Megasquirt Support Forum (MSEXTRA)

Any way to read the stock ignition coil negative trigger timing in relation to crankshaft angle? I'm interested in using it to datalog stock timing curves and or set up a Megasquirt so you can simply adjust the curve advanced or retarded away from the factory stock curve. I'm thinking spark map all zeros would equal stock timing and add or subtract degrees from stock if you trigger off stock coil negative. Any reasons why this could not work or some code made to work?
Thanks

Fit a timing disc of some sort and a pointer - if one doesn't already exist. And use a timing light. But a forum for your particular make may already have the advance curve.

I've done that before, but it's a little schetchy leaning over a CVT clutch spinning at 8000rpm. I'm in the forum but I'm in uncharted waters there and here it appears. All 6 pages worth here.
http://www.dootalk.com/forums/topic/147 ... k-install/

I tried making a datalogger to do this using an Arduino but it just wasn't fast enough to accuratly measure the time between ignition (interupt1) and TDC sensor (interupt2) at anything over about 2000rpm on a four cylinder motor. I suspect someone with more skills or access to a faster processor could do it though

Edit:
Funnily as I wrote that I realised I was measuring the time at the coil, had I used an inductive pickup on a single spark plug lead I would have been able to do it! oh well

You need a timer with a precision and accuracy of 1us.

James

yellow-fever wrote:I've done that before, but it's a little schetchy leaning over a CVT clutch spinning at 8000rpm. I'm in the forum but I'm in uncharted waters there and here it appears. All 6 pages worth here.
http://www.dootalk.com/forums/topic/147 ... k-install/

I dunno your actual engine, but most road are 'all out' advance wise by perhaps 3500 RPM.

Thanks for the replies! :]
Its already connected to the factory VR sensor and both the Microsquirt and stock ECU are reading the 36-2 wheel correct and playing nice together all the way to top rpm of about 8000. I just figured that since Megasquirt already can decode the 36-2 wheel with enough precision to control timing, maybe if we added an inductive pickup at a spark plug lead from the stock ignition, the Megasquirt could simply watch for the inductive pickup pulse in relation to the 36-2 wheel it has already decoded. If it could do that, some smart person could calculate the formula to output a usable number in degrees before TDC. We could then make sure it is where it needs to be by adjusting the number one tooth with a timing light to be sure its calibrated correct just like when setting up a custom wheel and checking for timing drift with RPM increase. That would allow us to make a stock map to work from. Its a 2 stroke with a wasted spark set up so it would see one pulse before TDC and one pulse before BDC every 360 rotation of the stock 36-2 wheel.

An easier more user friendly way would be to use the stock ignition signal to the coils to feed the Microsquirt as an ignition trigger. Have the Microsquirt still using the 36-2 wheel, Set the Microsquirt to output a coil signal timed to the "trigger" signal from the stock ECU but using the 36-12 wheel for accuracy.
Setting the tables to zero would equal stock map. + from 0 would be more more advance and - from 0 would be less advance once you got the wheel set up to read zero. You wouldn't even need to figure out the stock timing table and could add or subtract timing any where you wanted. The stock ECU would still pull timing when the stock tricky to decode knock control needed to and it would pull from the base timing and still work correct. Hmmmmmmm :]

I wanted to do the same thing when I got started with my project.
Eventually I let it slide because the work involved wasn't really worth it, and, how 'complex' could a regular distributor's ignition curve be between the known initial advance and max mechanical advance?
The only thing adding randomness into the mix is the vacuum advance.

I made up a timing table based on experience with the old distributor and fuel used, and you know what, the first drive I made with the MS3x box hooked up, I already felt an improvement in certain RPM ranges.
I've been playing with the ignition curve ever since and ended up with a much happier engine in all rpm ranges, instead of just 'some' ranges.

If you have a way to data log it now, say if it is OBD2 using something like torque, you can then more or less recreate the spark table using the Histogram / Table Generator in MegaLogViewer HD.

Capture a good long log that covers all driving ranges.
Load that into MLV HD
On the Histogram tab, set the X & Y Axis to the table you are looking to use.

It will use the data to show you what the factory tune was doing at the load and RPM.

See this:
https://www.youtube.com/watch?v=2O96QB6GURg&t=10s