B1gRed wrote:
texasscott1 wrote:
The extra air (oxygen) injected into the exhaust stream ignites any fuel that wasn't burned during combustion thus lowering HC (unburned hydrocarbons) emissions. Because of this the exhaust temperatures with a working AIS will be hotter than without.




I don't dispute but how is the extra oxygen ignited?
When air is introduced into the hot exhaust stream the added oxygen combines with any unburned fuel causing it to reignite.

The popping from the exhaust is actually caused by the very lean mixture during decel (lean misfire). During decel the very lean mixture isn't always ignited so when that cylinder full of unburned fuel hits the hot exhaust stream and the extra oxygen from the AIS it ignites - bang.

The coasting enricher eliminates most all of this at higher rpm decel by making the pilot circuit richer. At lower rpm's though the vacuum signal isn't great enough to hold the enricher closed.

Believe me, you don't want anything that eliminates the O2 sensors.

Will removal of the AIS, harm a 2009 FI bike?Or cause mechanical failure? I removed mine, and the bike seems to run great,(no popping on decel) But, I don't want to cause any damage.....

I haven't heard that it'll cause any damage but accorfing to Yamaha it will make it run leaner at cruise and idle.

William wrote:
Will removal of the AIS, harm a 2009 FI bike?Or cause mechanical failure? I removed mine, and the bike seems to run great,(no popping on decel) But, I don't want to cause any damage.....

I also have an 09 with AIS removed. Mine also runs great. I think that's one of the ultimate questions of this thread... will it harm the bike. There are differing opinions. The consensus seems to be it may run lean. The question is will it run too lean. All FIs seem to run great without AIS but want to know if it will cause damage in the long run.

When Yamaha told me it would run leaner without the AIS they didn't say how much.

Keep an eye on the plugs and if little specs of aluminum start showing up on the insulator it's time to make a change. And cooler plugs won't help when the problem is a lean mixture.

Speed density systems use a programmed set of variables to deliver the fuel requirements of the engine. It reads things like engine temp, throttle position, 02 sensor, etc and delivers a set fuel curve.

Being the animal it is it doesn't look to me like it would be able to adjust much.

If the Power Commander eliminates the o2's (I don't mean remove them) then the only way I can see that it works is to increase the hold time on the injectors. If it does only that then the rest of the variables such as engine temp and throttle position is ignored. At least I would think.

Right now I'm thinking I would rather take my chances with leaving the speed density system to do it's thing.

At this point I doubt if Yamaha knows or any body else. If the FI bikes start coming in with failed valves and pistons at 40-50-60 thousand miles, then we'll know. IMHO

Would it be worth putting an AFR monitor on? At least it would give you an idea of whats going on wouldn't it?

River wrote:
Would it be worth putting an AFR monitor on? At least it would give you an idea of whats going on wouldn't it?
I've always wanted one of those for my bike just never could afford it. They are nice though and useful.

I think Auto Zone has a kit for about $185.00, of course you have to put a bung in for the o2.