Q twin tip exhaust and carbon issue

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Q twin tip exhaust and carbon issue

Postby avera01 » Thu Mar 22, 2018 6:42 pm

Just checking if this is an issue and what to do:

I noticed that for a while I have had to clean black carbon residue from the tips of the exhaust. However now I have noticed carbon residue on the floor of my garage and upon inspection saw the same carbon residue at the connection between the exhaust and the mid-pipe, along the bottom edge.

I checked the two nuts and they are tight, can’t turn them any more. It appears as there might be a leak.

Is this normal and if not any suggestion? I am going thinking that I may have to take the two bolts off and retighten the connection and or replace the two bolts. I am concerned about an exhaust leak.
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Re: Q twin tip exhaust and carbon issue

Postby Brian » Thu Mar 22, 2018 7:09 pm

Let's start with generation, are we talking ND or NC? Carbon will weep out at the exhaust connections and that doesn't mean an exhaust leak when system is hot, won't hurt anything. My larger concern is your description sounds like excessive carbon from exhaust. Lots of short trips can cause that, car never gets to full temp and combustion is not efficient resulting in abnormal carbon deposit levels. But might be tune issue with the car. Some carbon is normal, massive carbon deposits usually means tune is not ideal. That can be as simple as need a fresh set of spark plugs and/or coils, to a better tune. When was last time plugs were changed? What is the plug gap? Coils have how many miles on them? Running header? Running a Tune? If running a Tune, perhaps a TDR tune?
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Re: Q twin tip exhaust and carbon issue

Postby avera01 » Fri Mar 23, 2018 3:48 am

Hi Brian,

Its a 2016 ND automatic GT. The car is not driven a lot, has about 4300 miles mainly on short trips of a few miles with 1 or 2 monthly trips of 100-200 miles (part of the South Florida Miata Club adventures). I usually drive it in Sport mode (with paddle shifting) to keep the RPM higher in its power range plus the exhaust sounds "sweeter" cruising around the 2500-3000 rpm range and not a deep rumble or loud sound. The exhaust tip shows a light film along the bottom inside edge maybe 1-2 inches wide and 1/4" deep. I would not call it massive.

The car has not been tune since bought new nearly 2 years ago. Did not think it needed it given the low mileage. Everything is stock except for the exhaust and sound minor cosmetic stuff.

The garage floor appears as splattered carbon drips coming from the connection given that the droppings appear underneath the connection vs near the tips. This may have been occurring for a while as I did not notice it until recently and the splatter is a buildup over time.
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Re: Q twin tip exhaust and carbon issue

Postby Brian » Fri Mar 23, 2018 5:38 am

Okay, short trips will leave a lot of moisture in the system, not enough time for it to bake out. Normal that moisture in the system will weep out at the connections and take carbon with it to the floor.
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Re: Q twin tip exhaust and carbon issue

Postby avera01 » Fri Mar 23, 2018 7:32 am

Thanks, that is good to know. I guess that just means more and longer driving trips (more fun).
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