MicroSquirt.com read only forum (Jan.15,2018)

We are using a Microsquirt on a 2 cylinder turbocharged Honda CX500. We installed a CX650 case that has two crank VR sensors, 80 degrees apart. I get spark on both plugs but the timing is wrong, engine pops and bangs, wont idle. Am using the dual spark mode. The base timing measured with the timing light is 32 degrees. Set the advance table to 26 flat.

PLease suggest some settings for the offsets for ign1 and ign2. I've tried dozens of combinations and none work correctly.

Thanks

If it's popping and banging,, your spark is at the wrong time, but you need to identify which one. Favourite would be to disconnect a plug and try and get it running on one cylinder, although I assume you have the following set up with just one tooth on your wheel/flywheel, if you don't that will explain some of your problems.
I think 800vtwin or grippo will be able to add some specifics.

If you post your msq that will help much.

Grippo, I did as you suggested in the png, used the wizard and then messed with the advance for IGN2. Didn't work. I have two marks on the crankshaft flywheel, one in yellow at 27.5 BTDC of cylinder 1 and a white mark at 27.5 BTDC for cylinder 2. With 27.5 as base timing, I tried various numbers in IGN2 advance, 0.0,27.5,-27.5,80.0,-80.0 and only see the yellow mark on the flywheel with the timing light for cylinder 2. As a WAG I tried 350 degrees and the white mark showed up, but the engine did not run well. Attached is the msq file with 350 degrees.

What can I do to move this project along?? I have been going back and forth with Matt for a month, trying different suggestions and getting nowhere.

Elliott

P.s. I tried -27.5 in the base timing and then get no spark on cylinder 2.

Base timing on a CX 500 is 15 degrees @ 1000 RPM, advance starts @ 1750 with full advance of 37 degrees @ 5500.

This is for a stock motor but the values will get you started, remember a turbo motor will function as NA untill it develops boost so these figures will get you started.

Are you reading your advance values with an adjustable timing light? Looks like your system is operating in wasted spark mode from the figures you have supplied.

The stock CX coils are CDI coils they are not intended to be fitted to an Inductive system: I presume you have fitted your mS as an inductive system.

The right hand cylinder #2 fires 280 degrees after the left cylinder #1

The stock CX ignition operates in an unusual way by fact of it having two sets of pick ups for each cylinder - one for static timing and one for dynamic timing, I presume you are only using one pick-up for each ignition event?

Hope this helps

Sean

SunsetMoto wrote:The stock CX ignition operates in an unusual way by fact of it having two sets of pick ups for each cylinder - one for static timing and one for dynamic timing, I presume you are only using one pick-up for each ignition event.

This is like an XT600 IIRC, and I think this will be the problem. If you remove one lug, it should be OK and wire the VR sensors as per the schematics, it should work. I think a few folks have used the Logic Level Outputs to trigger the CDI boxes on other bikes, again IIRC.

You have specified Dual Tach inputs which means the odd-fire angle is obtained by the placement of the sensors (80 deg apart instead of 180 deg). So you need to set the #2 offset (odd angle) to 0 not 350 deg. Secondly, in dual spark mode, trigger offset needs to be negative. What this means is that you have to go past tdc the first time (so the tach pulse occurs ATDC hence trigger offset is negative) and then it will predict the next tach pulse and start dwelling and prepare to spark at some advance before the next tach pulse for that cylinder arrives.

Try this link and see if it helps: http://www.megamanual.com/seq/multichannel.htm It was written for the Sequencer, but the definitions and concepts are the same for microsquirt.

Here is the challenge I'm facing. This engine is not like a Harley V-Twin the fires both cylinders on the same revolution. This engine fires the second cylinder 360+80=440 degrees after the first cylinder fires. I tried to enter -440 but It won't take more than -359. Seems to me, looking at the data log that it is firing 80 degrees apart, i.e. the 5 ms delta-t. Now and then delta-t is 15 ms, seems like it should be 15 + 5 ms. Please tell me what I should enter for the offsets for this engine.

Thanks
Elliott

Run it in wasted spark fashion and fire each cylinder every revolution. Unless the pick-up wheel is spinning at cam speed, I'm pretty sure that is how Honda did things too.

The timing on your setup should take care of itself by the position of the dual sensors. We need to start from basics. How many teeth are on the crank flywheel - by that I mean teeth that are sensed by the dual sensors, not starter teeth ?

If there is one tooth, as there should be, then each sensor becomes an independent cylinder, so with 0 trigger offset, and in cranking with injectors disconnected, and table advance in the cranking area set to 0, or use trigger rise mode, you should fire at 27.5 deg btdc on each cylinder if the sensors are positioned in this way. That is, it should fire immediately as soon as the VR input is sensed, and both sparks should occur at the same relative offset to TDC for each cylinder. It doesn't matter what the cylinder offsets are as long as the sensors are offset the same way. If they aren't then we have to fool with odd angle, but only odd angle to get both to spark at 27.5 deg btdc, then you can fool with trigger offset to get it to spark at 0 deg. Then you can put in a table advance without trigger rise and it should all work.