Power Commander III Two Bros Carbon - Wrist Twisters
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post #1 of 7 Old 10-09-2008, 09:30 PM Thread Starter
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Power Commander III Two Bros Carbon

I live in Utah around 4500 ft. elevation and own a 2002 919. I have a two bros carbon full exhaust and a power commander III. There is a specific map in the power commander's database, but it seems to be running a little rich (despite getting 45 mpg+) as indicated by the black residue on the exhaust tip. Does anyone know if a better map is available or am I wrong to think that it is running too rich?

Any response would be helpful.


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post #2 of 7 Old 10-09-2008, 09:46 PM
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My stock setup with a 17t front sprocket only gets 36 mpg!

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post #3 of 7 Old 10-09-2008, 10:29 PM
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I average an indicated 45mpg, but that is with a 15/45 setup so i know im getting less than 45. Just convenient to say i get 45mpg. Setup might be to rich, but some things are better left alone.

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post #4 of 7 Old 10-09-2008, 10:35 PM
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Throw a K&N air filter on it. It'll lean it out some.
Iridium spark plugs might help too.

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post #5 of 7 Old 10-10-2008, 12:02 AM
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Carbon accumulation on the outlets does not necessarily mean it's running rich. When the engine is started cold the a/f ratio is necessarily rich, and in a process called carbon migration the excess partially burned fuel is carried back through the exhaust with the water vapor (a normal byproduct of internal combustion), depositing throughout the system. As the mufflers heat the condensed water evaporates, leaving the carbon behind, and since the outlets don't get hot enough to burn it off it stays there

The only way to determine the a/f ratio accurately is to run it on a dyno with an IR bench to sense the constituents of the exhaust gas. You can also do a series of plug chops at various rpm and throttle settings, but this method is very hit or miss. Unless it's chuffing soot at higher speeds I wouldn't worry about it.


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post #6 of 7 Old 10-10-2008, 08:22 AM
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i get 29-34 ... but i drive mine like i stole it

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post #7 of 7 Old 10-12-2008, 11:14 AM Thread Starter
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Thanks for the quick reply. Good to know. I don't notice any large deposits of black, so I'm not going to worry about it. As for the performance of the bike, I couldn't imagine it being a more consistent spectrum of power. Thanks for the help.

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