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Oilhead surging

No CAT-code plug, and no socket or wiring for it even if I wanted to install one.

When the Oilhead first came out, Bob Lentini published an article about tuning tweaks on the new engine to boost the midrange torque for the US market. One of the tweaks was to install the Pink versus the Yellow (I think) CAT-code plug. Doing that richened up the fuel to air mix slightly. So I rushed to the dealer to buy the $17 plug. Only to find out when I got home with it, I had no plug at all and no where to put it. So it is resting for 19 years in my parts stash.

That must have been a pain at the time. I have read other places about the units shipped with cats not having sockets for the plugs. In that case I believe that the three pins on the Motronic are hard coded in the wiring harness.

I've read a lot of what Rob wrote, and have been through the coding plug intake tubes stuff a couple times. The one thing I'll say is that Rob's work was hamstrung by the lack of datalogging tools. I've tested different plugs and logged the AFRs on my 1150. I couldn't find anything that would fuel any richer than the pink plug. Even if I could, closed loop adaptation would negate the changes. An active oxygen sensor makes these Motronics very stubborn and brings them back to 14.7. On the 1100s the situation is different. I believe that the beige plug and no plug run an open loop fueling pattern.
 
+1 on the Booster Plug--just installed one this morning and I have to say that I would not have recognized my bike. No more surge, much more power, smoother idle. a great machine before, wonderful now(1994R1100RS with catalytic converter)
Tony

Glad the test worked out. It's been my experience through measurement that the effects of the BoosterPlug get adapted away over time by the Motronic. I can't say for sure that every model does because I only have data from 1150s and 1200s. The effect can be made permanent in a couple different ways: pull the O2 and go Open Loop or shift lambda by, for example, adding a Wideband O2.
 
My 99RT was a terrible surger even after tedious careful tuneups. 1st generation Techlusoin in open loop, O2 sensor disconnected made a huge difference. I sold it to a friend and let the Techlusion go with the bike.
2001 RS, a mild surger but not bad. I knew the Techlusion would make it go away completely so that's what I did. By then it they had a version with factory plugs so no wire splicing to install. Like the first one I ran it in open loop mode with the O2 sensor disconnected. It's been trouble free for 10 years. It also has GS tubes (can you say honk!) and 90 fewer pounds than the RT. Runs strong, runs smooth, I love it! TB's still good, no ticking or sync issues. Best BMW I've ever had.
 
Here is a surging candidate that wjg04oh found the other day. While riding with an AFR gauge he noticed that his motorcycle (which has an LC-1 installed), was running Open Loop and leaner than Closed Loop above 3500 RPM in first, second and third gear. After he posted it I tried the same thing and got the same results.

Because we are both running our Closed Loop 6% richer than stock, the AFR we recorded was in the vicinity of 14.4/6:1. If we had been running with a stock O2 sensor that would have been a very lean 15.3:1 and with some cylinder fueling/air mismatch, which is inevitable, it might reach 16:1.

Because Wally noticed this, I think we now have a very clear data point showing that stock bikes at 4000 RPM and above, at small throttle angles (1st, 2nd, 3rd gears, level terrain), exhibit very lean fueling, and could easily be prone to stumbling or surging in those conditions.

To me, this is an exciting finding, certainly not anything I expected. Here is a graph showing the leaner than Closed Loop fueling on my R1150RT.

fisrtsecondsurge.jpg
 
Sent injectors from my '04RT to RC engineering for cleaning today. I want to really find out just how good my 1150 will run after I installed the LC-1. Wasn't going to bother with injector cleaning and balance check but I think this should be done especially if you use an LC-1 wideband sensor.
 
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