GM speed sensors & ECM suggestions

[Michael Baxter]

swagaero <swagaero at flash.net> writes:

 >> Caddilac Northstar minor reprogramming and away you go.
 <<

 Yea know, I was wondering if a Cadillac or big Buick ECM might be the best
route. Were there some Northstar ECMs that were pre-EEPROM? May not be the end
of the world if they were EEPROM...more later.

 >> "Curtis L. Martin" <cmartin at america.com> writes:

 >> Different sets of plastic gears inside the transmission calibrate both the
speedometer and the VSS signal to the rear axle ratio and tire diameter of the
car.  There are also aftermarket "buffer" boxes that will allow adjustment of
the VSS signal to a certain extent without swapping speedo drive gears (messy
task on a 700R4/4L60 transmission :)
 <<

 Unfortunately, this is drive-train is going in a Jeep. It'll have an
intermediate housing without a speedo drive in place of the tail housing. The
speedo drive is in the transfer-case.

 >> Give me a little time and I can do the math to say what the frequency of
the VSS should be based on actual vehicle speed.
 <<

 I appreciate the offer but, don't waste any of your time yet. When this
project is a more concrete I may hit you up for some help.

 >> You also missed one.. what are you planning on using for an ignition
 system?  You are almost forced into using one of the computer advanced HEI
ignition (either distributor based or Opti-spark) in order to make use of the
computer controlled timing (which has to be there in order for the knock
sensor to work)
 <<

 Well, I was hoping to go distributor-less. The Northstar ECMs probably can do
that but, I don't know about hooking up to a 4L60E control module.

 If I do use a distributor, it'll have to be fabricated. The AMC V-8s used
either Prestolite BID or Motorcraft Dura-Spark IIIs for electronic ignitions.
I have the latter now.


 TMatthe at aol.com writes:

 >> Do you have a GM Turbo 350/400 tranny? Howell Engine dev. has a VSS that
screws onto the tranny at the speedo cable, but you don't need VSS if you
ground the P/N wire in the ECM harness. Engine speed can be read if you adapt
a GM 7 pin module to a magnetic AMC dist.
 <<

 I currently have a TH-400 but, it doesn't have a speedo drive as I mentioned
above. If I end-up using a complete dist., nice to know I can use my current
magnetic pick-up for engine speed.

 >> The EEPROM GM ECM is really what you want, but no one to my knowledge has
a software pkg. to reprogram these for sale yet to my knowledge...
 <<

 Yes, that's what I'm beginning to believe. I imagine it's only a matter of
time before someone writes software for the EEPROM ECMs. Wonder if I can go
ahead and use one by having one of the companies that does custom
reprogramming (Hypertech, The Turbo Shop, ...maybe JET) burn the chip? Then
just wait until the aftermarket catches-up. Of course, this will only work if
one of them can indeed burn custom GM EEPROMs?

 >> These devices are nothing more than a disc that "clicks off" magnetic
signals to a hall effect transistor, and should be somewhat easy to adapt. GM
speed sensors give off 8000 pulses per mile I believe... Dakota Digital, a
manufacturer who produces digital dashes for almost any vehicle, might be a
good resource for speed sensors as well as information about the pulses per
mile.
 <<

 Provided I can get a trigger wheel with the same # of teeth, I looks like it
shouldn't be a problem. But it still scares me. :-)  Thanks for the info. I
have a couple of friends helping me with this project and at least a couple of
sources for trigger wheels. We'll digest all of this and see what's available.

 >> Hope I gave you ::some:: info :)
 <<

 Oh yea!


 John Hess <JohnH at ixc-comm.net> writes:

 >> There are several sources for the geared tailshaft.  This is not a real
obstacle.  I would recommend the 4L60E because you can more easily program it
for your shift points and it remains dead accurate under a wide range of
conditions.
 <<

 That's why I was leaning towards the E version. I haven't made a decision
yet. The tranny will be purchased outright from Premiere, Art Carr, B & M,
etc.  I'll end-up choosing the one that will work-out best for this
application.

 >> Go ahead and use the TPS computer (either 86-89, MAF- or 90-92,
 MAT). There are several reputable tuners who can program the Memcal
 according to your engine statistics.
 <<

 Except that neither one of those would give me sequential right? I'm aiming
for MAP.


 Thanks for all the info./input! I'll probably have more questions after I
digest all of this and I'll certainly run them by the list 1st before carving
anything in stone.

 -- Michael Baxter, 74172.1164 at Compuserve.com
 http://ourworld.compuserve.com/homepages/MBaxter
 From Reno, NV USA on 08-Oct-1997 at 11:31:14 PDT

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