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Old 05-07-2013, 12:09 PM   #9
Apple Jam
Forest Flyer
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Joined: Aug 2007
Location: Mt Hood mud flow
Oddometer: 6,681
Originally Posted by Apple Jam View Post
...could this (SAS) air injection be smoothing out throttle at low rpm?
I mean, it's purpose is to heat the cats at idle/warmup....
...was this, just maybe, causing more backpressure and lowering power output at very low rpm?

Edit: 07 -990FI
Also, kinda curious.....What opens the reed valves on the heads, vacuum from exhaust, or pressure from the SAS pump?
Originally Posted by Head2Wind View Post
The SAS is a passive (no forced pumping) system as far as the injection of air into the exhaust system, so it requires a pressure depression in the exhaust port to allow air to flow past the reed/check valve and into the port. When valve is activated and air is flowing into the port, this will make the exhaust appear more "lean" to the O2 sensors and the ECU "should" react with more fuel, which with these engines tends to mellow them out on the twitchness meter. These engines also tend to respond well to pulling back the timing a little at small/low TPS openings, which indirectly effects the AFRs that the O2 sensor sees (goes richer when less advance).......

You can read the many threads about tuning and using the TuneECU app, eliminating the 2nd throttle plates or modifying their action in the ECM. There are many opinions on how this affects the ridability of the bike and whether its good/bad. Generally people will maintain the secondary plates to soften the hit.
So my theory may have been *kind of-ish* correct !!
SAS might just go back in,,,hmmmm.
As I understand it, the only disadvantage is a mess of hoses and some decel popping that I had only very slightly with the Akros.

AWESOME technical response, H2W !!
"got no problem with keeping truly roadless areas as wild....
On the other hand, if it has been logged or mined and roads already exist,,
...then that land should be open for public use" (peterman)
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