Also seeing no RPM (on two-stoke engine with 2p per rev)

the ocho · Post by **the ocho** » Mon Mar 20, 2017 4:03 pm

I have a CoilX module hooked to the v- side of the coil. It's wired up to the RCP per the direction but i'm not seeing anything on the RPM input.

I also have a Cherry hall effect sensor set to a toothed gear on a jackshaft - it also is showing 0 at it's rpm signal. It is wired with a 1k ohm pullup.

any ideas where to start diagnosing those issues?

the ocho · Post by **the ocho** » Sun Mar 26, 2017 4:14 am

figured out the issue with the hall effect sensor - it was a DOA sensor, replaced and everything is happy there.

still working on getting a working signal out of the CoilX. I've heard of other guys being able to pick up pulses on other systems using the kill switch wire because it grounds the ignition circuit to kill the engine. I may try running that to a rpm pulse input and see if the system will pick it up.

the ocho · Post by **the ocho** » Mon Mar 27, 2017 2:30 am

So I hooked the CoilX module to the kill switch wire on the snowmobile motor (which just grounds the ignition) and was able to generate a signal for RCP to pick up. It's a wasted spark system on a two stroke motor, and RCP was set up for 2 pulses per rotation. I'm recording RPM numbers that are 3 times too high (idle is usually around 2k, and i'm seeing 6k)

Any guesses why it's a little funky?

Also - the RPM readings are a little noisy. I think I can smooth it out a little with some averaging but I don't want to dilute the data too much. It's probably because of the super over sampling causing the readings to really bounce around but it's kinda big swings in numbers (+/- 500 rpm). I had it set to 5hz but i'll bump the recordings up a touch and see if I can get anything more steady.

Post by **brentp** » Thu Mar 30, 2017 3:54 pm

The CoilX is specifically designed to filter out common signature of the coil flyback 'ring' seen on the primary winding of a typical ignition coil. Explanation here: https://wiki.autosportlabs.com/CoilX

The signal you are seeing might be different than what CoilX is designed to handle. Suggested is to inspect the signal using an oscilloscope to see what the signature looks like.

One idea based on your use of the hall effect sensor might be to use another hall effect sensor on the crankshaft; that should produce a very clean RPM signal.

The pulse per revolution setting controls how to map pulses to the actual RPM. We're releasing in the next app the ability to set 1/2, 1/3 and 1/4 pulse per revolution which will account for setups like yours.

Advanced pro-tip: you can edit the config file and change the "ppr": 1 line to "ppr": 0.3333. Save it and load it back into the app, then write it back to RaceCapture.

the ocho · Post by **the ocho** » Mon Apr 03, 2017 2:15 pm

yeah - the signal must be changing as the RPMs pickup and drop. I'll see if I can find a scope, if not i'll have to keep testing other inputs off the engine to try to find something that will work.

(attachment shows the data from the hall effect sensor on the jackshaft looking good, and the engine bouncing from between 6 pulses per rev to 2 pulses per rev)