[Diy_efi] Why I asked about the GM V-6 MPFI

[Bill - Comcast]

Jim Conforti and others have hacked the DMEs in enough detail to change 
anything you want.  They just haven't released the information into the 
public domain as has happened here in the GM world.  

You can do MPFI with a '749 without a crank trigger.  The magnetic speed 
sensor in my 928 worked fine as the '749's VSS input and there is a road 
speed constant in the calibration that will allow you set the number of 
pulses per mile.  I think I used 6200 or something like that.  The 
reluctor in the 928's distributor  worked fine to trigger the GM 
ignition module also so you might get lucky there.  All I had to do to 
the distributor was remove it's guts,  weld down the centrifugal 
advance,  and reassemble the the same stuff back into it. The Porsche 
distributor cable connector even fit into the GM ignition module with a 
little help from my Dremel.

Knock sensing is an issue.  The sensors are matched to the application 
so you might have to play with different mounting locations and 
techniques to dampen or accentuate the noise to the correct levels.  It 
is likely the BMW sensors would work,  I think I would start with them.  
I do not have a working knock sensor right now,  the overhead cams in 
the Porsche V8 are very noisy and I haven't played with it enough to 
make it work yet.

More details and pics of my 928 setup are in the '749 twiki on the GMECM 
page.
http://www.diy-efi.org/twiki/bin/view.pl/Gmecm/1227749

If you come up with any additional '749 info while working on this,  or 
if you want to document your conversion,  the twiki is a great place to 
put it.  Just click the 'edit' button at the bottom of the page and type 
away.

Rip that DME outta there! :-)

Bill
928s Vortech/749


Joe Boucher wrote:
> I have a '89 325i.  I also came across a turbo just right for a 2.5 liter
> engine.  Turboing the 325i is a big temptation plus playing with the fuel
> and spark maps.
>
> BUT, as best I can tell, no one has hacked the Motronic 1.1 FI computers to
> any kind of detail like the GM ECU's.  Which surprises me, as the size of
> the memory chip used in the Motronic is really small.  2k or 4k?  And that
> is the size of the maps and programming.  But I could be wrong.
>
> So, the voices in my head keep telling me to piggy back a GM system onto the
> 2.5.  The list of road blocks to do this are short.
>
>
> Engine timing.
>
> The MPFI system would require some kind of crank trigger.  The spacing of
> the disk slots on the crank could be copied on to a computer controlled,
> laser cut disk and the disk sandwiched between crank pulley and the harmonic
> balancer.  The BMW crank position sensing system (60 minus two knobs) is on
> the harmonic balancer and the bracket could be useable for mounting the GM
> sensor or maybe the BMW sensor would work.
>
> Or, use a TBI system.  There is a lot of room in the BMW distributor cap.  I
> haven't looked at the details, but mounting a GM HEI reluctor ring (the
> pointy thingies) might be easy.  But turboing would be easier with 749 ECM
> code.
>
>
> Speed input to the ECM.
>
> The hardest part of converting my carbed '81 Suburban to an '89 TBI system
> was the speed sensor situation.  The 700R4 on the back of the TBI engine I
> bought had the electronic sensor and not the cable drive.  After installing
> everything, successfully running the car down the road, THEN figuring out
> the output of the tranny speed sensor needed conversion to a step wave, I
> should have pulled the tranny and had the output shaft converted to a cable
> system and bought the in-line speedometer cable sensor.
>
> The BMW uses a sensor on the differential which detects the pinion ring
> teeth.  I doubt the number of teeth will equal 2000 or 4000 pulses a mile.
> Some kind of converter circuit is possible, but I can't do that.
>
>
> Knock sensing.
>
> BMW didn't start using knock sensors till 1991.  Mounting a GM knock sensor
> on the bimmer block might be a challenge.  I have a Bosch knock sensor off a
> Volvo, but am not sure it operates the same as a GM sensor.  I don't HAVE to
> have a knock sensor, but it sure would be nice.
>
>
> Any thoughts would be appreciated.
>
>
> Joe B.
>
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