RE: 153 vs. others

[Land Shark <lndshrk@xxxxxxxxxxxx>]

tom murphy asks:

>Hello BMW Experts!  A few people have told me that the DME in the early
>E30's ('87 ?) is
>not as good as those in the later E30s.  Specifically, that the 153 is more
>fragile, and that it has
>one half the data points as the later E30 DMEs.  It was suggested that if I
>went to a newer DME, my engine would run more smoothly, with a little more
>power, better gas mileage, and less
>pollution.

 Tom.. whoever told you that is half right, and half up-in-the-night...

 The 153 DME, M1.1 has a hardware problem in that the current rating of
 one of the components isn't what it should be.. in certain cases a back
 EMF can be caused in the Check Engine lamp circuit which blows the entire
 DME irreparably.. the fix from BMW for this was a diode inserted into
 the wiring harness of the vehicle.. bulletin 12 07 88 (1678) dated Jan 1990

 This problem is also in vehicles which use the Other M1.1 brain, 150 for the
 the big sixes.

 The fix is a small "diode harness" inside C-101 on the E30, pin 12..

 Now onto "half the points".. simply.. NOT!

 The 153 still uses 16 WOT control points.. and some 3D tables for midrange,
 just like all the others.. BUT do note that the MAPPINGS for a 1987 vehicle
 are different from that of the 1988-1991 M20B25 motor by BMW design, and that
 this is controilled by Variant Code, not part number.. i.e. A 380 DME coded
 for a 1987 325iS will have the same maps as the 526 DME coded for an 87..

 Jim C.

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