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Thread: dual fuel pump set up for tracked E36 M3

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    dual fuel pump set up for tracked E36 M3

    I'm sick of having to run a full tank for a 20min. track stint. I've heard you can mount a second fuel pump in the tank pretty easily to stop the right turn starvation problem. Does anyone have some advice or info on how to accomplish this? I've seen Clay's second pump kit, but I already have a spare pump and just wanted to make sure I do it right.

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    Bimmerworld sells a kit that should take care of this problem.

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    Quote Originally Posted by vortecM3 View Post
    I've seen Clay's second pump kit, but I already have a spare pump and just wanted to make sure I do it right.
    Quote Originally Posted by NakNak View Post
    Bimmerworld sells a kit that should take care of this problem.

    its not horrible, and I've done it before, but its just a constant flow circuit

    both pumps run constantly (both powered)

    driver side pump return = return from engine
    driver side pump feed = passenger side pump return
    passenger side pump return = driver side pump feed
    passenger side pump feed = engine feed

    should be pretty easy to figure out from there.. just a loop

    driver side return from engine, feeds the passenger side "siphon" area, which then pumps fuel to the engine, and then cycles again
    "Torque is like cowbell... you can never have too much." - Michael Cervi


  4. #4
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    you really can just revert to the pre 96 fuel pump system and put a walbro 255 in there instead of dual pumping it and run it till empty.

    when i was looking into the dual pump options eons ago, you had to also wire a switch to turn off the secondary pump to avoid it overworking/overheating - leading to a short life, but i would think the kits now have compensated for that.

    regardless I haven't seen anyone with a pre96 fuel setup who required a large tank of gas unless they had a weak fuel pump or another more significant problem...i just like keeping it simple.


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    Quote Originally Posted by M Dizzle View Post
    when i was looking into the dual pump options eons ago, you had to also wire a switch to turn off the secondary pump to avoid it overworking/overheating - leading to a short life, but i would think the kits now have compensated for that.
    Yes, running the pump dry is what worries me about the driver->passenger secondary pumping idea. Is that what the bimmerworld kit does? If so, I guess the worry is invalid..

    Here's a DIY writeup: http://www.google.com/url?sa=t&sourc...FPZ7Wl_aKvjpZw which advocates a different scheme: both pumps feed the engine via a tee-piece, and the return from the engine drains into both sides via another tee-piece. My concern about that scheme is that small differences in fluid resistance and pump strength would eventually lead to all the fuel being on one side. But perhaps that's wrong, because the return-side tee-piece would act as a leveling siphon. This setup apparently does work well.

    regardless I haven't seen anyone with a pre96 fuel setup who required a large tank of gas unless they had a weak fuel pump or another more significant problem...i just like keeping it simple.
    My '92 325is has the standard pre96 setup. It's pretty good but just recently I've been getting starvation in thunderhill #15 (fast right-hander immediately following long slow right-hander).

    This is new behavior, and I don't know why it changed. Perhaps because the recently-installed 240hp S52 uses more gas than the old 218hp M52 did. Perhaps because the pump is getting tired. Neither of these explanations is very satisfying.

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    This is relevant to my interests...Was having starvation problems in the carousel at Tremblant. Subscribed!

  7. #7
    GGray's Avatar
    GGray is offline Did someone say racetrack BMW CCA Member
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    Quote Originally Posted by M Dizzle View Post
    you really can just revert to the pre 96 fuel pump system and put a walbro 255 in there instead of dual pumping it and run it till empty.

    when i was looking into the dual pump options eons ago, you had to also wire a switch to turn off the secondary pump to avoid it overworking/overheating - leading to a short life, but i would think the kits now have compensated for that.

    regardless I haven't seen anyone with a pre96 fuel setup who required a large tank of gas unless they had a weak fuel pump or another more significant problem...i just like keeping it simple.
    That would be false. I have two 95 M3's both suffered from low fuel problem. One I put a new pump it, theory failed.

    I ended up using the two pump solution both work equally well its just a case of which one you prefer or think works better. If your on tracks with not many hard corners it will not show up as such a bad problem. I use to go to road Atlanta and Barber where it would show up in certain corners much worse than others.

    I can literally run until the reserve light is on. Before around 1/4 tank sometimes more the cars would stumble.
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    Quote Originally Posted by GGray View Post
    That would be false. I have two 95 M3's both suffered from low fuel problem. One I put a new pump it, theory failed.

    I ended up using the two pump solution both work equally well its just a case of which one you prefer or think works better. If your on tracks with not many hard corners it will not show up as such a bad problem. I use to go to road Atlanta and Barber where it would show up in certain corners much worse than others.

    I can literally run until the reserve light is on. Before around 1/4 tank sometimes more the cars would stumble.

    I have a '95 M3 with just a walbro 255 running ~370 rwhp on track turbocharged and my car will starve for fuel at ~5/8th of a tank on a sharp right hander (T7 at Harris Hill Road) FWIW.

    -Mike
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    Quote Originally Posted by flink View Post
    Yes, running the pump dry is what worries me about the driver->passenger secondary pumping idea. Is that what the bimmerworld kit does? If so, I guess the worry is invalid..
    yes, the BW kit runs the dual pump in a loop system
    "Torque is like cowbell... you can never have too much." - Michael Cervi


  10. #10
    NeilM is offline Member BMW E36 M3 Expert
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    Quote Originally Posted by flink View Post
    Yes, running the pump dry is what worries me about the driver->passenger secondary pumping idea. Is that what the bimmerworld kit does? If so, I guess the worry is invalid.
    Exactly: not a problem in real life. My BW setup has been working fine since 2003 and allows running on track into the reserve light zone. The standard return system from the fuel rail means that the driver side transfer pump never actually runs dry.

    @OP: you say you already have a second fuel pump, but you don't say what second fuel pump. The stock E36 fuel pump doesn't have the necessary return fitting.

    It's perfectly possible to piece together your own dual pump setup, but by the time you've figured it out, tracked down all the hoses and adapters, etc., buying the BW kit look like better use of one's time.

    Neil
    Last edited by NeilM; 08-30-2011 at 09:24 AM.

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    Quote Originally Posted by NeilM View Post
    Exactly: not a problem in real life. My BW setup has been working fine since 2003 and allows running on track into the reserve light zone. The standard return system from the fuel rail means that the driver side transfer pump never actually runs dry.

    @OP: you say you already have a second fuel pump, but you don't say what second fuel pump. The stock E36 fuel pump doesn't have the necessary return fitting.

    It's perfectly possible to piece together your own dual pump setup, but by the time you've figured it out, tracked down all the hoses and adapters, etc., buying the BW kit look like better use of one's time.

    Neil
    Agreed. I put in the BW dual pump kit on my '95 M3 race car (since sold) and it worked down into the low fuel light, even on turn 2 at Willow Springs (180 degree fast right hander).
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    Quote Originally Posted by NeilM View Post
    @OP: you say you already have a second fuel pump, but you don't say what second fuel pump. The stock E36 fuel pump doesn't have the necessary return fitting.

    It's perfectly possible to piece together your own dual pump setup, but by the time you've figured it out, tracked down all the hoses and adapters, etc., buying the BW kit look like better use of one's time.

    Neil
    I guess I could find a way to figure all this out, but for BW's price I guess it makes more sence to pay the piper. I'm glad to see my M3 isn't the only one with this problem

    Quote Originally Posted by flink View Post
    Yes, running the pump dry is what worries me about the driver->passenger secondary pumping idea. Is that what the bimmerworld kit does? If so, I guess the worry is invalid..

    Here's a DIY writeup: http://www.google.com/url?sa=t&sourc...FPZ7Wl_aKvjpZw which advocates a different scheme: both pumps feed the engine via a tee-piece, and the return from the engine drains into both sides via another tee-piece. My concern about that scheme is that small differences in fluid resistance and pump strength would eventually lead to all the fuel being on one side. But perhaps that's wrong, because the return-side tee-piece would act as a leveling siphon. This setup apparently does work well.
    Wow, what a great writeup, thanks for the link it deffinitelly points me toward BW's twin pump convertion.
    Last edited by vortecM3; 08-30-2011 at 05:20 PM. Reason: Automerged Doublepost

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    I went ahead and bought the BimmerWorld kit because I didn't want to spend tons of time researching every component and then piecing it together. They also provide excellent support, so if you get stuck or something goes wrong, you know you're going to be taken care of.

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    Quote Originally Posted by snk328is View Post
    I went ahead and bought the BimmerWorld kit
    You'll have to tell us all how the installation goes and your performance results.

  15. #15
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    I actually put it in last Fall.

    The install itself was easy with the instructions that the kit came with. Pay close attention to the orientation of the driver side pump. the fuel level sender/float needs clearance in order for an accurate fuel gauge reading.

    I can run the car down until the fuel reserve light comes on and still have no starvation under cornering.

    Very happy with the kit.

  16. #16
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    If I put a second pump in it seems that as long as there is fuel it wil not go dry till very low which would then put the other pump dry and car out of fuel anyway.

    I am right now attempting to remedy this in my car. I am gonna use the long dark hose on the return unit and attach that with hose clamps to a pump in order to send fuel from drivers' side to the passenger. I will do up a picture so you know what I mean.

    I am using the OEM fuel tank and both cap units as I crafted a total 8 an system from pump to return. I believe there may be pics in my albums....

  17. #17
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    (bump)

    I've been looking at the design of the pre-96 e36 fuel setup. I'd heard that it uses a leveling siphon, but that is not the case - the fuel return port on the passenger side assembly terminates right at the top of the tank. If it was a siphon, it would have a tube which runs to the bottom of the tank.


    The pre-96 OE fuel system uses the residual pressure in the return line to propel fuel out of the driver-side tank and over to the passenger-side tank where the pump is.

    The still-high-pressure fuel returning from the engine goes through a tube to the bottom of the driver-side tank, through a u-bend then exits a sprayer nozzle. That nozzle is immersed in fuel. It points upwards, into a second tube which leads over to the passenger-side tank. So the nozzle blows the surrounding fuel up 12" and across to the other tank.

    So in steady state, all the fuel is over on the passenger side. Any excess fuel spills across the saddle into the passenger-side tank.

    And this explains why the starvation takes so long to recover after you've stopped turning the car: at full throttle the residual pressure is much lower and that nozzle isn't able to blow fuel as effectively.

    Armed with this knowledge, I see that M Dizzle's suggestion to upgrade to a higher capacity pump makes heaps of sense - you'll have better residual pressure at WOT so the fuel transfer will be improved.

    I don't have a clue how the post-96 design works.

  18. #18
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    Does anyone have a diagram of the post-96 design? I found this link that has a diagram on page 2. http://www.pumpkininc.com/content/doc/guide/ag-8.pdf

    Is that correct?

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    I was going to start a new thread, but this one popped up tonight.

    I have an early (3/94) '95 M3 that I used to be able to run down to less than 1/4 tank with no problem. Recently, it began starving at 1/2 tank (7 or 8 gallons burned), and I started having hot start problems. I figured the fuel pump and/or discharge check valve was leaking, so it made sense to go ahead and put in the BW kit with two new fuel pumps. I installed it with the loop configuration described above (per BW direction). Last weekend at Road Atlanta I was starving a bit at 1/2 tank in T1 and really bad in T7.

    I know many folks seem to have good results with this setup, but I'm thinking I may need to change over to the "tee" configuration. What else could it be?
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  20. #20
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    Most people - including me - use the second pump to fill the accumulator on the main pump. It works great. And we've never had problems with burned out pumps. We don't bother with a switch either. Just run them both.

    I don't know of anyone using the T configuration.

    The BW kit is a good way to go if you don't feel like sourcing the parts. But there is nothing magic in the kit. Just use two pre-95 pumps and some fuel line is all you need. We usually make our own.

    I had previously backdated to a pre-95 pump from my 97. It was better but the problem was still there. Two pumps fixes it.

    I suspect it's something else. Regulator? Filter? Flaky wiring?
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    Quote Originally Posted by PCarroll View Post
    I suspect it's something else. Regulator? Filter? Flaky wiring?
    Me too, but at >1/2 tank there's no problem. I need to do some troubleshooting to make sure the DS pump is even running.
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  22. #22
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    Quote Originally Posted by m3bs View Post
    Me too, but at >1/2 tank there's no problem. I need to do some troubleshooting to make sure the DS pump is even running.
    You should check to be sure the DS pump is wired correctly. If you've switched the wires, I believe the pump will run backward. I installed the BW kit earlier this year - used to get starvation between 5/8ths and 3/4 tank, and now have no issues going below 1/4 (haven't tried to see how low I can go). That being said, I wasn't such a fan of the BW kit. Instructions are somewhat iffy, the kit included the wrong mix of hose clamps, and it really seems to need a 45 or 90 degree fitting to avoid rubbing on the access panel (thanks, Home Depot!). If I were doing it again, I'd give the VAC kit a try. It may not be any better, but worth a shot.
    Cliff

  23. #23
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    If you want to bring the BIG hammer to bear on this issue - behold - the 2L swirl pot of final solutions. I can run the tank dry and still make another lap before I need a tow.

    Last edited by sped here; 09-07-2012 at 02:01 PM.
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  24. #24
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    I guess hot fuel isn't as big of a problem on an NA car.

  25. #25
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    Quote Originally Posted by PCarroll View Post
    Most people - including me - use the second pump to fill the accumulator on the main pump. It works great. And we've never had problems with burned out pumps. We don't bother with a switch either. Just run them both.

    I don't know of anyone using the T configuration.

    The BW kit is a good way to go if you don't feel like sourcing the parts. But there is nothing magic in the kit. Just use two pre-95 pumps and some fuel line is all you need. We usually make our own.

    I had previously backdated to a pre-95 pump from my 97. It was better but the problem was still there. Two pumps fixes it.

    I suspect it's something else. Regulator? Filter? Flaky wiring?

    I have a secondary pump waiting; do you have or anyone have a diagram that can highlight this? this is for an e46 m3...

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