View Single Post
Old 12-21-2011, 04:19 AM   #30
roger 04 rt OP
Beastly Adventurer
roger 04 rt's Avatar
Joined: Nov 2011
Location: Massachusetts
Oddometer: 2,297
Originally Posted by Poolside View Post
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.

If you want to skip the narrative, a direct answer is near the end. Will send you a PM about IICE AIR, thank you.

The aircraft I operated for a couple decades had a 300 HP, six-cylinder horizontally-opposed engine (like three Boxer engines back to back to back ;) ). There were three main power management controls: throttle, propeller speed (think if it like the transmission), and fuel mixture. It was fuel injected in much the same manner as the R1150 engine, except there was no fuel computer (or O2 sensor!). Engine management was (and still is) a duty of the pilot in that aircraft (a Beech A36, kind of an R1150 of the air).

Getting engine management right in an aircraft is a critical duty. Get it wrong and you: damage the engine, run out of fuel, travel more slowly and/or spend more money for the same trip--or all of the above. If you want to get anywhere in a hurry, you get to cruising altitude, set propeller speed and throttle for 75% of full power (where you will operate for a few hours) and lean the mixture.

I had a single-probe EGT (exhaust gas temperature) system which I later upgraded to a 6 probe (one per cylinder) gauge.

Here is how power is managed (from memory, not from my checklist):

Annual Inspection: Full rich fuel-flow is checked and set to specification for full-power, mid-power and idle, at sea-level.

Take-Off: Hold Brakes, Tank switch to fullest tank, mixture to Full Rich, propeller to full RPM, throttle to Wide Open, at full power, release brakes and take off. (If taking off at an airport above sea level, lean mixture to spec.)

In flight leaning:
Best Power Setting: from the Full Rich setting, lean mixture to peak EGT (first cylinder to peak in a 6 probe system), then richen mixture to 100 degrees F below peak EGT.

Best Economy Setting: from the Full Rich setting, lean mixture to peak EGT (first cylinder to peak in a 6 probe system), then lean mixture to 100 degrees F below peak EGT.

An interesting side note: the one place the engine was NEVER operated was at the Stoichiometric mixture of 14.7:1 as it is neither the Best Power point nor the Best Economy point.
roger 04 rt is offline   Reply With Quote