MoTeC Global Forum

Hi all
What would be causing the RPM on the dash to be 1000rpms out, sure it’s idling at about 1000rpms but say is saying 2000rpms.. its a msd crank trigger with 4 magnets so set up at 4 to 1… on a spd input
Thanks again for all the help..

Hi,

Have you checked with a scope that you are only seeing 4 pulses per revolution? Do you have the sensor type set and the levels are correct for the sensor output?

Can you post your configuration?

Hi Stephen thanks for the reply.
Here’s the settings for the RPM signal.. Ive updated the voltage threshold to 4.680 from 1.498 to see if that makes a difference, as read that the MSD grid pulls 12v. I’ve not tried it yet to see if that makes a difference.. how do you check with a scope?

Stephen Dean wrote:Hi,

Have you checked with a scope that you are only seeing 4 pulses per revolution? Do you have the sensor type set and the levels are correct for the sensor output?

Can you post your configuration?

Hi,

If you go online with the Dash and got to Online | Monitor Channels, scrolling down to the channel that you want and double clicking in the channel will bring up the oscilloscope view, you can use this to see what the signal looks like to the Dash. As this is just equally spaced teeth, it becomes harder though to determine how many teeth are being seen per revolution.

An external scope can be used with one probe on the tacho signal out of the MSD box, and by wrapping a piece of insulated automotive loom wire around the Cylinder 1 ignition lead and connecting this to the second channel in the oscilloscope, you can read the number of pulses coming from the tacho output, and see the ignition pulse for Cylinder 1 which you can use to count the teeth.

Thanks Stephen I’ll give that a try..

Stephen Dean wrote:Hi,

If you go online with the Dash and got to Online | Monitor Channels, scrolling down to the channel that you want and double clicking in the channel will bring up the oscilloscope view, you can use this to see what the signal looks like to the Dash. As this is just equally spaced teeth, it becomes harder though to determine how many teeth are being seen per revolution.

An external scope can be used with one probe on the tacho signal out of the MSD box, and by wrapping a piece of insulated automotive loom wire around the Cylinder 1 ignition lead and connecting this to the second channel in the oscilloscope, you can read the number of pulses coming from the tacho output, and see the ignition pulse for Cylinder 1 which you can use to count the teeth.