Q's on custom fuel system

[oldskoolZ]

I searched and searched but couldnt find a direct answer. I wanted to run a pretty much complete new fuel system, and use the feed and the return as a feed, and have no return and no pressure regulator, iv seen it done on some cars i was wondering if its possible on L28. Thank You

[naviathan]

Pardon? No return and no pressure regulator? How would that work?

[RTz]

I've done return-less systems a couple times, but they still require regulators. The only way you're going to skip the regulator is by modulating fuel pressure electrically, via the fuel pump.

 

One example is this car...

 

 

It doesn't appear to be regulated, but it is... its remote mounted.

[v8dats]

very clean!

i love your work Ron!

[BRAAP]

I have also ran pseudo returnless system. I ran the supply and return lines in the trans tunnel, regulator on the firewall directly behind the valve cover. The supply from the regulator to the fuel rail was returnless, hence the pseudo returnless term.

Whenever the topic of returnless fuel routing comes up, the debate of possible issues always arises, though we haven’t heard any confirmed data to back up any suspicions, yet. I personally haven’t experienced any issues on mine, my returnless section was rather short, and I didn’t really put much running time on it before selling it. It did help in cleaning up the engine bay and simplify the fuel rail plumbing. This could be taken even further by placing the fuel pressure regulator back at the fuel pump so there is only one line, supply, running up to the front of the car. Some OE manufactures are doing this currently, some with regulators and I think I heard somewhere that some are pulsing the fuel pump as the means to regulate fuel pressure, no pressure regulator, though I can’t confirm that.

 

Here is the typical general fuel flow routing that we are used to dealing with;

 

 

 

 

Pseudo returnless as I used;

 

 

 

 

As installed in my race car. The black fuel pressure regulator on the firewall where the supply and return lines come to, and the short returnless supply line out to the fuel rail;

 

 

 

 

The dead end at the fuel rail;

 

[veritech-z]

Late model (97-02) Saturn S-cars had the regulator built into the fuel filter, and it was located back by the tank. They cost about $90 to replace.

[oldskoolZ]

Thanks for the ideas, I'll prolly try a few diff arrangments b4 i settle, thx again.

[RTz]

I'll prolly try a few diff arrangments b4 i settle

 

2+2 b4?

[oldskoolZ]

Sry ron come again? But ne way, Iv come up with an idea soo brilliant my head would explode if I even began to know wat i was talking about. Wat if.....now keep in mind, Im young, Im a flegling mechanic, so if this idea is absolutely retarded, just tell me....but wat if you had the feed go to a "T" , the feed goes into in one leg, and another leg goes to the fuel rail wich has a dead end, the other leg is the return, it has a purge valve that releases the pressure at 37psi...heh?

[BRAAP]

Sry ron come again? But ne way, Iv come up with an idea soo brilliant my head would explode if I even began to know wat i was talking about. Wat if.....now keep in mind, Im young, Im a flegling mechanic, so if this idea is absolutely retarded, just tell me....but wat if you had the feed go to a "T" , the feed goes into in one leg, and another leg goes to the fuel rail wich has a dead end, the other leg is the return, it has a purge valve that releases the pressure at 37psi...heh?

 

Nope, not retarded at all. Though my mad subliminal skills are WAY powerful as you designed exactly what I described above, and quoted again below.... (You left yourself wide open with that one. I’m just playing so don’t take it personal. If I did offend you, I apologize and will delete my joking.)

 

 

…….. This could be taken even further by placing the fuel pressure regulator back at the fuel pump so there is only one line, supply, running up to the front of the car. Some OE manufactures are doing this currently…..

 

Pseudo returnless as I used;

 

 

 

 

 

 

Another way to describe your brilliant design, again, place the fuel pump AND the fuel pressure regulator back at the tank. You can use the fuel pressure regulator AS the TEE itself as you described, (see drawing above) and it keeps the pressure at whatever pressure you set it at, 37 PSI in your example, throughout the entire line all the way to the injectors.

[oldskoolZ]

nope not offended at all, but ok i see wat u wer sayin, i was mislead by the fact that ur illustration shows a pressure reg. with a vaccume opperated diophram, rather than a pressure activated valve, like i wanted to do, any idea where i could get such a "pressure activated valve"?

NOTE: pressure regulation via said "pressure activated valve" would regulate fuel pressure more instantly at higher rpm's as apposed to that second lost from a vaccume opperated diophram. Hence a faster throttle response.

[BRAAP]

Thanks for being a good sport.

 

The fuel pressure regulator as used in 99% of all EFI systems are a “pressure activated valve” as you described. The pressure comes from a spring above the diaphragm and that is what maintains the fuel pressure, (the spring is represented in my cheesy sketch of the fuel pressure regulator above.) The vacuum signal is there to keep the pressure difference at the injector nozzle the same no matter what the manifold pressure is. i.e. at idle, manifold pressure is down a few PSI and as such the vacuum signal drops the fuel pressure in the regulator that same few PSI. That is how 99% of EFI fuel pressure regulators function. Though with aftermarket EFI, you can essentially eliminate the vacuum signal and program your fuel map, (injector pulse widths,) to compensate similarly, if you so choose, though most people retain the vacuum signal.

 

In short, you were/are on the right track.

 

As for where to get the multi port fuel pressure regulators? Well, the OE ’75 and ’76 Z car fuel pressure regulators have two outlets and look very much like the regulator in the sketch above, though it isn’t adjustable. The adjustability is just a fine tuning aid, not a necessity, just a luxury. Most aftermarket Fuel pressure regulators have multiple ports like the Mallory 4307M I used.

 

http://www.malloryracing.com/ProductDetails.aspx?brandId=6&productID=8815762&majID=225&minID=2259&selection=0&minselection=4

 

It has 4 ports. I used one for a pressure gauge, one was the fuel supply from the pump, another for the fuel out to the fuel rail, and I plugged the last one. My Fuel pressure regulator was my “TEE” in that system.

 

Hope that helps,

Paul

[oldskoolZ]

yes this deff helps, and at the risk of sounding redundent, or like an idiot, I couldnt jst have this presure releif valve and only have this releif valve, and i need this vaccume signal, or ill have to lengthin the injector pulse?