Exhaust Butterfly Control

[Mac-427]

My last LS7 car was a 427 Corvette Vert. As with our Z-cars, it had vaccum controlled butterfly exhaust valves that opened at a certain RPM. I bought a controller for it that allowed me to open and close the exhaust butterflies with a floor mounted switch. Does such a kit exist for our cars, and has anyone tried one? Thank You

[MonroeZ28]

Take out the fuse in the panel in the trunk on the right side labeled" exh flap" F8 it's a 10amp fuse. This will make the baffles stay open all the time. Car now sounds awesome all the time.

[608RS]

look up the Forza Exhaust Controller, he's also on the forum. i installed it on my 2ss to control my NPP. Great option if you want the ability to tone it down on the fly

http://www.forzacomponenti.com/exhau...troller_d.html

[Mac-427]

Thanks men, appreciate the help.

[Hunt-man]

What are these exhaust valves for? Why do they even put them in?

[chip4]

This is from the corvette forum, I'm sure the EFC tuning is similar on the 5th Gen Camaros:

8. Q: What is the NPP Dual Mode Exhaust Option and how does it work??

NPP is the Regular Production Option (RPO) code for the Dual Mode Exhaust Option first offered to non-Z06 Corvettes in 2008 as an $1195 option. LS3 engines equipped with NPP get a bump in horsepower rating from 430 to 436. Modeled after the exhaust on the Z06, the exhaust uses a butterfly valve over one of the exhaust exit pipes (two total, one per muffler) to vary the exhaust output. It works similar to exhaust cut-outs popular on the street rods.

NPP Exhaust Valves

The exhaust control is operated by engine vacuum pressure. The system is tied to the pcm and monitors rpm and throttle position to measure "driver intent". Under normal circumstances the exhaust valve is closed and it routes the exhaust gas out of the other pipe after it passes through the baffle chamber of the exhaust. In this case it is quieter. If the driver accelerates hard the valves will open at 2,800 rpm as long as the driver is above 80% throttle. Between 30% and 80% throttle the exhaust will open during acceleration at 3,500 rpm.

The valves will be open for the first two seconds that the car is started. It requires time for the vacuum pressure to build to close the valves. After that The operation of the NPP is normally closed, open on demand. Have someone stand behind the car and bring up the RPM to 3,500 and you should see the valves open. The butterfly operation is tied to the throttle position sensor and the RPM. It uses the throttle position to determine driver intent.

Under normal operation the valves work as follows:
◦Below 30% throttle and 3,500 rpm the valves are closed
◦Above 30% throttle and 3,500 rpm the valves will open
◦Between 30% throttle and 80% throttle and above 3,500 rpm the valves are open
◦Above 80% throttle and above 2,800 rpm the valves are open

[Hunt-man]

How does the valve add horsepower? Seem that it would reduce it.

I'm gonna pull that fuse. . I've always wanted it a bit louder.

[chip4]

Originally Posted by Hunt-man

How does the valve add horsepower? Seem that it would reduce it.

I'm gonna pull that fuse. . I've always wanted it a bit louder.

Hunt-man you sure do ask a lot of questions.
A lot of factors and components are involved in engineering an exhaust system: Valve timing /overlap, throttle position, exh flow, pipe diameter/length, cat, muffler placement, etc. One component: Adding or I should say "tuning" backpressure at certain (lower) RPM’s, has been known to improve scavenging effects of the engine pulses which help increase power/torque in a particular power band in some engines.

[Dropspeed]

Originally Posted by Hunt-man

What are these exhaust valves for? Why do they even put them in?

Originally Posted by chip4

Hunt-man you sure do ask a lot of questions.
A lot of factors and components are involved in engineering an exhaust system: Valve timing /overlap, throttle position, exh flow, pipe diameter/length, cat, muffler placement, etc. One component: Adding or I should say "tuning" backpressure at certain (lower) RPM’s, has been known to improve scavenging effects of the engine pulses which help increase power/torque in a particular power band in some engines.

While the above answer is correct, it is much more simplistic on the Camaro. With the valve in the closed position, exhaust gas is routed through the muffler chambers and through the inner tips so it will pass db limit testing on the normal drive cycle. With the valves open, the exhaust flows through the outer tips and straight through the muffler.

Even though forums like to argue this, HP is increased with the NPP exhaust valves open because the restriction of the muffler chambers is taken out of the equation and backpressure is reduced slightly. It is minor (3hp range), but there is an increase.

Now if you take a Dodge Challenger and bypass or leave the valve open you will set off a check engine light and the vehicle will run rough as the exhaust valves are tied into their emissions control system closer to the middle of the car and are being use to adjust backpressure etc as noted above.

-Matt

[Hunt-man]

Ha! Yes I seek knowledge so, yes I ask a lot of questions. Thanks for the answers.

I pulled the fuse and ran around today. It seemed to skip when it was just started. Later I didn't notice any difference. It sounded good. Took it to Costco and found another Camaro parked next to me. Nice couple in an orange and black one.

[Mac-427]

I'm the guy who started this thread and have followed it closely. As a consequence, I took a look at the 10 amp fuse involved, tested it and found it was working fine but my butterflies remain constantly open. I love the sound, but still want things to work right. Has anyone experienced the butterflies sticking open, and if so, what is the remedy? Thanks again for your thoughtful and informative answers.

[Snowmanvii]

Be careful though if the police in your area are not car guys. Pulled my fuse and got pulled over for exhaust being too loud.

[608RS]

Originally Posted by Mac-427

I'm the guy who started this thread and have followed it closely. As a consequence, I took a look at the 10 amp fuse involved, tested it and found it was working fine but my butterflies remain constantly open. I love the sound, but still want things to work right. Has anyone experienced the butterflies sticking open, and if so, what is the remedy? Thanks again for your thoughtful and informative answers.

are you the original owner of the car? you'll want to investigate your dual-mode connections near the rear-right wheel and make sure nothing was disconnected.

[clarkkent]

Is the Z28 NPP different than the SS/1LE/ZL1 NPP? If it's the same, it's nowhere near as complex as posted above from the Corvette.

It's open from idle to 1,500 rpm, closed 1,500 rpm - 2,000 rpm, then open from 2,000 rpm to redline

The mild2wild switch will only allow always open or factory control, which is like pulling the fuse and putting it back in. No "stealth mode", flaps always closed option

You can get the Forza 3 way wireless controller, which is plug and play but expensive. It does open, closed, and normal operation.

Or, for like $20, you can wire your own 3 way switch in that does the same thing. I have the 3 way switch wired in and it's great to be able to go into "stealth mode" when needed (look at post 9 here http://www.camaro5.com/forums/showth...t=stealth+mode)