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Thread: High idle pressure with big pump?

  1. #1
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    High idle pressure with big pump?

    hi.
    I've posted here before about maxing out a walbro 255
    hooking it directly to the batt help a grip. thx.

    now, i've turned it up acouple psi is legitimately maxing the pump.
    fuel table is maxed, but nothing is happening.


    my concern is with the bigger walbro 450 idle pressure will be too damn high.
    will an adjustable fpr help me out there or is the stock return hose the problem?

    There's a guy who had high pressure with that pump but used pwm to tame the pump at idle.
    but if a nice regulator would work instead. if not i'm getting ms3.


    maxed pump by jet jones, on Flickr

    Here we go again by jet jones, on Flickr

  2. #2
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    Use a higher flowing aftermarket regulator and if that is not enough, go to a 3/8 or 10mm return line.

  3. #3
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    Thanks for the quick response
    i can do all that, but then what was the point in asking here.

    it's just a pain to run new hard line then i have to braze on a bigger end to the pump holder. argh
    on top of buying nice $350 fpr that might not do anything.
    But like i said if u cool dudes think a fpr won't work then ms3 to pwm down the pump at idle seems less of a pain.

    idk, i think i read on other forums that idle is like 50-60psi at idle on evos or audis but they have different sized fuel stuff.

  4. #4
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    I have installed a Walbro 450 on a totally stock E34 M5 S38 engine. The rail and FPR seems identical to other BMWs of that time.

    Idle pressure was fine and everything worked like stock. I say try it, you might get lucky and avoid spending without need.

  5. #5
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    Another option just to throw this out there is to get a boost-a-pump and with a boost activation switch.


    86 325es, 2.8L m50, S476sxe, MS3pro Ultimate, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.07 @ 149.65 mph, best 60 foot 1.30

  6. #6
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    It'll be fine with an FPR and stock lines. Also, what FPR are you buying that's $350?! Yikes!

    Mike
    IG: mikevanshellenbeck

  7. #7
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    Quote Originally Posted by someguy2800 View Post
    Another option just to throw this out there is to get a boost-a-pump and with a boost activation switch.

    Whoa, didn't know this existed.


    I am running two Walbros in line inside the tank, secondary pump turning on with a Hobbs switch via a relay at 15psi.

    Don't buy a $350 FPR.
    "Be who you are and say what you feel because those who mind don't matter and those who matter don't mind."
    -Dr. Seuss
    DIY BMW Tools. Charlie For President

  8. #8
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    A boost-a-pump is $250. An FPR is $150. A Hobbs switch is $50. Tuning around the issue is free if you can DIY.

    I use a boost-a-pump that is boost activated with a 320LPH pump. With a massive pump you are just pumping your fuel in circles most of the time if the car is a street car. I like the second pump under boost only idea as well — popular with 135/335/535 hotrodders and others.

  9. #9
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    ok thx for the ideas i'll just put it in see if it doesn't over run the reg then see what i should do next.
    using ms3 to turn down the juice at idle seems like the best way. try it out on mon.

    Quote Originally Posted by MikeE36 View Post
    It'll be fine with an FPR and stock lines. Also, what FPR are you buying that's $350?! Yikes!

    Mike
    http://www.iemotorsport.com/bmw/item/NUKEfpr.html



    they have another one but it looks like its if u want to turn it up not down maybe.

    http://www.iemotorsport.com/bmw/item/e30adjreg.html

  10. #10
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    Many of us use the aeromotive 13109.

  11. #11
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    hey, just for future people
    ya it did make stuff rich as hell.

    i don't have a fp gauge but it took hot idle from 13.1 to 11.7 afr.
    going to tune it tomorrow and see if it's "ok" just like that. i figure it's ok.

    Idle PW @ 12.7afr with the 255 is 1.6,
    1.3 with the 450.
    also the 450 is much quieter somehow.

    255 v 450 by jet jones, on Flickr

  12. #12
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    ya ok idles good
    aaaannddd... it worked.
    25psi here i come

    next thing to max taking bets.

    it worked by jet jones, on Flickr

  13. #13
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    Quote Originally Posted by Robocop View Post
    ya ok idles good
    aaaannddd... it worked.
    25psi here i come

    next thing to max taking bets.

    it worked by jet jones, on Flickr
    Looks like you need bigger injectors to me... even though you're on the rich side but only at 240 kpa you're already maxed out the injectors. You're not going to get to turn it up anymore than where you are really and should probably even turn it down so that your injectors aren't running static.

    E36 DYNO TUNING WIRING PARTS

  14. #14
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    ha. ya it was just a test run. the 02 is maxed out it was probably more like 7:1 or something.

    this is it as it sits.
    i'm having an issure with the EBC where it just cuts out at 5,700 for some reason and goes back online with -5psi.
    trying to figure it out. but anyway i think these injectors still have alittle left in them.

    semen dickas 80# 18-19psi they're 95% dc. i thought they would support allot more power oh well.

    graph by jet jones, on Flickr
    Last edited by Robocop; 05-31-2019 at 07:56 PM.

  15. #15
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    If you're on Ethanol #80 won't get you very far of course.

    E36 DYNO TUNING WIRING PARTS

  16. #16
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    well i'm new to the game my man.

    what do you recommend for like 550?
    i made 480 ish and that feels not so fast.
    hope the 80's can get me to 500hp at least.
    Word on the street is the 58mm turbo is ready to hit maximum over spool pretty soon too. shit.

    the crappy kevlar clutch has sacrificed it's life to me completely
    and now a pucked ceramic boi is next in line.

    everything is kinda lining up for the achieving the next plane of turbo existence.
    Last edited by Robocop; 06-04-2019 at 10:31 PM.

  17. #17
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    There is plenty of factors at play here and not enough info about your setup.

    but #80 injectors on E85 with 50 psi base pressure will be right around 86% DC by 7000 RPM with a lambda of 0.8 (11.76 AFR) @ 20 PSI of boost.

    I would be surprised if you're not close to 550 on E85 @ 20 psi though.

    You boost control needs quite a bit of work. I would disable closed loop control until you have a solid base duty cycle table for boost control giving you a nice smooth curve. Then work on closed loop/PID.

    E36 DYNO TUNING WIRING PARTS

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