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

Finally I found some time to try to get my car running with MS-II and it works.

I reloaded the 2.1 firmware as I had no luck getting it to work with 2.34 firmware. As I mentioned before, I had the problem that I did not have ignition output when the engine was cranking.

With 2.1 firmware the car started right away with the settings that I already posted before. That ist the falling edge of the Hall signal set to 16° BTDC set with the dizzy and the other settings being:

Ignition Input Capture: rising edge
Cranking Trigger: trigger rise
Coil Charging Scheme: normal
Spark output: going low

After that I reflashed the new 2.35 firmware and it works with it, too.

What I do not like at the moment is that at idle the ignition timing is moving around as much as 400µs which is approx. 2° crank angle. I do not know how much it is when the engine is running at higher rpm, but in transient operation it will probably be a lot more. This is the fact with all algorithms that I tried. It's clear that when having the hardware falling edge set to 16° and wanting the ignition to occur at 18° BTDC for example, the engine has to rotate 178° degree between the falling edge of the Hall sensor and the ignition event.
The problem is that I need the falling edge set to 16° for starting/cranking. If I set the falling edge to 40° BTDC and change the settings in MS-II accordingly, the timing gets much more precise and the timing is rock steady at idle. Unfortunately I cannot use the falling edge for cranking then. A calculated cranking trigger has to be used, which makes the car much more difficult to start.

What I tried next is to turn the dizzy, so that the rising edge was set at 16° and the falling edge at 71° BTDC. I tried to use the falling edge for ignition input capture (which is set to rising edge as it is inverted) and used the rising edge for the cranking trigger, with the settings being:

Ignition Input Capture: rising edge
Cranking Trigger: trigger fall
Coil Charging Scheme: normal
Spark output: going low

With these settings I do not get any signal on the ignition output when cranking!
What might cause this problem??? All I am changing is the cranking trigger setting from "trigger rise" to "trigger fall" and there is no output.
Please give me some advice, cause otherwise either the timing at normal operation is not very accurate or the car is very hard to start depending on what is "optimized".

Cheers,

Tadek

Tadek,

Trigger rise and trigger fall don't work the way you think.

'Trigger rise' means use the same edge of the signal as you have set for the ignition input capture.

'Trigger fall' means use the other edge of the signal. It is specifically for specially designed wheels where the tooth wide has been developed to give a specific amount of advance.

In most cases, trigger rise is what you want - this gives spark at your 'trigger offset' while cranking.

Lance.

Hi Lance,

thanks a lot for the explanation!

Even if the "trigger rise" and "trigger fall" setting works differently than I thought on the cranking trigger, the effect should be tha same.
When ignition capture is set to rising edge, using "trigger rise" for cranking trigger means using the "same edge" while "trigger fall" means the other edge. Does this make any difference then? I do not think so.
What might be the reason, that I do not get any output from MS-II when cranking with the cranking trigger set to "trigger fall"? Or do I have to use a shutter wheel with a certain width of the slots to have it work? As I said it is a shutter wheel with very roughly 30 degree slots and 60° of solid material in between.

Another thing of interest is, can the number of "skipped pulses" at angine start be reduced to make the engine start faster. I now that this would have to be done in the Megasquirt-II.ini as well, and with 2 skipped pulses it works but further reducing the number does not seem to work.

Cheers and thank you once more for the advice,

Tadek