Oilhead Tech Pages

Rob Lentini

R1100 fuel injection/surging/fixes -- 4 parts

Part 1 of a 4 part series:

My original four part article was originally posted to the IBMWR tech site in the spring of 1996. This new version has been updated to parallel the information in the Zero=Zero procedure found at the same site.

Motronic 2.2 overview (2.4 is almost the same):

The Motronic receives the most important input signals from the Hall-effect triggers (engine speed and TDC) and from the throttle butterfly position sensor (throttle opening angle). The amount of air drawn in is calculated from the throttle opening angle and engine speed. Precise data are determined with the aid of the air NTC (intake air temperature), and oil NTC (engine temperature). CO values on the special version with three-way catalytic converter are performed by the oxygen sensor.

The things to remember here are that the most important Motronic inputs are 1) engine speed, 2) TDC (top dead center, for ignition timing reference) and, 3) throttle opening position.

Many of you have heard about "Cat Code" plugs, and how many have achieved drivability improvements by removing this plug ... but what is it? It's a "map".

You say: "What is a map"? Well, think of the Gulf War "cruise" missiles. They had a "map" electronically installed to compare stored data to what they were overflying on the way to their targets. Motronic is much the same way. The R1100RS/GS series has six (6) different maps available in the later series control units to "custom tailor" parameters to meet emission/country-specific specs. No less than five (5) cat code plugs are specified for R1100RS/GS configurations! Each one is distinctly different in emissions, performance, and drivability.

(Note: CCP configurations are different for Motronic 2.4 installed in R1150 versions. Data on those is unknown as of the writing of this article)

Part 2 of a 4 part series:

Recalling Motronic input sensors and imbedded "mapping", here's what I've learned.

Point 1): Some of you have been pulling the cat code plug (CCP) to see if your bike runs better. What are you REALLY doing? - By removing the CCP, you are installing the "R1100RS without cat map". You are then running in "open loop" mode. Emissions and fuel consumption will increase and the catalytic converter, if installed, may be damaged.

- By removing this CCP, you are defaulting the Motronic control unit to "CO pot installed". Since you have not (presumeably) installed the pot, Motronic defaults to a "presumed" 1.8% CO mixture.

- Prove it: If you bring your bike to your dealer, and have them read fault codes, "1111" will be read, indicating a bad (not installed!) CO pot.

ANY changes you make in the previously mentioned Motronic sensors "could" trip a fault code. To BE SURE the faults are reset, and to assure lingering faults DO NOT cloud what you are attempting to achieve, YOU MUST remove and reinstall fuse #5 "Motronic" to clear the volatile fault memory! Do this EVERY time you change a variable.

In my opinion, removing the CCP is NOT the way to go, assuming of course that you are still running the stock catalytic converter/muffler. I measured CO readings that go from 0-2% CO (with CCP) to 6-8% (without CCP). Running open loop will eventually damage your converter. If you don't care, the cost is yours -- to both the environment and your fuel consumption. Some states, like AZ (mine), have emissions testing. Think about this!

Point 2):

If you have an aftermarket system installed, like my Staintune, your options expand.

Here's the bottom line: The STOCK "with CCP" configuration gives the best OVERALL performance/mileage combo. Although surging (prior to "Zero=Zero") could be detected, this stock combination is the BEST compromise, in my opinion. Without a doubt, it is also LEGAL and safe for a catalytic converter.

I evaluated seven (7) different map configurations on my R1100RS. GS and R folks might experience differences due to compression ratios and cam timing.

BTW: CCP connections were made to configure the Motronic unit in accordance with BMW data. I made up a four-wire jumper connector with spade terminals so I wouldn't have to buy all the different CCPs. Connection pins are related to the pin numbers you will observe on the pin-side of your CCP. Early "Beta" pre-production R1100RSs were "hard wired" for catalytic converters, and have no CCP socket.

1. R1100RS without cat, no CCP connections, CO pot installed:

2. R1100RS with Golden Yellow CCP, 30-87 connections, no CO pot

3. R1100RS with CCP, 30-87 connections, with CO pot (to observe if pot can be coinstalled with O2 sensor)

4. R1100RS - CH (Switzerland) with cat, Dove Blue CCP, 30-86-87a connections, no CO pot

5. R1100GS without cat, Beige CCP, 30-87a connections, no CO pot

6. R1100GS with cat, Rose Pink CCP, 30-87-87a connections, no CO pot

(Note: This CCP when matched with GS Intake Tubes (see http://www.ibmwr.org/r-tech/oilheads/R11pwmod.shtml) can significantly improve mid range torque on RTs and RSs)

7. R1100GS - CH (Switzerland) with cat, Mahogany Brown CCP, 30-86-87-87a connections, no CO pot


If you recall part 1 of my previous two posts on this subject, you will remember that the BMW Motronic data I referred to mentioned that there are three most-important inputs to the Motronic control unit:

  1. Engine Speed (from the Hall transmitters)
  2. Top Dead Center (TDC) (also from the Hall transmitters)
  3. Throttle Position Sensor (TPS)

The TPS is mounted on the outside of the left throttle body. It's the square shaped black module with a connector on its bottom side. The TPS is a rheostat, or variable resistor. Connected to the throttle butterfly, it transmits an input to the Motronic based on throttle opening--anywhere from idle to wide open. The Motronic compares the TPS to all the other sensor inputs to give the proper (we hope) engine management for existing conditions.

The adjustment of the TPS is very critical to engine performance (remember the 3 important inputs!) Adjustment is made by loosening the two socket head screws, the ones with blue paint on them, and rotating the sensor to achieve correct adjustment.

The BMW MoDiTec analyzer is the tool your dealer also uses to set the TPS. First they will clear any faults in the system. Then the technician will rotate the TPS until a particular display is achieved. The screws are then tightened, and the adjustment rechecked by opening and closing the throttle. The tool does not read out the actual voltage from the TPS to the Motronic.

Should you adjust the TPS yourself? For most owners, I would say no. The TPS adjustment is a very precise procedure and has a direct correlation to the throttle butterfly adjustment set at the BMW factory. My subsequent "Zero=Zero" http://www.ibmwr.org/r-tech/oilheads/zero528.shtml article gives full instructions on how to do this, assuming it is _required_. Do not tamper with the TPS or you could damage your engine and void your warranty!

Part 4 of a 4 part series:

Here's how to put together the preceding three part experience I have had with my R1100RS. Please note that I did all my experimenting on my bike, an R1100RS--not a GS with different engine compression and cam timing.

In review, you need to be SURE that ANY drivability problems are NOT a result of a fault in the Motronic system. To be SURE, have your dealer read and correct any faults he detects. Your WARRANTY covers this, as do EPA and DOT regulations.

Assuming a clean bill of health, CONSIDER the following mods:

  1. Advanced Ignition Timing (similar to my K75 article on the web)
  2. Valve Lash Increase
  3. Super-Accurate Throttle Body Synch

1. Advanced Ignition Timing:

Most manufacturers set the ignition timing for the typical vehicle with poor fuel quality in mind. Modest performance gains may be achieved by REASONABLE increases in initial advance. Dyno testing on my RS showed a 2-4 HP increase in power across the entire RPM range. Assuming you are NOT experiencing ANY pinging or detonation, you can easily advance the ignition timing by about 3 degrees. Here's how to do it:

  1. Remove the small rubber cover on the clutch bellhousing (just inside the right throttle body).
  2. Remove the black cover on the front of the engine. This covers the alternator drive pulleys/belt.
  3. Notice on the lower (crankshaft) pulley that the three timing plate securing screw are exposed, and that the timing plate (which the Hall transmitters are mounted on) can slide CW and CCW in three slotted holes.
  4. Put the tranny in 5th gear and, while observing the flywheel with a good flashlight, move the rear wheel to rotate the engine. You will be looking for "OT" (top dead center), "Z" (full advance) and "S" (the 6 degree initial advance mark).
  5. Warm the engine and observe, with a timing light, where initial advance is taking place. With the engine at 1000 RPM or less, the advance will be very close to "S". Turn off the motor, loosen the three screws holding the Hall transmitter plate, and tap the plate in a CCW direction from the front to the end of slot travel. Tighten down the three screws and recheck the timing. Be SURE the idle RPM is 1000 or less! If your R1100 is like mine, the timing will be advanced 50% further than the "OT" to "S" mark, for about 9 degrees of initial advance. If so, put everything back together and, if during your test ride you detect no noticeable detonation, you are in business.
  6. Run PREMIUM fuel with advanced ignition timing to prevent detonation and engine damage!

2. Valve Lash Increase

If you are like me, try this. I like low and mid-range driveability and throttle response. My R1100RS would not idle for several minutes on cold mornings until I increased valve lash. Increasing valve lash FIXED the problem, and I've lost no discernable top-end power. Increased valve lash is equivalent to closing the valves sooner--"milding" the cam timing.

Set the valves COLD from/to:

Intake: Spec: .006" to: .012"
Exhaust: Spec: .012" to: .014"

Your idle will be MUCH smoother and throttle response immediate but controllable. Increase in valve noise is minimal. Valves will run cooler.

3. Super-Accurate Throttle Body Synch

Many R11 riders have reported the benefits of being anal retentive in the synching of the two throttle bodies. Surging can be dramatically reduced just by synching the throttle bodies VERY precisely. Here' how to do it:

  1. Buy/borrow a mercury manometer or Twin Max. Vacuum gages just don't hack it.
  2. Loosen the crossover synch cable for the right throttle body to assure some free play.
  3. Loosen the throttle cable on the left throttle body to assure some free play. (97 and newer Oilheads have a split throttle cable arrangement to each throttle body)
  4. Loosen the crossover cable on the right throttle body.
  5. Install the mercury manometer or Twin Max.
  6. Set BOTH air bypass screws to 1.5 (2.25 turns for a GS or R) CCW from fully seated.
  7. Aim a medium to large fan at the front of the engine - Warm the engine for at least 15 minutes.
  8. Check mercury levels or Twin Max reading . Adjust one or both of the blue paint-sealed throttle stop screws (on the inside of the bodies) to achieve balance AND 1100 RPM. Very little tweaking should be required, and probably just one side. This is a very accurate MECHANICAL synch.
  9. Adjust the synch crossover cable to balance the mercury at 1500 RPM (just barely off idle). (For 97 and newer, set both throttle cables to .5mm free play, then adjust either for correct synch)
  10. Reset throttle cable free play at .5 mm. (Note: Do not readjust the stop screws when doing future synchronizations. Use only the bypass screws.)

Well, that' it. Except for:

Dow Corning Gear Gard "M" in the tranny and final drive to increase shifting ease This stuff is available in quart bottles at bearing stores. Mix 3-5% by volume in tranny, final drive, and for others, fork oil. Shifting and fork oil "stiction" essentially go away.

Enjoy your 'R'. There's sooo much potential, but it's up to you.

Rob Lentini

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R-Tech pages maintained by: John Petty for the original author(s) and the Internet BMW Riders
Last Update: 09 September 2010