55 -> 63L fuel tank swap - what all is needed?

[NigelStu]

My rusty, dented, original 55L tank needs to be replaced in the race car. Trying to make sure we can race at 9/10ths-10/10ths for 2 hours, 5 min without starving. Initial thought was to replace the current tank and add in a surge tank.

But in addition to adding a surge tank, I've also considered changing over to the 63L tank. I've been poking around here, e30tech and specE30 but have not been able to find a clear answer to what all is required to swap out the system.

Considering that I will be running a ~2L surge tank, is it possible to set-up this system with stock parts/pumps?

My thought is:

• 63L tank with early-model low-pressure transfer pump feeding the surge tank, driver side opening blocked off.
• stock early-model in-line high-pressure pressure feeding fuel rail
• return line going to surge tank
• overflow line from surge tank to stock return inlet on low-pressure pump.

Will this work?



How is the in-tank transfer tube in the 63L tank 'activated'? Does it require a fitting or something on the late-model pump to work? Will over-flow from the surge tank be enough to create suction needed to transfer fuel from driver side to pass side?


TIA

[IronFreak]

I can't give you an answer but I know that "GrandRoyaL" might be able too. He's down in Brazil but he just bought my 63L to replace his 55L for the exact same reason. maybe he has some insight that might be able to help you out.

[jlevie]

Take a look at http://www.facebook.com/l/CAQFyGUBcA...d.php?t=157887

As it (or a variant) will be more likely to give you what you need. For maximum endurance where class rules allow I'd run the 63L tank with two early transfer pumps feeding a 1-2gal surge tank and an external high pressure pump. I don't think a single transfer pump pump feeding a surge tank is going to give you the ability to suck the tank dry. You need to be able to pull fuel from both sides.

[NigelStu]

Thanks Jim - I found your linked post earlier - great idea and information in there, but I'd like to know if a 63L tank can still work without the extra pump. (ChumpCar rules I'd need to account for the extra pump).

Main question is: will the internal siphon work with the early-model low-pressure transfer pump mounted on the passenger side OR does it need the 88'+ pump?


No need to suck the tank dry, would just like to get as close to 2 hours as possible. Based on calculations, we are using about 7.5 gallons per hour. Driver limit is at 2 hours. So basically we need 15 gallons of usable fuel with no starvation occurring. Surge tank will prevent the starvation, just need to make sure that the fuel from the driver side on the 63L tank makes it over to the transfer pump.

[GrandRoyaL]

yes , i just aquired the tank from IronFreak ! it will be a while until i get it here in brazil...

i will try all methods on the topic posted above and will think of other things if all fails...

just for information :

Yes the early model vw golfs and jettas that used a dual pump setup similar to the e30 used a fuel accumulator. They cost a shit ton so don't run out to your local vw dealer to get one. IIRC ireland sells a cheaper accumulator for under $100. Its rumored to be a cheaper audi accumulator but no one ever post a picture or part number. I plan on purchasing one when I get my car back together.

for the vw part : # 533 201511a

http://www.rmeuropean.com/Part-Numbe...N_A58C52C.aspx

Cheap !

also found this :

http://www.r3vlimited.com/board/showthread.php?t=166977

[jlevie]

Thanks Jim - I found your linked post earlier - great idea and information in there, but I'd like to know if a 63L tank can still work without the extra pump. (ChumpCar rules I'd need to account for the extra pump).

Main question is: will the internal siphon work with the early-model low-pressure transfer pump mounted on the passenger side OR does it need the 88'+ pump?

The siphon depends on a steady high flow rate into it, and it really isn't very effective at moving fuel as compared to a transfer pump. Nor will it get the last of the fuel from the left side. So with only one pump fuel can pack on the left side. Before I went to a dual pump setup I saw that happen at about 3/8's of a tank. With the dual pump setup, I can suck the tank down down about 3 gallons before there is any hint of starvation and have run it down to 2 gallons with minor (raceable) starvation issues. My consumption rate under race conditions is 1 to 1.2 pounds per minute, depending on the track. I'd need a 20 gallons of fuel to get to 2 hours. Your consumption rate is somewhat less, but it is going to be darn close to the tank's capacity.

No need to suck the tank dry, would just like to get as close to 2 hours as possible. Based on calculations, we are using about 7.5 gallons per hour. Driver limit is at 2 hours. So basically we need 15 gallons of usable fuel with no starvation occurring. Surge tank will prevent the starvation, just need to make sure that the fuel from the driver side on the 63L tank makes it over to the transfer pump.

Well yes you do need to suck the tank dry. You need 15 gallons and a 63l tank holds 16.6 gallons. Allowing for .5 gallon in the surge tank that means the tank and surge tank combines will only have 2.1 gallons left in it at 2 hours. My guess is that at the point where the siphon is pretty much useless there can be close to 2 gallons in the left side

Using a larger surge tank means that you don't have to suck the main tank down as far. But that would be a lot more obvious than a dual pump set up. Especially in a car that doesn't have the cover on the left side.

[roguetoaster]

Please do keep this thread up to date, our Chump team is working on the exact dilemma. Also big thanks to Jim for his input.

[TobyB]

Jim's right on. A single pump in a late tank just doesn't track very well.
The other thing that a large surge tank does is let you get more
of what's left out of the main tank- it gives the low pressure pumps more of a chance
at catching some slosh here and there as you hit the aero wall going down the main straight.
Thnking along the same lines, it would seem to make sense to open up the holes to the
'catch can' that surrounds the pump- since you no longer need a reservoir around the
pump, you want fuel to be able to ENTER the can quickly when it can, to be sucked up
as fast as possible by the low- pressure scavenge pumps...

t

[NigelStu]

Are both sides of the later-model tanks the same depth? and the same depth as the passenger side of the early-model?

[jlevie]

Are both sides of the later-model tanks the same depth? and the same depth as the passenger side of the early-model?

Both sides of the tanks are the same depth.

[kallikak]

Main question is: will the internal siphon work with the early-model low-pressure transfer pump mounted on the passenger side OR does it need the 88'+ pump?

That's what I'm going to try. I don't see why it wouldn't. The later tank only has 1 pump as well and has to rely on siphoning to move fuel from left to right.

[jlevie]

That's what I'm going to try. I don't see why it wouldn't. The later tank only has 1 pump as well and has to rely on siphoning to move fuel from left to right.

True, but that system was never intended to see the G forces that racing imposes on the fuel. It works fine on the highway where side forces are almost non-existant and rate of fuel consumption is much lower.

With a single pump in the 63L tank I've seen starvation with about 6gal left in the tank. So I don't think the siphon is all that effective.

[kallikak]

Valid point. I was thinking that it wouldn't be any worse than either factory setup. Given that I have both an early and late tank with the associated fuel pumps, I may investigate your idea of putting a transfer pump where the second fuel level sender used to be.

[seatown88]

I will echo what jlevie has said about the single pump starvation, while I have also heard starvation in a couple of corners in PRO3 cars at an indicated half tank or higher. I have not personally experienced starvation from a starved pickup (clogged filter because of a rusted tank, yes) yet, I have been warned to look for it. I do however, start each race with the fuel tank topped off to meet minimum race weight as I come off the track. And since I real sealed my fuel tank I installed a new fuel pump so the flow should be fairly adequate.

That being said I do intend on modifying the system to prevent any possible chance for starvation in the near future.

[porschelou]

Lot's of good inputs above. Just wanted to relay what we did with our 86 325e ( sporting a 3.5L ). We race Chumps and Lemons and needed to try and reach the 2hr mark.

Note - Left and Right are as you sit in the car. Left is drivers side / Right is passenger side.

1. Pulled the factory 55L tank
1a. Mark the 3 lines that route to the tank( there are hard lines that run toward the high pressure fuel pump on the frame - this is where the soft hoses connect). 1- is the high pressure line, 1 - is he return line , 1 - is a vent line..
2. Bought a good used 65L tanks
3. Took the low pressure pump from the stock 55L tank and installed it on the left side of the 65L tank ( you will need to use a file and shorten one of the tabs on the tank so the locking ring locks in)
4. Installed a new 318i pump ( high pressure) on the right side. Use a 318i pump because you need a Return input and High Pressusre output. The 325 pumps only have a High Pressure output.
5. Ran the output of the low pressure pump side to the return side of the high pressure pump ( this will keep pushing any fuel from the left side to the right). I just used fuel line and ran it across the top of the tank. I think there were a few spots (on the body) I had to hit with a hammer to make sure this hose wasn't pinched at all.
6. Connected the high pressure pump output to the line running to the fuel rail ( had to use a brass reducer I got from ACE hardware to match the fuel line sizes). Need to use High Pressure Fuel Line not just cheap fuel line.
7. The return line from the fuel rail gets connected to the siphon line on the tank. There is a nipple on the 65L tank (left side) that the return line goes to. This is also the "siphon line".
8. Removed the high pressure pump from the frame rail ( don't need this anymore)
9. Extended the factory high pressure pump wiring and supplied power to both pumps.
10. The 325e only had one fuel pump cover under the back seat so I added another one above the low pressure pump so I could work on it. Went to the junk yard and got a cover from a 325i. Once I got it on it looks factory ( as long as the inspectors don't figure our this was a "e" car).
11. Replaced the filter

We have a done a 24hr race a VIR last year after I completed the conversion. Ran well - we got about 1hr 45min out of it before we got nervous and brought it in for fill up. Never starved. We just found out that the WOT switch on the TPS was bad so the car was never running switching to the WOT map so our fuel mileage would have been worse because of that. Doing Watkins Glen in April - we will give it a new test then :)