Parallel vs. dead head [Archive]

ss dave

10-13-2008, 08:26 AM

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

10-13-2008, 10:07 AM

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

10-13-2008, 10:16 AM

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

10-13-2008, 10:36 AM

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

10-13-2008, 10:55 AM

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

10-13-2008, 11:11 AM

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

10-13-2008, 12:06 PM

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

10-13-2008, 12:22 PM

Does the pressure come back down the straightaways?

parsonsj

10-13-2008, 12:46 PM

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

10-13-2008, 01:23 PM

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

10-13-2008, 01:30 PM

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

10-13-2008, 01:35 PM

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

10-13-2008, 01:53 PM

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

10-13-2008, 02:20 PM

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

Hammered

10-13-2008, 02:53 PM

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

10-13-2008, 07:49 PM

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

10-17-2008, 07:41 AM

camcojb

10-17-2008, 08:08 AM

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

10-19-2008, 06:56 AM

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

01-26-2009, 05:21 PM

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. :doh:

jp

TT302Z28

01-26-2009, 07:15 PM

MSI in Roseville, CA. Modifies C6 Z06 Corvettes all day to 600+RWHP without having to modify the fuel pumps or tanks.

What does the LS7 in the Vette's come with?

CarlC

01-26-2009, 08:42 PM

That Russell hose keeps coming back to haunt you JP!

parsonsj

01-26-2009, 08:51 PM

I know! I thought I'd seen the last of it, but nooooo.

Anyway, I hope this fixes the problem.

jp

ss dave

01-27-2009, 07:33 AM

Up date, I pulled the Aeromotive pump and replaced it with the largest Bosch pump made, 300lph, more than enough for my LS7. In fact Holley states it would be good for over 800hp.
Now, with limited test time, I'm not starving the pick-up, but get fluctuations at 3/4 WOT. The pressure will drop 8-10 psi.
We think a vacuum regulator will help, as opposed to my current Weldon, but I won't know for probably two months, when I finish upgrading the rear suspension and stuff!

The stock 2008 LS7 pump flows minimum 188lph @ 52.9 psi @ 12v
Walboro GSS340 255lph = 67gph = 404 lbs good for 800hp
Bosch 044 300lph or 80 gph @ 72.5 psi better yet.
Quieter than my A1000, probably cooler too.

parsonsj

01-30-2009, 01:07 PM

I got the new elements yesterday and installed them. Last night, I did a test of the pump that tells me the filter made a huge difference.

I disconnected the fuel line in the engine bay, and ran the pump. Fuel shot at least 10 feet in a huge glug of fuel. Before, it would just gurgle out of the hose.

OK, I didn't actually mean to coat my garage in 93 octane (I forgot the hose was over at Brown & Miller), but the test showed how much restriction the filter was.

Here's a pic of the new BMRS hose (PTFE inner liner, polyester outer braid, and guaranteed on pump gas indefinitely):

camcojb

01-30-2009, 01:08 PM

love a happy ending............... :1st:

John McIntire

01-30-2009, 04:16 PM

So John, would it be safe to say that the experince that you and others have had with their cars running poorly after extended periods is due to a dirty outlet filter? The outlet filter being so dirty that the fuel pump was trying so hard to push fuel through it that it started to cavitate and in turn heating the fuel up and the cell, and the car running poorly because of the lack of volume and pressure at the rails?
This is a good find on your part! Hopefully when you get it all back together and running you can give us an update as to how the car runs on long trips. I have put off converting my car to EFI for awhile, well one for lack of time, but I wanted to see what came of this topic because I really didnt know how I was going to plumb it. I'd rather go with the traditional setup with the regulator up front by the fuel rails and run the return line all the may back.
Thanks for sharing this info with us!

On a side note, I used Russell line on my old carb'd SBC and after a few weeks of running it I noticed that my fuel pressure was low, and I cleaned the filter and everything ran fine for a few more weeks, then the same problem. I couldn't even go WOT. I don't really remember any black particles in the filter screen, as it was a stainless mesh type, I think 10 Micron. Doesn't look to be that Russell hose is up to snuff, does it?

parsonsj

01-30-2009, 04:54 PM

Van B

01-30-2009, 05:37 PM

So John, would you think I would be best off to plumb mine with hard line all the way to the engine bay and make sure to use teflon braided line everywhere else?

parsonsj

01-30-2009, 06:02 PM

would you think I would be best off to plumb mine with hard line all the way to the engine bay and make sure to use teflon braided line everywhere else?Absolutely. That's my setup now. Hardline all the way to a fender bulkhead (and back since I'm using a rail-based regulator), hardline in the rails, and just some teflon inner lined flex line from the fender bulkheads to the rails.

Bonus: no gas smell. (that is, once the gas that ended up on the floor during my pump test evaporates)

jp

CarlC

01-30-2009, 08:34 PM

Same here except for flexible teflon lines at the tank as well. Zero gas smell in the garage.

andrewb70

01-30-2009, 11:10 PM

Teflon lines are the only way to go. Seriously!

When I worked at Holley they were doing some testing on various hoses to see how they stand up to everything from race fuel to E85. Race gas was actually easier on the rubber hose than street fuel. In the end it was found that all of the fuels deteriorated the rubber hose to some extent. The Teflon hose is impervious to just about all fuels.

Andrew

Vegas69

01-30-2009, 11:29 PM

:lmao:
love a happy ending............... :1st:

parsonsj

02-01-2009, 10:29 AM

I gotta get my car back on Mike Norris' dyno. I swear it has more power. Maybe this lack of gas has been a problem all along.

Anyway, hours of driving later, no fuel pump problems.

What will I do all day now?

jp

CarlC

02-01-2009, 08:37 PM

Breath in the aroma of latex paint being chewed up and stained by 93 octane.

B Schein

02-03-2009, 06:21 PM

Those are some nice looking hoses.John did you get to meet Wade and the guys from BMRS at PRI.

parsonsj

02-03-2009, 07:22 PM

No, I just called them up. I talked to Penny on the phone, and Scott made the hose.

jp

Fuelie Fan

02-04-2009, 12:00 PM

Teflon? Do you mean nylon hose? Pretty sure the OE's use nylon-12

parsonsj

02-04-2009, 12:11 PM

The liner of the hose is PTFE. See more about it here (http://en.wikipedia.org/wiki/Teflon).

jp

JRouche

02-04-2009, 07:28 PM

The liner of the hose is PTFE. See more about it here (http://en.wikipedia.org/wiki/Teflon).
jp

Hey John, I have literally hundreds of feet of stainless braided hose in various sizes with teflon liners. I would like to use it for the car. It was for another project and its just sitting around. What I would like to know is what fittings to use. The teflon looks to be pretty thick, maybe a lil over a 1/32", close to 1/16" just by looks, and its stiff. Can I use AN type compression fittings with it for fuel?? Whadda you think. I know the liner is pretty slippery and would hate to have the fitting pull out. Any advice would be great. JR

CarlC

02-04-2009, 07:29 PM

The nylon/plastic tubing is really nice. If I ever build another LS/EFI setup I will likely spring for the quick-connect OE type connections and nylon/plastic tubing.

CarlC

02-04-2009, 07:33 PM

Hey John, I have literally hundreds of feet of stainless braided hose in various sizes with teflon liners. I would like to use it for the car. It was for another project and its just sitting around. What I would like to know is what fittings to use. The teflon looks to be pretty thick, maybe a lil over a 1/32", close to 1/16" just by looks, and its stiff. Can I use AN type compression fittings with it for fuel?? Whadda you think. I know the liner is pretty slippery and would hate to have the fitting pull out. Any advice would be great. JR

That could be the stuff, but compare the bend radius to Aeroquip and Russell. There are dedicated connectors for use with teflon hose. Aeroquip makes some very nice parts, and, the ferules can be replaced making them life-long investments. The ferules have a fishhook type gripping mechanism made specifically for this application.

Aeroquip has a downloadable catalog on their website

parsonsj

02-04-2009, 07:34 PM

Can I use AN type compression fittings with it for fuel??I think you can probably use the ferrule style fittings. I'd definitely pressure test it before putting it into service though.

jp

parsonsj

02-04-2009, 07:35 PM

Uh... Carl said it much better than me.

jp

andrewb70

02-04-2009, 07:47 PM

Hey John, I have literally hundreds of feet of stainless braided hose in various sizes with teflon liners. I would like to use it for the car. It was for another project and its just sitting around. What I would like to know is what fittings to use. The teflon looks to be pretty thick, maybe a lil over a 1/32", close to 1/16" just by looks, and its stiff. Can I use AN type compression fittings with it for fuel?? Whadda you think. I know the liner is pretty slippery and would hate to have the fitting pull out. Any advice would be great. JR

I believe there are teflon specific fittings. I personally like going to the local industrial hydraulic store and have them make hoses for my projects. Look at Aeromotive hoses in the power steering section.

Andrew