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Thread: Rexxer ECU tuner

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    Registered User gregory's Avatar
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    Rexxer ECU tuner

    Anyone have experience with Rexxer ECU tuning. Was reading the article in the new ON and the symptoms described sure sound like what I'm going through with my 99RT, 37,000 mi. Popping on downs and the idle could be better. I set the valves and balance the throttle bodies myself so I'm pretty sure there right. Any feedback would be appreciated before I go out and spend $600.00 bucks on a Rexxer unit. Thanks

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    Registered User roger 04 rt's Avatar
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    I saw the article too and looked into it.

    The Motronic in the R1100 and R1150 is not a "flashable" ECU.

    If it was flashable, changes would only be effective in the open loop fueling part of the map. I'm not really sure which BMW motorcycles this would be an effective tool for.

    RB

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    Registered User ANDYVH's Avatar
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    Be aware that "popping on downs" as you put it, is NOT in any way detrimental to the engine and is not a running fault. It is only a lean/closed-throttle condition when the bike is pushing the engine on coast down with the clutch out. It is done solely for emissions control and is a common factor in modern engines. It is also one reason our bike have the large volume mufflers common to the stock exhaust. That large volume muffler is a resonator/damper for the popping.

    Setting the valves and balancing the TBs is a good thing for proper engine performance but has little if any effect on "popping". Adding fuel, or running a more rich fuel/air mixture does reduce or eliminate the popping. $600 is a lot to spend to reduce the popping. As to the idle, that can be addressed with TB balancing, and with a very slight "tweak" of the TPS voltage setting, to slightly increase the fuel/air ratio. Someone correct me if I am wrong on that.

    When I rebuilt the TBs on my 94 RS, I was in a rush for a weekend ride and I simply eyeballed the TPS setting. Heh, I could start the bike stone cold without the "choke" because it was running so rich. No popping for sure, but the plugs were also very black and my fuel mileage decreased significantly. Once I got back home I reset the TPS to the proper voltage setting and my fuel mileage returned to normal.
    Last edited by ANDYVH; 07-09-2013 at 05:54 PM.
    Woodenshoe to Cheesehead

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    Registered User roger 04 rt's Avatar
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    Setting aside the fact that the Rexxer won't work on the Motronic equipped, it would be a lot of money.

    When the throttle is closed, the injectors are turned off on the 1150 aren't they also in overrun fuel cutoff on the 1100? If they are, where would the fuel come from to pop?

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    Jammess jammess's Avatar
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    Quote Originally Posted by Roger 04 RT View Post
    Setting aside the fact that the Rexxer won't work on the Motronic equipped, it would be a lot of money.

    When the throttle is closed, the injectors are turned off on the 1150 aren't they also in overrun fuel cutoff on the 1100? If they are, where would the fuel come from to pop?
    Morning Roger,
    My 1150 had a tendency to pop especially on an up-shift when I chopped the throttle closed too much before I installed the LC-1 and richened up the mixture. I never had a clue what caused this popping. Also, had a tendency to pop when throttled back coming down hill as RPM passed through about 3.5K on engine braking. I can get the same effect with my '81 carbureted R100 if the mixture screws are set too lean, turned in. After installing the LC-1 and setting AFR to 13.5:1 have not heard a pop. However, I do begin to note occasional slight popping at mixture settings of 13.8 and especially higher.

    Side note: I am still at 13.1:1 and really like the way the bike runs.
    Jammess

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    Quote Originally Posted by Roger 04 RT View Post
    I saw the article too and looked into it.

    The Motronic in the R1100 and R1150 is not a "flashable" ECU.

    If it was flashable, changes would only be effective in the open loop fueling part of the map. I'm not really sure which BMW motorcycles this would be an effective tool for.

    RB
    Roger,

    Why do you think the 1100 and 1150 ECUs are not flashable? How else would the dealer install updates?
    Karl
    2007 R1200ST

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    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by kthutchinson View Post
    Roger,

    Why do you think the 1100 and 1150 ECUs are not flashable? How else would the dealer install updates?
    If there were updates it would have had to be by EEProm replacement which I've not heard of. I'm no expert but you only hear of chip replacement.

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    Registered User ANDYVH's Avatar
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    Aha,.I learned something today,..my day is done.

    So, going on the premise that the fuel injectors are at zero flow during closed throttle/clutch engaged coast down conditions, then what would be combustible in the cylinder when the valves are closed, ignition occurs and the bike momentum is "pushing" the engine to pump more air than it can get against the closed throttle plates? High vacuum in the cylinder sucking combustibles up past the rings on the bottom of the intake stroke?

    Two things for sure prove the popping is caused by the bike coast-down momentum against closed throttle plates:
    1. If you add any throttle the popping stops, so that indicates the injectors spray in enough fuel for consistent combustion,
    2. Or if you pull in the clutch the popping stops, that indicates the engine is able to go to idle at which time the injectors also spray to maintain idle speed.

    If the injectors do indeed go to zero flow during coast down conditions, then the injectors must again flow at idle to maintain the engine running. Is the Motronic also getting vehicle speed input to tell it when the bike is moving against a closed throttle?

    Back in 07 I modified the stock muffler on my RS to get easier breathing and a bit more sound. Got both, and a LOT more popping on clutch out decel. Plus the bike was definitely running more lean. So I added a Techlusion system, and in the process of dialing in the settings I found I could eliminate the popping entirely, at the expense of fuel milege and sooty plugs and a sooty muffler outlet. So I kept dialing back the Techlusion settings until I got a reasonable response. But the process of dialing in the Techlusion and the results I got with a freer flowing exhaust proved to me what causes exhaust popping on decel. It definitely is NOT back-firing as is wrongly claimed by many, including magazine writers and technicians.
    Woodenshoe to Cheesehead

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    popping not equal backfiring?

    guilty I guess.

    I suspect but do not know that the 1100 also cuts off fuel entirely in overrun-throttle-closed condition.
    It will still pop a couple of times when the throttle is closed abruptly, I assume using residual vapor lingering upstream.
    I don't think it is useful to try to get rid of that.
    If you go from 3/4 throttle to 1/4 though it will pop and burble quite a bit.

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    Quote Originally Posted by Roger 04 RT View Post
    If there were updates it would have had to be by EEProm replacement which I've not heard of. I'm no expert but you only hear of chip replacement.
    The (one) picture I have seen of the inside of the Motronic showed a socketed ROM with a sticker on it.

    You don't socket a flash chip - no need to ever remove it.

    Whether the ROM is one-time-programmable or UVEPROM or EEPROM cannot be determined by this picture.
    You would put a sticker on the thing just to identify the contents anyway, whether or not you wanted to cover the UV window.

    Even an EEPROM is seldom reprogrammable in-circuit as the programming voltage is higher than the read voltage.
    Generally you remove the chip from the circuit and use a separate "programmer" device that can support the dual voltages.
    Hence the socket.

    Flash chips were concieved from the get-go with in-circuit reprogramming in mind, using a single voltage, and typically being partitioned into pages which can be individually and independently erased and programmed. Some have a protected boot block.

    P. S. I hesitate to mention it but Gregory have you thought about just pulling the CAT CODE plug?
    Last edited by scott.lambert; 07-10-2013 at 03:11 AM. Reason: spelling, ps

  11. #11
    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by scott.lambert View Post
    The (one) picture I have seen of the inside of the Motronic showed a socketed ROM with a sticker on it.

    You don't socket a flash chip - no need to ever remove it.

    Whether the ROM is one-time-programmable or UVEPROM or EEPROM cannot be determined by this picture.
    You would put a sticker on the thing just to identify the contents anyway, whether or not you wanted to cover the UV window.

    Even an EEPROM is seldom reprogrammable in-circuit as the programming voltage is higher than the read voltage.
    Generally you remove the chip from the circuit and use a separate "programmer" device that can support the dual voltages.
    Hence the socket.

    Flash chips were concieved from the get-go with in-circuit reprogramming in mind, using a single voltage, and typically being partitioned into pages which can be individually and independently erased and programmed. Some have a protected boot block.

    P. S. I hesitate to mention it but Gregory have you thought about just pulling the CAT CODE plug?
    I've been communicating with a guy ingreece who has modified, cylinders, heads, pistons, cams, intakes and exhaust on his 1100. He has also loaded several new EPROMs. Pretty sure they aren't reprogram able.

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    P. S. I hesitate to mention it but Gregory have you thought about just pulling the CA

    P. S. I hesitate to mention it but Gregory have you thought about just pulling the CAT CODE plug?

    I tried that years ago on my 1995 R1100R.
    Yes it ran smoother (mine suffers from hunting or surging at part throttle).
    While the bike ran great. It drank fuel.

    I reinstalled the plug. I still have the problem.
    I even took it to a dealer in SanJose that was supposed to know how to make it stop.

    Didnt help. Then at the 1st Redmand, OR. National Rally, I had a card installed to see if it would help.
    Nothing. Card was removed at the Rally. I keep this bike ONLY because the Suspension Group had nothing to to do with the Fuel Management Group in designing this bike.

    I tell everyone that asks, 'how do you like the bike'? That samething.

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    Quote Originally Posted by james1300 View Post
    I still have the problem.
    Well, I think I have had my air time on the subject already in a different thread.
    I'm just sayin', it's cheap.

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    Quote Originally Posted by Roger 04 RT View Post
    ...cylinders, heads, pistons, cams, intakes and exhaust...
    Well that sounds like fun. Straight pipes? hah hah.
    The boxer has its limitations. Unless you can ADD cylinders...

    But, I think for less money an S1000RR will still beat it, unmodified. I demo'd one in Sedalia.
    Frenetic and pretty close to terrifying. I didn't leave "sport" mode. "Sport" is the only thing that kept it from being terrifying.
    I got the impression that if the computer ever fails it will just self-destruct immediately, like that experimental fighter jet with the wings turned around backwards?

    I think I need to start being happy with the boxer the way it is.

  15. #15
    Registered User gregory's Avatar
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    Quote Originally Posted by Roger 04 RT View Post
    I saw the article too and looked into it.

    The Motronic in the R1100 and R1150 is not a "flashable" ECU.

    If it was flashable, changes would only be effective in the open loop fueling part of the map. I'm not really sure which BMW motorcycles this would be an effective tool for.

    RB
    Thanks for the reply. I talked to the folks at Rexxer and they said that my RT might be flashed. It depends on the Motronic unit. There are 5 versions with different serial numbers. Some are locked, some not. To be continued. Thanks, Gregory

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