Parallel or dead head?

[HWYSTR455]

JMAC - Yes, in theory, bank 2 bank is more susceptable to hammering than SEFI.

Jody- You've certainly drawn my curiosity here. I was also under the impression that you want the regulator as close to the injectors as possible, which allows for a faster reaction time to pressure variances. I understand (and have seen others with) your setup, with the regulator in the rear, though it goes against all the design theory I've been taught or researched, so I'm trying to understand. You're saying you see no variations in pressure? Is it possible you're just not seeing it? What types of rail pressures do you use? Generally higher pressures, like 60+?

I've seen 'recommended' system maps by manufacturers of pumps, and as I recall, all recommend the typical bypass system with the regulator either on the fuel rail or right at the fuel rails. I have lately also seen several aftermarket projects that use dead head systems, which has made me wonder.

I'm getting ready to help a friend with a fuel system project that is a big block supercharged application. Space is a premium, and if possible, a dead head in this case would be an answer to the packaging. Maybe I need to go back and re-research the topic, since it seems my knowledge may be dated.

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[camcojb]

Originally Posted by HWYSTR455

JMAC - Yes, in theory, bank 2 bank is more susceptable to hammering than SEFI.

Jody- You've certainly drawn my curiosity here. I was also under the impression that you want the regulator as close to the injectors as possible, which allows for a faster reaction time to pressure variances. I understand (and have seen others with) your setup, with the regulator in the rear, though it goes against all the design theory I've been taught or researched, so I'm trying to understand. You're saying you see no variations in pressure? Is it possible you're just not seeing it? What types of rail pressures do you use? Generally higher pressures, like 60+?

I've seen 'recommended' system maps by manufacturers of pumps, and as I recall, all recommend the typical bypass system with the regulator either on the fuel rail or right at the fuel rails. I have lately also seen several aftermarket projects that use dead head systems, which has made me wonder.

I'm getting ready to help a friend with a fuel system project that is a big block supercharged application. Space is a premium, and if possible, a dead head in this case would be an answer to the packaging. Maybe I need to go back and re-research the topic, since it seems my knowledge may be dated.

.

I am currently running 52 psi and have added a boost reference line to the regulator for 65+ psi under boost. But I have also run the rear regulator at much lower pressures.

Regulator on the rails is the normal way to do it, may even be the best way although it hasn't been proven out with me. One thing it does cause is very hot fuel is being bypassed to the tank. I and many others have had issues with the hot fuel heating the tank enough to cause fuel pressure issues and shutting off the pump. Won't likely be an issue with short trips in town, but on longer runs on a freeway (like Power Tour) or during track use it becomes a big issue.

You could add fuel coolers to the return line I guess, but that's just more junk to bolt on the car. I moved the regulator to the rear of the car years ago after I saw GM doing it on the Vettes (got the idea from a local EFI tuner). Never had a fuel heating issue since, and with my fuel pressure sender in the rails see no variance in pressure at all, no vibrating needle, nothing. That does not mean it isn't happening, just that I can't see it on the gauge or in a/f logging, and the car runs fine this way. I was told the dampner was used as much for noise and resonance as anything, which is an issue in a brand new super quiet insulated car with a warranty, not so much in an older hot rod like we build. I sure haven't heard anything.

Jody

[HWYSTR455]

Hot fuel shutting off the pump & pressure, like from the pump failing from the heat?

I did the Power Tour with a bypass setup (Gen6/Aeromotive), and drove 3300+ miles in 7 days, some days 9 hours or more straight, only stopping to gas & eat. I never suffered a fuel heating issue (pressure rise/drop), or pump failure, and this was 80-90+ degree weather, bumper to bumper stop & go at times. Maybe I just got lucky? The only area that would in my setup absorb heat would be the rails themselves, every other area was either away from radiant heat or wrapped.

New vettes are dead head? I've never noticed, or looked for that matter!

Hm, maybe I'll take a shot at dead heading my friend's project. Would give him ammo though if he had problems with it! Sure would make life easier though, that's for sure! Thanks a ton for your input, greatly appreciate it!

Oh, how did you run the boost reference line back to the regulator?

.

[camcojb]

Originally Posted by HWYSTR455

Hot fuel shutting off the pump & pressure, like from the pump failing from the heat?

I did the Power Tour with a bypass setup (Gen6/Aeromotive), and drove 3300+ miles in 7 days, some days 9 hours or more straight, only stopping to gas & eat. I never suffered a fuel heating issue (pressure rise/drop), or pump failure, and this was 80-90+ degree weather, bumper to bumper stop & go at times. Maybe I just got lucky? The only area that would in my setup absorb heat would be the rails themselves, every other area was either away from radiant heat or wrapped.

New vettes are dead head? I've never noticed, or looked for that matter!

Hm, maybe I'll take a shot at dead heading my friend's project. Would give him ammo though if he had problems with it! Sure would make life easier though, that's for sure! Thanks a ton for your input, greatly appreciate it!

Oh, how did you run the boost reference line back to the regulator?

.

2005 Power Tour there were at least 6-8 guys that I personally saw stranded like us with the fuel heating issues. I was in a borrowed car that I didn't plumb, we ended up adding 20' of coiled copper tubing in an ice chest to the return line to make it through the tour.

Vettes, GTO's, and others have been regulated at the rear for many years now.

[parsonsj]

Many of you may remember my car and its fuel problems at Pigeon Forge. I actually over-nighted a new A1000 to Bill's house/shop and replaced the pump in an attempt to fix it. My car was doing the 30 minute boogie -- and it just started that weekend. During the actual run through the hills, I had to stop every 10 minutes or so to let the fuel pump cool down.

'll know in a day or two, but it looks like my problem was dirt simple: I had a dirty fuel filter. (sorry...)

I've just now gotten my car back together after that (it now has an integrated iPhone/stereo and A/C). I also re-plumbed the fuel system to route it away from my headers, and added an Aeromotive fuel pump controller (shout out to Steve Rupp: he's the man), and put in an RPS Street Twin clutch.

I've been doing a lot of shakedown runs (adjust the clutch, fix the alternator whine in the stereo, see if the defroster works, etc.).

Wouldn't you know it, my car crapped out just like it did in Pigeon Forge. This time I measured the temperature of the gas in the tank (easy since I just filled it up). 78 degrees.

The fuel rail temperature was 108.

A re-read of Aeromotive's website (I run all their stuff: A1000, fuel filters, regulator, fuel rails), and I happened on a little gem that said a restrictive fuel filter on the suction side can cause cavitation of the fuel pump. So I pulled my filters out and examined them. The suction side filter was fine: no noticeable debris. But the pressure side was black with chunks of my old Russell SS hose in it! Why I didn't check that at Pigeon Forge is beyond me. I checked the suction side, but not the pressure side.

I think the pressure side filter had enough restriction that the fuel pump was working too hard to push fuel through it... over time (say.. about 30 minutes) it would overheat and cavitate.

I've heard reports of the 10 micron filter needing to be replaced often. Anybody else heard of that?

Anyway, a new element is on its way. Sometimes the little stuff matters.

jp

[Vegas69]

That would sure do it John. I have a screen BG 10 micron in the front. What Jody said makes alot of sense. On a carb setup your return fuel does not see engine temperature because it's bypassed in the engine compartment instead of after the fuel rail. In essence you have an engine temp of say 200 and that is going to heat the fuel way up in a fuel injected setup unless you bypass in front of the rail. I have mine bypassed at the frame rail just inside the engine compartment on a carb application. I have measured my fuel pump temp and fuel tank temp after 1 hour and it's only ten degrees above ambient temp. I also used aluminum 1/2 fuel line as much as possible since it disipates heat way better than AN. Mine are on the outside of the frame as well where they get plenty of cool air.

[parsonsj]

Latest news:

Aeromotive Tech Support tells me my scenario is common: the 10 micron filter gets dirty, forcing the pump to deal with fuel pressure in excess of 100 psi in order to put 40 psi at the rails. After some time, the pump gets hot, the fuel goes into cavitation, and it fails.

They recommend that you replace the 10 micron element after 100 miles or so after a newly built car or a newly built fuel system is placed into service, since the new system is the dirtiest it will ever be.

Add in my hose problems, and the whole scenario makes sense.

So there you go: an EFI vapor lock problem that has nothing to do with deadhead vs after-rail regulator plumbing.

jp

[JRouche]

Re: dead head or bypass. I think bypass is a better system for the street. With a properly set up regulator. Its ALL in the regulator. If the pump is up to the task for the injectors, the tank is properly baffled and sumped, the pick up is at the right location (below main tank, at sump level) and the lines are of sufficient size. It all comes down to the regulator. If its not giving consistent pressures and flow to the injectors you will have problems with consistency for HP and torque and drivability on the street..

A dead head system will over heat the pump in a street car. Its cavitating and pumping within itself. Trying to make its own bleed off, so it pumps back into itself, back into the tank as cavitation.

With a bypass system the regulator is the dead head. It should be coupled with a pump that can supply it with enough pressure to keep it on full regulation. So then it can bleed off the necessary fuel to the injectors and still bleed of the remainder back to the tank. But it needs to be operating at a full pressure (from the pump) so its at full head pressure all the times. So in essence its like a dead head system, locking the pressure, its determined pressure, at all times for the injectors. The advantage is it will still allow fuel flow when its at peak pressure.

A fluid pump needs to have some flow, even at max pressure, its what cools them. No fans. Take a look at a high pressure washer, the better pumps have a bleed. That bleed cools the pump.

A dead head fuel system works fine for a race system. Only short races, some races may last what a hour or two (Thats long). Not like a street car that needs to last years under stopped traffic and not much demand.. Unless you pack a spare pump and tools for every ride

Im thinking a bypass fuel delivery system for a fuel injected car is the best. Not like the days of carburetors and mechanical pumps where a dead head system works fine. Low pressures and remember, they are pulling fuel (mech pumps) not pushing it, big diff. JR