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Well, I'm boiling my fuel...

7K views 45 replies 17 participants last post by  ArthurJGuy 
#1 ·
Consider my viewpoint on fuel system plumbing officially changed. My return style setup goes,

Dual in tank pumps -> -8 feed (with inline filter) to drivers side rail -> crossover -> passenger side rail -> Boost Ref Regulator -> -6 return to tank.


If I'm stuck in stop and go traffic or it's quite hot outside, my car will start sputtering and missing slightly at low throttle/RPM scenarios. At first I thought my plugs or wires may be the culprit, because my fuel pressure stays rock solid (on the gauge) while this is happening. But on a nice hot day, I set out specifically to make it happen (with a fuel can in the trunk). So once it started missing and such I pulled over, left the car running, and filled up a fuel can with nice cold fuel (it's illegal to fill a car while it's running here). So I pulled away from the gas station and at this point it's sputtering and missing like crazy. I pull over into an empty lot, leave the car idling, and dump the cool fuel into it. By the time I emptied the fuel into it, the car was running as smooth as silk again (well as smooth as donkey-dink cam goes). When I drove away, it was as nice and crisp as if I just pulled out of the garage...

So now I'll be re-plumbing my fuel setup,

Dual in tank pumps -> -8 feed (with inline filter) to regulator -> split feed into back of both rails -> crossover dead-headed -> -6 return to tank from regulator that was before fuel rails.


Any input/fedback on how the new setup would be run?
 
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#2 ·
I have the A1000 return style setup and I had a similar issue with mine. Mine was caused by to small of a vent (stocker). I took off my gas cap and drove it around to see if the problem persist and it did not. Just a thought and its cheap to check ;)
 
#3 ·
I guess I didn't try driving around with it off, but to check if it was a venting issue I did take the fuel cap off while I was filling the fuel can up at the gas station. So the cap was off for probably 5 minutes, then tightened it back up for the drive and it was still acting up.
 
#4 ·
Your second setup should heat the fuel much less. You're no longer using the rails as heaters for the 90% of fuel that is always getting recirculated back to the tank. Do the front crossover in an upward arch, so the the top of the arch is the highest point in the system. Any vapor that forms in the rails will migrate to the arch and form a bubble. This bubble will act like a cushion to reduce the effects of shock waves due to the injector pulses.

I'm running a #10 line from the final filter in the rear to a Mallory regulator that has 4 ports on the high pressure side. #8 to each rear rail, then a #8 arched crossover. So far so good. The only additional advantage I have is a external pump that is air cooled, instead of fuel cooled. Where the forward line passes through near the engine, I used foam pipe insulation wrapped in stainless foil tape to shield the exhaust heat from the fuel line. Also, each line from the regulator to the rails is insulated as well.

If you're running both pumps full time, consider staging the pumps. This will cut heat from the fuel pumps in half, and the secondary pump will last forever, as it's only on for short bursts.
 
#5 ·
I'm hoping that this arch here,

is high enough to do so, and I wont have to mess around with that if I don't have to. It is a -8 line as well.

I have some heat insulating wrap for the fairings on the race bike, and I was initially going to just use that and wrap my lines in the engine bay and beside the headers (under the car) and see how that worked, but then decided I'll do both. Change the way it is plumbed 'and' wrap anything near a heat source.

My 2nd pump is run off of a Hobbs switch already. It's the Lonnie's Double Pumper setup.
 
#12 · (Edited)
Most outfits selling expensive AN plumbing will recommend the fuel-heater topology, because they get to sell you more AN plumbing. I have yet to hear an actual explanation of why that arrangement would have an advantage, based on fluid mechanics. As some of you fellows get older, you may come to realize that a lot of things get passed on as fact, that have only an intuitive, rather than a scientific basis. "Ram air" is a typical example where the science is counter intuitive.

I have seen setups that simply entered one rear rail, crossed over, and dead ended into the other rail, making over 750 RWHP with no issues whatsoever.
 
#13 ·
I have seen setups that simply entered one rear rail, crossed over, and dead ended into the other rail, making over 750 RWHP with no issues whatsoever.
That's actually what I was debating doing just to get by, since I've got the fittings to do so in the garage. Then if the issue is gone, I'd buy the y-fittings or a regulator with more ports (haven't decided yet).



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#22 · (Edited)
And, I'll bet a perzillion dollars not a single one of them can tell you why.
I've got an open mind, and am the first one to admit that there's more that I don't know than do. And, I'm sure they are all fine gentlemen and are good at what they do. But every time I've asked an "expert" why it's better, they typical answer is "I've built 6,000 cars and been doing this for 200 years, and I say it's better."
 
#23 ·
I am on the fence about which is better...can't explain why one would be over the other

but I do know I have setup cars with maggie heat generators on them, with the regulator after the rails, and have no issues with fuel boiling etc at all. maybe I get lucky or maybe the maggie rails somehow keep the fuel cooler? they are much more of a mass of aluminum than say a stock rail (which is relatively thin metal tubing)
 
#24 · (Edited)
Are there any manufacturers placing FPRs before the rail on a return style system?

I thought that fuel rail temperature mainly affected return-less setups.

Seems like your problem is the dual pump setup.

Why can't you just install a fuel cooler to lower temps? Or increase fuel pressure to raise the boiling point?
 
#26 ·
Seems like your problem is the dual pump setup.
I took the secondary pump right out of the system. Still happened.

I turned the secondary pump into the main pump, and took the old main pump out of the system. Still happened.

I'm trying a few more things, but just one at a time. I'll post the results.


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#27 ·
That is certainly odd. I can drive my GTO in stop and go rush hour for 45 minutes in 115 degree temperatures here in Phoenix, AZ and not have any problems with the Lonnie's double pump setup boiling the fuel, with both pumps on full time. Do you have any of the fuel lines run right next to the exhaust or something? Maybe try driving around with the gas cap off to make sure something isn't causing a bit vacuum or something is blocking the vents?
 
#29 ·
Hmmm, thinking outloud. Boiling is very hard to do when high pressures are maintained. Even if they fuel gets really damn hot, the high pressure keeps it in a liquid state. I don't think your issue is heat, but rather something else.

- FWIW
 
#35 ·
When I dump cold fuel in it rectifies the problem. The car runs great for the 30+ minutes before this happens. Then when it starts acting up, it'll stay that way no matter what I do (switch pumps, open gas cap, etc) unless I dump some cool fuel into the system. Then it smartens right up (for about 30 minutes).
 
#31 ·
In my experience, on OEM turbo cars, the regulator is ALWAYS after the fuel rail on the return line. They dont have issues with boiling fuel at any HP level.
 
#34 ·
At 60 PSI, the fuel will never boil. The problems all show up on the return side at atmospheric pressure.
 
#37 ·
When you say dump in some fuel, how much? Have you verified that the evap system is working 100% correctly?
 
#39 · (Edited)
The first time was about 10L/2.5 gallons (with a half full tank), every time after I just top up the tank.


Couldn't tell you on the entire EVAP system. But pressuring up the tank would be out the window with removing the cap would it not?

Edit: I guess I can turn all my EVAP stuff back on in the tune. I had it vented at one point so I had the DTC's turned off, but it's been hooked back up since the BlowCharger build. See if/what it lights up for codes.
 
#40 ·
Before driving the car remove the gas cap and see if you can get the fuel to boil. Once it gets hot its to late to try this. I still think its a vent issue.
 
#41 ·
I did that yesterday (had the cap off from cold) and it still had the same result.

But I just got back from driving around and around and around, and it actually seems to be gone *knock on wood*.

I took the hose off of the EVAP solenoid in the rear quarter that has the line from the charcoal canister, and I also put the line that goes to the EVAP sensor under the hood open to atmosphere.

So I'll have to mess around with both of those now and see where the issue may be.
 
#42 · (Edited)
I'm finally getting the time to start my blower/ fuel system install was just curious if they're any precautions with plumbing the lines I need to take or and tidbits you can give before the install? This will be my first blower/fuel system install so I'm not sure what to expect. I've been reading this forum every chance I can for useful information.
 
#46 ·
I know I'm late to the party, but I had this EXACT same issue.

My first return system was:

PUMP -> RAIL -> CROSSOVER -> RAIL -> REGULAR -> RETURN

and it would boil the fuel in the tank every damn time. Adding fresh cool fuel to the tank also remedied the issue. The tank was to hot to touch when this would happen.

I changed the plumbing to be

PUMP -> REGULATOR -> DUAL FEEDS TO RAILS -> DEADHEAD

and it never once boiled again. I ran it this way with multiple setups, including the OEM H2 fuel regulator setup, and I never had an issue at over 700 RWHP. I will continue plumbing fuel systems this way in the future.

Side note: I actually stumbled onto this post looking up fuel plumbing ideas for my Regal.
 
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