Tacho Gauge reading half

[Matt293]

Hey guys,

I have Microsquirt V3 running on my motorbike, 2 cylinder engine, the firmware is V3.830. I have the engine successfully running in full sequential mode controlling both fuel and spark. My problem is the original 12V tacho that is connected to the Microsquirt tacho output wire (pin 35) is displaying half the speed of the engine. Is there a way so it will run correctly?

I have had it running correctly when I was using Microsquirt V2 firmware MSIIExtra 3.21. I changed to Microsquirt V3 as V2 was playing up. I used the lastest firmware on V3 as it was a lot easier to setup C.O.P on a 2 cylinder engine running ITB. I do also have a Tach Adapter as a last result although not entirely sure it will work correctly as the engine is not in wasted spark mode.

Thanks in advance

[24c]

Interesting question Matt, I'm running "Dual Tach Inputs" but using the cam as the trigger wheel to get sequential COP & alternate injection. Everything is working out OK, as expected, but I wondered whether there was a "toggle" to tell the Microsquirt to double the cam signal revs, as it doesn't know whether it is a cam based or crank based trigger. When I run the MSExtra "twin trigger" code on another unit, I see 2 x the revs of the "Dual Spark" set up, with the same minimum (variable) speed setting on my test rig.

Interested in the answer too.
Mike

[grippo]

If you are seeing the correct rpm on the TS gauge, but the Tacho output is not following this, then there may be a bug in the code. If you post your msq I will test it out.

[Matt293]

Hi Grippo,

Here's there code for review.

I'm just curious does the Tacho Output get its signal from the IGN coil 1 and 2 firing signals, or does the module create a signal? The bike originally ran in wasted spark mode, so the tacho would be seeing 2 signals per revolution. The CDI had the output for the this. But now that I am running the bike in full sequential mode, it will only see a total of 2 signals for every 2 revolutions.

Thanks.

2013-12-29_08.08.05.msq

(31.16 KiB) Downloaded 80 times

[grippo]

When I scope the tach output using your msq I see a tach output every 360 deg, and I see IGN1 and IGN2 outputs every 720 deg, but this generates a spark every 360 deg, although because the engine is odd-fire, the spacing is not even. But the tachout signal is evenly spaced every 360 deg. And that is the logic of the tach output, it should put out a pulse for each cylinder every engine cycle.

The tach out signal is created, but it is based on the inputs you provide.

I tried changing the Dual Spark Mode to single crank wheel (wasted) and this also resulted in 1 tach output every 360 deg. So you should be seeing the same rpm as you were when running wasted.

[Matt293]

Thanks Grippo,

Is there a way to have the tacho output a signal every 180 degrees?

[grippo]

Matt,

Changing the tach output to every 180 deg on your 2 cylinder would require a code change which would not be trivial because a tach pulse is now done every tach cycle, and would have to be done twice as often. You might see if msextra code handles this.

Mike,

The ecu can distinguish between a crank wheel and a cam wheel even in dual tach inputs mode - there is an option further down "Dual Inputs Timing from 1 cam tooth". This is the same logic as "Dual Inputs" but tells the ecu where the wheel is mounted.

[24c]

You might see if msextra code handles this.

Currently in MSExtra 3.3.1 in "Twin Trigger" mode, with the same one trigger two sensor set up I am using in legacy v2 MicroSquirts (with various versions of firmware for testing), I am seeing double the RPM I see using B&G 2.890, & 3.430 in "Dual Tach Inputs" mode. I've asked the question on the MSExtra forum, because I'm sure this is wrong.

The ecu can distinguish between a crank wheel and a cam wheel even in dual tach inputs mode - there is an option further down "Dual Inputs Timing from 1 cam tooth". This is the same logic as "Dual Inputs" but tells the ecu where the wheel is mounted.

Sorry Al, I honestly thought the "Dual Inputs Timing from 1 cam tooth" was for a crank & cam sensor combo, and I do read the manuals... so that's really useful info...off to test now.

typo_in_docs.png

(135.15 KiB) Not downloaded yet

UPDATE & EDIT

The RPM is doubled and so now the camshaft sensor speed readings I was getting are truly crankshaft engine speeds,
RPM detection from 23,36 & 48 to 8000 RPM, no resets ... fantastic
Thanks very much, it's always the simple things & boy do I have some simple moments!
Mike

[Matt293]

I've changed the Microsquirt firmware to MSExtra V3.3.1, set it up and now the tacho is reading correctly.

Thank you for your help and advice