What's the ECU doing?

wfooshee said:

Basically, yes. If it's using the O2 sensor then it's basically a digital decision on the mixture: if oxygen is present then it needs more fuel, if there is no oxygen then it reduces fuel, and thus you bracket the ideal mixture.
The PCIII works by disconnecting the O2 sensor and substituting a constant table for the RPM vs throttle position; if the throttle is here at this RPM then change the ECU's calculation by this much.

If the bike runs that much better with the PCIII out then you probably had the wrong map loaded, or a generic map that didn't fit the equipment on your bike. If your map didn't accomodate higher airflow from the air filter, then it would have been running leaner than intended.

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UselessPickles said:

Also, the O2 sensor is a narrow band sensor; it can only detect whether the mixture is 14.7:1, leaner, or richer. The sensor is only used under certain conditions (such as cruising) to maintain an AFR of 14.7:1. At other times (such as moderate to hard acceleration), the ECU uses a preset base map and makes adjustments based on various sensors, like intake air temperature. The ECU cannot make adjustments to accommodate intake/exhaust mods when operating in this mode, because it is not using any kind of O2 sensor feedback. Using the O2 sensor feedback would not be desirable, because it can only target an AFR of 14.7:1, which is too lean for acceleration.

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RadioHowie said:

I'll be damned if these two posts aren't the most concise descriptions of the FJR's fueling operation I've read since I got my bike.

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UselessPickles said:

RadioHowie said:

I'll be damned if these two posts aren't the most concise descriptions of the FJR's fueling operation I've read since I got my bike.

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Considering the previous luck you've had with your bike, I'd be willing to bet that you're already damned anyway, which makes your wager worthless.

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