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Thread: ID this muffler

  1. #11
    Senior Member Cooter's Avatar
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    Its fuel injected. You'll be ok.

  2. #12
    Senior Member 34nineteen's Avatar
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    You could also look into the barometer sensor mod available on the Buelltooth site. Maybe the Buelltooth dude will swing by and drop some knowledge bombs.

  3. #13
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    Quote Originally Posted by Cooter View Post
    Its fuel injected. You'll be ok.
    K that’s what I was hoping!

    However I read through all their spiel at rev moto regarding the baro sensor, they make a convincing argument... alll the fun roads here are above 3k ft elevation, and I’ll be pushing it a little. Is the barometer worth the little extra insurance? $70 is def a good price point! But assuming the current “race only” ECU is tuned correctly, will it run better at altitude with the baro installed?

  4. #14
    Senior Member Cooter's Avatar
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    The ECM 'tunes' itself by reading whats coming out of the exhaust (The O2 sensor). Reads the sensors, adjusts the fueling, reads the sensors, adjusts the fueling, in a loop, like a circle. A Closed Loop. About 20 times every single second. Because the the adjustments are made according to what the engine it putting out, they are all inclusive of air density, humidity, temperature, gasoline quality, engine condition, etc. Thats why Buells don't have (or need) a barometer.

    This is why every single fuel injected vehicle for 40 years now, is built to work that way (CL). CL will always be more efficient (MPG), and it is safer (reads more variables), and will make more power in more areas (adjustable).

    In Open Loop the ECM is blind.
    If you inhibit the ECM's ability to adjust itself (Open Loop/ Speed-density tuning) you blindfold it to what it's pulling in or putting out, so it cannot adjust accordingly. *it only sees RPM/load, refers to the fuel map, and refers to RPM/load, refers to the fuel map. That theory could work ok (in the 90's) for single purpose engines, static RPM, or WOT only drag style applications in rudimentary FI systems that couldn't adjust as quickly as they do now. Computing power has exponentially increased since then.

    If you eliminate the engines ability to see how its running you have to add a fuel map modifier for elevation as air density decreases (a Barometer). But you LOSE it reading everything else. So you have to guess with an accurate fuel map tune or overcompensate with a rich mixture. Speed-density tuning can get very close to being good, but without the ability for continual adjustment (20 times a second) it can never be as good as a self adjusting Closed Loop ECM.

    *over-simplification warning.
    FWIW Rev-Mo is a great site, a very knowledgeable company, and super generous with their Buell love. We disagree on this point.

  5. #15
    Senior Member Endopotential's Avatar
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    Great post Cooter! Open vs Closed Loop was always a mystery to me, and this is the clearest explanation I've seen

    I'll give you one of Aaron's beers.

  6. #16
    Senior Member Cooter's Avatar
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    Cheers!

  7. #17
    Senior Member 34nineteen's Avatar
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    Yes, nice explanation.

    Now explain “open loop learn”

  8. #18
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    Gotcha. It does seem like it should work the way the factory has it set up, otherwise there would be a bunch of blown motors everywhere lol... I'll read a bit more about it and make my own conclusion. Thanks!

  9. #19
    Senior Member Cooter's Avatar
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    Remember: Closed Loop is when the bike is in part throttle cruise (which is most of the time/regular riding) and needs to be the most efficient. CL "targets" the most efficient 14.7 parts of air to 1 part of gas (stoic). Clean emissions and clean burning. Mods don't affect this because it is still reading what comes out of the engine (regardless of mods) and adjusting for its target. Reads the O2, adds or subtracts a little fuel, reads the O2, adds or subtracts... etc. In theory, CL operation doesn't need any fuel map at all, it's just reading output and adjusting input to get whatever target output you set.

    Remember the O2 is in the tail pipe, after combustion, so when the motorcycle needs power (more fuel) for big fast throttle changes like WOT. Things are happening too fast to wait to reference the O2 for whats already happened in combustion and adjust for the richer mixture you need for that power right now. You have to know how much fuel to put in before its burned and read by the O2. So if it can't use an O2 sensor, how does the ECM know how much fuel to give the engine?
    The ECM ignores it, and directly references a pre-set fuel map. Open Loop operation.

    The fuel map is a Load/Rpm map that is preset for the ECM to immediately reference at whatever Rpm/Load its at, when you whack open the throttle. That preset map is built by dyno testing the engine through the Rpm range at different loads and is adjusted manually for the bike to make the most power, 10:1-ish (note: NOT 14.7:1 part throttle cruising). THIS is the fuel map everyone talks about after changing their muffler. CL operation at part-throttle cruise is unaffected because, re-read that part.

    OK Aaron!
    With Open Loop Learn on, the ECM looks at the O2 sensor during OL to see what the engine is putting out. OL operation is still too fast to adjust like CL operation does, but can see repeated results and can modify the OL fuel map to be more accurate that point, so the next time you are at that point of the map (still in OL) it can add that little bit immediately from knowing its history without having to wait for a reading. Lets say you whack the throttle open at 3500RPM/ 90% throttle and it sees a lean mixture. It's too late to adjust input, so the ECM will add a little fuel to that spot of the fuel map. So the next time you are at 3500rpm/90% throttle, it will just refer to the now modified map and give the bike what it needs, from what it told it last time, still without waiting on the O2. The O2 is still reading an modifying for the next time its at that spot of the map.


    Beautiful right? Why'd you want to handcuff such a simple system?

    *Still greatly oversimplified. Some things are "wrong" but for off-point reasons. K.I.S.S.

  10. #20
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    My spec ops muffler has duel exhaust ports, I kept my exhaust valve hooked up, ran and sounded great. It's going on the Ully next.



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