"Cause you keep opening those NPP valves with your right foot!

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When the NPP valves open, you bypass the muffler, and the exhaust has a straight shot out.

 

"Cause you keep opening those NPP valves with your right foot!

Agreed. It's proof that you're a led foot.

 

If you run around in sport or track mode the majority of the time, the outside tips gets used the most.

 

Yeah Norm, lighten up on the gas, eh? :wink:

 

I may be incorrect here, but I believe the out side tips get carbon build up when our C7s are cold, like when you first start and or idle before it is up to operating temps. Not as a result of heavy footing it.

 

I'd say it's a combination of both - while the engine and exhaust are warming, combustion moisture can condense in the exhaust system and exit at the tips. Once the engine/exhaust is warm, there will be no possibility of condensation.

I used to put my Vette into Track before leaving my driveway, which of course opens the valves and allows the moisture to exit the outer tips.

I now drive the car in Tour until the engine/exhaust has warmed, and then switch to Track - this keeps the outer tips cleaner for me.
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If Norm has the NPP fuse pulled, that would explain it easily.

 

Norm if you want the sound, ( fuse pulled, borla x-pipe, and petal to the metal ) then extra work on the outside tips.

 

When the valves are open (which they are all the time since you've pulled the fuse), almost all the exhaust gasses pass through the outer pipes. Gasses are forced through the more restrictive path to the inner pipes only when the valves are closed.

 

My tips are clean and shiny. After 36 hours of rain, 7.22 in. on my WX station. Gonna take a nice drive up US 13 thru DE on Mon to New Castle. Norm: RT 1 still closed at Indian River Inlet. Assume it will be open by Mon.

US 13 is a smooth 65 mph limit three lanes each direction separated by acres of medial. Gotta get a "Signalink" ham radio device. My guess at 74 mph it'll be about a three hour round trip. Closest store! Ha Ha

 

Here's what the inside of the NPP muffler looks like. The solid pipe is the input to the muffler (bottom right) and output to the exhaust tip with the valve (top right). The perforated pipe is the output to the exhaust tip without the valve.

So you can see that when the NPP valve is fully open, pretty much no exhaust is going to flow into the muffler and the perforated pipe. When the NPP valve is fully closed, the exhaust gas is forced through those big holes in the solid pipe, into the muffler, through all the little holes in perforated pipe, and out the exhaust tip without the valve.

There are many times, especially in sport mode, where the NPP valves are open only partially, and you get some exhaust flow out both pipes, and an exhaust tone in between Track (full open most of the time) and Tour.

 

Here's what the inside of the NPP muffler looks like. The solid pipe is the input to the muffler (bottom right) and output to the exhaust tip with the valve (top right). The perforated pipe is the output to the exhaust tip without the valve.

So you can see that when the NPP valve is fully open, pretty much no exhaust is going to flow into the muffler and the perforated pipe. When the NPP valve is fully closed, the exhaust gas is forced through those big holes in the solid pipe, into the muffler, through all the little holes in perforated pipe, and out the exhaust tip without the valve.

There are many times, especially in sport mode, where the NPP valves are open only partially, and you get some exhaust flow out both pipes, and an exhaust tone in between Track (full open most of the time) and Tour.

View attachment 84793

Can you help me, I don't see the valve. Is it a butterfly valve I'm looking for?

 

I had never seen that picture before. Thanks, Bob!

 

So what are you cats using to keep your tips shinned? Mine seem to get dirty faster than any other part of the car. Would like to find a quick clean option. Shiny tips really stand out to me..

 

So what are you cats using to keep your tips shinned?

http://www.stingrayforums.com/forum...stingray-corvette-detailing/8680-easiest-exhaust-tip-cleaning-5.html#post347145

 

I have CQuartz applied on exhaust tips and wheels , both clean very easy with a wet cloth each time I wash the car. Best and easiest way I found yet. I clean the tips frequently also when I take her out for going on a dinner or so just give it a wipe with a paper tissue and you're done. love CQuartz !!!

 

Totally agree with you stingrayZ06! I too use Car Pro's CQuartz D-Lux -- available at many places including Amazon.

https://www.amazon.com/CarPro-DLux-...ng/dp/B00FPUIQWE/ref=sr_1_1?ie=UTF8&qid=1486932447&sr=8-1&keywords=cquartz+dlux

Just a half hour ago, after pulling into the garage, took a soft black microfiber (which had been cut into 8 pieces), put a little saliva on it and cleaned them, back to super shiny, in literally less than 20 seconds for all 4 tips. Toss the MF aside, then next time use another small piece, when all eight used, toss them into the wash by themselves, using the next MF, also in 8 pieces for the next 8 drives (always keeping several clean ones with me in my ride-along detail bag).

Use the black MF's only for cleaning the exhaust tips, wheels and the brake calipers. Less than 50 cents each here:

https://www.amazon.com/Cartman-Micr...A1XJ1A/ref=sr_1_1?ie=UTF8&qid=1486932280&sr=8-1&keywords=black+microfiber+towel

 

Driving around in track mode all the time.............unless you have some great roads there aren't you afraid of hitting a pot hole and flattening a tire? Stiff suspension and no give might cost some bucks. We were advised at the Corvette school track mode was a never unless smooth driving was guaranteed. Just curious if you've ever had a problem. thx

 

Track Mode changes the suspension damping for mag-ride equipped cars only, and those cars with larger wheels (ZF1, Z51, GS, Z06) and their low(er) profile tires will be the most susceptible to potholes.

Still, potholes suck no matter what you're driving. nthego:

 

Where has my coment gone ? Dont see it on my phone?

 

Are you referring to your post #18? As for the phone, apparently the download SRF app is not working for a number of members and hasn't been updated by the new owners. Try seeing if you use your phone's browser and go directly to the SRF site, log in, and you should see a 'mobile' version of the site that works fine.

 

I just finished installing a Flowmaster exhaust system on my base c7 with no NPP. Took first ride and like the sound but attracted the Sheriff rite away so I went straight back to garage. I hate that Flowmaster stamped their name on top of the tips. If I had seen this before I installed not sure I would have. Now it looks modified.

 

Thanks jsvette, I saw it on the web site. So I will uninstall the app...

 

My tips stay pretty shiny, except when they darken a bit. I keep a roll of paper towels in the cleaning kit bag in the trunk, quick dry wipe.....all clean. I may polish them once a year....maybe.

 

I only used Mothers aluminum polish and their cone foam polish tool, once. No cQuartz, no fancy treatments or ceramic coatings. Like Norm, I only use a little moisture with a little rag or soft paper towel, hell I even use napkins from Starbucks's with a little spit to keep 'em clean looking at our local C&C. Once shined up, easy pezzy.

 

After a drive I simply dampen a couple of paper towels and wipe down the tips. Works great, like I polished them.

 

Word of caution. If you track it in track mode a lot of heat exits the exhaust. The tips get discolored and will not buff out

 

Picture of NPP (larger tips) non NPP (smaller tips).

On the NPP, if you look into the outer pipes about 8", you'll see the valve mechanism.

 

Can I safely use fine bronze wool to polish the tips? In the hands of a novice idiot, will I end up scratching them? From what I have read, bronze wool can be used to polish stainless steel; therefore, I assume the fine bronze wool is softer than the stainless steel and would not scratch it.

Am I being an idiot?

 

Rodney, this what I use. It cleans, polishes and works great. I buy it on Amazon.

 

So what do the two valves above the rear end (differential) do?

 

Yeah I wondered that as well

 

Those are the AFM valves - open in V8 mode, closed in V4 mode so it still sounds more like an 8 cylinder.
Manual transmission, only active in "E" mode, automatic active most of the time depending on how hard your pushing the pedal

 

One minor correction: They don't actually close completely, or they'd choke off the exhaust flow. They're controlled by a PCM (pulse code modulation) circuit, and they vary the amount of opening in real time as the operating condition of the engine changes (primarily RPM and throttle opening, I think, but GM doesn't release this information).