Is there any way to modify the source code to compensate for axle ratio. Or could one just use a potentiometer inline with your speedo wire, or something like that.

If anyon ehas any has any ideas I'd love to hear em.

 

I have a dumb question, Does a 700r use a plastic gear that can be replaced like my TH400?

 

Ya there plastic, and easy to change. I'm just really curious if it can be done in the prom.

 

i was pretty sure speed was read from an optical VSS under the dash.at least on other C3 ecms it is.

 

I'm not sure but I know the pulse sending unit is inside my tranny.

 

If it's the '89 in your sig. that you want to change the speedo cal. on, you'll have to get a kit from the dealer and pull out the cluster to reprogram it. It doesn't go through the ecm.

 

The 747 uses an external DRAC (digital ratio something something converter). It's a little white plastic box that has "jumpers" inside of it to calibrate the VSS signal to gear changes / tire size changes. The VSS for the 747 is a 40 pulse per revolution (DC I think). This VSS uses a reluctor (metal ring with teeth) and a pickup to count pulses.

The 730 ECM uses a different VSS that has two gears, much like a speedometer cable setup. Except where the cable would go ther is a small "generator" and I think this type produces and AC signal.

Correct me if I'm wrong. These are my personal findings.

Go to ftp://ftp.diy-efi.org/incoming/ and look for drac2.pdf

 

Looks like only 92 - 94 used drac. I guess my 89 doesn't.

 

I wonder if you have speedometer gears. Maybe I didn't read the posts well enuf but I didn't even think that you may have speedo gears.

 

You can change it in the code but it doesn't help anything because neither the fuel or timing have any speed corralation. It's all about manifold pressure, engine speed, time, and the other sensors. Speed really shouldn't have anything to do with the basics BUT it would be nice ot have a table that takes away timing as speed increases.
Anyways, like I said, you can modifty how the ecm interprets the speed but it's usually too course of a change. The only thing that's effected is the TCC settings and maybe some IAC operation. Shift light if it's a stick. I didn't notice any difference and I went from 2.73's to 3.73's!!!
Even if you did change it in the ecm you'll still have the speedo off and cruise control will also bug out. Do a search, I remember a topic about this but I couldn't find it.

 

I do have speedo gears (which are meant for 3.08s). The unit in my tranny semds out a pulsed signal proportional to speed. My thoughts now are to build a simple curcuit to put inline of the signal and mabye have a dial that would aloow one to make small changes to the speed signal.


On another note: Why am I getting a "no high gear" flag with my scantool (winaldl). My TCC isn't locking up, where as it used to. All my paramters are correct, because the TCC locked just a few days ago. It still locks under the "max speed forced lockup" parameter. Just wondering if the no high gear signal is causing my problems.

 

http://614streets.com/drac.html

http://614streets.com/drac.html




http://614streets.com/drac.html




Did I mention http://614streets.com/drac.html ?

 

HOLY CRAP!!! Is that a neat link or what?:hail: