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Old 02-02-2014, 01:53 PM   #106
JRWooden
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Thanks Roger ... any guess as to why the F658GS does not have the SAS
(since the benefit is in closed-loop / light throttle mode)?
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Old 02-02-2014, 02:21 PM   #107
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My guess is modern FI engines run pretty clean. Due to a different state of tune, BMW felt they could meet emission standards without it.

Re the converter, what research I did, states if takes converter temp of 400-600 degrees Converter temp to even work. They work best at 1,200 to 1,600 degrees. Damage occurs when they reach 2,000 degrees.

That is pretty hot, when you consider combustion temp is around 2,500 degrees. That has to vary, when you realize the stock bike runs richer mixtures in open loop.

I wonder if the F700gs has SAS?
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Old 02-02-2014, 03:07 PM   #108
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Originally Posted by itsatdm View Post

Re the converter, what research I did, states if takes converter temp of 400-600 degrees Converter temp to even work. They work best at 1,200 to 1,600 degrees. Damage occurs when they reach 2,000 degrees.

That is pretty hot, when you consider combustion temp is around 2,500 degrees. That has to vary, when you realize the stock bike runs richer mixtures in open loop.
Lends credence to the idea that it is raw fuel that melts them down.
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Old 02-02-2014, 05:06 PM   #109
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We need a converter expert. I think it has the opposite effect. Richer fuel ratio's lowers combustion temperatures. If it was rich enough that it did not totally burn, I would agree with you. A plug reading would
be a clue.


Admittedly I am out of my pay grade. My old Ford pick up with dual converters has 4 oxygen sensors. 2 pre converter and 2 post. They are all the same type, so I don't know what they are measuring. A temp sensor would tell us or even measuring heat into and out of the converter would help. If there is a 200+ degree higher difference after going through the converter, then fuel is burning in it.
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Old 02-02-2014, 06:32 PM   #110
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I meant raw fuel, ie a missing cylinder. That is what burns down the cat. Slightly richer mixture, like what we are talking about the with the booster plug, isn't going to burn up the cat.

The main reason for a cat is the following chemical reaction.

2NO --> N2 + O2

To make this happen you need two things, a precious element and a low oxygen environment. You have two other reactions happening.

HC + O2 --> H2O + CO2
CO + O2 --> CO2

(yes I know its not balanced)
These are the three main reactions to make a 3-way catalyst.

Obviously there is some free O2 in the exhaust which starts the reaction with the CO and HC but not enough so the NO must give up its oxygen to complete the reaction.

Now you just need the temperature high enough to make all this work. For Natural Gas engines we run between 750F-1200F. Somewhere between 1250F and 1350F you will normally melt our substrate. NG combustion temps are slightly less then 2000F so like you noted, it seems odd that the exhaust alone would melt the substrate. Every time I've seen a substrate melt, raw, unburned fuel with oxygen is the likely culprit. This is not the same as a rich mixture.

Richer mixtures just bias that original mixture, in NG engines the right mixture is something like .008 AFR wide. Thus a control system that cannot keep the AFR at the right point will not convert emissions.

At any given operation temperature within the operation temperature window, you may see a 60F-80f rise across catalyst that is converting. When a converter doesn't work you won't see this rise. Its really hard to measure in a working engine because thermocouples aren't that accurate and the heat is created within the honeycomb substrate.

Now, what I don't know, is why gasoline engines use oxygen addition systems to a catalyst equipped engine.
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Old 02-02-2014, 06:58 PM   #111
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Super bowl was a bust wasn't it.
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Old 02-02-2014, 07:24 PM   #112
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I certainly didn't feel bad about writing that during the second half. I'm still a Broncos fan, and am consoling myself with the fact that its not as bad as the 1990 game.
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Old 02-02-2014, 07:56 PM   #113
roger 04 rt
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Quote:
Originally Posted by JRWooden View Post
Thanks Roger ... any guess as to why the F658GS does not have the SAS
(since the benefit is in closed-loop / light throttle mode)?
I don't know. There is extra cost and complexity so it can't be a desireabke addition from BMW's point of view. And most all of BMW's bikes don't have SAS. Maybe it was an experiment, maybe the 800 didn't run its best at low loading without it.

Quote:
Originally Posted by itsatdm View Post
We need a converter expert. I think it has the opposite effect. Richer fuel ratio's lowers combustion temperatures. If it was rich enough that it did not totally burn, I would agree with you. A plug reading would
be a clue.


Admittedly I am out of my pay grade. My old Ford pick up with dual converters has 4 oxygen sensors. 2 pre converter and 2 post. They are all the same type, so I don't know what they are measuring. A temp sensor would tell us or even measuring heat into and out of the converter would help. If there is a 200+ degree higher difference after going through the converter, then fuel is burning in it.
You're asking the same questions I had. Below is a chart that shows exhaust gas temperature at the top. The heavy red vertical line is stoichiometric, which is where exhaust gasses are hottest. Go richer or leaner and EGT goes down. However, at high power levels, cylinder head temperatures rise a bit as you richen the mixture and produce more power, not a concern for us.

As has been mentioned a couple times, running a few percent rich depletes the exhaust gas oxygen during combustion so the cat can't work as hard, further reducing heating. Cooler exhaust, less cat work, equals cooler cat.

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Old 02-03-2014, 06:39 PM   #114
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What does PPH stand for? How about CHT, I assume its Catalyst H_____ Temperature.

Basically it looks like what I was saying. You get a little rise in catalyst temp when the catalyst is lit off.
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Old 02-03-2014, 06:48 PM   #115
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Quote:
Originally Posted by MTrider16 View Post
What does PPH stand for? How about CHT, I assume its Catalyst H_____ Temperature.

Basically it looks like what I was saying. You get a little rise in catalyst temp when the catalyst is lit off.
PPH=Pounds per Hour, fuel flow
EGT=Exhaust Gas Temperature
CHT=Cylinder Head Temperature
then
Brake HP
Brake Specific Fuel Consumption (lbs fuel/HP/Hr.)

As you richen the mixture, CHT increases slightly at high power but EGT goes down.
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Old 02-03-2014, 07:04 PM   #116
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Originally Posted by MTrider16 View Post
What does PPH stand for? How about CHT, I assume its Catalyst H_____ Temperature.

Basically it looks like what I was saying. You get a little rise in catalyst temp when the catalyst is lit off.
MTR.... You might already know this, but the graph that Roger put up is for a fairly big aviation piston engine, for aircraft use. It does not have a CAT.
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Old 02-03-2014, 07:21 PM   #117
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I'm starting to see that. Swing and a miss.
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Old 02-03-2014, 07:24 PM   #118
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The chart neatly summarizes the effects of mixture on:

Combustion Heat
Exhaust Gas Temp (which interestingly goes down whether you richen or lean the mixture at lambda=1) many people believe leaner is hotter, but at 14.7, leaning cools exhaust and cylinder head.
Fuel consumption efficiency

And

HP sensitivity to mixture. Notice the the HP curve gets flatter at Best power mixture. That means that slight differences in injector performance have less effect with a richer mixture, helping to make the engine smoother.
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Old 06-02-2014, 12:56 PM   #119
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Originally Posted by jscottyk View Post
A couple of images for reference.

I think the valve that controls air to the SAS is #17 in this image.

Part #19 from the above images is #4 in this image.


The connector from BMS-K should attach to #17.
Hi Folks

I stumbled across this thread as I am trying to fathom if there is a PCV valve incorporated in the breather pipe 2 ? ..........and generally how the crankcase is ventilated ?
Also out of interest it appears that the reed valve/ secondary air system is not fitted to the Husky Nuda version of this engine, there is a blanking plate fitted in it's place

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Old 06-03-2014, 05:04 PM   #120
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I can't help much other than to say the valve - Part #17 and related tubing is NOT installed on the F650GS twin.
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