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f*cking little black spots

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  • #16
    Originally posted by Carlo M3
    Stino, you should report the exact location of the spots.

    If the spots are around your exhaust, the guys who previous replied are right.

    If the spots are around the whole back of your car, and are kind of liquid, you should check your car for oil leaks. When you are driving with an oil leak the bottom of you car and the back gets wet. Ask me how I know !!!
    My guess is that you know the same way that I know...driving dn tr 78 in jersey and i notice my car is smoking a lot.....when i get to work, i look at the back of the car and theres an oilly mess all over the back of the car... so i went to my mechanic and it seems i have the rear main gasket blown and thats where my huge leak is coming from....needless to say i can't drive the car because the rear main gasket is so close to the cats that there is a potential for a fire....can't wait to get my baby back next week..

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    • #17
      It is soot/water medium. the water makes it stick to the body then evaporates.
      keep it waxed.
      m.

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      • #18
        Originally posted by John
        its better to run leaner anyway.

        John
        What???

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        • #19
          Originally posted by Jess e30 ///M3
          What???
          Leaner = more power. Too lean = engine go boom. A little on the lean side is optimal, but it is a fine line and it's safer to be a little rich...but you will be losing power.
          "It is needless to say that self-propelling vehicles, like other machines, will never do as much for one who does not understand them as for one who does."

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          • #20
            Originally posted by AlpineRunner
            Leaner = more power. Too lean = engine go boom. A little on the lean side is optimal, but it is a fine line and it's safer to be a little rich...but you will be losing power.
            According to the Bosch books I've read, maximum power comes between lambda 0.85 (A/F ratio of 12.5:1) to 0.95 (14.0:1), depending on the engine. This is definitely a little rich, but not too much.

            The best fuel economy comes when the engine is running a lambda of about 1.05 (15.4:1), which is a little lean.

            Catalytic converters (at least the stock type installed on M3s) require a lambda of 1.0 (14.7:1) to function properly.


            Dean

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            • #21
              Interesting. That makes some sense because I know that at WOT and high RPM (when the engine is making the most power) the DME makes the mixture rich. I definitely could be wrong.

              However, I also know that, for example when you get a Maxx, the map comes rich to be safe, but then you lean it out to get more power (at least close to stoich). I'm curious as to what John will say about this.
              "It is needless to say that self-propelling vehicles, like other machines, will never do as much for one who does not understand them as for one who does."

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              • #22
                A common myth is that running rich is safe.

                The extra fuel washes the bores, thins down the oil and can cause spun bearings - without mentioning the cost of all that extra fuel.

                I suppose, too rich is better than too lean as at least your engine doesn't detonate and melt pistons, but given time, a too rich mixture will also wreck your engine.
                Steve
                Scottish Cecotto

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                • #23
                  Originally posted by AlpineRunner
                  I'm curious as to what John will say about this.
                  Yeah, I thought about calling John on that comment too, but I figured out what he meant was running excessively rich causes many issues in addition to spots on the bumper, e.g. loss of HP, poor fuel mileage, fouled plugs, excess carbon deposits (which can lead to detonation), etc., so that running on the "leaner" side of an otherwise overly rich mixture is better.

                  I think John's too smart to suggest we should run our s14s lean!

                  My car is on the richer side of rich, and I get the black spots.
                  "E30 M3 . . . it's the perfect toy for an upscale closet wild man." Car and Driver, 1988 M3 Road Test

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                  • #24
                    Originally posted by Mmark
                    It is soot/water medium. the water makes it stick to the body then evaporates.
                    keep it waxed.
                    m.
                    anybody know where the water comes from? how come normal cars dont do that? my friends B16a civic does it too. the back of my car gets so dirty its RIDICULOUS.
                    1990 M3/1998 M3 Sedan

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                    • #25
                      Originally posted by aaronmjr
                      anybody know where the water comes from? how come normal cars dont do that? my friends B16a civic does it too. the back of my car gets so dirty its RIDICULOUS.
                      Water is the byproduct of combustion.

                      Gas + Oxygen + spark = Carbon dioxide + water

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                      • #26
                        I think you guys misunderstood John, IMO he did not mean lean as in running higher than 14.7:1 stoich, he meant not running excessively rich which is correct in regard to making max power

                        water is a byproduct of the catalytic converter process, that's one reason OE exhaust systems are made from stainless steel type materials now
                        A friend will come bail you out of jail, but a TRUE friend will be sitting next to you in the jail cell saying, "Dude, that was focking awesome!"

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                        • #27
                          Well, the spots are all over the back of the car. I have no katalysator and no DTM exhaust.
                          Now that I look closer, they do look like little oil spots. The oil level stays pretty normal. I change the oil every 3000km.

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