BMW R1200R R1150R/T F800 K1200R R1100R/T R1250R RnineT Message Board

I ran a K&N for a couple of years on an 04 1150 R. I never noticed any performance gains but mileage suffered and the bike tended to run hot in warm weather. I have since switched back to the stock air filter and the bike is its old pleasant self again. Just one man's experiences yours may be different.................tkm

There's a lot of talk about the benefit of replacing the filter.

In any case, I'll agree with you that just the filter will not do much for performance, however making
access to cold air easier does improve engine performance. This would require more than just the filter.

Many will argue that oil filters are not as good filtering out smaller particles, and that they
require more servicing more ofter, and I'll agree on both arguments...
However paper filters also change their characteristics and ability to filter on very humid and hot
climates, and smaller particles may very well be burned and ejected along with the exhaust...

Both filtering methods have their downside, what is best ? I don't know, there are many variables to
what is best ! What is best to a rider in Riyadh where it is very dry and dusty and a rider in Bangkok
where is incredibly humid ???

Anyway, this is my first K&N, I also had the intakes of my R replaced and I personally did see an increase
of performance, will I stick to K&N or go back to paper filters ? I don't know, I'll make the decision after
the first filter service...

D.

tkm wrote:I ran a K&N for a couple of years on an 04 1150 R. I never noticed any performance gains but mileage suffered and the bike tended to run hot in warm weather. I have since switched back to the stock air filter and the bike is its old pleasant self again. Just one man's experiences yours may be different.................tkm

In layman's terms

A filter has two basic functions, allows passage of air (in the case of his post) and removes particles that if allowed to reach the cylinder can potentially affect the durability of the engine.

I underlined can potentially, because that is the critical parameter. In the racing and performance circles it is a well known fact that the K&N filters flow significantly better than most, likewise, realize that in racing typically two things take place A) Obtaining maximum perfromance from the engine and B) The engines get rebuilt fairly often.

In addition to that we also have to take into consideration the use and conditions that a filter will be in use. For instance, let's say that we will be using the filter on a 30K engine durability study where the engine is on a dyno, in a clean room, as opposed to the same study in the sand storms of the Sahara desert. Yes, the thought is quite extreme but allows for a clear picture.

So what is the answer:

The installation of a K&N filter in our bikes, everything else the same, will allow a bit more air into the engine, the O2 sensor will detect the added O2 and signal the ECU to enrich the mixture, within a built in range. All of this takes place while the engine is operating in the closed loop mode or when the O2 sensor is in the loop. Mind you that ino enrichment whatsoever will take place while the ECU is in the open loop mode (when a significant load is applied to the engine, like a brisk throttle opening) since in the open loop the A/F curve is pre-selected and the O2 is out of the circuit.

On the filtering end, the durability of your engine will depend on how dirty is the environment you ride and that is for you to invstigate and decide what filter to use. Everytime I looked into my filter box I found all kinds of insect parts, sand and smallish rocks, but I live and ride the trashiest and filthiest roads in Louisiana.

Enjoy.......