MS3 Pro - can't change ignition timing

[akl]

Hi, I'm having some grief with getting my engine setup. It's a Honda 35cc (GX35) with a Hall sensor and flying magnet hooked up to pin 6 (CKP+) and an ATV CDI unit getting the signal from pin 24 (tach out). I've got a spark, problem is I can't seem to adjust it.

Should I be running this as Basic trigger? The sensor is mounted around 20 degrees BTDC, could that be part of the problem?

Thanks!

[akl]

I should add that the spark appears to match the signal from the hall sensor perfectly, can't get it to deviate from the input. Also, the engine isn't running, it fired a couple of times but it appears that the ignition timing is off. Thanks

[Six_Shooter]

Your trigger offset angle is too high... or too low, depending on how you look at it.

Angles between 15 and 50 degrees are for whatever reason "invalid" and will cause the ignition system to lock at 15 degrees advanced and not deviate from there, even if the timing table commands a lower advance value.

So reduce it below 15 degrees (may require adjusting the actual sensor position) or use above 50, but you will need to read up on how to set that up properly.

[Paul_VR6]

Trigger angle needs to be at least a little past max advance. I would say 60deg is about the minimum I have used.
What type of trigger is it?
Also tachout is for driving a tachometer not spark, you should be using spkA which is pin 27 on the grey connector.

[Six_Shooter]

Trigger angle needs to be at least a little past max advance. I would say 60deg is about the minimum I have used.
What type of trigger is it?
Also tachout is for driving a tachometer not spark, you should be using spkA which is pin 27 on the grey connector.

Tacho can be used for spark and is recommended pin when driving an MSD box or ignition module. It's a stronger output than the spark outputs.

Trigger angle has nothing to do with actual spark advance, it's a setting used to tell the ECM when the incoming signal is relative to the crank position. On many dizzy based systems this is tyipcally between 0 and 10 degree BTDC. This will use "next cylinder timing", where the timing calculation is used for the next cylinder fired. Using trigger angles of 50 degrees or above will use "same cylinder timing", where the timing control will be for the current cylinder fired. Both ways have their pros and cons.

[akl]

Thanks for the advice, should be an easy fix!

I'd prefer to not relocate the sensor if possible. Could I run it below 15 deg and it will fire on the "next cylinder", and still have reasonable ignition adjustment? Is it a big deal to have the sensor off 5 degrees and add that 5 degrees on the advance table?

[Six_Shooter]

It's best if the actual trigger angle and the trigger angle in software match, this will create the most accurate table to actual crank timing.

However, same cylinder timing (>50 degrees) might work for you, and the table accurate. Check in the manual to see how to set it up and tuning of such.

[akl]

Couldn't find much on it but here's what I found:

For best accuracy at high revs or during transients, aim for the trigger to align at 60-90 BTDC. This also allows a
full range of timing (including ATDC timing should you need it for boosted conditions.) This range of trigger angle
is preferred for new installs.
For slightly better starting, but not quite such good running accuracy, aim for a trigger ~10BTDC or your desired
cranking advance. This is the typical trigger angle for TFI and HEI7/8. You cannot retard timing later than the
trigger angle. e.g. 9BTDC and lower are not possible with a 10 BTDC trigger angle.

I won't have a chance to work with the engine until Monday. At least now I have a better idea of what I'm looking for, thanks!

[Paul_VR6]

If you are using tachout for spark make sure you have selected that in software. Some cdi do need high current some don't most modern msd, etc are ok triggering off of the logic spark outputs.

[akl]

So I relocated the hall sensor and put the stock coil/magneto and was able to run the engine on fuel only. The hall is only sneding one signal per revolution into the engine but my rpm is twice what it should be. Any suggestions on what that might be? Want to fix that before I try to run spark off the MS3. Thanks!

[akl]

If I say it is a 2 cylinder engine the rpm reads correctly, is this an accepted practice? Or is there something else wrong?

[Matt Cramer]

Yes, for a flywheel triggered one cylinder, you typically cheat and pretend it's a two cylinder.