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jscottyk 11-14-2010 11:44 PM

Secondary Air System?
 
Does anyone have a diagram of the complete F800 secondary air system? Or a specific explanation of how it works on the F800 motor? I understand the principal of adding oxygen to the exhaust gases to make the for a more complete "burn off" of emissions, but I do not understand where on the F800 motor this extra air is being introduced in the exhaust system.

Anyone?

johngil 11-14-2010 11:49 PM

There is no SAS on the 800?

Of course, I've been wrong before. I'm an electrician, not a mechanic.

Is a SAS needed w/ fuel injection and a computer?

Lots of beer today...
Just asking out loud.

jscottyk 11-14-2010 11:57 PM

Hmm?

Check out hose #4 in the diagram in this post. It's my understanding that it leads to one of the SAS valves.

The Griz 11-15-2010 05:52 AM

The F800GS does not have a secondary air injection system.

Quote:


http://en.wikipedia.org/wiki/Seconda..._air_injection

Secondary air injection (commonly known as air injection, or colloquially smog pump) is a vehicle emissions control strategy introduced in 1966, wherein fresh air is injected into the exhaust stream to allow for a fuller combustion of exhaust gases. An implementation of the system has been trademarked by the name Air Injection Reactor (A.I.R.).
The hose you point to (#4) in your above post is in fact the crankcase breather hose that feeds into the throttle bodies. This is not a secondary air injection system. Basically what #4 is doing is that all of the gases from the crankcase are getting fed to the throttle bodies to be burned with the rest of the mix. This controls emissions of crankcase gases into the atmosphere. There are many ways a manufacturer can control emissions to get their bikes within EPA and Euro spec without the use of a secondary air injection system. This crankcase breather feed system is one of them. Another is the charcoal canister we find on the US (and some other country's) bikes. With this system, a vent hose from the gas tank is fed to a charcoal canister which stores the vented gasoline vapors. Then when the engine is started the stored vapors get sucked into the throttle bodies and burned with the rest of the mix. BMW uses both of these methods on the F650GS2 and F800GS, but not the secondary air injection system.

jscottyk 11-15-2010 07:40 AM

Thanks for the clarification. I think what is confusing me is hose #2 is shown on this diagram is listed as the crankcase breather. This is probably a semantics thing resulting from the German->English translation.

So, it looks like the #2 vents gases straight to the bottom of the airbox, while #4 goes through some sort of solenoid valve after first passing through a set of reed-valves in the cover (#5).

The Griz 11-15-2010 08:07 AM

Quote:

Originally Posted by jscottyk
Thanks for the clarification. I think what is confusing me is hose #2 is shown on this diagram is listed as the crankcase breather. This is probably a semantics thing resulting from the German->English translation.

So, it looks like the #2 vents gases straight to the bottom of the airbox, while #4 goes through some sort of solenoid valve after first passing through a set of reed-valves in the cover (#5).

They seem to both be crankcase breathers in some way. #2 is the crankcase breather hose if that is what is listed in the service manual. #4 might be some sort of supplement to the system??:dunno

jscottyk 11-15-2010 08:28 AM

Quote:

Originally Posted by The Griz
:dunno

Yep. Me too.

All the more confusing is the F650GS doesn't have the hose #4 or the reed valves.

dhillr 11-15-2010 08:53 AM

That looks exactly like the Air Switching Valve setup on the Air Suction System that I have on my '09 Concours....including the reed valves.... Manual is a bit vague but quick search found the explination below:

Air Swithing Valve (ASV) a valve in an air injection system that senses intake manifold vacuum and during heavy loads, dumps part of the air pump output to the air cleaner to reduce air injections system pressure.

Mine also connects to the airbox but I couldn't find a good flow diagram for the system.

Now I'm intrigued! Be sure to let us know what you find! :thumb

JoelWisman 11-15-2010 10:21 AM

Quote:

Originally Posted by jscottyk
Does anyone have a diagram of the complete F800 secondary air system? Or a specific explanation of how it work on the F800 motor? I understand the principal of adding oxygen to the exhaust gases to make the for a more complete "burn off" of emissions, but I do not understand where on the F8000 motor this extra air is being introduced in the exhaust system.

Anyone?

There is no diagram of the system I'm aware of on the publically available service DVD, or the dealer only RSD.

There is however a great video complete with animations at BMW university, a web site that's only available to BMW employees. I have no idea why BMW keeps stuff like this secret, but they do.

In any case, YES, at the least the USA variant of the F800GS does have what is commonly known as a "second air" system. The F650GS does NOT.

The system intake is through the right front corner of the air box, so it is filtered air that is injected when the system is operating.

Next up is an on off solenoid valve. This valve is mounted to the right front of the air box. It mounts from the bottom and is clearly visible from the top of the air box. Secondary air would confuse the oxygen sensor were it flowing all the time, so this solenoid valve is switched on by the engine management computer (BMW speak=BMSK) when desirable and off when accurate O2 sensor readings are desired. Some have complained about the click this valve makes, some are louder then others, I've never seen this valve fail, the BMSK has trouble codes to communicate if this valve is stuck open, stuck closed, or unhooked.

Next down the line is a reed valve. This valve is bolted to the valve cover. In essence it is a light weight high speed one way valve. This valve blocks the channel where second air is injected into the exhaust. One side of this reed valve has fresh filtered air at atmospheric pressure any time the second air solenoid is open. The other side has exhaust pressure. Exhaust pressure is not constant. Right as the cylinder exhaust valve opens, pressure goes up and exhaust accelerates through the exhaust system. Exhaust has mass, as the last of the exhaust leaves the cylinder, exhaust with mass is still flowing at high speed through the exhaust pipes. Since the cylinder is empty and exhaust valve closing, there is no longer any inlet to support continued flow and the exhaust begins slowing. The mass of the exhaust that was flowing forms a partial vacuum as it decelerates. This vacuum opens the reed valve and draws in secondary air. This action along with tuned air box, tuned header and exhaust, and secondary air inlet not only reduces emissions by adding more oxygen to promote afterburning, it improves volumetric efficiency and therefore horse power. This is why you will NEVER improve HP and runability through airbox mods, filter mods, header mods, or fancy slip ons. You may increase noise, or peak HP, but always at the cost of mid range torque. No aftermarket manufacture has the wads of cash or engineering brain power to design componants that work better then BMW original equipment.

NOTES: The factory optional Acropovic pipe was engineered by BMW and will improve HP extremely slightly while reducing weight and creating a pleasing exhaust note that drooled out most of the clicks and rattles from the noisy creaky 603 engine.

You CAN increase power some by screwing with the fuel mixture but emissions will go to hell and deposits will build up in the combustion chamber as well as in the exhaust and of course, the O2 sensor will plug.

END OF INFOMERCIAL, RESUMPTION OF SECOND AIR DESCRIPTION.

From the reed valve, the path of the second air circuit is through a channel in the valve cover into a channel in the head. For this purpose, there is a stand alone gasket between the valve cover and head. This gasket is entirely internal. If this gasket leakes, 2 things can happen. 1: exhaust pressure can enter the internal engine and raise crankcase pressure, likely leading to oil leaks. 2: oil can enter the second air circuit creating exhaust smoke and deposits in your exhaust system. For these reasons, this internal gasket should be replaced every time the valve cover is removed! Want to know if your dealer is adhering to this BMW reccomendation? Ask them if they stock this gasket the next time your in for a valve adjustment check. If they don't, I would politely decline to have your service completed untill they do stock this gasket. (note to self, check that my dealer does stock the second air gasket. Just kidding, we do :)
I believe not replacing the second air gasket is one of several reasons F800's develop more oil leaks then the F650's do, and the valve cover gasket is the weak point where the pressure creates oil leakage. Just as common the valve cover is warped, but in either case, using a whole tube of rtv to glue down the valve cover is not the answer ( insert video of bones saying "my god man! drilling holes in his head is not the answer, the artery must be patched" (startrek 4))

Last in the system are chanels in the head they exit right above one or both cylinder exhaust valves. I say "one or both" because I simply can't remember if there's just one or two channels. Sorry, perhaps I have a picture that shows the exits from the one and only rotax twin I've torn down. Will check and post the answer and link to picture if I do.

There you go, likely far more then anyone wanted to know about this system. Sorry for the super long post, I can't help myself. I LOVE this engine and all the super high tech details. Putting iPhone away now and going for a ride :D

The Griz 11-15-2010 12:02 PM

Very complicated explanation and didn't feel like reading trough the whole thing.....is clean filtered air actually injected into the exhaust at any given time? If so, then yes the bike has a secondary air injection system. If not, then no it doesn't. If all gases/fumes for the "secondary" system on the F8 are drawn from the crankcase to the airbox, then it is not technically a "Secondary Air Injection" system. The term and definition cannot be fudged. It either is or isn't a secondary air injection system.:deal

http://en.wikipedia.org/wiki/Secondary_air_injection

Secondary air injection (commonly known as air injection, or colloquially smog pump) is a vehicle emissions control strategy introduced in 1966, wherein fresh air is injected into the exhaust stream to allow for a fuller combustion of exhaust gases. An implementation of the system has been trademarked by the name Air Injection Reactor (A.I.R.).


PS, I don't believe that using the Booster Plug will richen the AFR of this bike so much so that "emissions will go to hell and deposits will build up in the combustion chamber as well as in the exhaust and of course, the O2 sensor will plug."


The Booster Plug doesn't richen it that much. In fact it only richens it an average of 6% across the RPM range. This will make those of us that are running a higher flowing air filter and higher flowing exhaust experience an AFR that we originally experienced when the bike was in stock form. Also, it will make the engine run cooler and last longer. The ECU simply cannot readjust/remap far enough to account for and K&N or Uni and a high-flowing aftermarket exhaust. Again, I've been experiencing it on my bike for 1.5 years after installing the Uni and Leo Vince: surging, more snatchy throttle, pop pop pop on decel and shift, engine running hotter, etc. All of which weren't happening in stock form.... That is the truth. And no, it's not that I wasn't hearing the popping because the stock exhaust masked it. It simply wasn't doing it before.

I'm getting the Booster Plug because I want to run a Uni oil foam air filter and the Leo Vince Carbon exhaust.


Just read all of the posts of the happy costomers who installed the Booster Plug or Accelerator Module.

Singletrack_mind 11-15-2010 01:10 PM

[QUOTE=JoelWisman]There is no diagram of the system I'm aware of on the publically available service DVD, or the dealer only RSD.

There is however a great video complete with animations at BMW university, a web site that's only available to BMW employees. I have no idea why BMW keeps stuff like this secret, but they do.

In any case, YES, at the least the USA variant of the F800GS does have what is commonly known as a "second air" system.




Thank you Joel for answering all my curiosities about this in one place, I appreciate it.

I had wondered about this ever since leafing through my new Haynes manual, and thinking to my self that I'd seen secondary air injection systems on other bikes, but didn't see any sign of the hardware I was familiar with on my GS. Glad to know where it is & how it works.

jscottyk 11-15-2010 04:54 PM

AWESOME! Thanks for such a thorough explanation Joel. That kind of post is why this place ROCKS!

Quote:

Originally Posted by JoelWisman
There is no diagram of the system I'm aware of on the publically available service DVD, or the dealer only RSD...

...Sorry for the super long post, I can't help myself. I LOVE this engine and all the super high tech details. Putting iPhone away now and going for a ride :D


The Griz 11-15-2010 07:03 PM

Quote:

Originally Posted by JoelWisman
This is why you will NEVER improve HP and runability through airbox mods, filter mods, header mods, or fancy slip ons. You may increase noise, or peak HP, but always at the cost of mid range torque. No aftermarket manufacture has the wads of cash or engineering brain power to design componants that work better then BMW original equipment.

Again, as I said before, very thorough and complicated post. However, folks, take some his opinion-based statements regarding this bike with a grain of salt, especially what I've quoted above. What I've quoted above is simply false. Runnability and power absolutely CAN be increased with airbox mods, higher flowing air filters, and higher flowing exhaust systems and headers. However, once these changes have been made and items have been bolted on, the owner MUST re-tune the air/fuel mixture to match the change in higher intake and exhaust flow. Otherwise, the engine will run much too lean resulting in hotter running temperatures and reduced power. This may be what Joel is talking about. However, again, in order to reap the benefits of intake and exhaust modifications, you must richen the air/fuel mixture to match. The onboard ECU will do its best to compensate and richen the mix, but unfortunately it cannot richen the mix on its own enough to reap said benefits. Contrary to what Joel says in his post, you CAN gain some power and better 'runnability' with airbox mods, higher flowing air filters, higher flowing air filters, and a higher flowing exhaust. But again, you MUST richen the air/fuel mixture enough in order to match the extreme changes in intake and exhaust flow you've made. Otherwise you're doing more harm than good. The only way to richen it enough is to manually tune the bike with a Booster Plug or Accelerator Module. These items will richen the mix enough to reap the benefits of the add-ons we speak of.

johngil 11-15-2010 07:07 PM

http://media.ebaumsworld.com/mediaFi...45/1000309.jpg

The Griz 11-15-2010 07:11 PM

Quote:

Originally Posted by johngil

Well that's just an odd announcement to make about yourself in a thread on a motorcycle forum.:scratch Hmmmm...Do you look like the guy kneeling down or something john?


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