Performance Exhaust Question
Melting Slicks
Joined: Apr 2021
Posts: 2,752
Likes: 2,323
From: Simi Valley, CA
2022 C8 of the Year Finalist - Modified
It opens the NPP valves, which control exhaust volume. The valves are only open or closed but they do that under different conditions depending on the mode. In sport mode they are open most of the time. Track mode, all of the time. Tour, closed most of the time, open under heavy acceleration. Weather, closed all the time.
Regardless of the mode, the valves are open for the first 15-30 seconds of a cold start,
Regardless of the mode, the valves are open for the first 15-30 seconds of a cold start,
Instructor
Joined: Mar 2022
Posts: 211
Likes: 149
From: Westminster, CA
One other thing to note too. at least for me since i have the exhaust in track mode 85% of the time. the outside tips show more soot than the inside ones. This for me is in the same category as brake dust from the z51 pads, a pain to keep clean.
E-Ray, 3LZ, ZER, LIFT
Joined: Sep 2007
Posts: 34,872
Likes: 12,305
From: NE South Carolina
It opens the NPP valves, which control exhaust volume. The valves are only open or closed but they do that under different conditions depending on the mode. In sport mode they are open most of the time. Track mode, all of the time. Tour, closed most of the time, open under heavy acceleration. Weather, closed all the time.
Regardless of the mode, the valves are open for the first 15-30 seconds of a cold start,
Regardless of the mode, the valves are open for the first 15-30 seconds of a cold start,
As you note, the rpm the NPP valves open is dependent on Drive Mode. When NPP valves are closed the exhaust is forced to flow into the muffler (rather than mostly straight out the outer pipes with the NPP valves) and go out only the two center pipes with more restriction and less noise.
Last edited by JerryU; Sep 3, 2022 at 11:19 AM.
