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Fuel Tank upgrade - fueling issues and E-85

6K views 52 replies 10 participants last post by  TMScrogins 
#1 ·
This post is pretty much a cross post from my other thread "Another AEM Infinity ECU Install on a Coyote" and I'll cover my fuel tank specifics here and not hi-jack my other thread.

I have been on the quest to convert my fueling system over to a FlexFuel setup so I can run either gasoline or E-85 on my fuel injected Coyote motor. I have pretty much upgraded most of the fuel system including, lines, filter, injectors, pump, ethanol sensor, etc. Engines will generally consume 30% more E-85 than gasoline due to the difference in fuel Stoich. Thus, being more thirsty it pushes and returns more fuel than typical for gasoline and the fueling systems needs to be able to handle this.

I took the roadster out last weekend and had all kinds of fueling problems leaving me on the side of the road 4 or 5 different times. At first, I thought it was the injectors since I had just swapped them out. With any amount of load on the engine it would start to die and stall. Even on the freeway. After limping back home later that morning, I began to pour through the data logs. The engine was going way lean. Upon further review, the injector pressure was dropping causing the lean condition caused by oscillations in the fuel pressure, and in some cases dropping to about 6 psi. It should be running at 55 psi.

After all the troubleshooting this is what I found. With the larger fuel pump (320 lph) in preparation for E-85, and the modifications to the return line on the in-tank pump hanger ports (I brazed in a 3/8" return line with an open dump instead of the stock 1/4" with the flapper valve), the problem had to be somehow related to this change. Theory 1 - no flapper/check valve at the end of the return line to create a little back pressure on the return line and the increased size from 1/4" to 3/8" was causing a loss in pressure (didn't seem reasonable but grasping at straws at this point). Theory 2 - I had met up with David Borden that morning and he provided this theory - the larger pump and lack of flapper/check valve may be creating a bunch of turbulence. Possible cavitation.

When running the pump with the engine off you can hear the fuel just really pouring back into the tank. Very likely aerated turbulence was causing the issue. I then swapped out the hanger for the original 1/4" return with flapper and the problem went away. In pulling the pump I had noticed that the fuel level was just shy of about 1/4 full. So I decided to pull the old hanger and replace it with the new modified hanger with the 3/8" open dump return and filled the tank up further. Turbulence went away and had solid fuel pressure. So, my unscientific conclusion is that when the tank falls below 1/4 the fuel return creates too much turbulence around the pump inlet port causing it to suck up air with the fuel. This would also explain why it was working fine earlier before the injector swap - it had more fuel in the tank. I either go back to the puny return and/or smaller fuel pump (neither of which I want to do), keep the tank above 1/4 full at all times or figure out a way to get this new setup to work.

I am using the Factory Five "complete kit" supplied Mustang fuel tank. And I'd say the baffling is nowhere near satisfactory especially when the tank is less than 1/4 full. This coupled with me running E-85 and being the tank is steel (not stainless) it will be prone to rust. I would probably need to treat it with some sealer.

I am going to upgrade the tank to deal with this issue. Here's the solution - Dave Boyd (Boyd Welding)!

I spoke to Dave Boyd about building me a tank as he has an EFI tank option for the Factory Five Roadster. However, I wanted some specific modifications to his tank.

Objectives: better baffling, sump, more resistive to high ethanol content fuel, larger fuel capacity.

Dave is going to make the tank to accept the new Aeromotive Phantom Flex pump assembly that I want to go with. In addition to Dave building the new tank with good baffling, this Aeromotive universal drop in unit comes with its own baffling/sump system that should further improve the situation. This tank is estimated to carry 22 gallons, doesn't drop down any further the the factory tank and mounts without the use of the tank straps. It bolts to the two vertical 3/4" tubes in the front and the horizontal 3/4" tube in the rear.

More info on the Phantom Flex system:

https://aeromotiveinc.com/phantom/



The only downside is that Dave only makes aluminum tanks. I would prefer stainless since I'm running high concentrations of ethanol in my fuel and that can be corrosive to aluminum. I may have the tank hard anodized inside but since I plan on running gasoline as well as E-85 and don't expect to keep E-85 in the tank for long periods, I think the aluminum will be fine.

Trevor
 
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#2 ·
:surprise:

Great...

Since I also have the MK4 complete kit factory gas tank I'm probably going need to resolve the same fuel issues.

You sir are dangerous to my wallet!

:grin2:
 
#3 ·
Well, I'm equally dangerous to my wallet!

With your blower and running E-85 you ought to be worse off than what I'm experiencing. 1/2" supply and 3/8" return with a really high volume pump or two, your fuel tank should look like a Category 5 weather front in there.
 
#4 ·
If you are having a tank built why not run the turn line as far away from the pickup as you can. If I see your fuel pimp correctly your pressure, vent and return are all very close together. This would create turbulence even if the tank is full. When I was doing my first fuel injection a few years ago I was told to keep the pickup and return as far apart as possible. That being said I agree you are getting some air or turbulence when fuel level is low.
 
#6 ·
I would have just put a length of rubber tubing on to the end of the 3/8" return port. That would direct the returned fuel away from the intake, and help prevent aeration of the fuel.

But, I'm considering replacing my fuel cell this year with an aluminum tank or a stock steel tank. Let me know how this works out for you.

The advantage of the Phantom system is that it allows you to install a small collector in any tank. The disadvantage is that it's not a great collector. Good enough for the average street car, but not good enough for the track. If I was having a custom tank made, I'd have a good 3 valve collector installed, and direct the return in to the bottom of the collector.
 
#7 ·
FWIW in the turbo 3.0 BMW I6 if we ran over a 40% E85 mix this was the pump of choice. Pumps were good for over 800 HP. We mostly ran between 18/22PSI boost pressure. Stock boost was 8/14PSI

Walbro Universal 450 LPH In-Tank Fuel Pump E85 Version F90000267

One of the things that might be different is both the stock high pressure pump & the Walbro performance replacement sat in a bucket like unit in the gas tank.

A search for BMW 335 E85 should bring up some pictures of the in car system.
 
#8 ·
Ironically, this is the exact pump Aeromotive uses in their Phantom Flex kit. I contacted tech support a couple of days ago to get more information on the pump itself and the tech indicated they use this pump. If you go to Radium Engineering's website, there is a tech article comparing a number of pumps including this one. It was at the top of the list. Unlike many of the rotary design pumps, this pump uses a dual channel turbine design giving it exceptional efficiency and runs whisper quiet.
 
#18 ·
This sender doesn't work with E-85.

Bob, out of curiosity, what are your thoughts about abandoning the fuel cell in favor of a more traditional fuel tank? Just curious.
The fuel cell is important for road racing and autocross. Not just for the safety, either. In a hard right turn, the fuel moves to the left side of the tank. As the fuel level gets lower, it starts to uncover the pick up, and the engine goes lean just as you're hammering the throttle.

The best part of the fuel cell is the collector. Even with only a couple of gallons in the tank, it won't suck air.

I'm curious also. Mine has a fuel cell that was purchased in 07 and had fuel in it for most of that time. My u dears tanning these are good for 10 years so it is coming due shortly. Do I put in a new bladder or just replace the fuel cell. It only has about 300 miles on it though.
After 10 years of fuel exposure, the bladder and foam will deteriorate and the tank will start to leak. You can also clog up the filter with foam bits.

Rebuilding the 110 tank is complicated. Fuel Safe says that this is a job best left to them because of the complexity. And, it's very expensive. By the time you pack it up, ship it, pay to have it rebuilt and shipped back, you might as well buy a new one. And you can get the job done in an hour or two, instead of a month.
 
#11 ·
Thanks to "Toy4Me". I spoke to Dave Boyd and he is going to weld in a return line bung away from the pump assembly. Great suggestion. I am going to first run the return line through the Phantom assembly. If I get turbulence, I'll abandon the Phantom return line port and plumb it into the new tank port. I'll have the option to go either way.

Bob, out of curiosity, what are your thoughts about abandoning the fuel cell in favor of a more traditional fuel tank? Just curious.

Finally, the position of the sender flange will be relocated away from the rear sloped area of the tank to be sure it is optimized for depth at the deepest portion of the tank which is more to the front. It should be noted that the ISSPro style sender has a molded cap that extends about 1.75" above the top plane of the tank. This is important to ensure the placement of the sender unit does not interfere with the 3/4" square structural trunk supports of the Mk4. Because the tank does not mount with straps, I should be able to easily space the tank down just a tad to provide any necessary clearance needed for this sender. The tank is 12" deep at the deepest section. So an 11" sender will be perfect.

FuelSafe sells them in various lengths and ohm curves.
 
#12 ·
Bob, out of curiosity, what are your thoughts about abandoning the fuel cell in favor of a more traditional fuel tank? Just curious.

FuelSafe sells them in various lengths and ohm curves.
I'm curious also. Mine has a fuel cell that was purchased in 07 and had fuel in it for most of that time. My u dears tanning these are good for 10 years so it is coming due shortly. Do I put in a new bladder or just replace the fuel cell. It only has about 300 miles on it though.
 
#16 ·
Just another data point... I ran e85 in my 2.3l turbo. I typically ran 20psi of boost and occasionally a 35 shot on top (you know, for good measure).
Fuel system was a stock 88 mustang fuel tank, with stock lines , stock fuel rail, bigger injectors, and a walbro 255lph in tank pump. Under boost, I ran around 80+ psi fuel pressure. I would suppose at least 350hp at the crank, as it ran 12.2s with about 3000lb race weight. That fuel system combo never cavitated or ran out of fuel on me. Of course, it likely wouldn't support 400hp at the fuel pressure i was running.
I ran the car like this for 7 to 8 years. Just saying, factory parts with a simple 255lph pump work very well if you are keeping it under 350-400 hp (crank) on e85.
 
#17 ·
Aha!

I knew there's a subtle somebody on this forum conspiring behind the scene for the rest of us to spend more money!

>:)

Saul
 
#20 ·
Bob,

Thanks for the input. I figured that out yesterday. ATL makes one that is E-85 compliant.

http://m.summitracing.com/parts/abt-ks210-12

Same design but an all fuel compatible sender. Talked with ATL yesterday and they are special ordering one in an 11".

Saul, sorry to do this to you but this sender is more than twice the cost of the ISSPro. I love spending your money along with mine.

Trevor
 
#22 ·
Looking this over a custom fuel tank is looking like a better option. Just the replacement bladder and things is going to be over 500 bucks. If it is a PIA to install and have to have fuel safe do it, not worth it at all. I have a local guy here who builds tanks. I'll give him the fuel cell as a pattern and have him fab me one up.
 
#24 ·
I 'think' I understand your situation and a thought occurred to me. Aside from relocating the return to be away from the pickup, it seems you are circulating a ton of fuel that is not being used. I assume this is so there will always be plenty under full load and E85. But it is overkill for gas and normal driving. Is my thinking correct ? My thought is, would there be a way to have a two speed pump? The speed bump could be automated based on fuel pressure(?) or some other parameter. Or it could be manually controlled.
 
#25 ·
I 'think' I understand your situation and a thought occurred to me. Aside from relocating the return to be away from the pickup, it seems you are circulating a ton of fuel that is not being used. I assume this is so there will always be plenty under full load and E85. But it is overkill for gas and normal driving. Is my thinking correct? My thought is, would there be a way to have a two speed pump? The speed bump could be automated based on fuel pressure(?) or some other parameter. Or it could be manually controlled.
Yes. Certainly overkill for gasoline. The problem I see with my setup is that I am running the two fuels on one tune. It's a FlexFuel setup. So I am not necessarily always running dedicated fuel of Gas or E-85. I could have any mixture of both fuels. So if I could figure out a 2 speed pump or two separate pump setup I would have to figure out at what percent Ethanol content to switch from one speed or pump to the other.

Interesting/creative idea.
 
#28 · (Edited)
The Fix

This topic seemed strangely familiar to me since I own and operate a pest control business. The "rig" a truck mounted 75 gallon chemical tank sprayer requires pretty much the same setup as our fuel tanks, it is built with high pressure pump(s) and supply lines that pump chemical anywhere from 100 psi to 350 psi and return lines that are designed to return, circulate and mix the chemical back to the tank without causing cavitation or foaming issues.

The fix

Trevor was on the right track, I believe the fix is to set up our tanks in a similar fashion as the "rig" by adding a separate return but instead of just using one return at a time we should be using both of the returns at the same time, one will continue to keep the pump cool and by adding a second return it should reduce by half the pressure and turbulance that would otherwise be directed solely toward the pump by a single return, also this could be further refined by adding a manual ball check valve on the "pump cooler" return this way we could set the return ratio at say 40/60 as an example.

One last detail, in order for the chemicals to be mixed without foaming, the return line end or "tip" is set low in the bottom of the tank, this keeps the return from catching air and foaming the chemical, we could actually have Boyd weld the return bung low in the tank say on the passenger side lower corner perhaps the outer side to help direct fuel towards the pump pick-up.

And Trevor, thanks for helping me spend my money, at the very least I would like to feel like I'm helping!

:wink2:

Saul
 
#29 ·
Ok, I like the idea of splitting the return into two feeds and dumping the fuel in as low as possible. However, plumbing a port down low in the tank seems like the fuel would be pushing against itself especially when the tank is on the fuller side. Also, if you ever need to service the retrun line and you've got fuel in the tank, it might be a messy proposition.

Perhaps another way to accomplish the same thing is leave the fuel return port at the top of the tank. And then use a fuel pickup tube to thread into the port at the top. We would just use the pickup tube in reverse (to dump fuel low in the tank) and have it maybe an inch shorter than the depth of the tank. Now its easy to service the tank and fittings/line with the tank full.

What do you think?
 
#30 ·
I don't believe it would make much difference pressure wise for the returning fuel to "push" it way back in but for the sake of servicing the reverse pickup tube from the top would be clean, in reality my "rig" is setup with the return tube on top but like I said the tip is set low in the tank.

I think this is the right way to build our tanks.

Saul
 
#32 ·
The GM "returnless" isn't really returnless. It uses a combination fuel filter and pressure regulator near the tank. It returns un-needed fuel back to the tank, and sends the rest to the engine through a single line.
 
#34 ·
Yes, please do

Thanks

Saul
 
#35 ·
OK. So yes ATL does make an E-85 tube float sender. But you have to special order an 11". They have a 10" and a 12". These run $265... Ouch! But here's the kicker. The 11" that I need is a special order and I was quoted a cost of somewhere between $700 and $800. :surprise: After being resuscitated I quickly ended the call.

Ugghhh. No freakin way. Well, Saul sourced an E-85 compatible sender from Classic Instruments. Their website does not indicate E-85 and they look identical to the ISSPro sender (perhaps the same sender). So I called them and you can order them in an E-85 compliant version. They charge $89 for the sender and an additional $35 for E-85 version which includes hard anodizing the tube.

Thanks Saul for the find. I ordered one.

Trevor
 
#36 ·
It works both ways thanks! and it's why you gotta love this forum.

:D

Saul
 
#38 ·
Doh!



The fittings in the two front corners aren't going to work. They will hit the 3/4" tube trunk structure supports. Fortunately Dave had not shipped the tank. After I brought it to his attention, he realized that the fabrication department didn't use the Mk4 template to locate the cross bars for this tank build. Dave stepped right up and is taking care of it.
 
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