Forcing Motronic Open Loop on 1150RT

[123abcXYZ789]

Hi There-

 

Does anyone know how to force Motronic into open loop mode on an 1150RT? I searched the archives and the only thing I found was disconnecting the O2 sensor.

 

Well, I've done that on mine, and it still feels like something is trying to lean out the mixture at fixed throttle openings (slow roll off of speed and power) and then a snap back to power (as if Motronic couldn't go any leaner, so it snaps back to a fixed reference).

 

Even with the O2 sensor disconnected, I wonder if Motronic still sees an erroneous signal from somewhere and keeps trying to lean out the mixture?

 

Thanks in advance!

[Allen Rowand]

Remove the Cat Code Plug?

[123abcXYZ789]

That's what I thought, too, but it doesn't change the effect. I read in previous posts that that might have worked on 1100s but not 1150s.

[Peter Parts]

Hi There-

 

Does anyone know how to force Motronic into open loop mode on an 1150RT? I searched the archives and the only thing I found was disconnecting the O2 sensor.

 

Well, I've done that on mine, and it still feels like something is trying to lean out the mixture at fixed throttle openings (slow roll off of speed and power) and then a snap back to power (as if Motronic couldn't go any leaner, so it snaps back to a fixed reference).

 

Even with the O2 sensor disconnected, I wonder if Motronic still sees an erroneous signal from somewhere and keeps trying to lean out the mixture?

 

Thanks in advance!

 

My observations as well on a Motronic 2.4. Seems odd but then nothing is documented publicly about the Motronics so who knows what logic hides in there. For sure, greatest mysteries relate to "learning" and memory.

 

Unhitching the O2 sensor means you are always open-loop. It seems to my butt-dyno to have no bad consequences because it doesn't do much on a sport-tourer of that vintage except on the dullest roads and then what it does is surge. I don't think removal causes the ECU to go into limp-home mode because my fuel consumption doesn't change measurably. (I rode around with an O2 cut-out switch for a while... so I have some basis for my opinion.)

 

Pulling or even changing a CCP is a major change of fuel and spark instructions to the ECU. For folks who fret about trivial issues such as oil change period in transmissions or a thou of valve lash, seems a monumental roulette shot in the dark. Not a rational game to play.

 

Ben

[Dave Faria]

You might try disconnecting the battery and make the motronic relearn without the O2 input. Are you sure the O2 sensor is working???

 

I think Ken/moderator on this list gave me this reference.

 

http://www.lambdapower.co.uk/diagnosis/diagnostic_index.asp#q9

[Peter Parts]

Thanks for interesting stuff in that link. My impression is that there are important differences between older Motronics and the way car ECUs work with O2 sensors... like in the first page.

 

Since the Motronic 2.4 does not operate closed-loop at idle, does the A/F zip up and down like every car-based write-up says?

 

I've been lazy and haven't ever 'scoped my sensor signal (black wire), yet. Anybody done so?

 

Ben

[123abcXYZ789]

Peter - How do you know that disconnecting the O2 sensor means it runs open loop? That's what I though, but I don't have a source, and my experience has shown, as I describe, that even with the O2 disconnected, the Motronic (or something) seems to be searching for the right mixture. It gets progressively leaner (I think, since it loses power) then snaps back to full power, just like I rememeber my old Saab with mechanical fuel injection when the mixture was set too rich and the O2 sensor circuit (a modulating valve on the control circuit of the fuel distributor) would try and try to lean it out, but reach its limit and then snap back to a middle ground starting point, and the cycle would repeat.

 

Dave - I've been playing with CAT plug jumpers, too, and each change is accompanied by pulling fuse #5 (killing power to Motronic) for 1 minute to clear its memory. I actually don't have the proper O2 (stock) for the Motronic. Long story, but the currently installed O2 is a 5-wire, wide-band unit for a previously installed Power Commander which I have now removed. So now I am running stock Motronic, but without any O2 connected (because the stock connector is only a 2-wire). So, as I said, I expected it to be running open-loop (limp-home mode, I thought) since the O2 was disconnected, but I surprisingly get this power band cycling happening. Very odd.

 

 

[Boffin]

With the O2 sensor disconnected the Motronic has to be in open-loop. Closed-loop is when the ECU uses the feedback from the O2 sensor to control mixture - with no O2 sensor there can be no closed-loop.

 

Peter - I scoped my O2 sensor when I suspected failure - a general roughness of running and poor fuel consumption (about 200 miles per tank) - it showed a lazy response, very slow to react and change sides of the 0.5V point. With a new sensor - bought from the folks at Lambdapower - I saw the square-wave response pretty similar to the one on the lambdapower website. My oscilloscope in a circa 1963 valve-job and so no pictures to capture

 

BTW, this was at idle - so the Motronic on my bike does seem to operate closed-loop at idle once up to temperature.

 

Andy

[Boffin]

123etc = do you have a twin-spark or single-spark 1150 - if the twin-spark a failing stick-coil can have strange effects on engine power response.

 

Andy

[Peter Parts]

snip

Peter - I scoped my O2 sensor when I suspected failure - a general roughness of running and poor fuel consumption (about 200 miles per tank) - it showed a lazy response, very slow to react and change sides of the 0.5V point. With a new sensor - bought from the folks at Lambdapower - I saw the square-wave response pretty similar to the one on the lambdapower website. My oscilloscope in a circa 1963 valve-job and so no pictures to capture

 

BTW, this was at idle - so the Motronic on my bike does seem to operate closed-loop at idle once up to temperature.

 

Andy

 

Yes, "lazy" operation is the basic indication an O2 sensor is dying.

 

You are the man with the 'scope (EICO 460?) so I hesitate to argue about the sensor at idle. It is possible you are observing some kind of map cell hunting (or dithering) between cells but not based on O2 feedback, when you 'scope the O2 sensor feedback.

 

I found lots of odd shifting around of voltage (oxygen readings) when watching the sensor with a purpose-built 3-digit DVM.

 

All I can say is that there seems to be little published dispute regarding 2.4 Motronic that feedback doesn't (can't?) be operating at idle, beyond 80% (??) throttle, and any time you move the throttle (degree of movement definitely undefined).

 

In as much as bikers move their throttle several times a minute on all but the dullest roads, that leaves not much opportunity for closed loop operation.

 

My general sense is that 2.4 was just crude a experiment in fitting an ECU with feedback to bikes (but necessarily, to bikes with cat converters, eh). At the time, the computers didn't have the moxie to do it well and the half-way system is best disabled into an all-time open loop map system. In other words, this generation of bike runs better by trashing the O2 sensor.

 

Anyway, that's my take on it.

 

BTW, you just can't replace a narrow-band sensor with a wide-band O2 sensor. Very different beasts. The ECU prolly thinks the sensor is AWOL, just guessing. It was a lapse of human-factors design for engineers to use the same mounting thread.

 

Ben

[123abcXYZ789]

With the O2 sensor disconnected the Motronic has to be in open-loop. Closed-loop is when the ECU uses the feedback from the O2 sensor to control mixture - with no O2 sensor there can be no closed-loop.

 

snip

 

 

 

I know that is the definition of closed-loop, and since I do not have an O2 sensor connected, by definition my Motronic is running in open-loop. But my point and question is: something is causing the mixture to progressively lean-out at relatively constant throttle, sputter and lose power, then snap back to health (just as one would expect an O2 sensor loop to be doing), as if Motronic is still getting some feedback from something, but what could it be?

 

One thing I noticed today, it seems to stop this cycling between lean and running smooth at speeds above 2500-3000 RPM. Maybe I should just follow the advice of another post I read (about surging) and always keep the revs high! A little bit tough while poking along in traffic.

 

 

[Boffin]

With the O2 sensor disconnected the Motronic has to be in open-loop. Closed-loop is when the ECU uses the feedback from the O2 sensor to control mixture - with no O2 sensor there can be no closed-loop.

 

snip

 

 

 

I know that is the definition of closed-loop, and since I do not have an O2 sensor connected, by definition my Motronic is running in open-loop. But my point and question is: something is causing the mixture to progressively lean-out at relatively constant throttle, sputter and lose power, then snap back to health (just as one would expect an O2 sensor loop to be doing), as if Motronic is still getting some feedback from something, but what could it be?

 

One thing I noticed today, it seems to stop this cycling between lean and running smooth at speeds above 2500-3000 RPM. Maybe I should just follow the advice of another post I read (about surging) and always keep the revs high! A little bit tough while poking along in traffic.

 

 

If you are running the bike at such low revs you are lugging it to a significant extent - 2.5K is the absolute minimum for the engine with _no load_ such as a low-gear steady speed. Remember, this engine as virtually no flywheel. It is not designed to thump along like a Harley.

 

The motronic will cut all fuel delivery with a closed throttle above about 2K rpm (I forget the exact figure) restoring it for idle below this. Closed throttle is determined by the TPS voltage. Perhaps you are getting close to these thresholds running the engine at such low rpm.

 

Andy

[123abcXYZ789]

You make a good point. Perhaps I should check TPS voltage setting at closed throttle to make sure it is not going out of range at closed, or near closed throttle openings.

 

Time to pull off the tupperware again!

[AndyS]

Remember you don't do a TPS as you would on an 1100, and can easily screw it all up.

 

Andy