had that issue on other platforms when using aftermarket fuel pressure regulators. So frustrating. On your setup do the fuel pumps prime when you open the doors ect like OEM?

 

[shushikiary]

Assuming you're asking me and not roywillems...

I already mentioned it, but no they dont prime. The enable for the megamoto GT H bridge is run off the ignition, which is why they dont.

I could put a schmitt trigger in that looks at the output of the stock LPFP controller and then turns on the enable and locks its self on until the ignition is off again. That would solve the problem, as then the pumps would prime when you unlock the car or open the door like normal.

 

[Cruizinmax]

Assuming you're asking me and not roywillems...

I already mentioned it, but no they dont prime. The enable for the megamoto GT H bridge is run off the ignition, which is why they dont.

I could put a schmitt trigger in that looks at the output of the stock LPFP controller and then turns on the enable and locks its self on until the ignition is off again. That would solve the problem, as then the pumps would prime when you unlock the car or open the door like normal.

Ah, sorry I missed it. IIRC the logic to pre priming the LPFP is to help save the HPFP from cranking without pressure. I think that was believed to be a contributor to failing HPFP's. Seems like an easier solution might be to run 1 of your fuel pumps off of the factory circuit and then your secondary pump off of the circuit you created.

 

[shushikiary]

If I do that then under WOT it throws the code for too high of current for the fuel pump, and gives me the triangle with the ! in it on the dash for a few seconds until you're done, but I could do that.

Currently just letting the pumps prime first is ok, but I'll likely add a circuit to turn the enable on when the OEM pump controller is on.

 

[shushikiary]

I put in the circuit and it works. Pumps turn on when I unlock the car, but this still wont fix the issue I'm finding out because of 2 things.

1. The check valve I got from precision race works doesnt hold pressure (I got a hold of them and took it apart and the flapper is aligned like its supposed to be, it just doesnt seem to hold pressure, though it does prevent the fuel volume past it from flowing back to the tank for at least a good 30 seconds.
2. The ECU only turns the pumps on to prime the system if the car has sat for a certain amount of time. Something like 10 or 20 minutes.

Thus I have to get in the car and start it quickly before the fuel flows back down the line even when it does prime the pumps, and if I was doing a quick in and out of a store or something the pumps dont prime at all.

This solution would work if the check valve held pressure for 30 minutes like EPA requirements. I get that they dont put such a valve in for flow restriction reasons, but I'm tempted to maybe put a different check valve in.... that or just deal with priming it by hand before I start it each time.

 

[JimmyNeutron]

I recently purchased the Precision Raceworks kit as well, although I haven't installed it yet. Since I plan to use a -8AN fuel line, Rob told me the same thing - my fuel line must have a flapper-style check valve. After purchasing a couple different brands and testing them (just by blowing through them) I found they all had the same problem... they don't actually hold pressure.

So far, I've only found one that actually passes the blow-test: Earl's Performance, part number 253008ERL for -8AN hose size (other sizes are available too). I bought mine from Summit Racing for $89.95. This is the only high-flow check valve I could find that uses a Viton seal (E-85 compatible) to seal the flapper. Other manufacturers use a Teflon flapper that seats against the aluminum valve body with no rubber seal, and this design doesn't hold pressure well at all.

Not sure what type of fuel line you're using but if you're upgrading to AN fuel lines, this is probably the check valve you've been wishing you had. I wish I could say definitively that this valve works but it will be another couple weeks before I get all my new parts installed.

 

[shushikiary]

Did you happen to test the Russell 650613? I've got one of those coming to try. And yes I got the 8an line from precision race works that came with a check valve in it, but as you said, it doesnt hold pressure. From the reviews on summit people have said that the Russel 650613 holds good pressure up to 70psi. Spec says it opens with 3psi of pressure, its a piston with oring seal, 6an center flow size equivalent rated for 150gph, which is 9 gpm, much higher than what the rating is for the filter housing.


Dammit, just got off the phone with Russel, its not E85 rated and the seal will eventually fail because of it.

I ordered an Earls and I'll give it a try

 

[JimmyNeutron]

I didn't try the Russell 650613 because it's not a flapper style design, and it also requires 3psi of differential pressure to begin to open the valve compared to only 1psid to pass full flow for the Earl's 253008ERL. The higher d/p requirement due to the piston style design of the Russel will definitely cause more flow restriction, but since it uses a o-ring to seal the valve disc, it will likely hold pressure very well. The Earl's 253008ERL does use a spring to hold the flapper closed, but 1psid to allow full flow is the best specification I could find on the market.

 

[matreyia]

I have the motiv ethanol kit with their fuel lines and PR stage 3 and my car idles over 72 psi. So far no issues at all.

If you did not change your lpfp sensor and hpfp sensor you may not be getting correct data comms from the old sensors. Mine have been replaced 2x already... they go bad often. Seriously.

 

[shushikiary]

Got the Earls on there, its doing great. Flows enough that my fuel pressures are fine (even when I hit 28psi this morning in the colder weather today). Holds pressure VERY well... almost too well. When you shut the car off and the pressure is back bleeding from the HPFP into the LPF system the pressure just keeps rising and rising, meaning your LPF system ends up at like 150 PSI and sits there for a good while.

If you let off the throttle right after a pull the pressure will also spike and hold as you're not using any fuel. So you'd better have good fuel connections and hose as it will test to make sure you can hold pressure that's for sure.

 

[JimmyNeutron]

Solved one problem, only to discover another... sounds like the fuel pressure regulator may need some adjusting. Have you tried that? Or is the transient pressure spike not even worth worrying about?

I've thought about modifying the Precision Raceworks filter/regulator from a returnless design to accept a return line from a regulator mounted to my port injection rail. That would definitely solve your new issue. Looks like it won't be too difficult to convert it - just need to tap and plug one hole, remove the regulator and diaphragm, and replace the regulator with a fabricated plate that the return line will connect to.

 

[shushikiary]

The FPR sits before the check valve, so what happens is on the fast burst of pressure that gets past the FPR before it can respond the check valve captures that high pressure. The FPR will hold fuel pressure at around 85 PSI where I have it set now.

If no fuel is used, as in coasting or after turning the engine off, I've found its holding that high of a pressure even over night.

Putting a return line to the passenger side of the tank wouldnt be hard, and my port injection fuel rail already has a plug on the other end of it made for a return line, so I could pull out the FPR and get a housing for it then re-plumb the whole thing so the FPR is after the check valve.

Another possibility would be putting the check valve in front of the FPR by somehow putting it in tank before the FPR, whic would be a lot less work. A couple of those press on quick connect nipples would do it with -8an fittings.

This works for now, all the line and everything should be ok to run at those pressures, but if it causes a problem I may have to move the check valve to in tank or something.

 

[shushikiary]

So I've blown 2 of those Earl's check valves, and blown a 3rd summit racing PTFE one. The Earls ones the viton seal eventually shreds, and the summit one the PTFE cone got blow back into the inlet fuel line and clogged it. The issue is the pressure rising at turn off above 145 like I mentioned.

I called Aeromotive about the problem and talked to their tech. Putting a check valve before the regulator wont work, putting a pressure regulator on the bypass outlet wont work either as then it wont properly hit pressure we target (the bypass wouldn't open until 2x the pressure).

The suggested solution we found was to put a second regulator in parallel to the check valve after the main regulator with a higher pressure settings than the main regulator. This way too high of a pressure can bleed off past the check valve, and because it doesnt need to be a high flow regulator it will seal like an OEM one.

The tech said he didnt know of any after market FPR's that would do that, I'd likely have to find an OEM FPR to use.... joy. So if anyone has an idea of one to use, let me know! For the moment I'm running no check valve while I try to find one.

I think this guy just might do the trick: https://www.ebay.com/itm/1-4-MNPT-A...m=392142510201&_trksid=p2060778.c100290.m3507


I called them and its ethenol good, just have to setup a bunch of fittings to make it in parallel reverse with my summit PTFE check valve.