pwdbychevy

I've conducted a search on how to recalibrate my speedometer w/o having to buy a box from Dakota Digital and it's confusing the heck out of me I'm using TunerPro to do this and haven't figured out where to go to change stuff. The article reads:

bit 7 set: = 96 mph
bit 6 set = 83 mph
bit 7 and 6 set = 73 mph
bit 5 set = 65 mph
bit 7 and 5 set = 58 mph (closest I can get.. pretty dead-on using a chase vehicle)
bit 6 AND 5 set = 53 mph (amazingly, I still have room to go)

Where can I access these "bits" in Tunerpro? Thanks in advance for your help, I'm still a newbie when it comes to doing this stuff. You can read the entire article in this thread - https://www.thirdgen.org/techbb2/sho...%2Bcalibration

JP86SS

iTrader: (1)

Create a new "ecu" item at location he said "bits at 8014"
This would be 0014 in the address box. Make one for each bit 5, 6, & 7 from what it indicates.
The location looks the same in ANHT/AUJP anyway.

pwdbychevy

That is where I get lost. I don't know enough about TunerPro to create a new ecu item. The screenshot shows what i think is the "create new ecu item" window. I right clicked on the VSS instrument panel pulse divisor in the constant table and selected "Edit item ECU info". Is this where I need to be? If so, where do i go from here. I appreciate your patience on this. I want to make sure I don't screw something up.

JP86SS

iTrader: (1)

You don't want to "edit" that one.
Create a "New" ecu item", then enterthe same start address etc and click the "bit mask array of flags" (that box below)
Then the idividual bits are there in the boxes.
They will be in the "Y" axis box. The bits 0-7 are actually shown as 1-8 so that is a little thing you'll have to deal with.
should be good to go.

Look at some of the error flag words to see how they are entered and it's easy to see what I'm talking about.

JP86SS

iTrader: (1)

I just noticed that the bits are backwards
box 8 is bit 0
box 7 is bit 1
box 6 is bit 2 ...
Sorry for the cornfusion

DENN_SHAH

iTrader: (1)

pwdbychevy, you may want to try the newer Super_8dm2.ecu file, it looks like it is setup to change the " Vehicle Speed Sensor Instrument Panel Pulse Divisor" already.

pwdbychevy

Ok, I got the Super_8dm2.ecu . There's actually two VSS items in the constant table. Which is the one that I have to play with the try to get my speedo back on track?

pwdbychevy

Ok, I got the Super_8dm2.ecu . There's actually two VSS items in the constant table. Which is the one that I have to play with the try to get my speedo back on track?

pwdbychevy

I appreciate your help JP86SS.

pwdbychevy

I'm not seeing any error flag words. I must be doing something wrong. Do i have to put something in the "Y" axis box? Are they supposed to be zero's or one's in there? Man this is confusing

DENN_SHAH

iTrader: (1)

i would say the Vehicle Speed Sensor first. you need the ECM to read the right MPH or as close to the right speed as you can get it to start with. once it is right, you may not need to make any other changes.
i haven't played with the "Vehicle Speed Sensor Instrument Panel Pulse Divisor" yet, so im not sure what a change to it does.
you can PM the guy who setup that ECU file & ask him what it does.

JP86SS

iTrader: (1)

Come on now, it's not that hard

Edit the second listed one on your v2 file.
See that the address is the correct one you are working with "14".
Click the "array of flags" box.
Close the ecu editor.
Now click on the item in the "flags" list box on the left.
When it opens you will see the bits.
Just click them on or off as desired to test the operation of the speedo correction.
Remember that this only changes the speed the ecm is seeing, not the dashboard reading. Need to change the gears to make that match.
Jp

JP86SS

iTrader: (1)

Take a look at this and you'll see what I was describing.
Theres a shot of the open item after I edited it and added the check box to the "flag" selection.
The order is a little screwy but it works.

Let us know if this fixes the speedo input. Some before and after data to give a better idea of where you made progress.
Jp

pwdbychevy

That's exactly what I needed to see Now it makes sense. Thanks. So what you're saying is that I can change the speed in the ECM but the Speedo will still show the same? My speedometer is electronic (1992), does that matter? Will I still have to change the tranny gears?

JP86SS

iTrader: (1)

I "believe" so because it runs of a signal from a buffer box that is triggered from the gear sender at a specific rate (4 pulses per revolution, IIRC)
The rate the gear turns needs to end up at 4000 pulses per mile at the ecm.
I haven't tried messing with those divisors that you are but my guess is that you can cheat the ecm value but the speedo has no adjustment for the buffer box output.

DENN_SHAH

iTrader: (1)

like JP86SS said, 4000 pulses per mile is the standard output which its best to be as close to that as possible
i didn't think about that it may have an older ECM in it & you may be using an external speed buffer.
if it has a ECM from a 91 or a 92, then the speed buffer is part of the ECM & then the ECM has an output to the cluster.

pwdbychevy

The ECM is a 91-92 Speed Density

JP86SS

iTrader: (1)

Just for my inquisitive mind to know, does the speedo get the 2000 pulse per mile output from the ECM that normally is used by the cruise control?
I didn't know that on those that the speedo IS driven by the ECM.
My stuff is old gotta uses gears.

92Z-666

iTrader: (2)

Wow this thread reignited... To anyone reading this still, the excerpt above is only PART of the article(if you can call it that) I wrote back in 2001. The link above leads to a TGO topic where I just posted the URL to the PRESENT location of the original article. Yea its technical in nature, and a bit scattered but the basic info is all there... including an original mistake(and correction) I made. I found the CAL location.. did the testing and article and brought it out from the shadows... then got some fill-in info from a helper and revised it a touch.

The whole concept was "If you have a 91/92 ecm, abd do a T56 swap.. do this to *almost* fix the speedo and its a free fix.

(shameless plug):

get the final piece to your T56 swap HERE: (I'm no vendor.. this is my ONLY product and I don't advertize and I need mo-money for NITROUSSSS LOL)


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

DENN_SHAH

iTrader: (1)

JP86SS, i will have to look it up, but i think the on the later ECMs the signal from the ECM that goes to the speedo also goes to the cruise too.

92Z-666, i had read that article quite some time back too, confused the crap out of me at the time,.. lol, but it did help me out.

as my setup is some what a little different from what a third gen has, instrument cluster from a 89 calais, cruise control & trans from a 92 pickup with the truck speed sensor, i use a recalibrated truck speed buffer to run the speedo & cruise with the VSS Teed off to both the buffer & the ECM. because the truck speed sensor puts out something like 128000 pulses per mile, the speed reading in my ECM was maxed out at 255 MPH by the time i was going 15 MPH. so my TCC would lock as soon as i got in second gear which is why i got into burning my own chips. i used TunerPro RT with 8d_v03.ecu to lower the VSS gear ratio from 230 to 12 which got the ECM to read with in a mile or 2 of the speedometer. on the dyno my speedo reads 59 MPH with the dyno reading 60, i think thats close enough.
one day i may remove the buffer & hook the cluster up to the ECM & see how close it is like that.

pwdbychevy

Will this work with a T-5 tranny?

92Z-666

iTrader: (2)

Both the INTERNAL and the INST modifier WILL "work" but the only useful mod for a T5 would be the internal one... to allow things like the TCC, shift-light, and speed-limiter(if used) to work more correctly. As soon as you change one of the 3 "INST" setting bits, your speedo will drop off so severely that it'd be useless for anything other than trying to convince a cop that you shouldn't get a ticket for 110 because your speedo said 20.

I'm assuming you're changing gears or something. such a subtle change requires you to change out the speedo-pulse gears in the T5. Can't do that on a T56.

92Z-666

iTrader: (2)

heh.. yep, in mine, I got injector-shutdown at 15 mph.

40 or 17 pulses per driveshaft rev as compared to 3 for common thirdgen so yea.. some hundred thousand per mile I guess.

Every time I puke-out a summary of something I did, I say I'm goin back to fix it later and never do. Glad you pulled yourself through it!

pwdbychevy

I went from 3.08 gears to 3.73 and at 80 mph my speedo read 92