Teaser: DIY stage 4 fuel system

[veer90]

Disclaimer: just got the whole shebang installed last weekend, currently investigating some minor hiccups possibly EKP related. Will post full DIY when it's fully sorted. Is working fine now.

About 3 weeks ago I started putting together a DIY stage 4 fuel system. My goal was for this to be the last fuel system upgrade my car will ever need, and capable of flowing 900 whp worth of E85. Conceptually, this is the same idea as a Fuel-It stage 4, except the bypass lines are all in the tank and it won't hurt your wallet nearly as bad.

System highlights:

• Bucketless design with twin hydramats. Bucket is only to hold the pumps and float.
• Walbro 450 primary EKP-controlled pump. Feeds driver's side venturi to deliver fuel over the driveshaft hump. In-tank filter bypass.
• Walbro 525 secondary hobbs controlled pump. Full bypass of all in-tank restrictions.
• DIY wiring harness for secondary pump with 40A relay, hobbs switch, and inline fuses
• 6AN steel reinforced feed line with Fuelab 10-micron inline filter
• All fittings through top hat tapped, sealant applied, and loctited. I hated the fact my old DIY stage 3 would occasionally leak through the top hat
• Port injection with 750cc injectors, Precision Raceworks FPR and 6AN return line.

The Walbro 525 is the oem fuel pump from the Hellcat Challenger/Charger. Combined with a 450 with most restrictions bypassed and 6AN lines should flow all the fuel I could ever need. The hardest part was making the setup fit, especially the fitting out of the driver's side top hat and the line down the side of the tank. But now that's done troubleshooting should be fairly straightforward, since there's no evidence of any fuel leaks.

Pictures:

Whole system minus the feed line and inline filter:


Fuel pump bucket:


Fuel sender:


Lines underneath the car (am I a certified zip tie master tech yet?):


This build sponsored by Home Depot

 

[noorj]

Looks good! I've only ever dicked around with the driver side tank when I did my DIY stage 3, so I don't know much about the other side of the saddle tank. Definitely cool to see all the pictures of the setup. Did you keep the in-tank pressure regulator on the passenger side? Not running a mechanical fuel pressure regulator then I guess? a flow diagram would be pretty sweet if you feel up to it

 

[veer90]

Looks good! I've only ever dicked around with the driver side tank when I did my DIY stage 3, so I don't know much about the other side of the saddle tank. Definitely cool to see all the pictures of the setup. Did you keep the in-tank pressure regulator on the passenger side? Not running a mechanical fuel pressure regulator then I guess? a flow diagram would be pretty sweet if you feel up to it

There's a mechanical FPR / return in the bay otherwise this setup wouldn't work.

The in-tank regulator is deleted and the filter bypassed.

 

[silverstreak18]

Good stuff man. I did the stage 2 DIY with a single walbro 450 and hydramat and have had zero issues. The hydramat seems to live up to the hype.

 

[veer90]

I'm pleased to report that it's not the EKP. The FPR simply needed adjusting with the new setup.

Initial logs look promising - note that JB4 logging is offset for fuel pressure for whatever reason. Since we know the EKP targets 5 bar fuel pressure which is 72.5 psi, it can be safely assumed that the flat portions logged as 66 FP_L is in reality 72-ish PSI. The same offset can be observed at idle, where it logs 65 for FP_L but 72-73 PSI Fuel Low Pressure in MHD.

This is much higher and much more stable fuel pressure than I had before, I'm stoked.

 

[Ask92]

I'm pleased to report that it's not the EKP. The FPR simply needed adjusting with the new setup.

Is there a reason that you kept the bucket vs going bucketless?

 

[veer90]

Is there a reason that you kept the bucket vs going bucketless?

It functions as a bucketless, the bottom is chopped off and the sides of the bucket only hold the pumps and fuel level float.

 

[Ask92]

It functions as a bucketless, the bottom is chopped off and the sides of the bucket only hold the pumps and fuel level float.

Yea duh I didn't really look at the picture close enough. Where did you source those large mats? Seems like those would take away any "theoretical" issues that bucketless may bring.

 

[veer90]

Yea duh I didn't really look at the picture close enough. Where did you source those large mats? Seems like those would take away any "theoretical" issues that bucketless may bring.

Holley 16-111

I got em off ebay

 

[noorj]

Is there a reason you're not using the boost reference on the fuel pressure regulator? You probably don't need it with 750cc PI injectors, but I'm just wondering

 

[veer90]

Is there a reason you're not using the boost reference on the fuel pressure regulator? You probably don't need it with 750cc PI injectors, but I'm just wondering

Short answer: was told by @V8bait @Payam@BMS and like 3 other people to use static pressure. You're right though in theory boost referenced would give me way more fuel.

Long answer:

Need to take into account base fuel pressure and max pressure the injectors can handle if I set up 1:1 boost reference, and that raises some questions.

I don't have a concrete answer for how much fuel pressure the port injectors (BMP 750cc) can handle. Precision Raceworks told me upwards of 150 psi but google tells me up to 8 bar / 116 psi for Bosch EV14K's. Some people have also told me no fuel pressure over 90 psi. So say the max is 90 psi, I need 56 psi base fuel pressure since I run 33-34 psi of boost.

If the EKP always targets 72.5 but consistently hits a lower pressure, will it run full tilt to compensate and fry itself?

I did fry an EKP once but it was an older EKP M2 out of my car with 90+k miles. Currently rocking an EKP M3 out of a 335is with low miles

 

[Payam@BMS]

Easy reason why I leave it static, take a look at walbros flow chart on the 267 part number.
After 80-90 psi flow just tanks dramatically. Leaving a base pressure at 70 then adding 30-40 psi, no flow and killing the pumps.
Leave it static at 70-80psi depending on how much boost you want to push. PI only needs about 40 psi base pressure, so it's simple math.

Found the links:
https://walbrofuelpumps.com/walbro-f90000267-fuel-pump-e85

 

[veer90]

Easy reason why I leave it static, take a look at walbros flow chart on the 267 part number.
After 80-90 psi flow just tanks dramatically. Leaving a base pressure at 70 then adding 30-40 psi, no flow and killing the pumps.
Leave it static at 70-80psi depending on how much boost you want to push. PI only needs about 40 psi base pressure, so it's simple math.

Found the links:
https://walbrofuelpumps.com/walbro-f90000267-fuel-pump-e85

Any downside to dropping base fuel pressure to say 50 psi? Will the EKP take a dump if I do that

 

[Payam@BMS]

Any downside to dropping base fuel pressure to say 50 psi? Will the EKP take a dump if I do that

I used to have it at 50 psi with 1:1 boost reference. No idea on the EKP side of stuff.

 

[veer90]

I used to have it at 50 psi with 1:1 boost reference. No idea on the EKP side of stuff.

How long did you run it like that before switching to static?

 

[Payam@BMS]

Not too long, I was testing a lot of different things back in the day. Static made the most sense to keep EVERYTHING happy

 

[Mikejones1208]

Was all the corrugated fuel hose on attached to the stock strainer 5/16? Considering doing this to my car and may order some lines and fittings to do so. Also were you still able to retain the stock venturi that moves gas from the driver side of the tank to the passenger? It looks like you were but im just double checking

 

[veer90]

Was all the corrugated fuel hose on attached to the stock strainer 5/16? Considering doing this to my car and may order some lines and fittings to do so. Also were you still able to retain the stock venturi that moves gas from the driver side of the tank to the passenger? It looks like you were but im just double checking

corrugated hose is 3/8" PTFE submersible hose from Radium Engineering

yes the venturi is maintained. but only one pump is feeding it vs. with a stage 3 setup both pumps are being bottlenecked by that piece.

 

[noorj]

found the stock system's flow diagram for those interested

 

[MoreBoost]

Really nice post Veer90.
Like you I decided to do my own dual pump system but I don't fully understand the FPR side of things so I've left my second pump disconnected for now.
I've looked at your setup and I'm afraid I still don't fully understand it. I want to make sure I don't blow a fuel line off, starting a fire.

My port meth setup is flowing lots of fuel. More than enough for my current requirements but in the future I'd like to have a direct injection only setup.
Once there's a hpfp solution.

I see that often a fuel pulse damper is fitted to systems like these to make the fuel pressure more stable. Avoiding peaks and troughs in pressure. Not sure how pressure looks when the second pump kicks in and turns off.