Triumphrat

Thruxtor

Hi All,
I have been reading a lot of info on this subject in this forum (both technical and informative) but still haven't quite grasped what AI actually does and what you gain by removing it with regards to a EFI
Thruxton.
Any plain english explanation would be most appreciated.

Thanks.

davidc

I think what it does is burn up any bits of fuel escaping through the exhaust - an anti-pollution device. Don't know about the EFI stuff though, but what I've gathered so far is the AI system is factored into the electronic readings of engine operations that go to the computer [?] of the machine. Have not yet sorted it out. Pipe bluing and engine temperature seem to be the leading reason for removing it on carburetted models, along with a nicer look and spark plug accessability. The pipes on my EFI Thruxton are in good shape at almost 1,200 miles - blue just near the head connection. My Bonneville's pipes, however, blued up down to the crossover with only a few hundred miles on the bike.

blacktiger

The injection of air into the exhaust ports allows any unburnt fuel to burn in the exhaust thus cleaning up the exhaust gases of unburt hydrocarbons before they exit into the atmosphere.
I've been told not to remove it on EFI models. Why? I don't know. I guess it may be something to do with how the O2 sensors read the exhaust gases.

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'02 Tiger955i in black.65000 miles.
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biker7

Sorry to say this but above two posters are a bit misguided.... common myths repeated which become accepted half truths when discussing AI on EFI bikes.
I just removed AI from my EFI Bonny. I will post a DIY in the next few days so if interested, have a look for it.
Cheers,
George
PS: I have discussed some of the nuances in multiple threads and yet members here still don't quite grasp it...some do, but many others don't and why I am not going to wax further as to why removing AI on an EFI bike is viable. I will capture some of this in a dedicated AI removal on EFI bike DIY thread.

davidc

Well why don't you simply "wax" accuracy and spill the beans about the AI system and an efi motorcycle?

biker7

Already have. Lots of discussion recently on this.
George

ohiorider

That sounds like a reasonable request from someone wanting to understand how the function of the AI is different on a carbureted bike vs its function on a EFI bike. I'm personally not interested in learning how to remove the system, since I will probably never own an EFI Bonnie, but a short explanation of how the AI's purpose is different on carb'd vs EFI bikes would be an interesting topic.

If you've already posted a thread that provides this info, could you provide the link?

Thanks,

Bob

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03 T100 Lucifer Org and Silv: 122/42 jets, TORs, 18T, UNI filter, no AI, Polaris bellmouth, Metz 880 tires, Prog. 440 shocks (105/150 springs), 11-1124 fork springs, Thrux fork caps, gaiters, MotoTwin low bars, 6024 lamp, htd grips, 12v outlet.

biker7

Purpose is the same Bob. TPS senses throttle position. As throttle closes, TPS tells ECM...ECM tells solenoid to open AI valve. Engine vacuum is maximum at throttle closure and therefore air is sucked, i.e. drawn/injected into annex exhaust chamber connected to exhaust port. Extra air is injected into pipes at combustable ratio with fuel dumped into pipes unspent from combustion upon throttle closure. Combination of air and fuel burns fuel outside of combustion chambers inside of hot pipes which act as heat source for post combustion that would typically just dump fuel into the environment without an A/F ratio conducive to burning...what happens without AI...less environmentally friendly. AI has very little to do with O2 sensor function as AI is only operative whan the throttle is closed.
Hope that helps,
George

97TB

What benefit do you get by removing it?

Forchetto

A reduction in exhaust pipe temperature and therefore less discolouration, reduction or elimination of popping noises in the exhaust and, some insist, that the constant blasting with gusts of cold air doesn't do the exhaust valves any favours.

I'd like to ask George if there is any sort of simple oxidation catalyser on the Bonnies pipes or silencer. All my modern bikes combine a SAI (secondary air injection) with one of those. The idea is that the excess unburned hidrocarbons are burned with the extra air and the catalyser turns the resulting CO into CO2.

Here's one inside a silencer:



And another stuffed into the downpipe itself: