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Old 12-20-2011, 08:47 PM   #29
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Joined: Apr 2003
Location: Long Beach, CA
Oddometer: 11,887
Originally Posted by roger 04 rt View Post

I see two choices for solving the "lean burn" Closed Loop weakness.

1) Take out the O2 sensor and go Open Loop all the time. (Unfortunately removing the O2 sensor input will not work. The Motronic ECU has other ways to mimic closed loop operation without having an O2 sensor input. All ECUs designed to operate a motor with a catalyst exhaust have this ability.) Or rechip or Powercommander or some other way to stay open loop. (Closed loop isn't bad, it just isn't done well in this BMW example.)

2) Put in an O2 sensor that can be reprogrammed to a different switching value than Lambda=1.

I wanted to keep the Cat Converter and the standard Motronic so the choice was #2.

It was a lot of work to figure it out. I don't think it will be a lot of work to implement a second time. My next efforts will be to determine the minimum change that will produce the desired results, and some fine tuning of the LC-1 parameters.

My conclusion is that the Boxer engine in the R1150 was not really designed to operate with a 14.7:1 mixture (Sure it is, all motors are. It's just that the BMW Motronic wasn't implemented to do it very well.) (lambda=1). So my two fixes:

1) A BoosterPlug to correct Open Loop for E10 fuel. (see p.s. below)
2) A programmable Wideband O2 Closed Loop sensor to richen Closed Loop operation.
It's really cool that you went for this, and especially cool that you posted up the data in this thread. Hats off to you for taking on this project!

In sort of an aside, I've been wanting to ask you about the FI aircraft operation you spoke about in the MOA thread. (Since I'm not a member, I hope you'll excuse me asking it here.) You mentioned that you leaned the motor to a Best Power of <14:1 mixture, and also a >15:1 Best Economy mixture. Was the process to lean the mixture to peak EGT, then go a little richer for a cooler EGT? Did the motor have an EGT sensor on each exhaust port?

p.s.: A -30C offset in the Intake Air Temp sensor will better make up for open loop leanness when using E10 fuel. The IICE Air has a -30C setting. If you want one send me a PM.


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Poolside screwed with this post 12-21-2011 at 01:07 AM
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