2 valve K100 airbox and MAF sensor delete. [Guide]

[Kaos]

You're, like many have before you, looking to delete your airbox.
Now therse a difference between Deleting the airbox and keeping the MAF sensor, which is the cheaper option and deleting the airbox, MAF sensor and the plenum chamber.
On beforehand i want to state I am not a mechanic, and there there might be.a design flaw that i have missed.
Also for this conversion I strongly recommend using a motogadget M-unit.

More warnings: this is quite a costly conversion, even when buying boneyard parts. Also your fuel consumption will increase. But hey, everything for the looks. BUT! Your bike will also have more "pzaz" when opening the throttle.
So all and all, its worth it.

Shopping list (mandatory)
°Motronic ECU v.2.1 or v2.2 and their corresponding wiring harnass.
Using the v2.1 requires you to also have an idle sensor and start module.
In CA(?) i believe also an output sensor for your exhaust [not sure]
°K1100 throttle body and Throttle position sensor.
For the podfilters you can use any kit on the market for the K1100 with 31mm filters
°4 valve k model ignition coils and sparkplug cables
You still need your 2valve sparkplugs but they most likely will need caps
°filter for the carter outlet
- important your bike will smell because of this. Usually the carter output gets led into the engine.
°4 valve k-bike airtemp sensor
This usually gets Installed by poking it into one of the pod filters or their installment tube.
°motogadget m-unit
- its not mandatory but it makes your life easier
° rubber vaccum seals that close of your throttle body +and install them on the k1100 throttle body gasoline inlet
° you will still need the k100 2 valve fuel pressure regulator (connected as on the k100) also known as the fuel pressure regulator.
° keep your throttle body engine mounting bodies.
° hall giver/sensor is the same on the k75, 100's and 1100.
[Recommended]
°4 valve coulant temp sensor
° longer throttle cable
° flathead allan key screw to replace the bolt under your throttle body lever
°you DO NOT have to replace your injectors if your current ones are working properly.

[Wiring the hardware]
Its straight forward, basically everything is plug and play as installed on your k100
Just pay attention to the afore mentioned fuel pressure regulator part information.

And here is the wiring diagram:
It also contains the parts needed.

Good luck converting and show your results underneath
And or do feel free to ask questions.

[Kaos]

Later ill make some time to provide all oem part numbers.

Update: I lied, I am way too lazy to do so.

[nlebi]

Hi there, impressive project! The quality of the diagram is very low, to an unreadable level ; could you maybe reupload it in a better quality? I'm currently in a similar process :D Cheers !

[Kaos]

Hi there, impressive project! The quality of the diagram is very low, to an unreadable level ; could you maybe reupload it in a better quality? I'm currently in a similar process :D Cheers !

Thanks for the compliment.
I've converted the image to a PDF, hopefully the doc wont compress too much.
if you have any struggles or questions, shoot me a DM. Explaining in Dutch could be easier.

[nlebi]

The conversion worked fantastic thanks! I'll let you know if I have further questions, I don't mind staying in English however, my Dutch is alright after living in Holland for 6 years but I have little experience in technical topis 

[Laitch]

I've converted the image to a PDF, hopefully the doc wont compress too much.

[Kaos]

 

[Swingmanu]

Hi all, new to this forum and to the BMW K family. I was donated a K75 that i want to turn into a dream bike :
Currently it’s in pieces and i plan on doing rear suspension modification, possibly front end swap and i was very curious about the MAF delete.
Some people say it’s impossible to get rid of it on a 8v K75. Then again i thought wouldn’t a resistor telling what to do based on the bike revolution be enough? I know it’s done in cars.

I wanted to ask if your modification would work for my bike ?

Again, new to this, trying to search as much as i can but this post seems pretty on the spot and last comment is recent so i hope getting some feedback.
Thanks

[Kaos]

It took me a while figure it out for a k100 and get it right.

for a k75 i would have to research the options. As it fires all 3  cylinders seperatly over 3 bobines where the k100 does not.
Which gave me the option to use 4v bobines. 
So timing comes in to play.
When I think of that it would rule out using the 4v ecu's as they fire 2 cylinders in sync leading to misfires in a k75.
Then there is the tps, which would either require modifying the throttle body of a 4v to a 3 cylinder input, which can be done. Or modifying the tps from a 4v to fit the TB of the k75.
So the biggest hurdle would be either the MAFS to it to respond to air temp with the current ECU, which require reprogramming and get resistances correct, or even a custom programmable ecu. They are out there, but then you're probably into it up to your neck. Or get a 4v ecu to have 3 seperate sparks instead of 2 in sync. Now at idle a k75 fires each cylinder at 0.12 seconds which increases with throttle, if you can manage that.. then yes.
So writing all this down, the complex answer is yes.
Investment and time wise, id say no.
BUT! Therse always the option to go for carbs. Which is also very sexy

[Laitch]

Then again i thought wouldn’t a resistor telling what to do based on the bike revolution be enough? I know it’s done in cars.
I wanted to ask if your modification would work for my bike ?

Based on your question and statement I've quoted above, my qualified response is No. You need more understanding and experience.

What you're asking, and what has been suggested might be done—using a 4-cylinder engine management system for a three cylinder engine—is the equivalent of human gender reassignment surgery in the corporeal world. It is a costly and complicated undertaking that will need plenty of support during and somewhat after completion. The degree of benefit is questionable. You'll need somebody to hold your hand through the entire process; Kaos is the perfect candidate for long-term support. Start using the site's personal message feature to lay the groundwork, then once the two of you are ready to begin, start a thread in the section below this area.

The suggestion to modify the Brick by removing the injection system and replacing it with carburetors is a more realistic and accessible goal. A few examples can be found; years ago, a conversion kit was available. Here is a recent example.

[Kaos]

Kaos is the perfect candidate for long-term support.

Well, yes. But actually no.

But as you managed state more eloquently "tips hat" than i managed to say,  carbs would be the best solution for this particular wish.

[Edit]
Or do what I failed to do, because this was a project of at the very least some determination. dare to lay it aside and build the dream bike with another base. I found out that what i wanted required a 4valve too late, and thus, this became the result. Now all the modifications you're planning to do can be done on other k's. Maybe your best bet lies within another model.

Otherwise. Yeah. Carbs is the safest choice.

[Swingmanu]

Thanks Laitch for taking the time. I absolutely need more understanding.
Again, i was gifted this bike and really want to make the most out of it.
I will be digging into this and maybe Kaos is right and another K model 16v would be ideal if i wanted to remove the carbs but i am not so convinced of doing it.
I rebuilt my CB750 the way i wanted it and didn’t install pods cause it runs so good the way it does with the air box.
For the K 75 i was simply very curious of the whole system. Maybe I let it be as is and focus on the bike’s geometry and esthétics.

Thanks again

[Kaos]

That is a wise decision.
And do keep in mind there are some absolute beautiful airbox replacements on the market that will also add to the aesthetics of the bike. From straightforward new, to 3d printed in colour of choice to carbon fibre. They could offer the finishing touch.
Also, open up a thread in the custom section to share your build, and or questions.