Spark_Fuel_Offset vs Auto-trigger?

[Dan_Austin]

My tuning seems to be coming along and I was re-reading the sections
dedictaed to sequencer differences. The Spk_Fuel_Offset looked
interesting, and made me wonder on my even fire straight six exactly
where injection was occuring.

I am using TS 2.05 and did not see an option for Spk_Fuel_Offset, but upon
browsing the ini, I see that is set to not be available if Auto trigger is enabled.

I currently have the 'Injection Timing Angle(deg)' set to 48. If I am understanding
what I have read, that would place the injection event, assuming timing of 20 degrees,
at 72 degrees before TDCC2, which is also assuming that Spark_Fuel_Offset is defaulting
to 0.

After re-reading that section and the Megamanual section on Injector Timing Delay, I
realize that my setting of 48 is likely a poor choice, largely influenced by the example
in the Megamanual. Before I start altering it to test the results, I hoped to see if
my understanding was in the ballpark.

[grippo]

Spark Fuel Offset is taken care of by Auto Trigger - there is no reason for the user to change it. The injection timing angle that you enter is referenced to TDC compression stroke of each cylinder. So setting it to 48 means you will inject on each cylinder 48 deg after TDCC. Injecting at 180-360 deg would be injecting during the exhaust stroke; 360-540 is the intake stroke. The default injection timing of about 540 deg, which is a good place to start, will inject close to when the intake valve closes. This sounds like not a good idea, but it is what OEMs use because fuel hitting the closed and hot intake valve gets vaporized and well mixed with the incoming air by the time it is ready to be ignited. The most important thing in injector timing is to NOT inject at a point such that fuel will be coming out during the intake/ exhaust valve overlap period (around 360 deg). Another thing to note is that there is a significant delay from start of injection and the time the fuel actually gets into the cylinder. This is due to open time plus transport from injector through the manifold and cylinder ports and through the valve.

[Dan_Austin]

I see my error. I was reading this section of the Megamanual http://www.megamanual.com/mt28.htm#sg
and failed to note that in the manual this setting was in percentage units, but the TunerStudio releases
I have used is in degrees.

540 degrees mad more sense, but after misreading that section I was thinking I needed to use the
Spark_Fuel_Offset and small delay degree to hit the injection mark I was aiming for. I'll correct
my mistake and adjust as needed.

On a side note, is there a place that lists the version change log? I have 3.770 running and see
that a 3.780 firmware is available, but no indication of what changed or if I might want or need
it.

[grippo]

Injector timing was in % of a tach cycle before Auto Trigger. When we switched to this, we made it in deg to better relate to the engine.

The only change for 3.78 was to fix broken logic for non-wheel mode. This won't affect most people using the Sequencer, since they have wheels and are in Dual Spark mode.