Page 1 of 1

Correction of the ignition point between cylinders in a two-stroke engine

Posted: Tue Jun 05, 2018 1:33 pm
by Yulas
Hi, I am watching the project for some time. I try to adapt it to my Trabant with a two-stroke engine with 2 cylinders. I made the wheel 36-1 and set the sequential ignition. It works correctly every 180 degrees.
What is missing.
In these engines, the TDC point is often not exactly 180 degrees. The factory ignition was set separately for 1 and 2 cylinder.
I am missing correction between 1 and 2 cylinder for the point of ignition.

I can set 2pcs of speeduino and set in the second "trigger angle" 179 or 181 degrees.

Re: Correction of the ignition point between cylinders in a two-stroke engine

Posted: Tue Jun 05, 2018 6:31 pm
by PSIG
Yulas wrote: Tue Jun 05, 2018 1:33 pm Hi, I am watching the project for some time. I try to adapt it to my Trabant with a two-stroke engine with 2 cylinders. I made the wheel 36-1 and set the sequential ignition. It works correctly every 180 degrees.
What is missing.
In these engines, the TDC point is often not exactly 180 degrees. The factory ignition was set separately for 1 and 2 cylinder.
I am missing correction between 1 and 2 cylinder for the point of ignition.

I can set 2pcs of speeduino and set in the second "trigger angle" 179 or 181 degrees.
Welcome, Yulas! You may already be aware of the Individual Cylinder Fuel Trim function in Speeduino, and there is potential to extend this useful function to ignition timing, allowing offset adjustment of ignition timing for each cylinder. This is a very useful function for typical engines, as it allows optimal fuel and timing to obtain best efficiency from each cylinder, and yours is no exception. While it is not yet available for ignition, the function allows correction in your case with pressed-crankshaft misalignment, but more commonly to avoid a "weak cylinder" limitation on performance engines — e.g., more power by correcting detonation that occurs in one cylinder of a boosted engine that limits the entire engine's potential.

While it would be great to have a full trim table for each cylinder as fuel has now, that will take development time and code space, though it may be possible to add a single ignition offset value for fundamental corrections such as yours. I will start a feature ticket for this, though it will have to be reviewed and pursued by @noisymime or a another capable coding member, so I can't say when or if the new function would be added.

:arrow: That said, there might be another solution available now — Oddfire Angles. I have not looked into this idea, and I'm currently limited on time to do so, but it may be possible to use this function to create a fixed offset of the ignition timing. Perhaps @noisymime or others could look into this possibility to get your Trabant going with proper timing.

David
Oddfire Timing Correction.png
Oddfire Timing Correction.png (2.96 KiB) Viewed 4309 times

Re: Correction of the ignition point between cylinders in a two-stroke engine

Posted: Wed Jun 06, 2018 8:15 am
by Yulas
Thanks for the quick answer :D
I check on the oscilloscope and give me information if there is a change.
Best Regards