RCP MK2 two stroke tach signal issues

[ftxmotorsports]

Hi all, using our RCP for the first time this weekend in our hydroplane. Have been learning what we can in the shop and are having issues with our tach signal--its steady at idle but anything above idle it freezes the tach display number---the signal is an ac magneto signal 6 pulse is my setting as I've always used with other tachs but not sure what to do with sample rate or timer speed? sample rate is currently 5hz, timer speed is medium.

thanks for any help from anyone who may have done a two stroke already!

Curtis

[brentp]

Hi -

What kind of signal do you have available?

RaceCapture/Pro requires a reasonably clean tach signal. For tapping directly into coils we have the CoilX adapter module which can help clean up the signal. Info here: https://wiki.autosportlabs.com/CoilX

[ftxmotorsports]

Hi Brent, as stated in my post its a 6 pulse ac signal produced from the magneto like most all two strokes have. the connection is directly to the stator/magneto output. I have the signal good at low rpm but it freezes at 3800 rpm and higher.

is this just a sample rate issue maybe?

Curtis

[brentp]

The sample rate you see in the settings determines how fast the current value is logged. It doesn't affect the quality of the signal, since the current RPM value is continuously sampled behind the scenes, calculated on every pulse from the source.

Does this AC pulse also drive the ignition coil as it does with other engines, as described in our CoilX wiki page?

[ftxmotorsports]

The ignition is driven by a separate coil on the coil plate behind the magneto. I know the voltage output of the ignition primary coil can be well above 500vac at times.

it uses a vr sensor as the trigger for the cdi which I know you dont reccomend using for a pulse input so I may be stuck having to install a hall effect sensor to use as my tach pulse provider maybe?

please remember-this entire system is AC-no DC voltage present in this ignition anywhere.

in a nutshell, I am trying to make the RCP read an AC 6 pulse (6 full waves per revolution).

I will read up on the coil -x shortly when I get a minute today

Thanks!

[ftxmotorsports]

We finally found an easy answer for two strokes with ac magneto ignitions--installing a regulator/rectifier on our ac magneto output gives us a regulated dc output wire which when hooked directly to the RCP pulse channel gives us what appears in the shop to be a useable tach signal. The pulse count appears to be the same as we have always used with ac capable tachs (the same as the number of generating coils on the stator plate). We will be testing again on the water this weekend to verify proper operation at speed under load.

Also, thanks to the forum, we realized that the reason we weren't successful data logging was because we had purchased a 64 gig mini sd which I now realize is incompatible with our RCP (must be 32 or smaller)

[brentp]

Fantastic, thanks for pushing through it! Great information for the future.

Please tag us on facebook https://www.facebook.com/AutosportLabs/ when you do your event and we'll share it!

[tfriest]

What regulator/rectifier are you using?

I have a Rotax 593 engine and I run the signal into a coil-x (that was modified with a bigger resistor to handle the high voltage) and that doesn't really work...

Basically my setup seems to give a reasonable measurement at idle (roughly 1500 RPMs), but at full speed it doesn't give useful readings... I've tried various pulses per revolution settings, but haven't gotten anything that reads correctly.

[ftxmotorsports]

I used a regulator designed for the stator I use in my engines (polaris twin two cylinder stator)but I bought one for an electric start model so it has the dc out-recitfied from the stators ac)--

So, I would look for an oem rotax regulator/rectifier from another engine/model that uses the 593 engine type with electric start-not being an electrical engineer, thats the best advice I can offer