Like many others, the speedometer on my car is not adjustable, although the ECM (7730) provides an adjustable speed reading that is visible via a scan tool.

My question is this.

Would it be possible to isolate that info and route it to a vehicle powered LED readout which could be located near the instrument cluster?

This would really make axle ratio vs. speedometer adjustment easy. All I would have to do is tweek the speed constant, and when I put the bigger tires on that could be easily adjusted too, not to mention it would be great to have a reliable speed reading.

 

Anyone? It seems like such a good idea!

 

With SD, the "pulses/mile" do not adjust the speedo - just the calculation for the VSS inside the eprom for calculations.

There is a "byte" in the start of the eprom that will make "factor" changes - you adjust it by turning certain bits "on and off". There was a post on this a while back where someone made this change and got an approximation of the various the change to the speedo based on certain combos of the bits.

Do a search on "speedo" or "speedometer" and you will find the post.

 

When I adjusted the "pulses/mile" the speed reading on my scan tool was correct although the reading on the speedometer remained incorrect. I know this because I compaired it with the speed reading on my GPS.

What I was asking was could this signal that is being displayed correctly on the scan tool be displayed on a stand-alone Led readout?

 

Not to my knowledge. Only through the "Heads-up" byte in the eprom, which allows you various factors depending on which bits you set. It is the only "correction" to pulse signal that is subsequently sent to the speedo. The one in the ECM is "after the fact".

 

Glenn, what's the "heads-up" byte?

 

Actually .... you can if you have the 730 F-Body. Dave Zug recently did this with his '91 Z28 Convertible that he added a 6 speed to. I should have mentioned this to the board when Dave first told me about it but I forgot Anyhow ...

http://www.delanet.com/~tgp/92Z28/02-730-vss4T56.html

Happy reading and Great job to Dave Zug!!!!!!

Tim


This was a Quote from TRAXION I found during a search, the problem is the site does not work. According to the thread Dave Zug figured out how to make the adjustments.

Any idea how to contact Dave Zug?

 

That's the post I am talking about with the "Heads up" byte. It doesn't work with the "Pulses/mile" though - that still only addresses the VSS reading inside the ECM. You have about 3 - 4 combinations that will change the speedo reading by a "factor", and then you must "fine tune" the speedo with appropriate gears.

Edit:
That link does not seem to be working.

 

You can find his new (temporary?) web page at:

http://www.eecis.udel.edu/~dzug/92z2...p/t56swap.html

 

Greg Westphal - Thanks for the reply! I really appreciate it!

Here is the article by David Zug:http://www.eecis.udel.edu/~dzug/92z2...0-vss4T56.html

I am a bit ignorant when it comes to Hex Data. Where can I find "the 3 high order bits at 8014"?

I loaded my Bin in the Buffer of the Pocket Programmer software and tried to edit the Buffer but could not find 8014. I found 8010 and 8020. I'm guessing that this is nowhere near where I need to be.

Do I need special software?

If anyone could point me in the right direction I would be forever gratefull! I would love to tinker with these parameters if I could find them.:hail: