modified k1100rs running lean

[GWK11RS]

Hi, Guys been a member for a while but this is my first post. I have a 96 k1100rs SE that I have done alot of work too, I put in a 3 row radiator, new fan, thermo switch to turn on fan sooner plus switch to turn on when I like,170 degree thermostat ( now runs at first long line above blue aria on gauge. Know for my problem I modified the engine with k1200rs cams (284 degree duration, 8.85mm lift) k1200 throttle bodies (38mm instead of k11 35mm) k1200 fuel rail( witch move the regulator and fuel lines away from the heat of the motor and radiator),and a 3 bar regulator from a r1150rs(k1100 reg. is 2.5 bar)the motor runs alot stronger from idle to 6000 rpm then seems to go flat, the fuel mileage went up from 48 to 50 mpg to 50 to 55 mpg. This is telling me that it leaned the fuel mixture out, and I was wondering if I put the k1200 fuel reg.(3.5 bar) if that would richen the mixture up where it belongs. Any help would be appreciated, Thank You.

[Scott_]

My 1st thought is if you are still running the original Motronic injector control, it is still running the "program" for an 1100: injector pulse time and such.......
Granted I don't totally understand how all the engine electronics fuction.
You are getting more air in/out of the motor with the 1200 TB's and the cams, but not an increase of fuel.
I don't know if increasing the fuel pressure will help the situation or not.
If fuel pressure is an issue, I'm supprised that the 1200 injector rail is working with the lower pressure of the 1100 system.

Would the fuel pump of the 1100 have enough pressure to start with?

I suppose as an experiment it would be cheaper to try the 1200 presure regulator than to try and fit the 1200 FI computer controller.

[CubPilot]

The only thing higher pressure is going to effect is the spray pattern.  Pressure does not control volume. You need to modify the ECU so that the injector pulse width (the time the pintle is off its seat) is greater.   One of the Electronics Gooroos on here might know if this can be done by re-programming or if the whole unit has to be changed out. There are some real electron brainiacs on here, one of them is sure to jump in.

[Rick G]

AS CubPilot says there is no real advantage to a pressure increase, you may get a very marginal increase but only in the .1% range.
You are getting into very complicated territory with a bosch system as the programing can't be changed easily without very overpriced software. All the manfacturers spend thousands of hours on rolling road dynos to get things right.
My suggestion if you want to get real serious about this is to investigat "MegaSquirt" injection. Google it the possibilties are endless with that gear.

[GWK11RS]

Thank you for the help. In my search for info before I did the change, I found that the k11 and the k12 have the same part # injectors and fuel pump. The only thing I saw that was different is the fuel pressure( k11 2.5 bars, k12 3.5 bars). I couldn't come up with any info about the motronics and if the k12 computer controller would plug into the k11's wiring harness or what I could change to make k12 motronics work. Oh I for got to mention in the first post the bike also has a Remus exhaust too. The pulse width is starting to make more sense to me know, so my next question is does any one know if the two motronics are interchangeable.

[wmax351]

The only thing higher pressure is going to effect is the spray pattern.  Pressure does not control volume. You need to modify the ECU so that the injector pulse width (the time the pintle is off its seat) is greater.   One of the Electronics Gooroos on here might know if this can be done by re-programming or if the whole unit has to be changed out. There are some real electron brainiacs on here, one of them is sure to jump in.

Fuel pressure does affect flow, as well as spray pattern.

The K12 and K11 should have a closed loop fuel injection system, with an O2 sensor. The ecu automatically adjusts the mixture. Increasing the pressure will only temporarily adjust the fuel mixture, before the ecu compensates.

In terms of motronic, I believe the motronic systems use an alpha-N or pressure density computation for airflow, rather than a Mass Air Flow (MAF) sensor. That means they calculate the air flow with the manifold pressure and throttle position.

That being said, altering the throttle bodies will drastically change the fuel mixture, hence the lean condition. The pulse widths aren't the issue, the amount of air the computer thinks is being taken in is.

Your best bet may be to install a megasquirt system, which is an easy install on the K11/K12. Then you can make your own fuel map.

You could try the K12 motronic. It may or may not work. The airflow is what matters. The displacement is secondary to that.

You may just want to go back to the K11 intakes. Unless you really know what you are doing, leave it to the engineers.

[frankenduck]

I've never understood why people want to put in lower temp thermostats and run the engine at a lower temp then it was designed for.

[Rick G]

I've never understood why people want to put in lower temp thermostats and run the engine at a lower temp then it was designed for.

big +1 on that

[wmax351]

I've never understood why people want to put in lower temp thermostats and run the engine at a lower temp then it was designed for.

big +1 on that

Big +1 on that as well. The engine runs BETTER at higher temperatures. The hot intake ports vaporize the fuel, which is why the choke/enrichment is needed at cold startup.

[GWK11RS]

I have found in all my year of tuning engines for best performance excess heat was always a power loss. My drag car will always run quicker when the temp is between 100 to160 degrees then at 180 or higher. My 1980 Honda CBX 6 cylinder( witch I have owned for 30+ years) drops power worse then the drag car the hotter it gets. 200 + degree temps in today's vehicles is more for emissions then the good of the engine, the CBX goes through more oil the hotter it runs, the K11 was using a quart of oil every 300 to 400 miles last summer at 200 degrees and was real uncomfortable to ride in hot weather and traffic. So far this year since all the mods I did over the winter the bike has used about 1/4 of quart of oil in a 1000 to 1100 miles and is alot more comfortable to ride even in traffic.

[frankenduck]

So, what thermostat did you use? (Brand, part number.)

[Rick G]

IMO if you are using a 1/4 quart of oil in 1100 miles then the engine has problems. I have been running these bricks for 10 years and never do they use more than maybe 1 pint fot 5-6000 Kilometers. If they use more then there is a problem.
As for keeping temps down in your drag car thats fine because engine life isn't exactly the prime purpose of the exercise.

[frankenduck]

According to the BMW K1100 Service Manual the permissible oil consumption is 1,875 miles per gallon of oil.  That works out to a quart every 470 miles.  :eek: (Which of course is ridiculous.)

It seems to vary by bike (individual bike, not type) but on the Ks I've owned they generally burn a quart roughly every 2,500-4,000 miles.

[GWK11RS]

The thermostat I used is a beck/arnley part # 143-0793, 170 degree, for a 94 toyota corolla with 1.6 liter engine. back before catalytic converters most manufacturers recommended 195 stats in winter for better heat and 160 stats in summer. Like I said before, running these engines at 200 to 230 degrees is for the emissions and the cat. But that is my opinion and the way I like to run any engine I have that does not have to pass emissions tests. Every one else has there own opinion, I won't change mine and I don't expect any one else to change there's because thats what makes us all different.  P.S. I would still like to know if a k1200rs motronic MA2.4 will go in inplace of the k1100rs MA2.2 motronic or do you have to rewire the bike for that change.

[frankenduck]

Just an FYI but that same t-stat was used in the initial  83 K100s - long before BMW introduced cats on bikes.

[frankenduck]

P.S. I would still like to know if a k1200rs motronic MA2.4 will go in inplace of the k1100rs MA2.2 motronic or do you have to rewire the bike for that change.

You'd probably want to look at the pinouts, compare sensors, etc... to determine Moronic compatibility.

Not directly related but as an example when I put a K1100 ABS I brain on my K75 to run a K1100 ABS front end, all I had to do was move a wire from one of the pins to another (main power to the ABS controller) in the wiring harness connector to get it working properly.

[wmax351]

The thermostat I used is a beck/arnley part # 143-0793, 170 degree, for a 94 toyota corolla with 1.6 liter engine. back before catalytic converters most manufacturers recommended 195 stats in winter for better heat and 160 stats in summer. Like I said before, running these engines at 200 to 230 degrees is for the emissions and the cat. But that is my opinion and the way I like to run any engine I have that does not have to pass emissions tests. Every one else has there own opinion, I won't change mine and I don't expect any one else to change there's because thats what makes us all different.  P.S. I would still like to know if a k1200rs motronic MA2.4 will go in inplace of the k1100rs MA2.2 motronic or do you have to rewire the bike for that change.

Its all about design. What an engine is designed for is what you want. Higher temeperatures get better atomization and vaporization of the fuel.

My race team (berkeley Formula SAE) usually run our car at about 220* (on plain water in a 2.5 bar radiator cap). Its a gsxr600, modified with custom fuel injection and manifold. We have a lower temperature thermostat than that, but the temperature goes where it goes, and we want it to go to these temps.

There are many factors in the temperature. Oil flow, viscocity, clearances, etc. The fact that it uses that much oil at normal temperatures is bad. Cooling it down only affects the block, not the pistons. That causes a differential expansion, making the pistons a tighter fit on the cylinder, which prevents some oil leakage, at the expense of wear. This is part of the reason why running engines cold does extra wear; clearances aren't what they are supposed to be.