Exhaust when cold only appears to come out of passenger side.

**jhAudi** · 02-14-2021 03:06 PM

Fairly new owner of an 18 S5. I have notice that when cold (which it has been here), the condensation "vapor" only comes out of the passenger side of the quad exhaust pipes. The drivers side anecdotally feels to have a slight vacuum into the drivers side exhaust pipe where as I feel almost or nothing exhausted on that side. First noticed this on the backup camera but today started it up and took a look for myself.

Anyway, I don't know if Audi has some system to direct exhaust to one side when cold. Seems odd but I figure there would be some experts on here that could explain this behavior. If not I would guess there is some major leak prior to the tailpipes on the driver side. However I don't see any cold condensation vapor anywhere from the car than the passenger side which is easy to spot and seems normal from a cold started car.

**theroidee** · 02-14-2021 03:24 PM

Funny you post this now, I was just about to do the same. The identical thing happens with my 19 S5 SB. Upon cold start exhaust appears only from the right tailpipe and nothing from the left.

I have a remote starter and I see this happen every time.

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**jhAudi** · 02-14-2021 03:49 PM

At first I thought it was an just my imagination but today I took the time to check the flow in out and the flow out on the passenger side is strong. The drivers side is somewhat of a vacuum where no vapor at all is exhausted and seems to pull into that side. Glad someone else has seen this so maybe it is normal. The car performs fine though. Hopefully someone knows that this is a normal thing for the S5.

Another side item is the car is pretty loud in a good way when I start it cold in the garage. When driving generally very quite except when stepping on it then you get a good sound.

**joy_mai** · 02-14-2021 03:49 PM

'21 S5 SB here, same exact thing thing as your are describing. Wonder what some possible causes are.

**SHCKR** · 02-14-2021 04:31 PM

The exhaust in our vehicles is valved. If you look at it immediately in front of the rear muffler, there is an electrical box on each side. It controls the valves. The exhaust shuts off drivers side until the catalytic converter warms up, then it opens the other side. I think it's an emission thing.
I find it really annoying myself, and I know a lot of people simply unplug the connectors for the valves, forcing them to stay open all the time.
I haven't done it myself yet, but I think I might in the near future.

B9S4 all packages

**JohnEnglish** · 02-14-2021 04:55 PM

Yeah it’s normal. Depending on the valves state, you can have exhaust coming from 1, 2, 3, or all 4 exhaust tips (if you have a S model).

**jhAudi** · 02-14-2021 05:37 PM

Thanks for the info. Nothing to worry about which is what I wanted to hear.

**CurvesAhead** · 02-14-2021 07:18 PM

I think it causes the Cats to heat up quicker, thus reducing emissions!

**Burrcold** · 02-15-2021 07:49 AM

Your car also starts in Comfort (regardless if you have Dynamic set on start up). If you cycle through to Dynamic once started, you will hear the valve open up.

**theroidee** · 02-15-2021 09:24 AM

Originally Posted by Burrcold

Your car also starts in Comfort (regardless if you have Dynamic set on start up). If you cycle through to Dynamic once started, you will hear the valve open up.

Does this mean that when in comfort exhaust is emitted only from the left exhaust pipe?

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**Burrcold** · 02-15-2021 11:41 AM

Originally Posted by theroidee

Does this mean that when in comfort exhaust is emitted only from the left exhaust pipe?

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I believe so although I don't drive very often in comfort.

**SHCKR** · 02-15-2021 12:39 PM

Originally Posted by Burrcold

Your car also starts in Comfort (regardless if you have Dynamic set on start up). If you cycle through to Dynamic once started, you will hear the valve open up.

What do you mean? If I have it left in dynamic, how long does it take, and what are the triggers to switch to dynamic? Also, I can clearly tell the difference if starting in comfort or dynamic....

B9S4 all packages

**Burrcold** · 02-15-2021 03:02 PM

Originally Posted by SHCKR

What do you mean? If I have it left in dynamic, how long does it take, and what are the triggers to switch to dynamic? Also, I can clearly tell the difference if starting in comfort or dynamic....

B9S4 all packages

The engine mapping defaults to a comfort mode even if you leave it in Dynamic. If warm, the exhaust will sound slightly better but still not full on dynamic until you cycle the drive select once through. Try it and you will hear the valve open as you cycle back to Dynamic. I'm assuming it's an emissions thing...but it's definitely a thing. Did it my S4/S5 and does it in my RS5 as well.

**theroidee** · 02-15-2021 03:26 PM

Originally Posted by SHCKR

What do you mean? If I have it left in dynamic, how long does it take, and what are the triggers to switch to dynamic? Also, I can clearly tell the difference if starting in comfort or dynamic....

B9S4 all packages

If you do a search on this topic, you’ll find a lot of valuable info. Basically, you need to either cycle the drive modes or shift to S upon a fresh start to get both exhaust and transmission back in dynamic. Both are in comfort no matter what your individual settings are or if you left it in dynamic when the car was shut off.

To me, that’s insanity. It’s not that way at all on my GM performance cars.

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**theroidee** · 02-15-2021 03:29 PM

Originally Posted by Burrcold

I believe so although I don't drive very often in comfort.

Neither do I but I do have the engine transmission in Auto so when I go switch to S they go to Dynamic and I certainly feel and hear it.

But having these settings in Auto means it’s in Comfort until I put it in S or get on it. So, I go back to my original question — is only the left exhaust open until the car gets switched to S or driven aggressively?

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**Burrcold** · 02-15-2021 03:50 PM

Originally Posted by theroidee

Neither do I but I do have the engine transmission in Auto so when I go switch to S they go to Dynamic and I certainly feel and hear it.

But having these settings in Auto means it’s in Comfort until I put it in S or get on it. So, I go back to my original question — is only the left exhaust open until the car gets switched to S or driven aggressively?

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If you use Auto, the valve will open if you are driving harder. If you stay in actual Comfort, I don't think the additional valve ever opens (evident on some used S4/5 models that have one side where the tips are black but the other side that looks almost new).

**theroidee** · 02-15-2021 04:24 PM

Originally Posted by Burrcold

If you use Auto, the valve will open if you are driving harder. If you stay in actual Comfort, I don't think the additional valve ever opens (evident on some used S4/5 models that have one side where the tips are black but the other side that looks almost new).

Wow, that's a little odd and troubling.

**JohnEnglish** · 02-15-2021 05:03 PM

Originally Posted by theroidee

Wow, that's a little odd and troubling.

This happens with lots of cars. It a big part of why car manufacturers are moving towards the "fake" exhaust tips. People were complaining that one was dirty and one was clean and that they're too difficult to clean.

**theroidee** · 02-15-2021 05:09 PM

Originally Posted by JohnEnglish

This happens with lots of cars. It a big part of why car manufacturers are moving towards the "fake" exhaust tips. People were complaining that one was dirty and one was clean and that they're too difficult to clean.

One product, two words — steel wool.

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**Burrcold** · 02-15-2021 05:20 PM

Originally Posted by theroidee

One product, two words — steel wool.

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Even better...two words...Ceramic Coating.

**theroidee** · 02-15-2021 05:22 PM

Originally Posted by Burrcold

Even better...two words...Ceramic Coating.

Could be...I prefer old school personally.

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**flyken74** · 02-15-2021 05:48 PM

In comfort or D on other mode. Driver side valve open up at 15k rpm.

**Burrcold** · 02-15-2021 05:54 PM

Originally Posted by theroidee

Could be...I prefer old school personally.

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I guess. Ceramic coating is preventative, steel wool is restorative. I prefer to keep things the way they were meant to be, not bring them back.

**JohnEnglish** · 02-15-2021 06:57 PM

Originally Posted by flyken74

In comfort or D on other mode. Driver side valve open up at 15k rpm.

**CurvesAhead** · 02-15-2021 07:16 PM

Originally Posted by JohnEnglish

Ha! The entire exhaust blew off my car at 15k!

**theroidee** · 02-15-2021 09:18 PM

Originally Posted by Burrcold

I guess. Ceramic coating is preventative, steel wool is restorative. I prefer to keep things the way they were meant to be, not bring them back.

That’s good.

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**flyken74** · 02-16-2021 12:57 AM

Originally Posted by CurvesAhead

Ha! The entire exhaust blew off my car at 15k!

Lol. 1500 rpm.

**jhAudi** · 02-18-2021 05:17 PM

Last night I started it cold and put it into sport mode after backing it out. Checked exhaust and still just the passenger side exhaust putting out anything. Must need to completely warm up to get it to open up both sides.

**SD Nardo** · 02-24-2021 10:24 PM

AWE Touring exhaust solves all this and sounds awesome 😉

**DCB1951** · 02-24-2021 10:47 PM

Right after a cold start, my RS5 seems to put out exhaust only on the driver side, not the passenger side. Anyone else see this behavior?

**Burrcold** · 03-05-2021 10:14 AM

Originally Posted by DCB1951

Right after a cold start, my RS5 seems to put out exhaust only on the driver side, not the passenger side. Anyone else see this behavior?

Yes. On a cold start (in an RS5) exhaust only comes out of the driver's side (today was pretty cold so I tested it and could see the "smoke" coming out of the driver's side...then I switched to Dynamic and it started coming out of both sides).

**CurvesAhead** · 03-05-2021 10:48 AM

Originally Posted by Burrcold

Yes. On a cold start (in an RS5) exhaust only comes out of the driver's side (today was pretty cold so I tested it and could see the "smoke" coming out of the driver's side...then I switched to Dynamic and it started coming out of both sides).

This is true for the S5 too, how much better was the sound starting in Dynamic? I'd try it on my car but it's in storage until the weather warms.

**Burrcold** · 03-05-2021 12:44 PM

Originally Posted by CurvesAhead

This is true for the S5 too, how much better was the sound starting in Dynamic? I'd try it on my car but it's in storage until the weather warms.

I had a B9 S5 as well and both sound much better once both sides open up in Dynamic.

**S4mcsleeper** · 12-06-2024 04:30 PM

Can you elaborate on how to open all 4 tips? I have the stock sport exhaust package and I know that it is valved. I also see only exhaust coming out of the passenger side/right side when I am idling whether it’s warned up or cold. But I have a pretty intense tune, and I would like to have all four tips open for better airflow. What’s the process for making that happen?