Lets talk SAS

[Bulldog9]

I'm aware of what the SAS does, be it on an automobile or motorcycle.

On the E-5 V85, it looks as though there is an electric air pump that pumps air into the exhaust stream to do what the SAS does (help catalyze unburnt fuel in the cat and 'spoof' the tailpipe emissions by adding fresh air).  The MGX 21 had one way reed valves that pulled fresh air in but allowed none out or to backflow into the airbox. The V85 is different. With the pump it is active much like how it works on automobiles..

I've seen several threads on this, but have a few observation/questions.

1. All the threads say to keep the pump plugged in to avoid an ECU error CEL. Does this mean that the air pump will still function?
2. The 'block off plates' and caps isolate the SAS pump and the exhaust ports. Rendering the system inert but in place.
3. The lack of air being pumped into the exhaust stream will help eliminate popping on decel.

Here is my main question. Will the lack of air in the exhaust stream resulting in cleaner/leaner exhaust gasses cause the ECU to lean out the already too lean fuel trims even more?

[Moparnut72]

The V85 may be different but my '26 V7 850 has a electrically controlled purge valve, no motor. I deleted mine, it helped but I still have surging in low gears at lower rpm. I don't like running through the neighborhood in 1st at 3,000 rpm. Pretty much the only gripe I have with the bike. If I warm the bike for several minutes before I leave in the morning it will be a bit better.
kk

[Kev m]

@moparnut72 - are you confusing the EVAP and SAS systems? SAS doesn't have a "purge" per se.

BullD, just to be clear, SAS doesn't "spoof" anything, it helps to burn off HC's leftover after combustion. So it ACTUALLY cleans the exhaust gasses.

Traditionally with vacuum controlled systems it would likely work most during times of high vacuum (low throttle/idle), which I think would coincide with open loop operation anyway.

I would assume electronic control would mimic this and actuate during open loop when it wouldn't effect fuel mixture. But this is just theory on my part, I've not fooled with them.

[Moparnut72]

Kev, I am not totally sure how or when it works but it is part of the evap system. What I believe happens is that the valve opens and pulls air through the evaporative canister into the intake manifold further leaning out the intake mixture. I may be totally all wet but that is what it looks like to me. Whether it does it during open or closed loop I don't know but probably open.
kk

[Kev m]

Kev, I am not totally sure how or when it works but it is part of the evap system. What I believe happens is that the valve opens and pulls air through the evaporative canister into the intake manifold further leaning out the intake mixture. I may be totally all wet but that is what it looks like to me. Whether it does it during open or closed loop I don't know but probably open.
kk

So EVAP systems store HC's (fuel vapors) that "evaporate" (where abbreviation comes from) and then draws it off to burn as part of normal combustion. As you note it enters upstream of the combustion chambers.

SAS - Secondary Air Systems inject air into the exhaust system near the exhaust valve to help afterburn of HC's that weren't fully consumed by normal combustion.

Two pretty different and separate systems.

[Bulldog9]

So EVAP systems store HC's (fuel vapors) that "evaporate" (where abbreviation comes from) and then draws it off to burn as part of normal combustion. As you note it enters upstream of the combustion chambers.

SAS - Secondary Air Systems inject air into the exhaust system near the exhaust valve to help afterburn of HC's that weren't fully consumed by normal combustion.

Two pretty different and separate systems.

Kev, yes, I'm aware as said that the SAS added air helps to catalyze the unburnt fuel in the exhaust gasses in the catalytic convertor, but the added air, especially in automotive designs dilutes the particulates in the exhaust stream by adding fresh air or in other words spoofs by resulting in lower tailpipe measurements. It is generally only used until the engine is up to temps in automotive conditions. And yes the EVAP system is as you describe.  Two separate emissions systems.

Moparnut - I havent tested if it is a pump or an electric valve that allows the addition of air to the exhaust stream. I read something on GT that indicated it was a pump.

[Kev m]

I continue to push back on your term spoof.

For it to be a spoof you have to be fooling someone or something.

Afaik, no automotive emissions tests are taking place with an air injection system active as the majority application on cars these days is to more quickly heat the cat con.

But in the end the emission system is designed to reduce what comes out of the tail pipe. The injection system isn't designed to dilute that, it's designed to add oxygen to the oxygen depleted mixture to allow more burning thereby actually reducing emissions.

[Bulldog9]

I continue to push back on your term spoof.

For it to be a spoof you have to be fooling someone or something.

Afaik, no automotive emissions tests are taking place with an air injection system active as the majority application on cars these days is to more quickly heat the cat con.

But in the end the emission system is designed to reduce what comes out of the tail pipe. The injection system isn't designed to dilute that, it's designed to add oxygen to the oxygen depleted mixture to allow more burning thereby actually reducing emissions.

Spoof...... 

[Kev m]

Spoof...... 

       

[SIR REAL ED]

It appears that Kev m is talking about a Secondary Air System, and Bulldog9 is talking about a Spoof Air System. 

Two different things that use the same acronym.

Tricky things those acronyms....

At first I assumed Special Air Services.....

or maybe, https://www.acronymfinder.com/SAS.html

[Dr. Enzo Toma]

"Will the lack of air in the exhaust stream resulting in cleaner/leaner exhaust gasses cause the ECU to lean out the already too lean fuel trims even more?"

The SAS is downstream of the combustion chambers, so SAS wouldn't directly affect AFR. The o2 sensors may see a difference when the SAS is operating, but I suspect the ECU might account for SAS operation and disregard or compensate for that signal when it's active. I don't know that, just a theory. If it were the case, an inoperable SAS that's still in place seems like a better approach than a removed one, if you're going to stray from stock.

What is there to gain though besides lessening decel pop? I enjoy a little decel pop 

[nc43bsa]

At first I assume Special Air Services.....

I assumed San Antonio Shoes.   

[Dukedesmo]

Quote from: SIR REAL ED on Today at 12:36:29 AM

At first I assumed Special Air Services.....

___________________ ___________________ ___________

I'd tell you, but I'd have to kill you...     

[SIR REAL ED]

Quote from: SIR REAL ED on Today at 12:36:29 AM

At first I assumed Special Air Services.....

___________________ ___________________ ___________

I'd tell you, but I'd have to kill you...     

In that case I'd like to change my guess to Social Anxiety Support...

You make an excellent case for not defining the acronym one chooses to use.  It saves a lot of unnecessary bloodshed.

[Bulldog9]

"Will the lack of air in the exhaust stream resulting in cleaner/leaner exhaust gasses cause the ECU to lean out the already too lean fuel trims even more?"

The SAS is downstream of the combustion chambers, so SAS wouldn't directly affect AFR. The o2 sensors may see a difference when the SAS is operating, but I suspect the ECU might account for SAS operation and disregard or compensate for that signal when it's active. I don't know that, just a theory. If it were the case, an inoperable SAS that's still in place seems like a better approach than a removed one, if you're going to stray from stock.

What is there to gain though besides lessening decel pop? I enjoy a little decel pop 

The 02 sensors are after the SAS and before the CAT. I'm just wondering if the lack of the air added by the SAS at the exhaust port would raise the A/F ratio (making it appear richer) and cause the ECU to cut fuel trims making an already lean fuel mixture leaner. If the SAS is designed to improve catalyst function in the CAT Convertor and it is removed if it is a necessary or beneficial system.

[kingoffleece]

I'd ask Hamlin.

[Moparnut72]

The 02 sensors are after the SAS and before the CAT. I'm just wondering if the lack of the air added by the SAS at the exhaust port would raise the A/F ratio (making it appear richer) and cause the ECU to cut fuel trims making an already lean fuel mixture leaner. If the SAS is designed to improve catalyst function in the CAT Convertor and it is removed if it is a necessary or beneficial system.

Thought to ponder. Interesting idea.
kk

[Dr. Enzo Toma]

My thought was that the ECU would know when the SAS injection pump is running, and disregard the air-injected reading it gets from the downstream o2 sensor during that time. That's how I would expect it to work, doesn't mean that is the way it is though.