mguidry629

iTrader: (6)

The car I pulled the motor/pcm out of had a 110 speedo guage. The guage on my car is 140 or 160, can't remember, but it's higher. I think the needle is reacting as if I had the 110 guage, which is throwing the accuracy off. I have the speed tuned in the pcm and it's getting an accurate reading, so that's not a problem. I used a GPS and datalogging to tune the PCM speed.

Is there any way to make this pcm work with this guage, or do I have to switch the clusters?

How does the speedo guage work? I mean how does it get it's signal? Straight from the PCM via the VSS?

Gojira94

iTrader: (4)

There is a speedo conversion factor in the PCM, IIRC. How the PCM is getting its info to convert for this will depend on the transmission. Did you use the 4L60/700R4 from the 93 as well? Or do you have a 4L60E or T56 (and what year car was it from if T56)? Not sure how many teeth are on the VSS reluctor in the 4L60/700R4, but the 4L60E has 40 and the T56 has either 11 or 17, depending on which year it's from.

Oops, overlooked the 4L60E in your sig. That's the 40 tooth reluctor, so you need to change the speedo conversion factor for your 155MPH speedo.

mguidry629

iTrader: (6)

The 4L60 that was originally in the car had a red plastic gear that turned another gear on the VSS. The 4L60E has the metal reluctor (I guess it's picked up magnetically by the VSS). The other problem I had was the donor car had 2.73 rear end and my car has 3.23. I tuned that out with tunercat the best I could. I know in the constants tables theres 4 or 5 settings for the speedometer, but I just used the speedo calculater function and put in my actual speed vs speed shown and the pcm is pretty accurate now, within 1 or 2mph at 55mph, according to my GPS.

Simply put, datamaster is telling me I'm doing 55, my GPS about the same, but my speedo guage is at 50. Even at 30 or 35 it's 5mph off. I haven't really tried above 70mph to see how far it's off.

I don't have tunercats in front of me right now, but you're saying I should be able to change the conversion factor in tunercats and that will affect the way the guage will read?

Gojira94

iTrader: (4)

If you're off by a pretty consistent amount, you might look at tire (wheel assembly total diameter) size as part of the equation- see p.34:

http://www.tunercat.com/tnr_desc/tnr_manual.pdf

Sorry if this is review... not sure how you went about it the first time through.

Lastly, also possible the speedo head needs adjustment if everything else is dead on. Any chance you have access to another 155MPH cluster if all else fails?

mguidry629

iTrader: (6)

My tunercat has an option where you can plug in the actual speed vs speed shown, and it calculates that into the different fields. That's how I tuned it.

Only other cluster I have is the 110mph, which is what is original to the trans/pcm. I'm sure if I switched it out it would solve my problem, but I'm hoping to keep the 155mph. Wouldn't any 155mph cluster do the same thing since the pcm is programed to deliver the signal to a 110mph cluster?

Maybe the cluster itself must have it's own way of calibrating the signal, regardless of what you change in the pcm.

Think of it this way: on the 155 guage, let's say needle pointing straight up is 80mph, but on 110 guage, needle straight up is 65. My needle is moving as if it's on a 110 guage. I'm not sure if you can ever change that without changing the cluster back to the original one that came with that pcm.

Gojira94

iTrader: (4)

Think I didn't explain adequately. I think you're exactly right about the needle position. What you need is a conversion factor in the PCM to change the scale. I went and did a little homework. The old speedo is 115MPH and the new one is 150. If you divide 115 by 150 you get 0.7666666666666667. So it would seem the needle sweep needs to be scaled down from 1:1 to 1:0.7666666666666667. I'd hit up Solomon at this point to see how he does it. I'd have originally thought the speedo would use its own scale and just be correct without changing anything in the PCM. Time to admit I'm not sure and ask someone who probably is sure.