Number of teeth / cylinders conflict

[jimmy76]

Hello,

today I wanted to make the first steps with my 2nd MS2Extra project. This is a Porsche 944 turbo which has a dual VR setup.
On wheel with 132 teeth and a 2nd with a single reference 58.6 BTDC.
After flahing the latest release 3.4.2 I started to change the trigger wheel settings. But I always received the "Number of teeth / cylinders conflict" error.
I've tried to make several modifications. No luck. Than I've falshed back the previous relesa 3.3.3. Same settings same error.
I've found threads that others could successfuly use this dual wheel setup (maybe on microsquirt).
I'm only trying to make the first steps on the desk but I do not know what is causing this conflict.
Thanks in advance

[jsmcortina]

That's too many teeth per cycle.

James

[jimmy76]

That's not a real limit.
There are cars running using this setup and microsquirt.
Could it be that microsquirt could run this trigger wheel but MS2 not??

[jsmcortina]

Best ask them what they did then... I only wrote the firmware.

James

[jimmy76]

Here is the microsquirt msq they were using.
Whom shall I ask?
I can post the msq used for those cars if that helps.
I have already made the 2nd VR input with the LM1815.
It seems that the config accepts 120 instead of 132. (So a number where 3600/ X = is integer)

And I've found this on megamanual:
http://www.megamanual.com/ms2/code.htm
That a microsquirt code could be my solution. Just I do not find anything how to get that code onto a MS2 board.

Thanks

[jimmy76]

I've missed the attachment.

[kjones6039]

I've missed the attachment.

That is some OLD firmware, for sure!!

Ken

[jimmy76]

Do you mean that with an old firmware I could use this 132 teeth trigger?
I've tried all whic are available on the dowload site.

[racingmini_mtl]

This is not an MS2/Extra code but the old original MS2 code from B&G. Use your link to the Megamanual for instructions on how to load and use that code. And use the msefi forum for help (link at the top). By the way, that code works on both an MS2 and a Microsquirt (again look at the instructions there).

Jean

[rickb794]

I would (if it could be done) modify the trigger wheel.

132 divided by 3 is 44, so removing 2 teeth and leaving ever third will give you a 44 tooth wheel.

44 teeth with a cam position sensor will work with Extra code.

A 36 -1 wheel would be ideal and would run the motor well with a single coil or wasted spark and batch fired injection.

[jsmcortina]

If even the code thinks it can support it, 132 teeth per rev is a lot of interrupts coming in. On MS2 I would be wary of the reliability of that at high revs.

James

[jimmy76]

This 132 teeth weel is where the starter motor is connected. So a single missing one would cause unreliable start.
I'm using 36-1 trigger wheel with my other project (using MSExtra) it works perfectly. Just on this car I do not want to make such mods.
Interesting is that the motronic 1.0 from 1985 doesn't have a problem with this trigger setup.
And as I've read there were successfull projects with microsquirt.
But I was not aware that MS-II and microsquirt is different in code. I thought that if I implement the 2nd VR on my MS-II
I can use the MSExtra code without a problem.
I give a try with the B&G 2.920 SW. I hope I can get some support on that.
As a first test on desc it accepts a 132-1 setup. But if I connect the crank wheel pulser audio as input I see half the set rpm.
(I've also tried with 36-1, and the same.)

[dontz125]

The boxed MS2 (V3.0 or V3.57 motherboard) use the same code (with a few pin-out details) as the MicroSquirt. What you're missing is the difference between B&G code and MSExtra code. While the B&G code may technically allow you to specify and operate with 132 teeth, if I read his comment correctly James is concerned about the processor's physical ability to *ping!* that fast at high revs without getting confused and losing track, perhaps with unfortunate consequences for your engine.

A simple frequency divider circuit would drop this down to 66 teeth per rev, which would keep the chip much happier.

As for the Motec, how much did it cost in 1985 ... ?

[jsmcortina]

Interesting is that the motronic 1.0 from 1985 doesn't have a problem with this trigger setup.

Easy to do if you design an ECU specifically for this trigger arrangement.

James

[rickb794]

Even if he knocked it down to 66 teeth it is going to be close if not at the limit at the full rpm capabilities of that motor.

It will also need a cam sensor for more than one coil or anything sequentialish.

If you wish to hide stuff, perhaps a CAS of some type might be a viable solution.

If it was mine it would have a 36-1 + a position sensor on it.

[jimmy76]

I'am thinking about such a solution with a frequency divider.
I think 66 won't work as it could not be divided by 4.
I was thinking about 44. Maybe that could work. But I'm not sure if 3600/44 should not be an integer?
I've read such limitation somewhere.
Than the only solution could be to divide by 11. Than it'll be 12. It could be divided by 4 and 3600/12 = 300.
What do you think? Could it be a solution?

Thanks for all the advices!

[subwoofer]

The problem with frequency dividers: phase. Dividing by three introduces three possible timings of the edges unless a mechanism is built to positively reset the divider.

[jimmy76]

I thought about that. Than I should use the 2nd VR, the reference sensor, to initialize my divider.

I do not know in depth how the calculation works in the SW with such a dual wheel setup.
Is the 2nd reference is used as the missing tooth in other setups? And the rest of the timing calculations
run from the 1st VR?
In this case is the 2nd VR input only used once per KL15 cycle? Or is it reseting the calculation every time it occurs?

Do you know if the 3600 / number of teeth = integr limitation is valid for the Extra code?

[racingmini_mtl]

Do you know if the 3600 / number of teeth = integr limitation is valid for the Extra code?

Yes it is.

Jean

[jimmy76]

I've considered my possibilities.
The B&G code is able to handle the 2 VRs with the microsquirt mod. But in that case I loose the injector PWMs.
And the car has low imp. injectors.
And I'd lost all the features of the extra code.

So I've tried the 'divider' solution.
I've taken an old PIC12F675 and my long forgotten assembly knowledge. Basicly I've divided the 132 teeth with 11 and multiplied by 3.
(I'm measuring the length of the 1st tooth out of the 11. Multiply by 0.66 and start a timer after the 4th....)
So it is 36 teeth and using the 2nd VR single reference signal to mask out the 36th.
Outcome is a 36-1 pattern.
I've only tested it on my desk using the crank wheel pulser audio generator and it seems to be OK.

If anyone is interested I can share my code.
I'll test in the car some weeks later.