Pre 7/93 K1100 Motronic 2.1 compatability with 91-92 K100rs?

[Freelancer]

Hey fellow Brickers,

Its just as the title asks. Is the Pre 7/93 K1100 Motronic MA2.1 compatabe with 91-92 K100rs/89-91 K1's that also used Motronic MA2.1?

I have heard conflicting reports from very credible sources and don't want to start an arguement. So I would like to know the particulars. Such as:

If not compatable, Why?

Is there a possibility of a work around?

Is it just the O2 sensor or is there more to the problem?


If anyone has some info or knows someone who is knowledgable please explain.


Thanks,
Freelancer

[wmax351]

I don't think it would be compatible. The Motronics on the k bikes use Alpha-n fueling, which calculates based on throttle position. The o2 sensor is used to pull the mixture back to stoichiometric.

The real sticking points are going to be:

- Different sized throttle bodies, with differently set up throttle plates
- Different sensors
- Different displacement
- Different injectors and related systems
- Different fuel maps
- Different Ignition maps

People who say it will work are probably right. It will work. It won't work well. You are introducing variables into the equation, and asking to make trouble for yourself.

You seem torn with a desire to monkey with stuff. If you want to monkey with things, get a microsquirt/megasquirt system and a wideband oxygen sensor, and tune it properly.

[frankenduck]

Exact same heads, TBs, coils, injectors.  The cams are different but, given how similar the engines are, I'd be willing to bet that it's a shape issue and that TDC is in the same place so the timing is most likely the same.

My GUESS would be that what would work best would be to swap in a K1100 FI wiring harness which has the right connectors for the that Motronic and an O2 sensor.  Then run an exhaust (K1100 stock, Staintune, Remus) that has a bung for the O2 sensor.

However, since the mapping of the K1100 Motronic was de-tuned to meet a voluntary Euro max 100hp standard you might get less hp than from a K100RS4V Motronic though.  Then again, if you're going to do your own eprom that wouldn't matter.

[rbm]

Article in BMW ON for February 2009 entitled "Engine Upgrade: A K1200 Engine in a K100 Frame" by Paul Ford describes the process of adapting the K1200 engine into a K100.  Paul used the Motronic 2.4 from the K1200.  The article should be at this link:  http://www.bmwmoa.org/features/engine_upgrade/BMWMOA_ON_engine_upgrade.pdf.  I have the article if you can't find it online.

Also, Themason has recently posted to K100-forum about a K1200/K1100/K100 Frankenbike.  It might be worthwhile to see what you can learn from his knowledgable friend.

[Freelancer]

@Duck-
I'm not sure that a harness change would be necessary. Here are the reasons that I suspect such:
1)The early '93 K1100 rs's used motrinic 2.1 and ABS 1.
2)The early '93 and the '91-'92 ecu's appear to be physically identical, I just don't know if the connector is the same :dunno2:.
(The '94-'97 Motronic 2.2's were physically different in shape and had different connectors.)
3)The Catalytic Converter was standard equip from '91-on in some countries and was an option in the rest of the world.
4)There is only one wire harness available for the '91-'92 4v K's. This leads me to believe that the factory harness has an O2 port somewhere.
5)The compatable models shown on the parts search in the link below also suggests it could work, but such parts sites are often wrong
http://www.bmwmcchattanooga.com/products/BMW-Motorcycles/1991/K100RS/CONTROL-UNIT-MOTRONIC-KAT/1032465/13611464649.html

So if the connector is the same then it might work. Only way to know for sure is to see if the connector fits, though I'd rather know before shelling out cash for one.

If it does get to the point of having to change harnesses, then it seem like I might as well go with an after-market set-up what with an OEM replacement(if available) costing . ????

Maybe a working 91-92 oem ECU will pop-up some where soon and the question will be more academic at that point. Still would be good to know exactly how the 2 motronic MA2.1's differ.

@rbm-
Thanks for the info. It fits wth my own planned K 120rs Frankenbike project that I posted up in the Bar. Alas, the current question has more to do with having a back up ECU for my 91 K100rs. The 91-92 motronic 2.1 is getting hard to find and I'm wanting to find back-up options for a couple of reasons.

First reason is the Boy Scout philosophy of be prepared.

The second reason is that I'm toying with the idea of dropping in a Harman chip but won't do so until I have a back-up in case Mr. Murphy visits.


Thanks for the input so far guys,
Freelancer

[frankenduck]

In the US, up through 91, ABS was an OPTION on K bikes. How do I know this? Well, to start with, I've owned both ABS and non-ABS K100RS4V bikes that did, in fact, have different wiring  harnesses. Next, the parts catalog has different part numbers for them.

Take a look here: http://www.ascycles.com/Illustrated_catalog2/MicroList.aspx?id=51709&catID=61&catname=General_electrical_system&bindName=Chassis_wiring_harness&bindCat=61_2725

Finally, I've attached clips from BMW NA sales brochures from 91 and 92 that show ABS as an option in 91 and standard in 92.

I've also attached clips from 92 and 93 BMW NA sales brochures that show that the cat on K bikes was not introduced in the US until the 93 K1100LT.

The Motronic for the non-cat K100Rs4V is part 13611464479. The Motronic for the catted K1100LT is 13611464649.

The Motronics have the same box and look the same but they are different because one has pins for input from an O2 sensor and the other doesn't.

If you have any EVIDENCE, other then hearsay, to support the notion that the US K100RS4V ever had a cat then please share it.

I've seen a couple of very early 93 LTs (I could tell they were early because they had K100RS4V peg plates) but never checked to see if they had an O2 sensor or to see if they had a US VIN.

(Not trying to pick a fight here. Just trying to educate you.)

[frankenduck]

Also, what are the last seven digits of your VIN? The VIN decoder will tell you whether your bike has a cat or not.

Here's a  VIN for a 92 US K100RS4V: 6494066  No cat.

[Freelancer]

Hey Duck,

No prob. I know that my bike doesn't have a cat. What I don't know is weather or not it has an O2 lead.

And btw, the A&S website you posted brings up the wrong year K100 whenever I click on the 91-92 K100rs 4v. When I click it send me to a 2v k.
This is why I said that I don't have a lot of faith as to the accuracy of the online parts catalogues. I've found similar issues with the Chattanooga parts directory.

Also don't doubt your experience. My experience is fuzzy due the fact that 88-91 was right after I left germany and wasn't riding(Trying to be responsible school stuff). My point is that I remember the clean air laws and BMW being the first MC manufacturer to offer the Cat as an option in some countries and as a standard feature in others. I just can't remember which years.

Point is that I don't doubt that it wasn't until '93 that it was offered here in the US.
Its that I believe that it was an option or standard in other countries from '91 on. This combined with BMWs love of standardization and what some of the parts directory's list is what has me asking if any one has actually checked to see if they mate up. I mean, the Harman performance chip that fits into my '91 ECU is the same one that goes into the pre 7/93 1100rs.

Anyway-
The question may soon be moot as far as I'm concerned. If it is to much of a hassle to find a working Motronic MA2.1 I'll just go with the after market MoTeC or Megasquirt system. Either of those will be cheaper and lighter than swapping in a 94-later harness & Motronic. Also, the later Motronic 2.2 has issues with running on a non-ABS bike from what I hear(Please correct me if I'm wrong on this).

Again, thanks for the info,
Freelancer

[frankenduck]

Why would a non-cat bike need an O2 sensor?

What are the last seven digits of your VIN?

2V RS link: http://www.ascycles.com/Illustrated_catalog2/MicroList.aspx?id=51752

4V RS link: http://www.ascycles.com/Illustrated_catalog2/MicroList.aspx?id=51709

I don't think that de-ABSing a 94+ has any impact on the ignition. Why do you think that braking and ignition have anything to do with each other? They have completely separate control units.

[wmax351]

O2 sensor is not for the cat, it is for correcting the mixture to stoichiometric (and richer/leaner) which provides better efficiency and power. It does help the catalytic converter, as stoichiometric products are easiest to remove with the catalytic converter.

This is especially the case with the motronic bikes, which use throttle position to determine fueling, rather than an airflow meter. Small changes can skew the mixture, and the O2 sensor corrects for it.

[Freelancer]

Why would a non-cat bike need an O2 sensor?

I don't think that de-ABSing a 94+ has any impact on the ignition. Why do you think that braking and ignition have anything to do with each other? They have completely separate control units.

wmax351 anwered your first question.

Also, It has been my thought that with the way most manufaturers back then ran a common base harness that just plugged in the optional systems. I admit that I may be incorrect here. I just can't find a part# for a harness that would run the optional emissions system and also have a hard time believing that BMW would go to the trouble on such low number production runs.

Again, am completely willing to admit that I am in error here. Just now have an academic interest as to what the early 1100's wire harness and ecu hook-ups/mountings look like.

Again, this is all academic due to the information that rbm and wmax351 have given about the possibility of cost effective aftermarket replacements for this system.

O2 sensor is not for the cat, it is for correcting the mixture to stoichiometric (and richer/leaner) which provides better efficiency and power. It does help the catalytic converter, as stoichiometric products are easiest to remove with the catalytic converter.

This is especially the case with the motronic bikes, which use throttle position to determine fueling, rather than an airflow meter. Small changes can skew the mixture, and the O2 sensor corrects for it.

You sir are truly a scholar and a gentleman.

I am following you Megasquirt on a K75 thread and as my project hits that point in the far future, I'll be asking you a fair number of questions on how to do and where to go to become edjucated in the dark arts of FI

Thanks guys,
Freelancer

[frankenduck]

I just can't find a part# for a harness that would run the optional emissions system and also have a hard time believing that BMW would go to the trouble on such low number production runs.

ABS and non-ABS main harness: http://www.ascycles.com/Illustrated_catalog2/MicroList.aspx?id=51709&catID=61&catname=General_electrical_system&bindName=Chassis_wiring_harness&bindCat=61_2725


Cat vs. non-cat FI/Motornic wiring harness: http://www.ascycles.com/Illustrated_catalog2/MicroList.aspx?id=51711&catID=61&catname=General_electrical_system&bindName=Engine_wiring_harness&bindCat=61_1080

http://www.ascycles.com/Illustrated_catalog2/MicroList.aspx?id=51709&catID=61&catname=General_electrical_system&bindName=Engine_wiring_harness&bindCat=61_2724

[wmax351]

A good source for education on EFI is www.megamanual.com. Its a little outdated for some of the more cutting edge megasquirt development, but it has a very good primer on fuel injection theory and operation, which doesn't require a degree in mechanical engineering to understand.

[Freelancer]

Well after spending an evening on the A&S website, "using a pc rather than a beatup phone", I found my answer.

The 93's 2.1 motronic will work because it was offered on cat bikes all the way back to '89. Thing is that you will have to swap in the emmission ECU harness that has the O2 sensor.

The confusion on my part was that there is only one main chassis harness and didn't think to look at the ecu's harness as being separate.

Mucho thanks to Duck for your patience and to wmax for your aftermarket technical knowledgs,

Freelancer