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Old 12-04-2012, 06:45 AM   #119
roger 04 rt OP
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Joined: Nov 2011
Location: Massachusetts
Oddometer: 2,098
An update and some new info:

Lately I've moved my Lambda setting from 0.94 to 0.92 which is another couple percent richer. I did this because I noticed that just as the bike was finishing warm-up (while riding) I liked the cruise performance just a bit better than once it went Closed Loop. The biggest difference between a minute before to after Closed Loop is a few percent more fuel. I'm not sure just where I'll stop adding fuel.

There are a couple IC engine performance curves I've found that you might find interesting. Although NOT specifically for an Oilhead, interesting nonetheless.The first is HP vs AFR at various power levels:


The second is flame front speed as a function of mixture (note that it is Fuel Air ratio not AFR). This shows pretty clearly that as you richen the mixture, you speed up combustion. It looks to me to be the equivalent of 2-3 degrees more advance for an AFR of 13.8 compared with 14.7, at 3000 RPM. At 6000 rpm it might be 4-5 degrees if I'm doing the math right. Because of this effect I have been paying close attention to any hint of knock. There doesn't seem to be any probably because even though the timing advances some, knock resistance of richer mixtures is better.



So the bottom line is that when you richen the mixture several percent you're probably getting a triple benefit: a bit more torque from the extra fuel, a bit more torque from the more advanced (relatively) timing, and better efficiency due to better running and therefore into higher gears several hundred RPM sooner than at 14.7:1.

roger 04 rt screwed with this post 12-05-2012 at 03:43 AM
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