In various threads there have been discussions about the functions of the Motronic MA 2.2 (R1100) compared to the Motronic MA 2.4(R1150). During the testing of my LC-1 Wideband O2 installation, by using its AFR recording capability and the GS-911's real time value recording capability I was able to confirm most of the MA 2.4's fueling functions (block diagram below).
As with the Motronic MA 2.4, there is almost no published information on the MA 2.2 used on the 1100s. Since we know that the sensors are virtually identical between the two Motronic versions and since they are both members of the Motronic MA family, I've taken a stab at a draft of the block diagram of the MA 2.2, below.
To build the MA 2.2 diagram, the MA 2.4 block diagram was used as a starting point. Then the Open Loop fueling capability was added for the Not CAT Coding Plugs with no catalytic converter and a CO Pot. In yellow highlighting I've identified either capabilities that exist in the 2.2 but not in the 2.4, or capabilities that I've measured on the 2.4 that may or may not exist on the 2.2. I'll comment on them in a moment.
The GS-911 doesn't seem to be able to data log realtime values for the MA 2.2 so that inhibits one of the sources used for figuring out the MA 2.4. However, if someone who owns an R1100 installed an LC-1 they would gain the many benefits of running a richer mixture and be able to capture data logs that would enable confirmation of the MA 2.2 functions. I'd be happy to assist in any way that I can. Until then some of the mysteries of the MA 2.2 will remain locked in its source code.
Looking at the MA 2.2 diagram's yellow highlighted boxes, here are some open questions:
Learn box: Does the MA 2.2 have a silent ability to learn and store the TPS range. It is likely that it doesn't, but it would be interesting to test and confirm this. It does monitor the TPS and can output an error code.
Fuel Tables box: What are the target mixtures of the No CAT fuel table? It seems from the CO adjustment Pot spec (1.5% ±0.5%) that it is likely to be richer, perhaps 14.0:1 in the cruising area. This could be easily confirmed with an LC-1.
CO Pot/No CAT/Adjust boxes: These functions are in the MA 2.2 but we don't know what they do. For example, does the adjustment add a fixed amount of time or does it add a percentage to all fueling calculations? Is there an RPM limit to this function? When in No CAT mode, is the fueling smoother than the lumpy limp-home fueling of the MA 2.4 with the CAT disconnected?
Compare/Adapt boxes: We know the MA 2.2 has all the sensors of the 2.4 and we know that it has a Closed Loop program. Does the MA 2.2 compare the Open Loop and Closed Loop fueling calculations like the 2.4, and thereby compensate for E10 fuel and other wear variations (e.g. air flow, fuel flow, fuel pressure, wear within the combustion chamber)? Or does it lack this capability and should owners of R1100s boost their fuel pressure to compensate, say, for E10's leanness?
An LC-1 installed on an R1100 could answer these and other questions.