Muffler Removal - a Definitive Answer (finally!)

[DAQ421]

After reading this and other threads I pulled the muffler today. I love the way it sounds. I bolted on a cheap Walmart tip for looks and to carry the exhaust well past my boot.

[riceburner]

However, I am still wondering if I need to put the CCP back in so that the O2 sensor can do its job?

Bob,
As I understand it, removing the CCP effectively changes the emissions control system from a closed-loop to an open-loop type. Therefore the cat con and O2 sensor is not doing quite the same job as before. In that case I'd say all bets are off - the cat con will not behave as Chris described above, and perhaps a muffler will be required.

I thought the CCP was merely a re-map chip to change settings that are used in the control of the fuel flow - NOT a vital part of the puzzle. Certainly I know for a fact that my 3 Rocksters have never been fitted with one. (First 2 were bought new, 3rd one was bought with 1200 miles on the clock and barely used).

[riceburner]

Can anyone answer if the o2 sensor still working even if you remove the CPP?
For me have sense what I read that the motonic uses the euro map when you remove the CPP and the only way to have the system working in a open loop mode is removing the o2 sensor.
I have a 2004 R1150R Rockster with K&N air filter and Y-pipe with stock can, the bike run fine when is cold, no surging, no popping nor backfire, but when the bike gets hot is terrible, very bad engine noise, popping, shake, etc...
The bike came with no CPP plug since new
If the 02 still working, I will try the techlusion 259
Please help...real answers... no especulations.....

I'd advise against running the bike like that. The exhaust heat will be trapped in the can and concentrated - making the gas exiting the can even hotter than it would be from a 'straight-through' can. It's hot enough to melt the pannier plastics.

http://www.flickr.com/photos/rockburner/6388779857/

[DAQ421]

I think I am enjoying the response of others as much as the new better noise.. Some people are just sure that a muffler is "required" and nothing will dissuade them. My response is "then buy an aftermarket pipe"..

[DAQ421]

priapismic's post serves well the saga regarding removal of the muffler and potential damage to the engine via added heat, et. al.

From my perspective I feel that it is important to understand, in a simplistic way, what is taking place.

First and foremost, in the oilheads we have a very rudimentary FI and lambda system. The O2 sensor is of the "narrow" band, read one of the first versions, albeit heated. It also inexpensive, if you ever have to replace it (recommended at 60K miles as it becomes sluggish) buy the Bosch standard part and splice the wires to keep the BMW plug. ($40 to $60)

Second, close loop is a term coined from the EPA testing of emissions where the vehicles are tested under laboratory conditions and the emissions tests are run at idle and cruise, read, steady state conditions, obviously nothing reflecting real time operation of the vehicle. As such the effect of the O2 sensor can only be had under these conditions.....read, steady state operation. Under such the ECU with the signal from the O2 sensor will try to get as close as possible to the 14.7/1 A/F ratio and I say as close because you have to factor in the proper operation of the engine.

Remember the basics of internal combustion.....a leaner the mixture, within reason, will produce the best mileage, along with increased combustion chamber temperature and potential rough running, surging, as the result of reduced fuel energy.

This is where the mysterious CCP comes in. Most US bikes have been equipped with the ill fated yellow plug, however, it is a well known fact US fuels are inferior to the European blends. The purpose of the CCP is to have the O2 sensor operational during the idle and cruising phases. On the other hand a fair amount of US bikes have been prey of the feared "surging" at cruise speeds, i.e. small throttle openings, because the O2 sensor is trying to get the A/F ratio in the lean range to improve mileage. A very common practice, by some of the savvy BMW Tech's was to remove and discard the CCP when the owner came in and complained about surging and in most cases this eliminated the surging.

With the removal of the CCP plug, the engine sees what is referred to as the "open loop" fuel map during all phases of operation The open loop A/F map is tuned for a slightly richer mixture, at the expense of fuel consumption and in general the engine operates better and has a crispier response. (This is a very basic explanation)

So now, let’s go to the pressure waves in the exhaust in the presence of a slight back pressure (read pressure that is induced by the length of the exhaust and the diameter of the pipes/components) that have a positive effect in the filling of the cylinder during the intake portion of the 4 cycle as it creates a vacuum that improves the filling of the cylinder and hence more power.

With the advent of the cat, the muffler ceased to be the element with the greatest pressure drop as the cat took over this function. If you were to tap the exhaust to take pressure readings, just before the cat, between the cat and the muffler and compare it to atmospheric pressure you would see that the greatest pressure or restriction is between the exhaust valve and the entrance to the cat.

Also take note that the O2 sensor is at the entrance of the cat to measure the amount of unburned O2 in relation to the standard 21% that is present in the atmosphere. So any change in the A/F ratio is done based on what is seen at the intake of the cat, this is done to insure the longevity of the cat, because they do have a finite life as the catalyst is consumed

So let us review:

• The O2 sensor in the oilheads only controls the A/F ratio at idle and cruise (inexpensive and slow response)
• For the O2 sensor to operate the yellow CCP (US bikes) will have to be in place
• BMW Techs have been known to remove the CCP (quietly) to assist with customer surging complaints
• The A/F map without the CCP is a bit richer in the idle/cruise conditions
• The cat converter is the major back pressure component in the exhaust and being placed ahead of the muffler it reduces the muffler contribution significantly.
• There is no damage that can become the engine via heat or otherwise by removal of the muffler....we identify with mufflers and expect a muffler. Besides what better way to remove 10+ pounds from the bike and look at that open wheel.

The mileage issue increase or decrease is very debatable and with everything equal, state of tune, operation and combustible, if there is a +/- change it should be very, very slight. With the CCP off there should be a slight mileage loss, everything else the same.

Well, this post is one of the reasons that I love this forum. My 04' does not have the CCP and as such I was, after reading what that meant on other forums and coming away still unclear on it all, looking at reinstalling my stock muffler. However, upon rereading this post I think I will leave it off for a tank (or two) of gas and see how she runs..

-Peter