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Title: Huge timing differences between two 1.8T 110kW engines Post by: doktor on November 16, 2024, 12:44:41 AM Here you see a timing comparison (KFZW) of a 1.8T AGU engine (M3.8.3, cable throttle, K03) and 1.8T AUM (M7.5, electronic throttle, K03S). The basic specs are the same - 110 kW, 210 Nm. The timing table for AGU is original, the one for AUM is recalculated to suit the AGU axes for the purpose of the comparison. There might be a slight error in the load recalculation, but I did my best to make it as small as possible. The engines themselves are very similar so why the huge difference? The turbo should not make a difference in timing as this is a purely load-related thing. The K03 might not reach such high airflow at a high power, but this is a similar situation like backing off the throttle a bit with K03S.
Can anyone please explain the following: 1. For AGU, the timing for very low loads (0.5 and 1ms) is very retarded compared to AUM, then at 1.5ms there is a HUGE upwards hump. Why? AUM does not display this behavior and advance is a monotonous downward function. 2. What is the reason for the very large difference (up to 14deg) for partial load cruising area? How does it translate to fuel efficiency? 3. It is a bit wild in the high power section, with steep slope in close areas. Thanks a lot for any discussion! Title: Re: Huge timing differences between two 1.8T 110kW engines Post by: prj on November 16, 2024, 05:48:46 AM Different head and combustion chamber. Small port head needs much less ignition advance.
If you have ever tuned them, you will know :) Title: Re: Huge timing differences between two 1.8T 110kW engines Post by: doktor on November 17, 2024, 12:39:38 PM Thanks, prj. I know of that but had no idea it has such an influence on timing tolerance.
What about the part load cruising area? I believe the port size plays virtually no role there. I guess both timings will work on both engines, but is there any advantage? To get the most power out of an engine (efficiency at high power), you basically want to run on the verge of knocking. But I don't know much about partial load. Does higher advance translate to higher efficiency, or is it more complicated there? Title: Re: Huge timing differences between two 1.8T 110kW engines Post by: prj on November 17, 2024, 03:28:03 PM As I said before, different combustion chamber.
It's not port size alone per se. I don't see any point of comparing this. The engine is not an excel table. Put it on dyno, tune to MBT, done. |