Timing, injection and spark advance

[Gringosteve]

Hi

I am reading up on how variable timing works and find these overlap diagrams useful:



Using Dashcommand I have been monitoring intake and exhaust timing and have found a similar diagram for our engine. What is now confusing me is how injection timing and ignition advance could be represented on the same diagram.

In the example above injection is drawn on as an arc.. Dashcommand shows me a range of angles for injection. Getting up to 200+ degrees. Would that be a 200 degree arc from TDC with fuel being pushed in for the whole 200 degrees at that at cycle?

Is there anyway of using the ignition advance figure to show where ignition is happening on the same diagram?

Apologies for any daft questions

Steve


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[Kodename47]

Be wary of injection timing, is that showing the DI or PI injection? If DI it certainly doesn't tie in with the values inn the DI injection table. The DI injection timing tends to be 300 degrees or more which is SOI and is degrees before TDC. Spark advance is before TDC.

[Gringosteve]

It is measuring DI timing rather than PI. I’m seeing low values (20ish) at low throttle and revs and over 200 when wider throttle

So if it is measured before TDC is the example diagram above wrong? It is showing 73 degrees after TDC. Very confused


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[Kodename47]

I would probably ignore those logged values then as I have no idea. As per the tables in the ROM, 360 deg would start at TDC at the start of the intake phase, 370 would be 10 deg before and 300 would be 60 degrees after. 200 doesn't tie in at all with any SOI value that is used or likely any EOI. Maybe it's some form of injector open time?

That diagram is likely for port injection which is different to direct injection in operation, you can inject later as you're not reliant on the intake valves being open. Even the port injection timing on the FA20 isn't really comparable to that.

[Gringosteve]

Thanks, will do some more logging. I have DI and PI injection duration logging separate. Must be measuring something differently I guess. Will do some more research

Thanks for your help


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[Gringosteve]

Definitely DI timing .. weird


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[four-mat]

I wish I knew WTF this meant

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[Spuds]

Originally Posted by Kodename47

I would probably ignore those logged values then as I have no idea. As per the tables in the ROM, 360 deg would start at TDC at the start of the intake phase, 370 would be 10 deg before and 300 would be 60 degrees after. 200 doesn't tie in at all with any SOI value that is used or likely any EOI. Maybe it's some form of injector open time?

That diagram is likely for port injection which is different to direct injection in operation, you can inject later as you're not reliant on the intake valves being open. Even the port injection timing on the FA20 isn't really comparable to that.

But in that case, why would di occur when the port was still open? As I recall, the tables would sometimes put the direct injection timing to before the intake port actually opens.