Advance and triggering setup

[Nack]

Hi to all.

I am setting up a VEMS unit on a KTM single cylinder engine. We are using a (modified) stock trigger wheel 18-1 setup. And standard throttle body, VR-sensor and injector. Software version 1.0.78rc2.

Now the trigger setup needs to be verified as we are getting backfires and the engine won't run.

Below our trigger wheel setup and alignment with respect to TDC:


And the following settings:


Now I have measured the VR-sensor signal and compared it to the ignition signal. This is done by wiring a resistor between the ignition coil wires and measuring the signal.

Now by driving the engine with the starter motor we get a reasonably constant 300rpm signal. The Ignition Advance is now measured entered in the Priming, Cranking and Afterstart settings dialog window:


Now we have started with 10 degrees advance and got the following scope picture:

But measuring the timing between TDC and the ignition trigger is measures 29 degrees and not 10 as it should be.

The following is with 20 degrees advance:

But measuring the timing between TDC and the ignition trigger is measures 31 degrees and not 20 as it should be.

The following is with 30 degrees advance:

But measuring the timing between TDC and the ignition trigger is measures 36 degrees and not 30 as it should be.

Comparing these last ones it implies that 10 more degrees of advance only is 5 degrees in reality. How can this happen?!

Has anyone any suggestions...

[MWfire]

try newer firmware, 1.1.6x, imho in that firmware you can fire that strange trigger wheel.

[Nack]

Does changing firmware version really solve this problem?! Is this a known problem with this firmware?
Sounds a bit strange to me to be honest...

[MWfire]

Does changing firmware version really solve this problem?! Is this a known problem with this firmware?
Sounds a bit strange to me to be honest...

Your setup is very strange.
And you set wrong width of toth. For 18-1 is 20(360/18), and gap is 36. Try that first.

[Nack]

How are these new values calculated? I've been using the online manual like this:



Angular width of tooth:
dec = 255 / (2 * imaginary teeth)
so
dec = 255 / (2 * 18) = 7,08 = 7


Angular width of missing tooth:
Angular width of missing tooth = (missing teeth + 1) * dec
so
Angular width of missing tooth = (1 + 1) * 7 = 14

I'll try your new values in a few minutes if my battery is charged again ;-)

[Nack]

These new tooth width values do not solve the problem. Still only getting about 5 degrees of real world advance when adjusting the advance in Megatunes with steps of 10 degrees...

[MWfire]

try 1.1.6x

[Nack]

I can only find the following?
http://www.vems.hu/wiki/index.php?page=MegaTune

Where the latest version is listed as 1.1.47?

[MWfire]

download vemstune.

[Nack]

Thanks for the help already, but I am a little reluctant to use another software package from the one I know.

Is it really the firmware version update that does away with the trigger related (?) problems I experience?! Thanks again

[MWfire]

Download
http://www.vems.hu/download/v3gui/VemsTune-Install-2010-03-08-testing.exe
With 1.1.6x i was able to fire spark in gap(missing toth) of trigger wheel at good position.

[Nack]

I have configured the unit as a twin cilinder and now seems to work fine...
Setting 10 degrees advance now is acutally 10 degrees advance!

Probably 1.0.78 is not capable of dealing with the single cilinder setup option?!

Let's see of the engine will start this way.

[[email protected]]

I'd bet its not been run on many single cylinders.

[lugnuts]

I once sold an Autronic SM4 ecu to someone using a lawn mower engine as a test bed

[Nack]

Still running firmware 1.0.78:

Our KTM engine isn't equiped with a secondary cam sync sensor. But I think we are getting trouble with that running a wasted spark setup.
As for now the ignition is fired every 360 degrees:


But also the injector is fired every 360 degrees. At 1500rpm and 12ms pulsewidth the injector patern as funcion of triggerwheel looks like this:


Unfortunatelly at higher rpm's the period of a crank revolution (360degrees) is less than the injector pulsewidth... So the injector-patern overlaps and stays open continuously.


Are there other ways to use the devide by two option for the injector settings and sync the injector at the intake stroke without the need to install an secondary cam sync sensor? Maybe trough some clever firmware option I am not familiar with yet?