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I am getting to the point in my build that I am going to start hooking up my Koso RX-2N. I looked at everything that came with it and the biggest thing I am hesitant about is installing the speed sensor.

I understand that it makes measurements between magnets to determine the speed, but I have a few questions:

-How did you mount the magnets? did you put them on the wheel hub?

-From everything I've read, the only distance prompt for the VSS is the tire diameter. Is there a specific distance away from the wheel center that this VSS is supposed to be mounted at?

Any help is appreciated.

Tire diameter will give you distance traveled per rotation (C=2(pi)r), they just did some math for you.
All it needs to generate a speed value is number of rotations per minute and how much you travel with each rotation so it doesn't care if it reads a tone ring on the hub or a magnet stuck on the rim as long as it knows how many beeps equal one rotation and the tire circumference (which they calculate for you from the diameter).

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The Koso gauge asks for 2 parameters when setting up the speed sensor. It asks for tire circumference (1000-2500mm) and the number of magnets being used (1-6). I don't think they recommend a specific radius to install the magnets at, but I would imagine the further out the better (for a cleaner signal using multiple magnets). Also, the more magnets you use the better, it should allow the speed to be calculated and refreshed quicker. I take it your drivetrain comes from a donor with a mechanical speedo? Otherwise, if it already has a VSS sensor you can use that instead of the magnets. It just takes a bit of calculation to determine the right tire circumference and magnet count to enter for it to read correctly.

Circumference should actually be based off the rolling radius, which will be about 1/2" less at ground level.

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Has anyone on here installed one of these guages and gotten the tach to work? Did you have to do anything special? It wont read my signal from the spark plug wire...

I've go a different Koso gauge in my car, but the speed sensor and tach signal wiring is probably the same. I actually epoxied the magnet to my driveshaft and put the sensor bracket on my driveshaft hoop for a clean install. Then just figured out the tire size and divided by the gear ratio. My ignition has a tach out wire that gives a 12V pulse every time it fires a cylinder, so all I had to do was hook that up to the Koso tach wire and set it for 3 pulses per revolution to work with my V6.
Kristian

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For your 3800 there should be a tach signal wire that comes out of the ignition control module on the coil pack. You should be able to connect that directly to the koso unit and you'll be good to go.