NOS Window Switch Cylinder Settings?

[Ninjazx71]

Hi All. I had the NOS 2-stage Window/WOT Switch installed in my 2010 Dodge Viper. I set the number of cylinders to "10" like it should be, but for whatever reason the RPM being displayed are 1/10th of what actual RPM are. This means that with my "Activation RPM" of 3,700 RPM, the engine would need to spin to 37,000 RPM before it activates. My shop found details and was able to set this to "00" instead, and the proper RPM show on the display and the system now activates at the correct RPM.

My question is, why do the RPM displayed/read 1/10th of the actual engine speed when setting up the unit for 10 cylinders? TIA!

[Ryan W.]

The controller assumes a single coil when set to multiple cylinders, and hence was looking for 5 input signals per revolution. But, and I'm making a mild assumption, you had it reading its signal from one coil, which in your case only sparks once every two revolutions. That would cause it to get a signal at 1/10 the rate it's expecting, reducing the RPM reading by the same amount.

[Ninjazx71]

Thanks for the info, you are correct. I'm just tapping into a single coil and it was showing 1/10th of the actual RPM. Are you saying I would have needed to tap into 5 cylinders? The wiring information doesn't show tapping into multiple coils, and wouldn't 5 taps give me 1/2 of the RPM (5/10)? Almost sounds like that value is telling the Window Switch how many feeds it should be expecting for the RPM.

[S2H]

Basically, the cylinder setting is how many pulses per combustion cycle that it's going to be seeing. Meaning how many pulses per 720° of engine revolution, or how many pulses per 8 cylinders for a V8, or how many pulses per 6 cylinders for a V6, or how many pulses per 4 cylinders on a 4 cylinder engine.

Example: A single coil trigger wire in a sequential coil on plug setup will be either 0 or 1 (I really don't know why they put 0 as an option, but it works the same as 0 or 1).
If it's a waste fire coil setup, it would be set to 2, because the coil will see 2 pulses per revolution.
If you were to tap into a stock GM F-Body ECU tach output, it will output 4 pulses per revolution so you would use 4 as your cylinder value.
A standard tach output from an MSD box or most aftermarket ECUs would output 8 pulses per cylinder. Hope this helps.

[Ninjazx71]

Thanks man, this does clear it up a bit. Just odd the instructions say that value should be directly set to how many cylinders the vehicle has. Either way it looks to be firing correctly now, and I'll make note of this in case the unit resets or something. Appreciate the help everyone!