speedometer recalibration
Thread Starter
Launching!
Joined: Sep 2004
Posts: 238
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speedometer recalibration I just got done putting a th400 in my car. I have the sensor, clip, and "pigtail". As far as getting the speedometer to work, what needs to be done? Right now I will be going 25, put it reads I'm going 70 or something like that. I'm assuming it can be chaged at the dyno, but how ?
thanks alot,
chris
thanks alot,
chris
when I switched to an M6, I had to change the gear size to make it work. I could not get EDIT to change the VSS info. My case was the opposite of yours. At 70 mph it would read 30, so I told it that I have 1.59 gears and now it is accurate.
If they can not change the VSS inputs you can play with the gearing. In your example if you multiply your current gear by 70/25 it will read the correct speed. Just make sure you have measured accurately the true relationship. You can also tell it that you have smaller tires, but that may mess up ABS/ASR (although that may not be an issue depending upon your mods).
If they can not change the VSS inputs you can play with the gearing. In your example if you multiply your current gear by 70/25 it will read the correct speed. Just make sure you have measured accurately the true relationship. You can also tell it that you have smaller tires, but that may mess up ABS/ASR (although that may not be an issue depending upon your mods).
Thread Starter
Launching!
Joined: Sep 2004
Posts: 238
Likes: 0
so the only way to know how fast I'm going by putting it on the dyno and reading the speed off the rollers. Once I see what "actual" speed I'm going, say 10mph, I must divide that number by what my car speedo is showing, say 50mph. 50mph divided by 10mph = 5 then what? I have 4.10 gears now, but I'm putting 3.73 very soon, so lets just say I have 3.73. Now what?
My friend has a 400 and we set the gear size=6 and the tire diameter=16.4 with 4.10 gear out back. That would be a good starting point and you can tweak it from there when you swap gears. We used a gps to verify speedo accuracy.
You can do it on the dyno or do it in advance. Go on the highway with a buddy. Have him his cruise control at 70 and match his speed. Then note your speed as shown on your speedometer. You'll know your speed and the refernce speed. You can do the math from there.
