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Thread: A/F Ratio kinda lean. Need Expert opinion and help.

  1. #1
    Member fishdonotbounce's Avatar
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    Jul 2008
    Location
    Blacklick, OH (Columbus)

    A/F Ratio kinda lean. Need Expert opinion and help.

    Ok so I recently boosted my auto P5 and decided to go with the simplest tuning solution that's been proven to work with autos. The Begi FPR and the FM o2 voltage clamp. Both are doing their job wonderfully so far but today I went on a test drive to get some data and I didn't really like what I saw too much.

    The car starts going rich like it's supposed to right before hitting boost around 2 in Hg. It goes from low 11's to high 12's between 0 psi and 5 psi. At around 5 psi, I am usually around 60-65 psi on the fuel pressure gauge. The gauge sender is positioned AFTER the stock FPR so it reads the pressure after it. This means that I am getting close to if not hitting the maximum output of the fuel pump and/or injectors at around 5 psi. If I go to full boost (7 psi) the fuel pressure goes up to 70-75 and my a/f ratio goes up into the high 13's which is not good.

    I've realized that if I gradually build boost, the a/f ratios will stay under the mid 13's even at close to full boost but if I were to punch it and go WOT, the fuel pressure spikes and the a/f ratio is in the 14-16 region which is extremely lean.

    Anybody have an idea as to what's going on? I know our fuel delivery system is pretty shitty but I thought that there was no need for an upgrade at low boost like I am running.

    I'd like some solid ideas and advice. No flaming, off topic or bullshit will be tolerated. Thank you.

  2. #2
    It would really help if you put the fuel pressure gauge on the other line that's before the stock FPR. That way you'll know the actual pressure coming from the fuel pump, not the pressure being generated by the BEGi.

  3. #3
    Member fishdonotbounce's Avatar
    Join Date
    Jul 2008
    Location
    Blacklick, OH (Columbus)
    Damn it Ogi. Go update that thread now so no one else makes that mistake. I'll have to change the setup once I have a moment to.

  4. #4
    Fine, it's done. Although in my How-To thread I only had the manual gauge that couldn't be read from inside the cabin anyway.. so I think that's why I never bothered updating it.

    Anyway, I put in a word about it. Here's some reading material.. and swap the locations of the BOV and MAF while you're at it.. try to put a bit more distance between them too if you can.

    http://www.themazdaforum.com/showthread.php?t=5967
    http://www.mazdas247.com/forum/showt...83569#poststop

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