R1100S motronic interchangable? Poor fuel mileage issue.
 

Hi Guys,

I have replaced my 2004 bike with a 2005 model which is in great condition. It's completely standard, starts and runs well. Mechanically it is in great condition. I have replacd the tyres and brake with new items. It rides well, rolls freely, just about perfect in every way but one.

I have fitted the same 25 litre tank I had on my old bike to this new one, but I get ~30 miles less from a full tank. I have removed the K&N filter the previous owner had fitted and replaced it with a paper one. I have done the valve clearances and given the bike a full service. I have confirmed that it's running on both plugs on both cylinders.

The only gripe I have is that it's got poor fuel consumption. I use it on exactly the same route on my daily ride to work and nothing about the actual use of it is different to my old bike.

I am thinking that perhaps the previous owner had an aftermarket system fitted and the bike mapped for more power. I do still have my old bike so I was planning to swap out the motronic units to test my theory. The thing is, they are different part numbers. My 2004 bike has a part number 7 684 428, wheres my 2005 bike has 7 658 618.

Do we think that I can wap these units out without issue? My gut feeling is yes, but I would like to hear from anyone who can give me a definitive, or at least a well-informed answer.

Pete.

I am not sure about your motronic swap, but I would try a new O2 sensor. What do the spark plugs look like after a good run?

I haven't checked the plugs after a run but I will . I have decided to just fit the older motronic and see what happens. I can't see there being any reason why it might end in disaster and they are both 2-spark engines. I'll run it for a week and check the fuel consumption and if it doesn't improve I'll swap out the o2 sensor.

Check to see if the Motronic encoding plug is still in the fuse box, I think that was a quick way for people to change the fuel ratio.

Aye I checked to make sure it has the standard plug just like the 2004 bike. I even popped the lid to make sureit hadn't been messed with inside somehow.

Hi Pete :
Just curious, what color are your Encoding Plugs ?
Are they Light Grey, Yellow , or another color ?

Both bikes have the same plug light grey almost white in colour.

Hi Pete :
Thanks, my Encoding Plug is also Light Gray ( though it looks White to me ).

You are fortunate to have two of the same bikes.
There's an app that gives a lot of info from the bikes sensors, it's called Motoscan.
With a small investment, less than $100 , you can compare the output from both bikes.
The app is called Motoscan, but you need an ODB 2 scan tool , an adapter cable and an Android based smartphone or tablet.

Here is a link :

https://www.advrider.com/f/threads/motoscan-app-for-bmw-motorcycles.1320275/

I have a OBD2 scan tool, icar pro or something - could make an adapter cable if I had the pinouts. Does ODB2 fully work with these 18yr old bikes?

The Motoscan app works with a certain OBD 2 chip. I have no idea if it works with other OBD 2 chips.
Here's a nice write-up.
https://www.bmwownersnews.com/2021/11/motoscan-and-obdlink-mx/

Here are some of screen shots of what the app shows.

http://forums.pelicanparts.com/uploa...1681759246.png

http://forums.pelicanparts.com/uploa...1681759283.png

http://forums.pelicanparts.com/uploa...1681759355.png

http://forums.pelicanparts.com/uploa...1681759382.png

Thank you that looks very interesting.

Couple of questions:

Is that the OBDlink MX+ or LX? What are the essential differences?

Does the app allow datalogging from the live data?

Thanks
Pete.

The Motoscan app requires an Android smartphone or tablet. I believe the app is free but some features like
Resetting Alerts cost more. This app covvers so many BMW motorcycles from ours to current ones with
all kinds of sensors, displays and alerts.

The OBDLink MX+ and OBDLink LX can be used on a car and OBDLink does have it's own free app you can download for cars.

The OBDLink MX+ has support for : Bluetooth, Android, Windows, and Iphones.
The OBDLink LX has support for : Bluetooth, Android, and Windows.

There is a setting in the MotoScan app to "Create Log File", but I never tried it.

Ah, so only the LX is required for bikes. I will look into it, thank you.

Well after a week of riding with the 2004 Motronic unit in, I've got 208 miles from 24.8L of fuel which is 8.4miles/litre or 38.2 MPG. Usually I can comfortably manage 9.4miles/litre or 42.7MPG which would give a range of 235miles or thereabouts and I could stretch that to just about 250mles if I rode very frugally.

So an improvement, but still not nearly as good as the old bike would manage with it's much more tired engine.

My bet is still on the O2 sensor.

I think I will swap them out. Not looking forward to is as they are an utter bra-stud to remove but needs must.

Have you taken a look at the spark plugs yet? Check if they both look the same. If your other O2 sensor is old better to just order a new one.

How long ago did you track the mileage on the old bike. is it possible that fuel blends have changed since then? summer fuel is different than winter fuel. and govt mandates have added more and more alcohol over the years

6 years daily commuting from 39k miles to 121k. Fair to say I knew the bike intimately. The old bike would do 8 full journeys to and from home to my current place of work but the new one will only just manage 7.

It's an interesting thought though as I know people who claim to have lost mileage on the new 10% ethanol fuel. I swapped from the old bike to the new one over a weekend so the difference was immediately apparent.

I thought I would follow this up now that the problem is happily solved. So it turned out to be a combination of two things - A poorly set TPS and a slghtly high idle speed.
I turned down the idle speed and it made a slight improvement. Since nearly all of my riding is in heavy/city traffic I invariably spend a good amount of time idling, and the 1500rpm idle speed was just burning up extra fuel sitting at lights or standing traffic. Added up over a week I guess it's significant enough to notice.

This still didn't bring my fuel consumption back to previous levels though. Last weekend I had time to adjust the throttles again and I also got my tester out and checked the TPS voltage. It was just over 0.5v at idle so I adjusted the TPS so that I have 0.370V at idle, and immediately I've gained over 10miles per tank of fuel.

Thanks for all the costructive input.
Pete.