Parallel or dead head?
 

For those of you with EFI, which would you recommend as a delivery system and why? Does one have clear advantages or is it application specific. Thanks

I'm running dead head. Easier to package, less potential for heating the fuel, etc.

Thanks Scott I believe your system is very similar to mine. I did a search on this subject on another forum and it was a 6 page discussion which included Jody and Steve. However that was almost two years ago. I was wondering if they had any more info that could help.
Scott what injector size, PSI , and tank do you currently have? Thanks

Fuel system plumbing will always cause a lot of discussion.

I'm running the stock LS7 40lb injectors at 60psi. I have a Rick's tank with a Walbro 255 pump. When I don't run out of gas, it works great. :D

I'll have a pressure drop when cornering with just 6-8 gals consumed from a full tank. It is the narrowed Ricks tank with a supposed 16 gal vol. I'm now thinking it could be my pump and pick-up.
Scott, I assume that when you say "run out of gas" you mean empty or close to it.
Do you have any issues with the dead head system and pressure drops at WOT?

I run a dead head system, have on the last few cars I've built. I have no pressure drop issues at all, dead steady. However, if the tank gets low enough (depending on cornering forces or acceleration rates) it will move away from the pickup and you'll see the pressure fluttering and dropping. That is not a return style or returnless issue, that's a fuel pickup issue.

A separate surge tank will eliminate this; even if the tank flutters a bit you have a separate 1-2 gallon tank that's always full to draw from. Works great in drag racing and road racing. I still think this could be incorporated inside one of Ricks tanks which would be the ultimate setup. I need to call those guys and see if they're up for trying it.

Jody

I ran the car out of gas on the Power Tour. I dropped the tank later this summer and checked it out, wondering why it wouldn't pick up gas when there was several gallons left. The sock/pickup was on the bottom, but the return hardline came back into the tank parallel to the pump/pickup. It was pointing directly at the bottom of the tank, between 1" to 1.5" to the side of the sock. I suspect what happened was once the level got pretty low, the returning gas was cavitating what was already in the tank. I took a tubing bender and turned and return hardline so it no longer pointed at the bottom of the tank and away from the sock. I haven't had a problem since, but I've been really careful about not getting really low on gas and always keeping an eye on the fuel pressure gauge.

Scott, I talked with Hector at Ricks yesterday and discussed the issue. It is not a system design problem, ie. parallel or Jerry Garcia (just thought of that and couldn't resist-sorry:P ). He had something very similar to my situation happen to another setup. They retro fitted the tank with a Bosch pump (330 lph); no problems after that- even on an extended trip thru the curvies. Apparently the A1000 pushes alot of fuel and will suck dry quickly on low volumes. He warned me of this initially-should of listened.

I dead head into the fuel rail and have never had an issue.

In fact.. the Z06 and the ZR1 both dead head. It's simpler to package and at our power levels very reliable.

Thanks Steve,
Sent PM

The real issue with dead head systems is what's called 'hammering', or hydraulic shock. This occurs when the 'column' of fuel in the rail is subjected to the pressure changes induced by the injectors opening and closing. To combat this, fuel dampners can be used, but it's better in high-volume applications to use the typical return style system.

Look at the dampners at this sight, and the explination of hammering.

http://www.injector.com/fueldampers....72ee3053fe9e5a

Yes, it is much easier to package dead-head systems, and with smaller injectors and demand, it's usually not a problem.

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would "hammering" be as much of an issue on a car with sequential EFI, compared to a car with a bank 2 bank set up, where all the injectors fire on one side simultaneously?

never had that issue, and I've always used it (dead head) with 75 or 95# injectors. The fuel pressure never wiggles at all, sender is in the rail. If I have an issue that's a cool thing to try, but no reason for it as far as I've experienced.



Jody

Jody, what kind of pumps & regulators do you run? Do the pumps you run use an internal bypass of any kind? Curious. I've always understood that with dead heads pumps don't last as long due to heat, and fuel pressure at WOT isn't stable. I've also understood that fluctuations of 4-5 lbs at WOT is in fact due to hammering, and to steer away from dead head systems. I personally have only used bypass styles to avoid these kinds of issues, and have never done a dead head, because of my understanding, but maybe I need to rethink my ways?

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my systems still bypass, just that the bypass regulator is located at the rear of the car instead of the front. I've used Aeromotive, WalBro, Bosch, and many other pumps, but currently have an Aeromotive pump and regulator. I do not see any pressure fluctuations.

Jody

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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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

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?

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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.

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

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.

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

thanks John.

Jody

Sounds like I'll be cleaning my 10 micron soon.:thumbsup:

And ill be ordering a few spares tomorrow.....

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

the deadhead system we were speaking of still has a bypass regulator, just not up front at the rails.

Jody

Then it's not really a dead headed system.

GM refers to it as a dead head system on the late Vettes, yet they still bypass at the filter where the regulator is built in. I bypass at the rear of the car with a regulator right off the pump, so I've always referred to it as dead head, as there is no return of the fuel from the engine. Whether that's the correct terminology or not, those who commented on having a dead head system early on in this thread were speaking of one that bypassed from the rear of the car, either through the factory Vetter filter/regulator, or from a rear mounted regulator like me.

Jody

Interesting...one of those deals where everybody has a different definition. To me dead heading is one fuel line and the pump bleeding off the pressure internally. Sounds to me like they are bypassing exactly like a carb setup. On the flip side after the regulator it is dead headed to the carb or injectors. I still think they should call it a bypass.:D

The dead head system I referred to when I started this thread is what Jody describes and has been used by others when building a new FI system. In that definition the dead-head or stop point is at one of the fuel rails. A more decriptive term probably would be a series system that dead heads at the rails (and bypasses at the regulator).
http://www.kinsler.com/Cat_31_Web_HT..._screen71.html

I suppose we could go with tank-based bypass and rail-based bypass. That's a TBB and an RBB where I work. We have lots of TLAs (three letter acronyms).

jp

I like that John. It's settled then, it is a RBB. yea.

Oops, my bust. I was thinking of it being dead headed at the engine, like a mechanical pump for a carb, the regulator at the fuel rails in my case. LOL Guess I have to get in tune with the terminology. Solly, I missed that point :) JR

I still refer to engines as "motors", so what do I know...................... :rofl:

Jody

Heck, I call them air pumps sometimes . . .

Haa. I know, I would rather call it like I grew up with, motor, but sure as snot Ill get an electrical engineer slappin my hand tellin me motors are electrical. Oh, no Sh*t, but they are motors for me, ever since dad showed me all about motors (engines). He called them motors and thats what they are. Heck, they are MOTOR vehicles under the current laws so thats good enough for me. Motor is what they are :) And for the picky, no need to correct anyone, we all know what is being said. Motor on!!! JR

Here's a picture of my new Brown & Miller fuel hoses. Expensive ($100) for the both of them, but not outrageous. Add up the cost of Earl's swivel-fit ano-tuff fittings and the the Brown & Miller stuff is about 10% more.

Of course, you can get any color fittings you want as long as it's blue and gold. :rofl:

They are rated forever on pump gas, and have NO gas smell.

Great shot, John. Love all that detail.