1994 325i (M50B25) decat?

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  1. 1994 325i (M50B25) decat? 
    #1
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    captain_chaos's Car Details
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    Hi, everyone
    I have a question. I have a 94 M50B25 engine which I'm soon going to be putting into my 316 coupe. Still not quite ready for the transplant because need to buy my coilover kit that would take the weight of the big 6 pot block. And decided that while I'm doing all this, might aswell use the time and recon all other parts, new powerflex bushes for the 325 back end that I have living in my room corner at the moment.
    I will be having to buy a new exhaust, so I thought, while it's out and not yet on the car, I would decat it. But! before go deep into the woods and make a lot of problems for myself I need to find out this.
    If I decat the standard exhaust, cut the cats out and weld straight through pipes in. Would this: 1. give me any power gain? 2. Would I need a remap or a different chip since there is no cat.
    I'm asking this, because as far as I know, the lambda probes sence the oxygen levels but since they are positioned before the cats, they must be sencing the built up gases due to the backpressure generated by the cat.
    So if I decat the exhaust, will this not tell the ecu that there is too much flow and esentially kill the power?
    Another part of this question. If a different chip or a remap is needed, then would it be possible (if i can somehow find one) plug in a pre 92 ECU from a M50B25 engine because as I read on this forum, all pre 92 BMW came to this country with no catalytic convertors.

    Thank you for having the patients and reading my longwinded question and thank you for any replies.
    Vlad
     
     

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    Ronnie's Car Details
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    Power gain would be very slight IMO, and no you wouldn't need a chip due to having no Cat as you have a Air flow meter that measures how quick the air is coming in so the gases going out quicker will make no difference.

    But a chip would improve things alot.

    You will have problems when MOT time comes though as with No cats you'll struggle to pass emissions.
     
     

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    captain_chaos (18-04-2009)

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    #3
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    captain_chaos's Car Details
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    325i
    Year of Manufacture:
    1992
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    Quote Originally Posted by Ronnie View Post
    Power gain would be very slight IMO, and no you wouldn't need a chip due to having no Cat as you have a Air flow meter that measures how quick the air is coming in so the gases going out quicker will make no difference.

    But a chip would improve things alot.

    You will have problems when MOT time comes though as with No cats you'll struggle to pass emissions.
    thanks very much mate, i just didnt know how decats worked on bmw's. cos some cars need remapin and some dont.
    and i got the MOT stuff covered
    thanks for the help mate.
     
     

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