R 1100 GS fuel injection control inquiry

Recently I tried to identify a source of my son´s R 1100 GS (oilhead) problem with wet spark plugs. It came out it was a defective fuel pressure regulator to cause the problem. Instead of required 3 bar pressure it maintained hardly 0.5 bar. The episode made me search for better understanding of principle of Bosch Motronic 2.2 fuel injection control. So far I have not succeded in finding a source of wanted information. Dear colleaques, if anyone knows, please explain it in a simple way. For example I wonder if the control unit (Bosh Motronic 2.2) prolongs the period of injection in case the fuel pressure is low. Why do oilhead engines have two Hall sensors on crankshaft? My old friend K 75 with L-Jetronic has air volume sensor in suction duct whereas oilheads with Motronic 2.2 do not have it. What is the difference between mentioned systems? Thanks. Please excuse my poor english.

Frantisek Vorel

K 75 RT, R 850 R.

Zitat von "sup"

Recently I tried to identify a source of my son´s R 1100 GS (oilhead) problem with wet spark plugs. It came out it was a defective fuel pressure regulator to cause the problem. Instead of required 3 bar pressure it maintained hardly 0.5 bar. The episode made me search for better understanding of principle of Bosch Motronic 2.2 fuel injection control. So far I have not succeded in finding a source of wanted information. Dear colleaques, if anyone knows, please explain it in a simple way. For example I wonder if the control unit (Bosh Motronic 2.2) prolongs the period of injection in case the fuel pressure is low. Why do oilhead engines have two Hall sensors on crankshaft? My old friend K 75 with L-Jetronic has air volume sensor in suction duct whereas oilheads with Motronic 2.2 do not have it. What is the difference between mentioned systems? Thanks. Please excuse my poor english.

Frantisek Vorel

K 75 RT, R 850 R.

Hi,
Your questions are very specific and require someone who is very with these devices to give you a specific answer, however, I may be able to get you on your way.

1. Fuel pressure is controlled by the pressure regulator and I don't think that Motronic knows about it (I could be wrong). It simply tries to start, and the injectors keep pumping the fuel in ... thus wet plugs. I don't think that there is a more complicated answer to that. L-Jet does not measure fuel pressure, it assumes that the regulator/pump system are doing their jobs. Motronic is probably the same.

2. Motronic vs L-Jet.. Motronic system is a computer system which reads information form sensors, converts them to numbers and makes appropriate decisions on how much fuel to inject. L-Jet is an analogue (electronic device) which reads the same info and also makes the same decisions.
The difference is that Motronic uses a computer program to decide and L-Jet simply responds to voltage / resistance input. Motronic can be modified by mod of programs (chip replacement) and L-Jet can not be. a good place to start is here:
http://en.wikipedia.org/wiki/Jetronic

Hi,

I have made a K-bike simulator to test motronic 2.1 on my K100RS and found following.
Input to motronic to change its injection duration are
1. water temp. 2. air temp. 3. engine rotation speed(HES) 4. CO pot. 5. throttle opening position(TPS), No fuel pressure signal is fed.

While engine is idle and at normal operating temp, The injection duration will double if water temp goes down to below 20 C.
Air temp change between 0 and 60 C result in +-10% change in injection duration.

My understanding why your R has two HES is to use Motronic 2.2 on both K and R bike. It needs two HES input to use it on for example K1100 .

You will find a lot of info for your R here.

Hi Ned, hi dond_tosi, thanks for the answers.

Surely i will take full advantage of their content. It is nice to have such a support.

Sup, Frantisek Vorel