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Fuel starvation solutions

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14
5
Exp. Type
Autocross
Exp. Level
10-20 Years
Austin, TX
'16 S550 GTPP, E85 (most of the time). I'm at the point where I'm fuel starving in long left-handers at anything less than 3/4 tank. Its even happening on some concrete autocross courses. I have pretty big aero and sticky tires (315 A052), and it wasn't this bad before the aero. I wondered if something in my nearly 100k mile gas tank and fuel system just needs servicing? E85 gum up a sock or something?

What's the best fix short of putting in a large fuel cell? Surge Tank? Any in-tank solutions?

I'm completely fed up. I don't mind keeping the tank above 1/4 or even 1/2, but keeping it topped off above 3/4 is too much I need to find a solution if I'm going to keep running this chassis.
 

JDee

Ancient Racer
1,818
2,020
Exp. Type
W2W Racing
Exp. Level
20+ Years
5 miles from Mosport
I'd just go to a fuel cell and racing pump system, once you start making big Gs in corners there's no easy fix. I don't feel there's a good solution with the stock tank, they starve badly on left hand corners, and if it's a long left or a left with a compression it will starve at anything below 3/4 of a tank. There's a lot of things you can try, but a fuel cell is likely the easy button. Turn 2 at Mosport was one place where it was guaranteed to starve with anything less than 3/4, it is a long downhill left with a lot of compression as it transitions to an uphill on the exit.
With the stock tank you need to top right off before every session, and for anything over 20 minutes you're likely going to start experiencing fuel starve. Especially true with cars making big HP/big RPM or big G's. This experience was with my former '16 GT PP1 that was much modified and running slicks, it had trouble with fuel slosh starvation even when on treaded tires.
 
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Carter on here rigged up an in tank transfer with a cheap pump from the passenger side to the driver's side. I replicated it and its worked great. That said, it is a cheap jerry rigged solution, so question is if you rely on it are you ok with the risk that it fails. That risk of course is higher than a proper fuel cell or external surge tank. So what are your priorities, cost or reliability?
 
14
5
Exp. Type
Autocross
Exp. Level
10-20 Years
Austin, TX
Carter on here rigged up an in tank transfer with a cheap pump from the passenger side to the driver's side. I replicated it and its worked great. That said, it is a cheap jerry rigged solution, so question is if you rely on it are you ok with the risk that it fails. That risk of course is higher than a proper fuel cell or external surge tank. So what are your priorities, cost or reliability?
If the failure just means back to fuel starving, that's better than some other outcomes.

That's interesting that just pumping gas from side to side is working. I'm not sure what that tells me about what the root issue is however. Doesn't the stock tank have a pump from side to side? I guess I'll have to open it up and see what the condition of things looks like.

Priority is reasonable cost, but not minimal cost. What I DONT want to do is spend $1000 bucks grabbing at straws and still have a fuel starvation problem on an autocross course or within one 15 minute session on track from a full tank.

Check out this string on the S197 side, but same issue: https://trackmustangsonline.com/threads/anyone-find-a-fix-for-fuel-sloshing-and-starvation.16346/

If you read through enough of it, you'll come across my "2 cents" posts there. I did the fuel-pump add to the passenger side with a switch and works well, I've tested it on a high-G triple left hander down to 1/8 of a tank.
Thanks I'll read that later tonight.

All good advice above. I'll just add that running E85 may exacerbate the issue a bit as fuel demand is greater. Are you running a return or returnless fuel system?
Its currently a bone stock Gen 2 GT fuel system (returnless) with E85. Injectors are bigger, but I was only pushing ~420 rwhp, so was not forced to make major changes (yet). Other mods may mean the car gets a return system next, and I may also go back to 93.
 
Yes the stock tank has a Venturi to siphon from the passenger side of the tank into the fuel hat, but the flow rate is much less than the pump flow rate. Only designed to allow you to run the tank down to empty putting around in your Hertz rental Mustang.

the risk is dependent on the sophistication of your tune failsafes and conditions at the time. But running out of fuel at WOT at higher rpm’s can do some real damage if fail safes are insufficient for the scenario.

I went the diy in tank route as I priced out a good surge tank and that was so expensive I figured then I’d just better go fuel cell, but wasn’t prepared for that slippery slope so ended back at the in tank diy setup.
 
14
5
Exp. Type
Autocross
Exp. Level
10-20 Years
Austin, TX
Chrome, has anyone looked into adapting the GT350 tank and setup into a GT? May be able to score a good one out of a wrecked chassis or something?
The high/low voltage from the GT computer wont work with the GT350 but maybe theres a returnless custom option with the 350 tank setup as a base.

actually I wasnt clear if the 350 has a proper pickup on each side and is setup to not suck air if one side or the other sloshes out or if its actually engineered to power through slosh with pumps and pickups on both sides capable of supporting the fuel needs of the car.

I’m reluctant to give up the stock fuel door and 16 gallon tank to run a small fuel cell. So I guess I’m leaning to surge tank at the moment.
 
350
364
I wondered if something in my nearly 100k mile gas tank and fuel system just needs servicing? E85 gum up a sock or something
I would start by replacing the fuel pump. Remember that the fuel filter is a "lifetime" part built into the in-tank fuel pump and is non-serviceable. It gets dirty and clogged like any filter but the only way to replace it is to replace the whole pump assembly. I broke apart my old fuel pump and the internal filter was disgusting, literally black gasoline came pouring out. It's also physically impossible to slosh 3/4 of a tank of fuel into 1/2 of a fuel tank. Fuel slosh and starvation is a real thing of course but I don't think it's your problem here.
 
14
5
Exp. Type
Autocross
Exp. Level
10-20 Years
Austin, TX
I would start by replacing the fuel pump. Remember that the fuel filter is a "lifetime" part built into the in-tank fuel pump and is non-serviceable. It gets dirty and clogged like any filter but the only way to replace it is to replace the whole pump assembly. I broke apart my old fuel pump and the internal filter was disgusting, literally black gasoline came pouring out. It's also physically impossible to slosh 3/4 of a tank of fuel into 1/2 of a fuel tank. Fuel slosh and starvation is a real thing of course but I don't think it's your problem here.
You have a good point there. It was 3/4 of a tank, indicated on the dash, when parked on a very very left leaning grid spot. Maybe it was 1/2 tank in reality on flat ground? .. but yeah, It should still be really hard to slosh the full 1/2 tank of fuel entirely into one side of the tank.

I'm going to have to get in there and see how bad that pump assembly is looking. I'm expecting to find what you found, a nasty gunked up internal filter.
 
Chrome, sorry out of pocket for a few days, all good stuff from the guys above. Note that the main fuel pump assembly has kind of a "cup", so it's not like you're pulling fuel from the bottom of the driver's side. If the "cup" can't refill fast enough in long enough & high-G enough left handers, then fuel starvation. The internal mod is literally pumping fuel right to the pickup point to overcome this.
As Scootsmcreggor mentioned, there is a small siphon pump that just equalizes fuel level in both sides of the saddle for normal driving.
Not really helpful, but my buddy has a S197 GT500, and it came factory with pumps on both sides, so no issues of course. Sounds like the GT350 might also have 2, but too bad that's not a plug-in solution for a standard GT...
 
my buddy has a S197 GT500, and it came factory with pumps on both sides
I wonder if he had an aftermarket set up, since while the S197 GT500 has two fuel pumps, my understanding is that they're both in the same driver-side hanger. The S197 fuel tank does have an opening and hat on the passenger side, but it's just a fuel level sending unit (so it can get levels from both side of the 'saddle', then combine the readings to display the result on the dash fuel gauge).
 
I wonder if he had an aftermarket set up, since while the S197 GT500 has two fuel pumps, my understanding is that they're both in the same driver-side hanger. The S197 fuel tank does have an opening and hat on the passenger side, but it's just a fuel level sending unit (so it can get levels from both side of the 'saddle', then combine the readings to display the result on the dash fuel gauge).
I'll defer to you on this one. Just going by what he mentioned to me, and I assumed the 2nd one was passenger side. The 2nd sending unit item, etc. is on all of these S197/S550 cars it seems - the slow venturi pump to even the saddles and measure both sides. (When I added my extra pump, I had to go back in, because I had interfered with the passenger sending unit and was getting weird readings. )
 

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