npp exhaust dumping fuel?

blackknight0512 · 12-17-2018, 10:36 AM

My car has 3,000 miles on it and i have noticed that gradually i have been seeing more and blow build up on the outside 2 tips of the npp exhaust. When i wash it (typically once a week), I polish the tips so i am only talking about a week or so of driving, and the 2 inside ones i hardly have to touch, but the 2 outside ones are black. Wouldn't that indicate that the air is basically just blowing through the 2 outside tips? I know air goes where there is least resistance, would this indicate the valves on the inside are not opening at the same rate as the outside? I leave exhaust on track, if that helps. Just curious why only 2 out of 4 tips seems to be dirty.

parish8 · 12-17-2018, 10:38 AM

When open most of the exhaust will come through the outside pipes since there is less restriction there.

sdmcss · 12-17-2018, 10:48 AM

Track mode is your answer. When in track mode the outside tips are being utilized at 80%. If you use any other modes you will see less buildup. If you pull the NPP Fuse you will see even more as the flap will be 100% open.

People who have tuned their car to E85 have little to no build up since its a cleaner non carbon burn.

I hope this helps! I had the same question when I bought mine.

Gasoline_Farts · 12-17-2018, 11:44 AM

Mine is the same. Leave it in track, outside tips get black, inside look clean.

this picture might help, you can see that if you have the NPP in track, the flaps will be open the majority of the time and it will be a LOT of work for the exhaust gasses to reach the other tips.

blackknight0512 · 12-17-2018, 12:28 PM

Quote:

Originally Posted by sdmcss

Track mode is your answer. When in track mode the outside tips are being utilized at 80%. If you use any other modes you will see less buildup. If you pull the NPP Fuse you will see even more as the flap will be 100% open.

People who have tuned their car to E85 have little to no build up since its a cleaner non carbon burn.

I hope this helps! I had the same question when I bought mine.

Great bit of information. Thank you for sharing. So basically Sport/tour will force more airflow to the middle 2 tips with the flaps on the outside being more closed.

CrazyCatGuy · 12-17-2018, 01:47 PM

Quote:

Originally Posted by sdmcss

When in track mode the outside tips are being utilized at 80%. If you pull the NPP Fuse you will see even more as the flap will be 100% open.

Can anyone tell me if the exhaust tone is noticeably louder when the fuse is pulled? I figured the valves would open 100% in track mode.

Also, where is the fuse for the NPP?

Thanks in advance.

zx9rmal · 12-17-2018, 01:53 PM

Quote:

Originally Posted by CrazyCatGuy

Can anyone tell me if the exhaust tone is noticeably louder when the fuse is pulled? I figured the valves would open 100% in track mode.

Also, where is the fuse for the NPP?

Thanks in advance.

The fuse is #51 in the fuse box under the hood, passenger side. I always have my exhaust in track mode. I did pull the fuse, but the difference was almost imperceptible so I put it back so I can change modes if my wife wants a bit less sound.

SSDan · 12-17-2018, 02:10 PM

Quote:

Originally Posted by zx9rmal

The fuse is #51 in the fuse box under the hood, passenger side. I always have my exhaust in track mode. I did pull the fuse, but the difference was almost imperceptible so I put it back so I can change modes if my wife wants a bit less sound.

I found and did the exact same thing with fuse #51. So I went into the main menu and set track as the full time default for the exhaust and I run sport for everything else. Two years ago I also painted the inside of all four exhaust tips with black hi-temp paint and haven't looked back. No more cleaning the insides - just a quick wipe down of the outsides when washing - all done!

VinnAY · 12-17-2018, 02:31 PM

I didn't notice any diff between Track and the fuse pull.

CrazyCatGuy · 12-17-2018, 02:45 PM

Quote:

Originally Posted by zx9rmal

The fuse is #51 in the fuse box under the hood, passenger side. I always have my exhaust in track mode. I did pull the fuse, but the difference was almost imperceptible so I put it back so I can change modes if my wife wants a bit less sound.

Quote:

Originally Posted by VinnAY

I didn't notice any diff between Track and the fuse pull.

Cool, thanks again you guys!

Laststandard · 12-17-2018, 04:04 PM

Quote:

Originally Posted by VinnAY

I didn't notice any diff between Track and the fuse pull.

Biggest difference is the NPP valves will still close in track mode while on the highway - 6th gear / low rpm / low throttle.

Gasoline_Farts · 12-17-2018, 04:36 PM

i tried pulling the fuse, and also noticed little to no difference (after i bought all the parts to make a remote control fuse switch)

Alpha1BC · 12-18-2018, 08:58 AM

Quote:

Originally Posted by blackknight0512

Great bit of information. Thank you for sharing. So basically Sport/tour will force more airflow to the middle 2 tips with the flaps on the outside being more closed.

Correct. There are only valves for the outside tips, and those valves will either be commanded open or closed. All changing driving mode does is change under which conditions the valves will be closed. For instance, Tour exhaust mode will keep the valves closed 90% of the time unless you're doing a WOT excel launch, while track will keep the valves open most of the time except for cruising at higher speeds and lower throttle input. Closed valves forces the exhaust gas through the suitcase muffler while open valves let exhaust gas flow through the muffler bypass. There is no "partially open" state for the valves, they're either going to be fully open or fully closed.

That's also why there's no change in volume when pulling the fuse. The valves are open by default from the valve spring setup and then the actuator holds them closed. No fuse = no power to actuator = valves always stay open, so going without the fuse will be the same as track mode with the exception that the valves will also stay open at high speed/low throttle conditions. In that case, you might get a little more sound on the highway, but that's about it.

zx9rmal · 12-18-2018, 10:55 AM

Quote:

Originally Posted by SSDan

I found and did the exact same thing with fuse #51. So I went into the main menu and set track as the full time default for the exhaust and I run sport for everything else. Two years ago I also painted the inside of all four exhaust tips with black hi-temp paint and haven't looked back. No more cleaning the insides - just a quick wipe down of the outsides when washing - all done!

I did the same with except track as the default for suspension as well. Great combo with the lighter steering and better throttle response.

12-17-2018, 10:36 AM	#1
blackknight0512 Drives: 2018 1SS 1LE Join Date: Feb 2012 Location: Southwest Florida Posts: 135	npp exhaust dumping fuel? My car has 3,000 miles on it and i have noticed that gradually i have been seeing more and blow build up on the outside 2 tips of the npp exhaust. When i wash it (typically once a week), I polish the tips so i am only talking about a week or so of driving, and the 2 inside ones i hardly have to touch, but the 2 outside ones are black. Wouldn't that indicate that the air is basically just blowing through the 2 outside tips? I know air goes where there is least resistance, would this indicate the valves on the inside are not opening at the same rate as the outside? I leave exhaust on track, if that helps. Just curious why only 2 out of 4 tips seems to be dirty.

12-17-2018, 10:38 AM	#2
parish8 Drives: 17 SS a8 Join Date: Feb 2010 Location: omaha Posts: 1,678	When open most of the exhaust will come through the outside pipes since there is less restriction there. __________________ dropped a valve in the 6.2. now running a drop in rods and piston 5.3 best et 5.83@121 with the 5.3 http://www.camaro6.com/forums/showthread.php?t=465472

12-17-2018, 10:48 AM	#3
sdmcss Drives: 2018 Camaro 2SS 1LE, 1985 MCSS Join Date: Dec 2014 Location: Kansas Posts: 266 View My Garage	Track mode is your answer. When in track mode the outside tips are being utilized at 80%. If you use any other modes you will see less buildup. If you pull the NPP Fuse you will see even more as the flap will be 100% open. People who have tuned their car to E85 have little to no build up since its a cleaner non carbon burn. I hope this helps! I had the same question when I bought mine. __________________ 2018 Camaro 2SS 1LE, White, M6, MRC, NPP, ELSD Past/Current: 2011 Camaro 2SS Convertible, M6, Silver Ice Metallic, Inferno Orange Interior and Stripes - SOLD 2007 Monte Carlo SS, LS4, Summit White, Silver Rally Stripes - SOLD 2006 Impala SS, LS4, Black on Black - SOLD 1985 Monte Carlo SS

12-17-2018, 11:44 AM	#4
Gasoline_Farts Drives: 19 SS 1LE Join Date: Nov 2018 Location: NV Posts: 140	Mine is the same. Leave it in track, outside tips get black, inside look clean. this picture might help, you can see that if you have the NPP in track, the flaps will be open the majority of the time and it will be a LOT of work for the exhaust gasses to reach the other tips.

12-17-2018, 02:31 PM	#9
VinnAY Account Suspended Drives: 18 1SS/1LE Join Date: Jun 2018 Location: Missouri Posts: 939	I didn't notice any diff between Track and the fuse pull.

12-17-2018, 04:36 PM	#12
Gasoline_Farts Drives: 19 SS 1LE Join Date: Nov 2018 Location: NV Posts: 140	i tried pulling the fuse, and also noticed little to no difference (after i bought all the parts to make a remote control fuse switch)

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