Parallel vs. dead head

[ss dave]

Curious what others are running and why. Are there advantages to one system or is it application specific.
I have a LS7 with 44# injectors setup with a parallel system and I will have an ocassional drop in fuel pressure, it is most likely due to starvation of the pickup. But I'm just wondering if a dead head system might compensate for some of this and keep pressure more consistent. Thanks

[ss dave]

I just did a search and came up with a 6 page thread on the subject. However that was almost two years ago. Wondering if anyone in that thread can shed some of their experience on this matter.

[parsonsj]

Well... we can talk about my setup.

I've been running a parallel system in my car for several years. No issues at all, not during road racing, autoX, or street driving. I drive it all the time and have never had an issue with my parallel setup.

But...

I recently switched to a Vintage Air Front Runner (as I'm adding a/c to the car). Part of that involves a switch from a racing alternator (80-90 amps at 1400 rpm) to a street alternator (140 A at 900 rpm). My idle voltage jumped from 12.2V to 14+V.

Why does that matter?

Because on the car's most recent outing, I had significant fuel problems, and it's possible that they were caused by added heat from the fuel rails being slowly pushed into the fuel as the fuel circulated to the tank and back.

With the added voltage at idle, the fuel pump (an A1000) saw 14V instead of 12v. I'm wondering if that was enough to cause the fuel to overheat over time. In other words, my alternator was acting a bit like Aeromotive's pump controller.

So... I've got a temp sensor and gauge on its way to me, and I'm going to monitor fuel pressure and fuel temperature to see if that's what is happening. If so, I'll switch over to a deadhead setup and see if the fuel temps are significantly reduced.

If you can wait a couple weeks... we might have some real data on the two setups.

jp

[ss dave]

John if you keep me posted you'll be my favorite moderator, lol. My car will be back in my hands in two days and I am going to experiment. I'll check the rails, tank and lines with a heat gun at idle and after a run, etc. I have been conscientious about keeping 13v or greater to that A1000. I was told that was necessary for maintaining 58 psi, but from what I've read it isn't beneficial at low RPMs, therefore the purpuse of a controller.

[Payton King]

I had the yellow 69 with a belt problem

I researched this long and hard plus have a little expierence with this as well.

Aeromotive told me the best way is to run a system with a return line...which is for super high horsepower drag cars. Jody, who now owns Mali2ude, has run dead head systems on cars up to 1000 hp.

An A1000 flows a ton of fuel so a lot is bypassed. Running it through the engine compartment and back to the tank is bringing heat in the system...thus heating up the fuel. When I was using an A1000 with 14 volts, and it was deadheaded, the fuel would still heat from the pump in the tank and the heat created recyling the fuel so often. Feel the tank after driving and it was quite warm.

My motor only makes 425 at the wheels which is close to 500 and some change at the crank. I went to a walboro 225, the only change, and my tank is cool to the touch after driving with no loss in pressure. I know Scott Gulbranson over at lateral G is running the same Walboro pump on an LS7 that made 500 hp at the wheels with no problems.

My opinion which means nothing. The fuel fluxuation is due to fuel slosh in the tank just like you stated. Fill your tank and see if you have the same problem. I think a deadhead system is the way to go. John I think you nailed your problem on the head. Fantastic car by the way.

[Vegas69]

I don't think Dead Heading a system is going to give you more consistent pressure. WOT is where you will have your problem dead heading. When your voltage changes especially from 12 to 14 volts your GPH will change which will probably mean you need to readjust your fuel regulator especially on a return style system. Dead headed not so much. Fuel systems seem to be a real gray area. Every application is so different. Going with a pump that is just large enough for your engine is important I think. There is no use pumping excess fuel through your return or dead heading. It will just make heat. I also think that having a large return is important if you are running that style system. Fuel actually grabs the walls of the pipe or hose. The bigger the less resistance. I have a Ricks tank and I don't trust the fuel gauge any farther than I can throw it. I don't let the tank get very low. I already ran it out of gas once. LOL

[ss dave]

When I initially researched this subject I was advised that the parallel system was superior in that it gave the injectors the most consistent pressures among other reasons.
I have a Ricks tank with a A1000 to supply the larger injectors and the HP. I was also warned of the heating issue so I installed a 12" in-line heat sink.
The tank is supposed to have a volume of 16 gals. the tank was not filled to full when it was initially used and I'm not sure of the exact full vol., but starvation would occur after 6-8 gals was consumed from a full tank (therefore I never ran to empty or close). After only 6 gals. used of fuel the pick-up shouldn't be exposed, so I'm trying to brain strom on a reason for the drop in fuel pressue.
1. The A1000 does have a large pick-up, just maybe the top of the pick-up is exposed, esp. cornering.
2. Maybe hot fuel returning to the pick-up is vapor, or partial vapor, I'll check this with a heat gun.
3. Maybe the pump is to big for my application and fuel is hot even prior to reaching the engine.
4. Mean Little Fuel Gremlins
I don't know but any thoughts are appreciated.

[Vegas69]

Does the pressure come back down the straightaways?

[parsonsj]

In my case, the pump would get very loud, and the car ran as if it were out of gas. My fuel pressure gauge was out of action (don't ask), and so I can only theorize that fuel pressure was down. But it had nothing to do with curves or straightaways.

Dave, if that's how your car is behaving, then maybe it is this hot fuel/vapor lock situation.

jp

[ss dave]

I'll have pressure drops even on straights at times. The fuel gauge is not exactly the most accurate, but I assume that I have had less fuel when it drops on straights as opposed to cornering.

[ss dave]

I just spoke with Hector at Ricks. He stated that the parallel system is preferable and that the A1000 is emptying the cache so quickly that even at moderate volumes this can occur ( not to mention hot fuel/ vapor). He has had experience with this. Switching pumps is probably the answer and is certainly worth a try. A Walbro 255 will work for mid to high 500 hp and a Bosch pump for 100-150 hp more. I'll know in a few weeks.

[Patrick]

I have a Rick's Tank that starves for fuel anytime it is at or below a 1/2 tank. It is even worse on right hand turns. I dropped the tank this weekend and pulled the pump..The sump and baffling or lack of is the cause. Lateral-g has a thread discussing this and some remedies...just search "surge tank".

John, I am betting that your A1000 is overheating. The A1000s are known to overheat in cruise type situations or under continuous use of 30 minutes or longer. Their pump controller is very similar to Kenne Bell's Boost-A-Pump in that it drops voltage when in the lower rpm range. Your race alternator was inadvertently protecting the pump with its lower voltage.

Patrick

[parsonsj]

Your race alternator was inadvertently protecting the pump with its lower voltage.

Yes, that's my current theory. I'll know more in a couple weeks.

jp

[Vegas69]

Maybe having an external pump isn't so bad after all on these Ricks Tanks.

[Hammered]

I'm putting out about 560 HP at the crank with a parallel system, Walbro 255 and RockValley SS tank. I've never had a starvation problem, even below 1/4 tank. I did have major fuel heating problems. I insulated my lines in strategic places, installed an Aeromotive pump controller which cuts the flow (but not the pressure) at rpms under 3k and I put a bunch of cruise timing in to get heat out of the exhaust. I believe my heating problems are gone, but I still want to insulate the fuel rails from the intake manifold which will require some machine work.

[David Pozzi]

I moved the fuel pickup of our Ricks tank before we even installed it. I had no faith that the pickup placed in the very front of the tank would work. I bent up a stainless tube that positions the pickup at the rear of the flat bottom section. It has worked out pretty well on a road course. If it get's down to 1/4 tank or less it will sputter, this is engine has a carb.

A "make up" tank is pretty useful for getting the last drop out of the tank.
David

[Fuelie Fan]

In my case, the pump would get very loud, and the car ran as if it were out of gas. My fuel pressure gauge was out of action (don't ask), and so I can only theorize that fuel pressure was down. But it had nothing to do with curves or straightaways.

Dave, if that's how your car is behaving, then maybe it is this hot fuel/vapor lock situation.

jp

Pumps get noisiest when they're pulling air, either from a low tank or a bad/loose fitting upstream of the pump.

[camcojb]

Pumps get noisiest when they're pulling air, either from a low tank or a bad/loose fitting upstream of the pump.

or really hot fuel...............

Jody

[Bored&Stroked]

From everything I've heard, it is better to run a bypass pressure regulator with a return line - to guarantee WOT fuel volume. The obvious issue is that with street or road course driving, that you can put a lot of heat into the fuel (not a good thing). I'm setting up a street/strip hotrod with a blown 392 Hemi (800 or so crank HP).

In talking with Jim Craig at Weldon, he recommended running a bypass regulator and a fuel-pump controller to reduce pump speed/volume when you don't need it. Their controller has a potentiaometer (sp?) (dial controlled switch) to give the driver control over the pump. Given that the car will spend most of its time on the street, the above setup should work out . . . guess I'll find out next summer when it hits the road!

[parsonsj]

I'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 (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 work, 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.

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

jp