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

Hi Guys

I have installed an independent dual injection setup with a V3 Microsquirt, using two Hall sensors and a single-tooth cam wheel, firing two LS2 coils.
Hall 1 is connected to the OPTO+ and - wires; and Hall 2 to the VR2+ wire (VR2- being ignored). The sensors have 1k pull-up
resistors so that when the leading edge of the trigger tooth enters the sensor the output goes high, and when the trailing edge
passes output is pulled low. After much messing about I now have some sensible spark events going on, but with the following
problem:

If I set input capture to trigger rise, Input 1 triggers on the leading edge of the tooth but Input 2 triggers on the trailing
edge. If I set trigger fall, then the reverse occurs. This is based on observing the spark occurrence, sensors are fixed and
trigger tooth leading edge is set to TDC which is correct starting advance for this engine. Ultimately I would like to be able to
use trigger rise or fall for cranking timing, not calculated.

Am I right in thinking that this is an inevitable result of using Hall sensors on these inputs? I tried using VR1 and VR2 but all
I got for Cylinder 1 was a gibberish kind of triggering and no fuel, hence reverting to OPTO as per documentation.

I am looking at inverting one of my Hall input signals using a PNP transistor, since it is evident that the processor input circuit
is inverting one of them already. Is this the right thing to do? Is there a good reason to pick one over the other? I am
thinking of inverting Hall 2 on the VR2 input. I am guessing that I should put around a 2k resistor between the Base and Hall
output, and that the impedance of the VR input will be massive enough that I can just put VR2+ onto the Collector with no
additional load resistance and leave VR2- disconnected. The Emitter will be connected directly to +12V. Does this sound about
right, or should I invert Hall 1 output on the OPTO input, or is there a simpler/better way?

Best regards

Nick

The option you should be using for your setup is the Dual Spark Option: "Dual Inputs, Timing from 1 cam tooth" The V3 microsquirt has two circuits for the 1st tooth sensor: opto and VR1 of a special 2-channel VR sensor detection chip; for the 2nd tooth sensor, you have only VR2 input going into the vr sensor detection chip. If the 2nd Hall sensor works on VR2, why not put the 1st Hall sensor on VR1 instead of opto ? Then they will both work the same.

The Trigger rise setting has nothing to do with Input Capture on the leading/ trailing edge. It applies, to both channels, only during cranking, and simply means the spark fires immediately when the tooth is detected. After cranking rpm is exceeded it sparks based on the table spark advance.

Thanks for the swift response. I am using the setup option that you describe. I have tried using the VR1+ input for Hall 1, since VR2 seems to work fine, but it appeared to be giving intermittent and multiple sparks in time with both cylinders and possibly at other times as well, and no fuel was evident. So I went back to OPTO again. But I will give it another crack, anyway. I feel I am very close to getting the thing started, just need to nail this issue.

I now believe that what I really have is a slow cranking problem. I have connected the sensors to the VR inputs and when cranking with the plugs out the sparks are happening at the right time (at TDC) on both cylinders. But with the plugs in, the motor limps over at a very irregular and pathetic speed (normal behaviour) quite possibly varying from 6 to 60 rpm as it passes compression and then gets a downhill bit. Cylinder 2 still seems to be getting regular sparks but cylinder 1 is getting irregular sparks, timed for both cylinders! It seems like at such low and iregular cranking speeds the controller can't quite decide what kind of motor it is bolted onto, and it ignores the cranking logic.

The motor is effectively a 90 degree v-twin, 880cc, 10.25:1, fairly hot cam. It is really not much different from how I previously ran it with home-made Hall-triggered ignition and a pair of carbs, just needs one decent bang and it should go. I have attached my settings and a log file in case there is a way around this issue.

Cheers
Nick

Much progress has now been made, including an excursion to MSExtra to try Twin Trigger mode (which will only work in wasted spark mode, it seems, but at least I could prove injectors, etc. are working). Have done a lot of cable screening, clean earths, etc. and returned to B&G V3.780. I now have clean trigger signals, stable cranking rpm, sparks at the right times, everything looks lovely except there is no fuel even though the logs tell me I am getting cranking pulsewidths. Also, according to the logs MAP is read OK for about 4 cycles then it just shows atmospheric pressure.

Is there a bug in the code? Independent dual spark with single tooth cam wheel and two offset sensors (setup 1b in the docs) is supposed to work but it seems it doesn't. Is there an earlier version that it did work in? Do I have to weld another tooth onto my cam wheel and run MSExtra Twin Trigger wasted spark?

I attach my latest msq and *BONUS!* datalog in case there is a solution out there, would be most grateful if someone could confirm the problem.

Many thanks

Nick

I ran your msq and the only thing I noticed was that the PW was set to 2 on the gauge and on the scope, but should have been much higher based on the input cranking pulse. That may be something in the code that got broken along the way since Dual Tach is a seldom used mode. But for now, as soon as I set the Injector Timing Angle (under General menu) to 0 the PWs started following the input Cranking PW. So I would give that a try.

In further testing I found that the problem with the fuel was due to the Auto Trigger option, which was not meant for the Dual Tach mode you are using, not being entirely disabled. It was disabled in the Ignition/ Dual Spark menu, but it also needs to be disabled in the File / Project/ Project Properties/ Settings menu.

In addition, control of fuel timing was not designed for this mode, particularly not with an odd-fire setup. You had the timing set to 62.5, which, in non-autotrig mode, is interpreted as a % of the tach cycle. This caused only 1 injection per rev, but if set to 0, you get 2 injections per rev per cylinder, which is what "simultaneous pulses" in cranking is supposed to give you. I found you could move it to about 20 or 30%, but much more than this and you could lose fuel. Also, it appears the timing is off by a factor of 2 because, again it was not designed for a cam wheel. So I would set this to 0 until you have the engine running decently, then if you want you can experiment with it to see if it helps.

Many thanks for looking into this. I'll try this out tonight and see how I get on. So amongst other things, I'll be using the Dual inputs, single tooth cam wheel option, and under the trigger wheel setup I'll have both trigger and cam wheel teeth set to 0 for no missing tooth wheels, will be interesting to see what happens!

Cheers

Nick

Great improvement, it is now trying to start, probably need to persevere with cranking parameters to get it to run. Headers are getting warm and it can string together a few cycles, so hopefully nearly there.

Many thanks!