[Poolside]

Originally Posted by roger 04 rt

The Wideband O2 project has taken the richer mixtures route so far. Although I'm considering getting a matched set of injectors and seeing how much the AFR can be pushed in the lean direction.

Injector balance does make a difference on aircraft motors. Far more so than on a road vehicle. As a pilot you certainly know much about what's explained below. But the injector issue that causes a surging problem on the 1100/1150 isn't really related to the injectors. It relates to batch injection verses sequential injection. For a 'continuous flow' aircraft fuel injection system injector balance is very relevant. Injector flow rate makes a big difference in an aircraft continuous flow system because the injector is merely an orifice. Fuel is flowing 100% of the time, and at the same rate, for the full 720° of the combustion cycle. In an aircraft continuous injection system, all injectors are on, all the time. An electronic fuel injector is on only a small portion of the time. In addition, the motor in an aircraft at cruise is operating at a very high 'percentage of full power' setting. Certainly a very high power setting compared to that of a road vehicle at highway speeds, which is closer to 15%. Any injector imbalance on an aircraft motor is amplified by the the continuous flow rate, and the high power settings. Any imbalance error is multiplied 10 fold at least. It's a cumulative error, you know? Injector imbalance on a road vehicle at highway speeds or lower doesn't make too much of a difference. The low power settings and intermittent injection period limits the accumulated error. Injector imbalance makes a little difference in smoothness, but it isn't a source of surging. The oilhead boxer motor has 'batch injection'. Batch injection, especially on a two-cylinder motor, makes a significant contribution to surging. It's a little hard to explain. To summarize it's caused by the fuel charge arriving in two pieces, not one. That's what 'batch injection' is, multiple cylinders are injected as a batch. The result is the fuel for one cylinder arrives in the intake port at a different part of the 4-stroke combustion cycle than for the other cylinder. Which means that at the moment the respective intake valve opens, the fuel for that cylinder will be at a different degree of vaporization than the other. Unvaporized fuel does not combust. The difference in available combustible fuel radically changes the power level for that cycle. A pretty good explanation of the fuel vaporization topic is in this Wall-Adhered Fuel patent. How did this happen? Because the Motronic ECU on the 1100/1150 is a single cylinder device. Bosch called it Monotronic. Here's how the 'mono cylinder ECU' works on a two cylinder motor. As far as the ECU is concerned it is operating a single-cylinder motor, but one that's one-fourth the total displacement of the two cylinders, and turning at twice the RPM. But all of the above aside, and as you've experienced, if the fuel mixture is increased a little it cures a lot of ills.