Newbie question- No spark on ducati L twin

[honda33cr]

Hello,

After trying and trying to get this thing running I am officially stumped. At first I could not get a reliable engine speed signal with the stock ducati vr sensor until I figured out that microsquirt could not read the vr during the compression stroke. The signal varied too much for the microsquirt to accurately read it.I solved that problem by converting the vr sensor to a 0-5 v square wave before taking it in to the microsquirt on pins 30 and 31. Where i am at now is that I have what seems to be a valid engine speed but I cannot get either coil to spark. I must add that I am trying to direct drive 2 coils. I put the coils on the scope and all that I can get to happen is for the coils to get a constant 12 v. Micro squirt is not pulling the coils down at all. I have attached a datalog and a msq and any help will be greatly appreciated.

Thank you
Matt

Some quick info on the bike:

It is a 2003 ducati monster--90 degree odd fire
The vr sensor is on cam timing with a 48-2 tine wheel

[grippo]

If you look at the datalog you will see that the rpm frequently jumps to 0 during cranking. I'm sure you can also see this on the MT gauge. You can also look at the Trigger+/- column - whnever you are cranking it counts down, meaning it is not receiving a tach pulse when it expects one. This means you have either a bad configuration, that is, one that doesn't match up to the engine, or you have a bad tach input. Your msq looks ok, so I don't think its that. You said your VR input was varying too much for microsquirt to detect it during the compression stroke. What did you mean by that - was the amplitude varying or the timing. If it was the amplitude, microsquirt doesn't care about the amplitude, it converts this to a 5 volt square wave. If it was the timing, you aren't going to help by converting the signal to a square wave, because microsquirt already does that and the conversion should not affect the timing. A timing problem is best solved by playing with the pulse tolerances during cranking - but I see you have already raised the cranking pulse tolerance to the max of 100.

What to do ? The first thing I would do is disconnect the coil outputs, so we don't have anything kicking back from that. Then crank and check if the rpms still go to 0. If they do, then we need to scope the tach input at the input to the opto circuit, pin 30, and if that looks good, then scope it at the ouput of the opto circuit where it goes out to the processor. Look for missing pulses, amplitide < 4 volts, erratic timing. You may have an output problem also, but you must fix the tach problem first.

[honda33cr]

Post by grippo on Sun May 18, 2008 10:46 am
What to do ? The first thing I would do is disconnect the coil outputs, so we don't have anything kicking back from that. Then crank and check if the rpms still go to 0. If they do, then we need to scope the tach input at the input to the opto circuit, pin 30, and if that looks good, then scope it at the ouput of the opto circuit where it goes out to the processor. Look for missing pulses, amplitide < 4 volts, erratic timing. You may have an output problem also, but you must fix the tach problem first.[/quote]

Thank you for your response. Here is what I found when I tried your suggestions:
Disconnecting the coils did not help the engine speed issue. I loooked at the input on pin 30 and it is a perfect square wave with no noise.(~ 0-5 volts) I also looked at the vr signal when I was trying to get a valid engine speed signal with just the vr sensor. The vr signal (on pin 32 and 33) is very clean but both the amplitude and period varied quite a bit. I know that you said amplitude does not matter but I think that it was getting so small that the microsquirt could not read it. The reason that I think it varies so much is having two compression strokes only 90 degrees apart and then "nothing" for 630 degrees. Any ways the microsquirt was dropping the engine speed signal much more frequently before I converted it to a square wave. (I have included a datalog with the vr sensor straight into microsquirt). I also tried cranking the engine with no plugs in it ( with the vr sensor hooked stight to microsquirt) and the rpm signal looked better but the trigger +- made no sense to me.( by the way what does the trigger +- exactly represent) I have also included that data log.

I do not know where the output of the opto circuit is. Do I have to take off the cover of the microsquirt? I am running out of ideas here and I really appreciate any help that you can provide.

[grippo]

The trigger+/- is a software counter that counts up when a wheel tooth comes in much faster than expected based on the last 2 teeth. It counts down when too much time passes without thetooth coming in. The processor sees a series of deltaTs, it compares the diferences to get times and check for timing that doesn't make sense. Once it is synched, it takes into account the missing teeth, so it doesn't lose synch because of that. You have 48 teeth, it is very unlikely that compressiion stroke time differences will make enough difference over one tooth to cause a loss of synch.

To scope the opto out circuit you have to look at the circuit diagram (it's on microsquirt.info) and yes you will have to take off the cover. You don't want to probe the processor - that is a sure way to fry it. You want to probe the output of the opto.

[honda33cr]

Hello,

I finally figured out the engine speed issue that I was having. I ended up putting a 15k resistor on the vr+ input and playing with the tach signal masking. I can now crank the engine and the engine speed no longer jumps to zero. The issue that I am now having is that I still do not have spark. I have attached my msq and a datalog. I feel that I am getting close but I just can't seem to get any spark. I really appreciate any help that any one might be able to provide

Thanks,
Matt

[SQLGUY]

Do you have any way to verify the drive signal to the coils? A scope would be best, but a 12V electrical test light might be usable as a second choice. If you check the signal at the switched terminal of the coils with a scope you should see 12V with a 3ms downward pulse every 150ms or so.

Or, you could try a test light across the two terminals of the coils; it should flicker a bit when cranking.

You should definitely have 12V on both terminals of the coils when not cranking.

If you're not seeing drive pulses at the coils, next things to check would be the wiring back to the ignition outputs from Microsquirt and the VB921's themselves.

[honda33cr]

I checked the spark outputs with a test light.( the scope is at work and I don't have access to it until Tuesday) What I found is that I have spark on output 1 but not on output 2. I disconnected the caps that I had on the outputs just in case they were interfering and that didn't help.The setup that I have now is a led test light hooked directly to each output and the other end of the light is hooked to a 12v source that is on the fuel pump relay. I tried changing the offset for output 2 in MT but that didn't make a difference either. I have verified that I am getting 12v to the coils while cranking it just seems that output 2 is not sending a ground signal at all. I know that I am very close here but I just can't figure out why I am not getting spark on output 2. If somebody could please look over the attached msq and possibly the data log and make some suggestions I would greatly appreciate it.

if you're not seeing drive pulses at the coils, next things to check would be the wiring back to the ignition outputs from Microsquirt and the VB921's themselves.

How and where do I check the"VB921's themselves"?

Thank you

[SQLGUY]

Since you're getting spark on one coil but not on the other, the easiest way to test the VB921's would be to pull off the Ampseal connector, pull out the red retainer, and switch pins 12 and 11. If, after swapping the pins, the other coil starts sparking and the the one that was sparking stops, that will pretty much isolate the problem to a blown VB921. The danger here is that, if it's something with one of your coils or your wiring that blew one of the VB921's, switching the pins may blow the other one - then you'd be seeing no spark on either coil after switching.

If you switch pins but don't see a change in which coil is sparking, then that would isolate things down to a problem with the non-sparking coil or the wiring to and from it.

I looked at your msq, and it is set up for dual spark, so uS defintely should be firing the two channels 105 degrees apart. I am curious, though, why you have 105 degrees of offset on a 90 degree engine.

One other comment: there's another guy who's been posting recently who is also converting a Ducati. His setup has two 6V coils that were originally wired in series at the primaries. If you have this setup, and you're switching to run each off it's own uS output, you'll need to either switch to 12V coils or add series resistors (2.5 Ohms or so, 2W or more).

[honda33cr]

I looked at your msq, and it is set up for dual spark, so uS defintely should be firing the two channels 105 degrees apart. I am curious, though, why you have 105 degrees of offset on a 90 degree engine.

Maybe I am misunderstanding the explanation of the trigger offset but here is how I understood it it. From the Mega Manual :

So in theory you can normally pick either +x° (BTDC) or -y° ATDC (where x° + y° = degrees between firings = 90° for a 8 cylinder, 180° for a 4 cylinder, etc.).... For example, if tach1 occurs at a trigger offset of +40° BTDC, tach2 occurs -320° ATDC (and there is 360 degrees between firing, so a 2 cylinder engine). For dual spark mode we always want a negative trigger offset, so you would use -320° instead of +40°.

So what I was thinking is that my trigger offset is -15 degrees, minus 90 degrees = -255 degrees. If you rework the original equation above
(x° + y° = degrees between firings = 90°) 90 degrees -x degrees = y degrees. which is what we are looking for. 90- (-15)= 105 or -255.

I can also see your explanation of 360 degrees-255 degrees = 105 degrees but it doesn't take into effect that the trigger offset is -15 degrees. Maybe I am not understanding the definition properly and I am more than willing to learn the right way if I am wrong.

I switched the coils and all of a sudden I don't have spark again. I am thinking that one of my coils was bad and I have now effectively blown the vb921s. I see that diy has the bosch replacements for $8 so I think that I am going to order 2 and buy 2 new coils. I am going to test the coils to make sure my theory is correct before I go spending money that I don't have to but the more I think about it the more it makes sense.

I am not familiar with the other guy who is adapting a ducati with a microsquirt but I am betting that it was a dual spark model which has two plugs per cylinder and slightly different coils. My Monster has only 1 plug per cylinder and the coils run on 12v. I didn't even have to mess with the supply circuit to the coils because the stock setup already had the power on the fuel pump relay .

thank you,
Matt

[SQLGUY]

The thing is that the trigger offset applies to both circuits, so the advanced offset should only be the offset between firings. So, if your tach signal occurs 15 degrees after #1 TDC, and #2 fires 90 degress after #1, you should have -15 for trigger offset and -270 (or is it -90?) for advanced offset.