MS for 75 degree common pin V-twin, fuel and spark

[turbodog]

Hi, all.
I am building a bike around a 1981 Yamaha XV920 engine.
The engine is 75 degree V-twin with common crank pin
I think I have a handle on the fueling part. Have read the success stories of the Buell and Harley owners, but near as I can tell, they aren't using MS for spark.

I want to do spark as well, for 2 reasons:
1. stock TCI box is discontinued, and destined to fail at some point.
2. I plan on running a turbocharger, at 8 - 14 psi max boost. The stock ignition timing curve is RPM-based only, no vacuum advance/retard. Not suitable for a force-fed engine.

The engine has 2 VR sensors, 75 degrees apart, on the crank. I plan to use LS1 'coil near plug' with igniters in the coils.

OK, on to the questions:
1. Am I right in thinking I need MicroSquirt Sequencer product for this engine? I think I read that it can be set up to run essentially as 2 one-cylinder engines.

2. I see no provision in Megatune to adjust for my cylinder angle. Am I just missing it? Can I use my pair of VR sensors to 'tell' MS what my Cyl angle is (this may be the same question as above, stated differently)?

2. Can I use the stock VR sensors, or am I forced to fit a missing tooth wheel on the crankshaft?

3. While batch fire and wasted spark might work OK (assuming the answer to #1 is favorable), I am tempted to fit a cam sensor. Does the cam sensor use up the 2nd VR input I was needing in Question #2?

4. Has anyone ever used a cam lobe as the exciter for a hall-effect gear-tooth sensor? I am assuming the camshaft is a ferrous material...

Thanks in advance, I look forward to interacting with you all.

- Rick

[turbodog]

Of course, as soon as I posted I saw the Moto Guzzi thread a few down from mine. Seems to answer a few of my questions.

Seems like if I'm OK with batch fire fuel and wasted spark ignition... I don't need the uS-Sequencer product (due to having 2 VR tach inputs 75 degrees apart?). But, a cam sensor will not be possible since I am using both VR inputs on the crankshaft. Correct?

Will the uS-Sequencer product open up any additional opportunities (as in enabling sequential injection and non-wasted spark... without fitting a missing tooth wheel.... not asking for much, am I?)?

Thanks again!

- Rick

[Matt Cramer]

This sort of trigger setup doesn't really allow for non-wasted spark - it can't tell if the cylinder is on the compression or exhaust stroke.

[turbodog]

Thanks for the reply. I understand that without camshaft position sensor, only wasted spark is possible. However, with current draw budget so tight, I hate to double the coil current draw.

So, I am seeking input on how to solve this. Would a GPIO board give me the additional VR sensor input I need to run 2 VR sensors on the crank and a cam position sensor? Is MS-II capable of this, and running COP (or coil near plug with ignitor built into the coil) ignition for a 2 cyl engine?

thanks...

[Matt Cramer]

I'm not sure the GPIO board when it comes out will be capable of adding more ignition triggering inputs, and there definitely isn't code for that at the moment. However, you could run a single crank sensor combined with a cam sync, using existing electronics hardware. You would, however, have to change the crank sensor to a missing tooth wheel type sensor.

[grippo]

You will NOT double the current draw with wasted spark. There will be very liitle extra current draw with wasted spark because once the primary spark starts, it constitutes a direct short to ground, and almost no current flows through the second plug.

[racingmini_mtl]

You will NOT double the current draw with wasted spark. There will be very liitle extra current draw with wasted spark because once the primary spark starts, it constitutes a direct short to ground, and almost no current flows through the second plug.

Al,

This is true only if you have 1 coil per 2 cylinders. If you have 1 coil per cylinder then you will double the current draw with wasted spark.

Jean

[turbodog]

Correct, Jean. The factory ignition on this engine is one coil per cyl. The uS-fired ignition must be this way also.

[Bruce Bowling]

This is true only if you have 1 coil per 2 cylinders. If you have 1 coil per cylinder then you will double the current draw with wasted spark.

I think the term "wasted" is what is throwing people off. Al is referring to the use of a wasted-spark ignition coil, this has one primary and one secondary, each end of which is fitted to a plug.

If the setup is COP, meaning individual ignition coils, then these are separate coils, with their own primaries and secondaries. If you put the primaries of wo coils in parallel then there will be N times the current draw.

One bif thing to note with the MicroSquirt is that the ignition drivers are designed to drive only one coil per bank. If you are running wasted spark then you need to use a wasted spark coil, otherwise use an external driver setup. I have a 4-channel induction ignition driver board that I will be releasing really soon to assist for those who want to run their COP setups with MicroSquirt and/or Sequencer.

Do not try to drive two COP coils in parallel with one MicroSquirt driver stage. You will blow the VB921 driver for sure. Also, the spark will be much reduced - the VB921 current limits at 7.5 amps and two primaries will see roughly half of this max current (depending on relative inductance/resistance). To the VB921, its load will had half the DC resistance and half the inductance (this is a parallel inductance situation), so it will jump to saturation in half the time during dwell compared to a single coil load.

Also, for COP setups, one should look hard at the coil-near-plug setups like on the LS1, LS2 engines - these have the driver, etc built right in. I just assisted a MicroSquirt setup (odd-fire ignition) with the use of external LS2 coils from MSD. Two ways to pull the drive for this off - one way is to use an external pullup to Vref on each IGN output and use this to trigger the coils. The other is to make a board mod on the uS which removes the VB921 ignition driver. Both setups require the use of an RF shunt capacitor, otherwise noise can filter back into the uS setup.

- Bruce

[grippo]

The engine has 2 VR sensors, 75 degrees apart, on the crank. I plan to use LS1 'coil near plug' with igniters in the coils.

2. I see no provision in Megatune to adjust for my cylinder angle. Am I just missing it? Can I use my pair of VR sensors to 'tell' MS what my Cyl angle is (this may be the same question as above, stated differently)?

2. Can I use the stock VR sensors, or am I forced to fit a missing tooth wheel on the crankshaft?

3. While batch fire and wasted spark might work OK (assuming the answer to #1 is favorable), I am tempted to fit a cam sensor. Does the cam sensor use up the 2nd VR input I was needing in Question #2?

- Rick

2. The adjustment for cylinder angle is under advanced ignition menu - it's called "Offset(deg adv) for second output" or something like that.

2,3. You can use either 2 independent VR sensors (dual tach input selection) in which case the cylinder angle adjustment is based on the spacing of the sensors, or you can use a single crank wheel VR sensor and a cam sync on the second input.