# Speedometer



## bblocher (Jul 30, 2008)

Unless you're not using the transmission you should't need to change anything. The speedometer signal, digital or mechanic comes directly from the transmission and connects to the speedometer. 

I think this is fairly standard but I'm no expect. You'll have to look at the car you plan to convert. If you did need to alter something for this you'd have to engineer something for this.

As for the motor controller, it has no idea how fast the vehicle is going. The speed output on the tranny is based on the output shaft and is aware of the differential gear ratio.


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## NeonGeek (Jul 12, 2008)

doesn't work that way on the Neon, the speed sensor goes from the transmission to the PCM, then to the Speedometer. least that's how its been explained to me from my fellow Neon community.


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## bblocher (Jul 30, 2008)

You "may" find, like my car, that the signal goes to both at the same time. The PCM/ECM does use this info to influence other things but might not actually relay it.

If it indeed does relay the signal then you'll need to first figure out if the signal is changed. If it's not changed you can rewire it directly, if it is change then things get more complex... a lot more. For example on my car for the RPM I found that the crankshaft sensor input to the ECM was different than what my ECM sent to my tach. I'm using a little microprocessor to create my new signal and you might could use something like this or create a small circuit to do the same. Hopefully you don't have to go down this path but let me know, I'll help any way I can.

Not sure what state the vehicle is in but the best thing to do is unplug everything going to the ECM and then rotate your tranny output shaft. My gauges are digital so it might be harder for you to test if the gauges are analog you might need to spin it up a bit faster before it reads anything. If it's still in the car you can jack up one of the drive wheels leaving the other on the ground. Spin the wheel and this should spin the output shaft fairly fast.


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## bblocher (Jul 30, 2008)

Sorry one other note. Do the tranny tests first with the PCM plugged in so you know the test is a good one, then unplug and try again. If you get speedometer movement in both cases you're set


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## 1clue (Jul 21, 2008)

After-market electronic speedometers like those from http://www.autometer.com work really well. You have the sensor anywhere it makes sense, in other words anywhere that one revolution always means the same distance. Could be the transmission output shaft, could be a magnet on the wheel, could be anything in between. The sensor makes a pulse every revolution, or 3 pulses, or whatever you want.

You calibrate by finding a "measured mile" meaning, some stretch of road you know is exactly a mile long. Push the button, drive the mile, stop exactly at the other side. Push the button. The speedometer counts the pulses, and then knows how fast you're going from then on.


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## bblocher (Jul 30, 2008)

1clue said:


> After-market electronic speedometers like those from http://www.autometer.com work really well. You have the sensor anywhere it makes sense, in other words anywhere that one revolution always means the same distance. Could be the transmission output shaft, could be a magnet on the wheel, could be anything in between. The sensor makes a pulse every revolution, or 3 pulses, or whatever you want.
> 
> You calibrate by finding a "measured mile" meaning, some stretch of road you know is exactly a mile long. Push the button, drive the mile, stop exactly at the other side. Push the button. The speedometer counts the pulses, and then knows how fast you're going from then on.


Sounds like the perfect solution for those who don't want to mess with building their own circuits or if you just don't like the look of your dash/gauges  Thanks for the link.


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## 1clue (Jul 21, 2008)

I bought AutoMeter Marine for my hovercraft, and I like them a lot.

Be careful though, a 5-gauge cluster of smaller, lower-cost gauges for me cost $450. You can drop several grand in getting your gauge cluster. That was almost 10% of the cost of the whole hovercraft.

That said, AutoMeter makes very fast, very nice and reliable gauges mostly designed around muscle cars. Or muscle boats. They assume that half their gauges go into a car which was built from the ground up or disassembled down to the metal and built up from there. They know the home muscle car fanatic's desire to do it their own way, and they consequently make it very easy to hook up gauges.

You can expand your search to dozens of brands. Go search on AutoMeter, then see what else each web site sells. They usually each stock 4-5 brands. You can extend that out as far as you want, I just mentioned AutoMeter because I went with them.

I guarantee that if you search long enough, you'll find a gauge that's perfect for how you want your dash to look, assuming you want to tear it out and put in a gauge cluster that looks nice.

I advise against going with the thing that sits on your local car parts supplier's shelves. They sometimes have one or two nice gauges, but more often the only complete sets you get are some cheap spin-off that is unreliable and harder to hook up.


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## 1clue (Jul 21, 2008)

One more thing about those gauges.

I was describing the "electric" models. AutoMeter (and most other good gauge companies) make mechanical and electric models. You probably will need an electric sender, even if your car had an electric sender already. For example, temp gauges all have their own scale depending on manufacturer. If you hook up an AutoMeter electric temp gauge to the original sender, you'll probably get the wrong reading.

You can find out for sure by looking at the specs for the gauge and for the car, in the service manual. The service manual has checks for what a normal sender puts out in different conditions.


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## NeonGeek (Jul 12, 2008)

alright thanks guys. and the current condition of the car...its in pieces. everything is stripped off it, cept the dash board and the interior wiring harness.


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## iss407 (Dec 6, 2007)

Just get a cheap GPS nav system. It will display the speed with more accuracy, and as a bonus tell you where you are!


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## order99 (Sep 8, 2008)

Now there's an option i'd never have considered...many thanks.


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## Jimdear2 (Oct 12, 2008)

Sorry to be negitive to an inovative idea, but think about lag time in the GPS, now think about cops with a radar detector that reads your "Right Now" speed.


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## dimitri (May 16, 2008)

Jimdear2 said:


> cops with a radar detector that reads your "Right Now" speed.


ever since I started driving my lead sled EV and became aware of energy it takes to push me forward and how little of it I have to spare, getting a speeding ticket suddenly became a thing of the past


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## iss407 (Dec 6, 2007)

There was not very much lag on the GPS unit I just used for a long trip, 3 or 4 seconds max. I can judge about how much my speed has changed in that short of time with a good degree of accuracy.


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