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2.5L idles rough when put in a chip

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  • 2.5L idles rough when put in a chip

    i just finished with my 2.5L the build uses VAC 2.5L stroker kit consist of CP 11:1, Sport EVO Crank, stock cam, and VAC Stage I head. when i put in the VAC chip that came with the kit, i couldnt get a good idle. the car hesitates and rpm jumps all over. however when i put in the stock 2.3L chip. the car idles nicely.

    Is it ok to run stock 2.3L chip on a 2.5L? what causes and how to get good idle with the chip? any help would be grateful.

    cheers,

    -teddy
    1988 E30 M3 Alpinewhite II 2.5L (sold)
    1997 E39 528i Platinum Gray

  • #2
    Don't run the motor on the 2.3 chip. The timing and fuel maps won't even be close.
    Call Tony at VAC and get his help, after all it's his stuff. I've always know him to be very helpful.






    NASA GTS5 #945
    NASA GTS5 Midwest Regional Champion ('09,'11,'12 & '14)

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    • #3
      Hi Teddy.

      The VAC kit has hi-comp pistons that require different fuel-timing specs. I have no experience with their kit, but am pretty sure there is a short manual that specifies what type of fuel injectors, or fuel pressure regulator is needed.

      Most likely you need either injectors, or a 3.5 Bar FPR.
      What about the AFM, does it need recalibration, or using the 535i AFM (same as Evo3)?


      [email protected]

      1969 2002 racecar
      1989 M3 racecar
      e39 Touring

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      • #4
        Lee,
        you think the motor is not getting enough fuel? i will look into the injectors and try the 3.5bar FPR as well. i'm currently running stock injectors.
        Lets see if recalibrating the AFM helps.
        1988 E30 M3 Alpinewhite II 2.5L (sold)
        1997 E39 528i Platinum Gray

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        • #5
          I'd say call VAC first. They will tell you what injectors, FPR or AFM to use with their chip.


          [email protected]

          1969 2002 racecar
          1989 M3 racecar
          e39 Touring

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          • #6
            will do. thanks
            1988 E30 M3 Alpinewhite II 2.5L (sold)
            1997 E39 528i Platinum Gray

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            • #7
              I'd rather get a proper chip for my build, than have to build a motor to fit their crap chip. VAC's chips and injectors suck, and I have 6 months of pulling my hair out to prove it. The only thing worse than their chips is their "tech support".
              What??? an E30 M3 for sale??? I'll be right there!!!

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              • #8
                Turner/Conforti may have a chip for your hardware combo. A custom chip can be made from a few dyno sessions by a raceshop, but the problem is that usually they will be dead-on with upper midrange and high rev, but won't spend enough time for idle, low rev and economy.

                Check with Turner/Conforti for which specs their chips are tuned.
                http://www.turnermotorsport.com/html...UCT_ID=071-250

                I have no experience with VAC but as they are where you sourced the parts, they will most likely be able to answer your questions.
                Last edited by LeeVuong; 08-03-2007, 10:06 AM.


                [email protected]

                1969 2002 racecar
                1989 M3 racecar
                e39 Touring

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                • #9
                  you don't say if you are still running a AFM.

                  If you are wouldn't you need the 2.5 AFM !...........

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                  • #10
                    AFM can be from a 535i as it has the same part # as the Evo 3 with 2.5 motor. Maybe this is what causes the problem. Still check with VAC what hardware you need with this new engine.


                    [email protected]

                    1969 2002 racecar
                    1989 M3 racecar
                    e39 Touring

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                    • #11
                      I spoke to Vac yesterday for my 2.5l biuld and they told the chip is for big injectors, and stock injectors will run lean.
                      -Darren

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                      • #12
                        Great. I believe I saw bigger (green?) injectors in the classifieds...


                        [email protected]

                        1969 2002 racecar
                        1989 M3 racecar
                        e39 Touring

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                        • #13
                          baxter E30 speaks the truth....

                          Dlance .. Tell VAC to keep their chip... and if you get their injectors, cross reference and confirm what injectors you got and what their flow rate is. If you are running a 2.5 off of an AFM, don't jack around and get injectors with the sport evo part # on them.... The one's VAC supplies likely are not one and the same.


                          Helvetica.. send that VAC chip back and find either the TMS base chip .... It should work with stock cams.... (do not buy the D-mod chip which is for much more radical compression, cams, etc )..... or if at all possible.. an iigo chip. I can't recall if there is an iigo chip for that application... pm sent.

                          LeeV. the 535i part and the sport evo use the same part #... this is DEFINITELY not the problem.
                          Last edited by M3 Adjuster; 08-03-2007, 02:15 PM.
                          Mark Williams
                          Dallas, TX

                          Nothing says "welcome to the neighborhood" like a search... oh wait... looks like they are all gone! :rastajake:

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                          • #14
                            Helvetica...what kind of 2.3 chip do you have? I have Dinan chip that was given to me by P.O. Have not installed yet. Have been hearing that it is a POS, but hey it is free. But this is the only one that will pass the smog in Cali. Any truth to this?
                            Lawrence

                            BMW CCA San Diego Chapter #192742
                            '90 M3 AWII - Garage Queen
                            '09 540i Touring 6 Spd - Son's DD
                            '03 530i 5 Spd - SO's DD
                            '03 Nissan Frontier Crew Cab - My DD & Range truck
                            '05 330i ZHP 6 Spd - Alternate DD
                            '15 Honda Pilot - Daughter's & Grandkids Hauler

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                            • #15
                              i have a friend with 535i, i'll borrow his AFM next week and see if that solve the idle. i sent an email to Chris at VAC, and waiting for his respond. im thinking about ditching the VAC chip and find other solution for this. thank you for your help guys.
                              1988 E30 M3 Alpinewhite II 2.5L (sold)
                              1997 E39 528i Platinum Gray

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