Buell ignition timing, cam-only solution possible?

[carlosfandango]

Hi All

I am building a buell chopper and would like to use the Megasquirt I bought years ago for a different vehicle (most people bin the buell EFI and switch to a carb instead, but I'm NOT giving in to that!).

I started off looking through the megasquirt docs as I have an MS1 processor, and came to the conclusion that I would have to purchase an aftermarket ignition system. Then I noted that the microsquirt code will run on an MSII and should be able to control the ignition timing on this oddfire engine as well, with the appropriate circuit mods of course. That will both be cheaper, and a much more integrated solution; thus it is my current plan.

However, despite searching all over the place and several days' worth of continuous reading (including this forum of course) I haven't found the answers I still need, so I hope someone will be able to help me. I have found other v twin setups, using crank wheels but as I shall explain I am trying to avoid this.

My basic problem at the moment is how to trigger. The buell motor does not have a crank sensor of any sort, rather it has a 7-1 'wheel' - actually a steel cup - plus VR sensor on the camshaft. This, I think I understand, will need to be changed, and that is quite easy to do. However, installing a crank trigger wheel of any sort would be awkward to say the least due to the compact nature of the engine layout. Not IMPOSSIBLE though, of course! I see here http://www.microsquirt.info/dualspark.htm that dual cam sensors, without a crank wheel, can be a suitable setup - unfortunately I am still a bit in the dark as to how this works, or how the microsquirt should be configured to work with it exactly.

I also found and read http://www.megamanual.com/seq/multichannel.htm but this refers to crank wheel setups as far as I can see.

Can anyone shed any light on this for me? I know it's one of the commonest issues with the MS, but I have looked in vain for solutions before writing this. I'm NOT looking for someone to configure my system in its entirety, OR supply me with a step-by-step 'how to', what I need to know more than anything is what can and what cannot work as a basic trigger setup. I'm happy to work the rest out myself!!

Thank you,

Richard

[Paul_H]

why not just use the dual spark option of 'Single Cam Wheel Input' as described on the Microsoft Dual Spark page as option 4.a. 'M-N Cam Wheel Only'. You might like to consider using a Microsquirt as they are invaluable on motorcycle installations where mounting space is limited. Obviously you would have to revise your trigger wheel to a more suitable higher tooth count wheel. Most fuel injected belt drive Ducati twins use a 48-2 wheel running at camshaft speed. If you are considering buying an after market ignition system you might as well spend the money on a Microsquirt to manage both fuel and ignition because in my opinion you will not get a better value for money solution.

[carlosfandango]

Hi Paul - thanks for the reply.

Well, I am a bit confused as you can tell from my post... so that's why I can't decide which setup to use here. I don't see any reason why a cam wheel couldn't do everything that I want, is the answer to your 'why not..' question - it's just that I can't understand from the various megasquirt pages whether this will support odd-fire, sequential (port) injection, and so on (the throttle body on the buell has 2 injectors directly over the inlet ports). Are you confirming that it does?!

Obviously, much that is not understood at the outset should become clearer with practical work and further reading, but if a crank wheel is or had been a MUST then I would rather tackle this with the engine on the bench....!!

Regarding the microsquirt: yep, that would be nice and as you say a heck of a lot smaller. But I have the V3 board, so an MSII board will effectively convert this to a microsquirt - running the appropriate code, obviously. Cost of that route is 100 pounds or so as opposed to 400 for the microsquirt - I don't know if you are in the UK or not, but if you are, you will know very well that we get screwed over for these things. And since I am building the whole bike, I guess I can make room for everything ;-)

Richard

[Paul_H]

Richard, judging by your post it is obvious that you already know that by doing the required mods on the Megasquirt II daughter board and using code version 2.8 or higher you will have the dual spark capability of Microsquirt . This capability allows the use of the two independant ignition outputs that will be required to configure your odd fire V twin. Because there are two injector output channels you can configure sequential (alternating) injection on a two cylinder engine. Using a missing tooth cam wheel with a single sensor you should be able to easily configure your engine for COP ignition and sequential injection.

[carlosfandango]

Yep, that's right. I understand the circuit modification requirements implicitly at least, as I am an electronics design engineer for a living. Doesn't pay well enough to do this engineering / bike building stuff though, not really. Anyway - soldiering on...

I should say that I am nowhere near getting this bike actually running yet - I am having the frame built this coming January and will probably not start trying to get a run until the end of February at the soonest due to other somewhat troublesome issues like drives and brakes etc., all of which require modifying! However, in the meantime, I would like to try and get my head around the injection issues to some extent so that I know what it is that I am doing when it actually comes to that. I should also say (I guess) that I have no problem with the engine cycling, and what happens where etc., it will be easy for me to fabricate a cam trigger wheel and appropriate sensor which has any number of teeth, and the missing tooth anywhere in the 720 degree cam cycle.

So far so good, it looks like I was off to a good start doesn't it! BUT... All I have been doing for the past week it seems is read everything I can about odd-fire setups, and try (in vain) to find a detailed description of a setup close in configuration to that which I am proposing. I also installed megatune so I could play with the settings in there. Result? More confusion, and no definite conclusion as to what I should be doing! I just can't figure out all of this trigger offset / oddfire small angle stuff and what is going to make this thing work. Furthermore, I don't know whether the angles specified should be halved if using a cam wheel, or whether this kind of thing is automatically accounted for.

Let's say (hypothetically at the moment) I make up a cam trigger wheel which has 24-1 teeth - only because any more would be a bit of a squeeze - then how would this wheel be positioned if cyl 1 (REAR in my terminology) is at TDC, and what would all these offsets be set to, and more importantly, WHY??! And what would the injector timing be for sequential injection? I really need to figure this junk out!

I'm still reading in the meantime...

Richard

[24c]

A little birdie told me you can mod the existing Buell ECU... http://www.ecmspy.com

The project has been closed, but you might find this site useful. As you probably know, a higher trigger wheel count gives a better resolution, so when the cam is doing half crank speed, it is more desirable to have more than your set up. I would go for a wheel count similar to what other V twin guys are doing, that way you could easily understand the changes/settings you have to make.

On this forum 800vtwin & norzilla come to mind, so search their recent posts and you should pick something up ...no disrespect to any others.

PS You might find it helpful to stick a degree wheel on the crank and make notes as to the engine order over a 720 degree cycle, that way you can relate your engine events to your trigger wheel, but more importantly you will have created a clear picture of what is required in your head.

[carlosfandango]

Hi 24c. Yep, I sure know what you're saying there about wheels.. I also already knew about the buell ecu and have read about this extensively (elsewhere obviously... don't want to go off-topic, but basically I don't have this ecu, and can't easily get one either - all I have is the motor, and the throttle body).

After my last post I formulated a cunning plan. Since the electronics side is the easy part for me, and I know what I am expecting to get from a correctly functioning timing setup, I have decided that I will build a variable-speed trigger wheel emulator using a PIC chip. An hour's programming at most. That way I can feed the MSII with any trigger wheel signal I want, and fiddle with the various settings in megatune until my 'scope shows me what I want to see, i.e., ignition trigger pulses at the correct times.

I have read various posts from the users you mentioned as well as several others from the chap that has helped me already in this thread - yep, I'm sure the answer is in there somewhere, but many of these individual's setups use crank wheels which I don't (or should I say won't) have. Everything is thus a giant ball of confusion for me as a result of today's reading, but that might be because I have tried to cram in too much in one go.

One thing is for certain sure however. I promise, as soon as I have all this figured out, I will post the results here!! Isn't this kind of thing a lot of fun though?!

Richard

[24c]

....but many of these individual's setups use crank wheels which I don't (or should I say won't) have...

So if you map your cam rotation with respect to the crank and the cylinders, you have the same info that the others use,

I hope you get it soon, 'cos its fun, but very frustrating until you do.

PS Building a simulator/rig is a good idea.

[Paul_H]

Let's say (hypothetically at the moment) I make up a cam trigger wheel which has 24-1 teeth - only because any more would be a bit of a squeeze - then how would this wheel be positioned if cyl 1 (REAR in my terminology) is at TDC, and what would all these offsets be set to, and more importantly, WHY??! And what would the injector timing be for sequential injection? I really need to figure this junk out!

I'm still reading in the meantime...

Richard

With the rear cylinder at TDC compression the sensor pole would allign with the centre of the missing tooth gap. Seeing that a tach event occurs on the first tooth after the missing tooth and using the number of teeth that you propose this would create a tach input at an approximate crank angle of 30 degrees ATDC. This would give you a -30 degree trigger offset and thus satisfy one of the main criteria of a dual spark configuration. All this does is identify where TDC is. The tach input for the front cylinder is created by skipping 12 teeth which relates to 360 degrees of crankshaft rotation, but because this is an odd fire engine you have to shift the tach input to get the timing right. This is where the offset for output #2 comes into play. Injection control is configurable with Megatune and there a lot of information in the manual about this.

Attached is an image of an engine cycle time line in crankshaft degrees that may help you get your head around these concepts. All of this is only my interpretation and may not be correct in which case you will only end up more confused, but hey you gotta start somewhere. The image is not a good one so zooming with your viewer may help.

[carlosfandango]

Paul - thanks very much for the image! I have drawn something that I believe to be similar, on a circle rather than a linear diagram. I have to be at work today so I don't have time to examine the diagram in detail now, but when I get back tonight I will compare the two to check for similarity. Superficial examination seems to show that we are in concurrence.

I'm starting to understand these concepts now thanks to all of this help. I still plan to go ahead with my 'wheel stim' unit as I described in an earlier post, with this I will be able - I hope - to get appropriate timing signals on the bench, without installing anything or cranking the engine to test everything. Still waiting for my MSII from Glen's Garage as well, but should be here in a few days!

Richard