Wei718

Lately I’ve been noticing one side of my exhaust tips are getting soot and the other side is pretty clean. Anybody else has the same issue? My car is a weekend toy rarely goes to redline.

JAhmed

Do you turn off auto stop start when you drive

GT3ED

It is obviously a major manufacturing defect by Akrapovic. I’m willing to swap you my OEM back box and tips in order to alleviate this major eyesore for you.😁

Wei718

First thing I do when I get in and I make sure of that. Don’t think I’ve ever let the auto start stop activated.

Haha! That sounds like a plan!!! Where do we meet? 😆

kart125

Is it a vlaved rear section? If yes I'd look at the vacuum line connection to valves... probably not connected properly on right side, leaving valve open all the time?

Lou L

I have the same issue< only noticed it when put on aftermarket exhaust, the stock exhaust funnels thru both sides, my was the drivers side which is the side the air oil separator is on, i was told, my Porsche dealership ran full diagnostics and said all was fine - I started a thread back about 2 months ago and posted pictures. mine was very dramatic

Wei718

Thanks for the advice! After installing the exhaust I made sure both valves are working by using the PSE button. They do open and close and I double checked by looking at the valves that they are working, I’ll check them again.

I think I was trying to look for your thread or post and I can’t find. I remember seeing a post stating the same issue. That’s good to hear though. Do you also have the Akrapovic exhaust?

Patrick3000

Here is the thread:

https://rennlist.com/forums/718-gts-...vers-side.html

8haggis

From my understanding, this is a perfectly normal situation to have on a Direct Injection European car. I can't confirm on my 718 yet as it is still waiting for engine transplant, but every modern EU car I have owned shows this sooting on one side heavier than the other. It is caused by 2 things, Direct Injection combustion behaviour, and European drive-by noise regulations. First, the soot. Modern gasoline combustion strategies have been moving towards more diesel-like strategies every year to improve efficiency and (mostly) emissions. This is done through higher fuel pressures and later injection timing, (basically speed up the fuel burn event as much as possible) and a side effect of this strategy is the generation of particulate matter. (The soot.) That is why cars are now coming with GPF (gasoline particulate filters) as the ultra-small particles are not too good for our health. So that is why there is soot on the exhaust tip - combustion is going well, not poorly.
Regarding the reason why it is only on one side of the car, this is due to drive-by noise regulations. To meet the criteria for the test, throttles are now installed into the passenger side exhaust on dual exhaust cars. This throttle is generally closed all of the time until you activate "sports exhaust" or really hammer it. Since the flow is so restricted on the pass side to avoid noise transmission on that side of the car (location for the regulator's microphones) very little soot is deposited over time. Even if you do goose it or run with sports exhaust on every once in a while.
If you bend down and look, you should be able to see the exhaust throttle.
Only confusing point on your original post, is the left and right soot arrangement. Are you RHD location?

Passenger Side (M340i)

Drivers Side

Wei718

Thank you for your through explanation! My car is left hand drive and apologize for the mix n matched layout of my photos. Now I’m more relieved that it is possibly normal.

TXshaggy

Well it’s not normal on a stock rear box.

Most logical explanation is your aftermarket unit is biased to one side for whatever reason.

wizee

I’ve observed this uneven soot distribution on a BMW M240i I used to have for the reason you described, but on my 718 Spyder with stock exhaust, soot distribution is even between both sides, the muffler valves are present on both sides, and the muffler valves on both sides open together.

I’m guessing something about the aftermarket exhaust system is biased to one side.

8haggis

Interesting. Porsche must have different exhaust design policy than Audi and BMW (maybe specifically to this issue of uneven soot.) The OP issue therefore may be due to single side throttle or more likely as was previously suggested in this thread, a miss-build of the aftermarket assy which results in uneven delta P across right and left sides. The OP might want to check if there is any observable difference in idle flow rates between the 2 sides and check back with the exhaust supplier if that is intentional or mistake.

Driv200

Only problem I understand from post is no redline for your weekend toy. LOL. Get some more time of that.

Hope you figure it out. Good read.

Wei718

I don’t recall having that issue with the stock box and like most are saying it’s probably the aftermarket exhaust. I can check in with my vendor to see if he’s seen something like that.

I may do a little experiment by forcing the valves to stay open and observe if anything changes. I’m only concerned with the engine and don’t mind cleaning my tips every wash.