Airbox delete on a 4v k100, understanding

[Rubachabra]

I tried searching the forum for any information regarding the airbox and found some information but i am still a bit confused about what i met when i disassembled mine in hopes of getting rid of the whole box

Would appreciate any explanation of what these various labelled tubes/parts are intended for. I am just a hobby mechanic so my technical insight is limited, my plan was to get rid of the entire unit and have the air temperature sensor mounted in one of the 4 tubes leading into the throttlebody

I labelled the connections/unit i dont understand with 1-4

English is my 2nd language, so certain technical words and abbreviation might be difficult to understand. Sorry about that. Would appreciate any help on the matter :)

[frankenduck]

If you right click on the images at your links and select "Copy image address" then you use the leftmost box above under the "B" above to insert the URL of the image.

For example, the URL for your first pic is https://i.ibb.co/6s11ryP/image3.jpg

[Rubachabra]

If you right click on the images at your links and select "Copy image address" then you use the leftmost box above under the "B" above to insert the URL of the image.

For example, the URL for your first pic is https://i.ibb.co/6s11ryP/image3.jpg
 

Thanks! :)

[Scott_]

In response to your questions.... the items you have numbered are for Emissions "oil recovery" of the engine vapors.
It's call a "cyclonic oil separator"

As the engine is running the crank case is intended to be in a "vacuum" state or negative pressure.
#1 is the filter media. usually garbage by now due to age.
#3 is the inlet to the media chamber #1.
#2 is the outlet of filtered air to the throttle bodies to be burned in the engine.
#4 is the oil return line back to the engine block.

Air is drawn from #3 into #1, and out #2 with the separated oil returned thru #4.

I've bypassed mine years ago.
Cap #4 at the engine block, connect #2 to #3 with a PCV(Positive Crankcase Ventilation Valve) valve and be done. Similar to what is done with automobile engines minus the filter.

 

[Rubachabra]

In response to your questions.... the items you have numbered are for Emissions "oil recovery" of the engine vapors.
It's call a "cyclonic oil separator"

As the engine is running the crank case is intended to be in a "vacuum" state or negative pressure.
#1 is the filter media. usually garbage by now due to age.
#3 is the inlet to the media chamber #1.
#2 is the outlet of filtered air to the throttle bodies to be burned in the engine.
#4 is the oil return line back to the engine block.

Air is drawn from #3 into #1, and out #2 with the separated oil returned thru #4.

I've bypassed mine years ago.
Cap #4 at the engine block, connect #2 to #3 with a PCV(Positive Crankcase Ventilation Valve) valve and be done. Similar to what is done with automobile engines minus the filter.

Thank you! This is the first time i've ever heard/learned about blowby/crankcase gas.

Just curious. Since there was an oil recovery system, i assume that there is some oil that follows the blowby gas. Does that trickle of oil just go straight into the air intake after this bypass?

Does the engine need any filtered air intake to avoid a vacume building in the crankcase? I am just watching some videos on the concept of PCV and in it the guy was talking about the crankcase needing ventilation

Can you use any PCV valve, or does the resistance in the valve have to fit the engine? (might be a silly question)

[Reinier]

I also want to remove the airbox from my K1100 and have the same questions.

Can you use any PCV value.
What are the specs of the valve on your bike ?

And would it be a good idea to install an oil catch can  before the valve ?

[Reinier]

Also in het original system the breaterhose goes into the cyclonic seperator that has 2 exits. 1 to the throttle bodies and 1 to the engine for oil return. And the Cyclonic seperator is basically a box with a sponge in it.

No pressure regulation at all.

So why do you need a PCV valve when you remove the separator ??

What am I missing.

[sooprvylyn]

You don't need a valve, you just need something that will prevent unfiltered air somehow getting back into the crankcase.
 I would recommend a small catch can though before whatever filter you attach as enough oil does escape the breather that it will get on stuff over time.

[Reinier]

Would it de a good idea to connect the crankcase breather hose to a catch can and the the air exit of the catch can to the air return hose of the Cyclonic separator ?
And maybe connect the drain of the catch can with the oil return ?

Basically replacing the cyclonic seperator with a catch can.
Then i should not need a filter And i will have a maintenance free system.

[Laitch]

You don't need a valve, you just need something that will prevent unfiltered air somehow getting back into the crankcase.
 I would recommend a small catch can though before whatever filter you attach as enough oil does escape the breather that it will get on stuff over time.

Can you describe your system, soopr?

[sooprvylyn]

Currently I just have a 15mm cone filter attached to the breather vent....and this is how I know you should install a catch can. Some oil is definitely expelled with the gases from the crankcase. It's not a ton, but it's enough that after several  rides you'll have some oil around the breather vent. My cone filter absorbed most of it for a while before I noticed it on the back of the engine block

I've been putting off dealing w it owing to lack of a good mounting location for the catch can, but i recently discovered sendcutsend to make custom brackets. My plan is to attach an oil catch can to it and again a small filter on the output.  In fact this post made me decide to get it dealt with so I've ordered a catch can today and will get a bracket made for it.

There is no need for any valve, but I do think at least putting a filter on it to prevent any potential particles from entering, and especially insects from deciding to make it their home .

This thing is really just emissions control.  The only thing that happens when it's disconnected from the intake system is that some oil and small.amount of unburnt fuel may enter the environment. Once i install the catch can ill reduce that a little. The bike will run just fine with literally nothing connected to the breather vent(til something gets into the case from that opening).
 

[sooprvylyn]

Would it de a good idea to connect the crankcase breather hose to a catch can and the the air exit of the catch can to the air return hose of the Cyclonic separator ?
And maybe connect the drain of the catch can with the oil return ?

Basically replacing the cyclonic seperator with a catch can.
Then i should not need a filter And i will have a maintenance free system.

Yes, if you want a totally maintenance free setup and are worried about emissions. You wouldn't need to empty the can very often. In a year I've had less than half an oz of oil come out the vent...probably around 5000 miles or so since I only ride 3-4 days/mo

If you aren't too worried about emptying the can once every year or 2, and you aren't that concerned about the relatively small amount of unburnt fuel escaping the system, then you can just vent it to a filter

[sooprvylyn]

Btw, if you are feeding the output back into the intake, you MAY want a pcv valve between the breather vent and the intake so the intake isn't pushing air back into the crank case.  If you vent out to the environment you don't need a pcv valve.

[Reinier]

Thanks sooprvylyn, great info.
Ik dit not think of the pushback from the intake.
Once or twice a year emptying the can I can handle.
I have seen catch cans that come with a small pod filter.

I do like the environment, but if I would be serious about it I would not be riding a bike from 1993.

And in Holland the emissions checks are on cars not on bikes

[Reinier]

I found this: Ik heb net dit geweldige item op AliExpress gevonden. Bekijk het nu!
€24,88 | Universele Auto Olie Opvang Kan Reservoir Tank Met Luchtfilter Slang Schoner Brandstofval Reservoir Auto Voertuig Collector Ketel
https://a.aliexpress.com/_EvVnkNr

It has the baffels and a metal wire ball ( instead of original  the BMW sponge ) that does not decay.
With the filter it can be installed pre pcv. And when I do not want to return anything to the engine I guess I'll just blick the outlet port.

When I later decide that does not work I can still a PCV value and connect to the throttle bodies.

I also like that it has a dipstick so no need to open it to check the level.

[Reinier]

Dear Laitch,
You are right I do not fully understand the workings of the cyclonic seperator. That is why I am asking questions.
There is little information to be found on the internet and what is there is inconsistent.
There are lot's of pictures of K's with pod filters but hardly any mention of what to do with the tubes connected to the airbox. Your link is a goed example, it tells that the airbox will be replaced by pods but not how.
There are even airbox delete kits available in professional stores but they also have no mention of what to do with the seperator.
Instead of rushing into this I am asking questions. Sees like a good idea.
And I like to hear from people who have already done this instead of just theories.

And as far as I know in the original setup there is no pcv valve on a K1100. So why is it needed when you replace the original device to seperate fumes from oil with another ?

And how would to much pressure buildup occure in an atmospheric ventilated system ? Does the filter create the pressure ?

And if the pressure can not be fully releaved through the filter should the output port then be connected to the throttle bodies?

[Reinier]

Thanks for the video.
That guy actually says that Honda has 2 solutions for the breaterhose. One of them being a tank to collect the crap.

If that tank would be sealed it would still have the same compression issue so I am assuming it is vented.

He does not say it in so many words, but that sounds like an oil catch can to me.
And exactly the solution I proposed.

Please explain what the difference is between his and my solution

[sooprvylyn]

Thanks for the video.
That guy actually says that Honda has 2 solutions for the breaterhose. One of them being a tank to collect the crap.

If that tank would be sealed it would still have the same compression issue so I am assuming it is vented.

He does not say it in so many words, but that sounds like an oil catch can to me.
And exactly the solution I proposed.

Please explain what the difference is between his and my solution

Yes, catch cans are vented, and they are specifically made for this exact purpose.

[sooprvylyn]

Catch cans are specifically designed for crankcase breather aspiration. There are 2 types, and often there are catch cans that can be converted between the 2..like the picture below.

There us an inlet where the crankcase gases go from the breather vent. Those gasses pass through a screen/filter which pulls the oil from the vented gas. Then there is either an outlet that you connect to the intake to recycle the gasses(emissions correct), or there is a vent to the atmosphere(won't pass emissions). You run one or the other. Either you remove and plug the cone filter and vent to intake, or you plug the output port and leave the cone filter on to vent to the atmosphere.

Inside the oem airbox was a similar device that pulled the oil out of the vented gases before recycling it.


100% the oil catch can must be vented or you will have the problems laitch mentioned.

[Reinier]

I said there is very little information on BMW K bikes cyclonic seperator on the internet. Like the exact inner workings.

And I do know how crankcase breather works.

That is why I don't understand why so often people introduce a PCV valve in the system when the cyclonic seperator is replaced by a catch can. With the information I have my conclusion is they are basically the same.

And did you Notice the information in your videos is conflicting ?
The first video says the a filter direct on you breather is slowly killing your bike. The second says that it is a perfectly good solution.

I never said anything about how I am going to place the pod filters. I got that part figured out. There is plenty of information on that subject.

An additional reason to do this mod is that the original BMW solution can not be maintained. The seperator can not be opened without cutting. And they placed a sponge inside. After 30 years that has decayed and the only place it can go is into the engine.
A good reason to replace it.

My question was very specific for the setup on a 30 years old BMW.

[Reinier]

By the way in the link of how you think it should be done the location of the pods is open for discussion.
They are placed in a straight line directly behind the radiator.
Which means you are blowing hot air over your air intake.
This is not optimal for performance.

[sooprvylyn]

The reason people say to include a pcv valve when using a catch can is because there is more potential for backpressure in a system that ain't stock. The stock system uses a tube with small ports that feed the back of the throttle bodies, and a bigger passage to the cyclonic separator. The small ports act on venturi principle so that backpressure will not pass thro those small ports as easily as it will the throttle bodies opening on full throttle.  The cyclonic separator is basically just an alternative to the catch can that bmw chose as it works well with what they designed and its self draining.

If you delete the airbox, you have a choice of venting breather back to the engine, or to the environment. The oil catch can can be used in either case, tho it's not technically called a catch can when it vents back to the engine.  If you vent it back to the engine thro the intake, you will need a pcv valve IF  there is any potential for backpressure  overcoming the breather and causing pressure buildup in the crankcase.

Do NOT block rhe breather of course.

Apologies to Laitch for my misunderstanding of what he was saying earlier. 

[sooprvylyn]

By the way in the link of how you think it should be done the location of the pods is open for discussion.
They are placed in a straight line directly behind the radiator.
Which means you are blowing hot air over your air intake.
This is not optimal for performance.

It's not so directly behind the radiator, the pods get pretty fresh air directly above the throttle body.  If there is concern you can get angled pods.  I haven't had any performance issues with my straight up pods

[Reinier]

That looks nice.
I was actually looking at a set of angled K&N filters.

I will try the catch can with a filter on top to ventilated.
This will reduce a lot of tubing making a cleaner instal.

Ventilating a bit is ok, my main goal is getting rid of the airbox and the only mess on top off the engine. Which probably means that some of those tubes are leaking. And replacing those special BMW tubes can get expensive.

This will probably be my winter project. At the moment enjoying driving after changing all controls dash and creating a totally new wiring harness.

[Laitch]

I never said anything about how I am going to place the pod filters.

You are correct. In English, the word if implies uncertainty, or the introduction of a hypothetical situation. Regardless, it appears your introduction to crankcase ventilation is complete. Scott's post explains just about all that's necessary to know about the cyclonic separator, especially considering its likely to be heading to the trash bin during your build.
 
Please post photos of your progress. Good luck with your build!