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Dead Head Return Fuel setup or no?

63K views 126 replies 28 participants last post by  67coupe 
#1 ·
Currently my car has your standard return setup with a -10 feed to both rails, front of the rails go to the regulator and then returned back to the tank.

Fuel system components consist of.

Glenns Sleeper tank with dual externally mounted Bosch 044s ran at all times (no hobbs)

-10 Feed -8 return

ID 1000s.

Fuel lab regulator with 1/2" return port.

My car is going to go through some changes this season and I wanted to clean up the look in the engine bay a bit and move the regulator as well. Its currently mounted on the the driver side valve cover. I was thinking of switching to a dead head return setup, feeding the regulator then feeding the rails from there and capping off the other side of the rails. Some claim lower fuel temps but some also claim some tuners HATE this method. Will there be any negative effects going to a dead head setup with my current setup? I will be mainly running Pump 93/Torco mix and sometimes E85.
 
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#91 ·
I did not measure it but snapped a pic of the inside of my Fuel Lab regulator.
 

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#92 · (Edited)
That pic verifies a lot. Thanks for posting it! Do you remember what p/n that Fuel Lab unit is?

From the research I've done there seems to be two price levels: $150ish and $200ish. My guess is that anything in the $150ish range will have the smaller return hole.

I'm shooting for 900hp and this doesn't mean that the smaller hole won't work for my application. I plan to run dual 340's (rated around 1200hp) and I will stage the second pump to come on later so the question becomes: How much fuel needs to be returned to the tank under full load/power with dual 340's and can that unused fuel flow through the smaller hole? Maybe dual 340's will overwhelm the smaller hole size at max power but dual 255's wont. I don't have much experience with regulators but I'm PRAYING that there are no downsides to having a "too big" of return hole so I'm trying to error on the safe side with the larger return hole.

If you're not having issues I certainly wouldn't change regulators but instead just keep what we've learned in the back of your minds.

ks
 
#93 ·
I just switched to a dead head setup, works flawlessly so far and my car is remote tuned by Kevin Dunn aka 04sleeper. Car starts up perfectly fine, even after sitting for days.
 
#102 ·
The system will loose any trapped air at first start. Thereafter, absent any leaks, it should never see air again. Like Joe suggested let the pumps prime for a moment and you will be good to go.
 
#105 ·
What an excellent thread. I’m still amazed at the level of tech this forum provides. By far the best source of information for these engines.

I currently have a lethal budget return system on my terminator swapped foxbody. Reading this thread has confirmed my suspicion that I’m over heating the fuel. It’s especially obvious during our oppressive summer heat (southeast).

For those with dead head setups:

1) How are hot restarts after a short soak (5 to 15 min)? With my system, the engine will turn over for 3 to 5 sec before struggling and slowly stumbling to idle.

2) Is a re-tune mandatory or recommend after changing to a dead head setup?

Ed,

For those of us with “mild” hp goals (550 rwhp), would converting back to returnless make the most sense?

Todd
 
#106 ·
If you have already invested in the return style hardware I would not spend the monies to go back to the returnless system, Todd. Both systems work well and in the FWIW category most of the race setups opt for the simplicity of the return style system.

The challenge(s) you need to manage are unnecessary heating of the fuel and subsequent return to the tank. Vacuum / boost pressure vacuum line signal delays and attendant uncontrolled return system pressure variances in the fuel rails. The good news is that all are manageable. If you still have a returnless system and use the PID control model that Sullivan Performance developed you can easily handle up through essentially 700 HP.

Things you want to pay attention to for a return style system certainly include placing the fuel pressure regulator away from engine heat. When you do this, you end up using a longer rubber signal hose to deliver the manifold boost or vacuum signal to the regulator. This can potentially produce rich or lean transition points as manifold pressures rise and fall because of the time delay in signal delivery from the manifold through a hose to the pressure regulator. Shorter hose is always better but in a typical balancing headache shorter gets you closer to the engine heat soak problem and longer gets you a manifold vacuum/pressure single timing delay.

When Ford designed the OEM fuel system they had a variation of the signal delay problem that was caused by the tank mounted pumps and normal delays in sensor readings. Their approach was to employ a second pressure test point closer to the injectors and the manifold. The sensor they used was the FRPS. The FRPS measures the delta pressure across the injector calculated as the difference between instantaneous fuel rail pressure and instantaneous manifold pressure.

Once the ECU knows what the actual delta pressure is it calculates a pulse width for the injector that is designed to produce the commanded AFR the tuner asked for. A lot of guys remove the FRPS when they switch to the return style systems because they have been frustrated by blown FRPS sensors prior to the change over to return style. While this is possible to do it is better to leave the FRPS in place, more on that in a minute.

The reason for the FRPS failures in the returnless system is the pressure spikes associated with a poorly adjusted PID — which is what the Sullivan fix is all about. Once you do the Sullivan fix in a returnless system the fuel surges and pressure spikes that kill an FRPS suddenly come under control.

The firs time return style conversions frequently eliminate the FRPS. While the engine will still run w/o the FRPS it will run much better with the FRPS even in a return style system. Remember those lazy to get to the pressure regulator manifold pressure signals that appear with longer hoses between the manifold and the pressure regulator? With the FRPS present the factory ECU can see the effect those slow to arrive signals have on fuel rai pressure. The factory ECU not only sees them it compensates for them by adjusting injector pulse widths in real time to deliver the tuner's commanded fuel charge to each cylinder irrespective of varying fuel pressures.

If you are already a return style system, consider getting the fuel pressure regulator away from the engine compartment heat and reinstalling your FPRS (if you removed it). Your ECU (and your engine) will like you for it.
 
#107 ·
Apologies Todd!

I thought I had posted a pdf of the Sullivan "fix" in this thread. It looks like I did not so here is a pdf copy of it. I lifted this out of the original thread about a decade ago — yeah, its been around that long. Those Sullivan guys were pretty sharp folks.
 

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#108 · (Edited)
Thanks for info Ed. I’ve read that Kurgan also has the fix for the returnless hesitation. I’m assuming he’s adjusting the same PIDs?

I guess I’m still undecided as which way to go.

For returnless, I still have a factory fuel hat and have squirreled away two junkyard FPDMs. I’d only be focus pumps (unless there’s a better alternative) and a tune away from converting back. The idea of having factory like operation is very appealing. Mainly OEM like start up behavior and not constantly pumping unnecessary fuel.

As for staying return, I’m not exactly clear as to what current components I can use. From what I’ve read in this thread, aftermarket fuel rails with a supply for each and a crossover at the end is ideal. Would the stock supply line work for my hp goals? Would the regulator in the budget return kit work (Division X two port)? Add necessary plumbing and fittings, converting to dead head is adding up to addditional money.

Would there be any concerns with both pumps running, or would staging them be ideal? Also, any known hot restart issues with dead head, or does the pressure in the rail prevent them? Finally, would a re-tune be necessary or recommended?

Sorry for the excessive questions. Thanks again.
 
#109 ·
These days it pretty much comes down to what your personal preferences and willingness to buy new stuff is, Todd. Both system styles can be made to work well for your intended use.

If you already have a return style setup the pregnant question is why buy more stuff to go back to a returnless style system. Similar questions going the other direction. Remember, both can be made to work well for you. My suggestion would be to use what you have rather than buying "new stuff".

If you have a regulator with one of the small bypass orfices in the return port, you might want to try it before stepping up to the next larger regulator — $200 or so is a fair amount of beer and pizza. At the 500 HP threshold you might be very satisfied with its performance.

This next comment is not meant to be deprecating. Why not take the best parts you have right now and lets build a 500 WHP engine that does the least damage to your pocketbook and produces the best smileage (smiles per driven mile).
 
#111 ·
I just finished converting my lethal performance budget return system to a dead setup and took it for quick drive. The exhaust note is different and the throttle is not as responsive. I’m pretty sure I have a fuel supply issue.

I relocated the division x FPR to the factory fuel line near the passenger strut tower, rerouted the retuern line and ran a new supply line to the factory fuel rails.

First thing I suspect is I’ve plumbed the FPR incorrectly. It’s a 2 port EFI regulator. Are the two -8 ports directional? I’ve searched everywhere for directions or a flow diagram but can’t find anything.
 
#113 ·
Ed,

I did find that diagram. What I’m unsure of, or want to verify, are the two “side” ports directional? E.g. is the input on one specific side? I do have the return plumbed to the bottom port.

Also, I did replace both fuel pumps (Walbro GSS342) as the old ones became very loud after what I’m assuming was repeated fuel heating. I’m want to confirm the FPR is plumbed correctly before dropping the tank again.

Thanks, Todd
 
#116 ·
Thanks Joe. I was afraid of that.

Just brainstorming here. So assuming my new pumps are good. What are the chances that using the stock supply line (5/16”) with a -6 return is causing a pressure drop at the rails now that the regulator is between the pumps and rails? Could the stock line be too small to keep up with change in demand?

I haven’t data logged the FRPS yet. I’ve got to borrow a laptop and add the SCT software. Will be doing that in the next few days.
 
#117 ·
Thanks Joe. I was afraid of that.

Just brainstorming here. So assuming my new pumps are good. What are the chances that using the stock supply line (5/16") with a -6 return is causing a pressure drop at the rails now that the regulator is between the pumps and rails? Could the stock line be too small to keep up with change in demand?

I haven't data logged the FRPS yet. I've got to borrow a laptop and add the SCT software. Will be doing that in the next few days.
This is a virtual certainty, Todd. Your feed line should be -8 with at least a -6 return. At WOT your engine will use most of the fuel the pumps can supply so the return requirement will be relatively small. At idle and in town driving speeds your engine will use very little of the fuel your pumps can supply and will return the majority (90%+) back to the fuel tank.

A 5/16 line is great for a carburetor or a >200hp daily driver. It is unsuitable for a performance engine of the type you have built. If you replace the 5/16 hard line with a teflon lined -8AN line I think you will find most of your fueling gremlins will disappear.
 
#119 ·
Thanks everyone.

I’m piecing together the hoses, fittings and hose ends to use a -8 supply vice the factory hard line.

Couple of additional questions.

Are the stock rails okay or will I need to replace them as well?

Currently, the adaptor on the rail is a -6. Will a -6 from the regulator to the rails be sufficient?
 
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