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noob EFI questions

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by blackadder, Aug 7, 2011.

  1. So I've decided to learn and do most of the mechanical work on my bike. I recently installed the 3-1 arrow on my street triple and am waiting for the cable to do the remapping. So far I'm addicted. I love learning the mechanics as much as I do riding! Few questions from me about the o2 sensor:

    As I understand for my triumph street triple the ECU operates in two modes: closed loop and open loop. At constant throttle or idle the ECU switches to closed-loop utilizing the oxygen sensor as feedback to stabilize a better air-fuel ratio. But, as soon as you give it some poke it switches to open loop and utilizes the map that has been manually programmed.

    Is this right? Does this apply to all injected motorcycles? Does turning the oxygen sensor off- for example by using TuneECU- mean it doesn't operate in closed loop anymore? I assume the closed-loop is able to compensate for varying fuels and/or temperatures and/or altitude. Then why do people claim better performance by disabling the o2 or having one of those bypass resistors?

    Many more questions. But I guess I'll start with that one. ;)

  2. Closed loop will force the engine to have chemically correct air to fuel ratio. Best power is at a slightly rich a:f ratio. Manufacturers will usually tune the engine to be very rich at high load because the extra fuel will quench the combustion a bit, stopping the piston crown and exhaust valves from overheating. The best bet is to get a book from the library about engines, and have a read. :)