Another Emerald K3 gotcha: wasted spark coil dwell time table

[Peter Carmichael]

Just got to the bottom of a long-standing misfire issue. The default coil dwell time loaded for my setup table was for a distributor fed by a single coil. i.e. 1.86ms up to 4500 rpm and 1.49ms for above 4500 rpm.

 

Running wasted spark, the coils are somewhat bigger, but fire half as often. For the Sagem coil pack (Sagem 2 526 055), 3.1ms is recommended. No need to change the dwell at higher rpm because the engine only goes to 7500 rpm where 3.1ms equates to 140 degrees. Each coil only has to fire once every 360 degrees, so there is plenty of time to recover. Going higher than 3.1ms would just heat the coil up unnecessarily.

[The Pikey]

Peter

 

god thats sounds complicated and I really really wish I could understand what you are talking about Theres so much to learn around here and it's great. Off to Google your post now 😶‍🌫️

 

jason

 

 

[Mr Locust]

Wait 'til you want to set up a barometric correction table....

 

Ian

 

Green and Silver Roadsport 😬

[Peter Carmichael]

Funny you mention that. I couldn't get a Baro signal to do anything sensible at all, so I implemented it as a MAP signal (same sensor, different hook in the software).

 

I was suspicious that it wasn't doing what I thought it was doing, so I disabled pressure corrections entirely. I also see that there are alleged pressure corrections for coil on-time - I'm tempted to experiment and see how much of a mess I can get myself into.

[Mr Locust]

As you have found, I was advised to use the MAP input for BARO as there was a firmware code glitch which meant the BARO designated pin was inoperative.

 

I never found any data for dwell time on the Denso plug top coils so guessed at 2ms with 5ms cranking which has worked well.

 

Reference your other post; I went down the full sequential route, utilising the cam sensor of the EU3 engine.

 

Ian

 

Green and Silver Roadsport 😬

[oilyhands]

Copied from the other Emerald thread, Emerald's response...

 

4. Coil on-time.

 

For the M3DK this is not user programmable and is fixed at 6mS during cranking and 3mS during running.

 

The coil on-time for the K3 is user programmable and there is no “default” setting. The coil on-time setting is determined by the users’ map that is in the ECU.

 

As with the ignition timing or fuel tables it is possible to set the coil on-time table for optimal results but also the reverse is true.

 

Whether the engine runs a single coil, wasted spark or sequential coil-on-plug it makes no difference to the coil on-time settings. The coil on-time setting determines how long the coil is charged for to provide optimal ignition performance and should be adjusted to suit the coil used.

 

The ECU limits the maximum coil on-time to 75% of the available time for each charge/spark cycle regardless of the coil/ignition type so, assuming the 4-cylinder engine has a single coil with distributor, and someone has programmed the ECU with a coil on-time of 6mS at 8,000rpm (3.75mS available for each charge/spark) it will actually result in a coil on-time that is limited to 2.8mS.

 

 

Oilyhands