Anton Largiader
Active member
This isn't bait. Seriously. I've read many, many timing threads and this has never been settled.
1) Since it seems the timing is closed-loop, what is the difference between being at one end of the timing band or the other, as long as the ECU can achieve the requested "Start of injection" value? Different 'authoritative' posts, including the FAQ, specify that it's better to be in a certain part of the graph.
I don't doubt there is a difference, but if the ECU wants 12° and gets it, does it matter how much it has to modulate the advance mechanism to get it? People claim to see operational differences with different timing settings but this has never been really explained. Could it be that adding 50% modulation to achieve the 12° isn't really the same as achieving the 12° with no mudulation?
2) Is the top of the graph really "advanced?" I was readjusting my timing last weekend because it was at the bottom of the graph. I slipped the belt one position forward on the pump sprocket (because I was at one end of the slot) and the timing value shot off the top of the graph. This should have retarded the timing, as I see it, because the engine rotates "forward" and this would have caused the pump to reach the same position later... i.e.; I retarded the timing. It's remotely possible that I observed this wrong, but I really don't think so.
- Anton
'98 TDI, 104k miles
1) Since it seems the timing is closed-loop, what is the difference between being at one end of the timing band or the other, as long as the ECU can achieve the requested "Start of injection" value? Different 'authoritative' posts, including the FAQ, specify that it's better to be in a certain part of the graph.
I don't doubt there is a difference, but if the ECU wants 12° and gets it, does it matter how much it has to modulate the advance mechanism to get it? People claim to see operational differences with different timing settings but this has never been really explained. Could it be that adding 50% modulation to achieve the 12° isn't really the same as achieving the 12° with no mudulation?
2) Is the top of the graph really "advanced?" I was readjusting my timing last weekend because it was at the bottom of the graph. I slipped the belt one position forward on the pump sprocket (because I was at one end of the slot) and the timing value shot off the top of the graph. This should have retarded the timing, as I see it, because the engine rotates "forward" and this would have caused the pump to reach the same position later... i.e.; I retarded the timing. It's remotely possible that I observed this wrong, but I really don't think so.
- Anton
'98 TDI, 104k miles