Exhauste Flapper Removal

markt111 · October 27, 2018

I've searched and see many different responses, is the flapper needed without a tune? just picked up my 2015 5.3 Silverado and plane to remove the large muffler but leave resonator, can I remove the flapper as well? is it only a sound/tone in V4 mode issue or will it cause more issues?

goeb34 · October 27, 2018

Its supposedly a thing for the v4 mode but just tune it out, its for the birds anyways

Centex14 · October 28, 2018

Mine is welded open. Couldn’t hear a difference.

2014 z71 LTZ
Volant Intake
Borla Exhaust
Diablo
Bilstein 5100
Rough Country Level

Ozer · October 31, 2018

Remove the muffler and the flapper in one piece then weld on new muffler or delete pipe. Thats what im getting done saturday. That way if you ever need to go back to stock muffler, its all there.

markt111 · October 31, 2018

well I had the large muffler and flapper removed and a pipe welded in its place, perfect sound a little throatiness without drone.

it does get a little helicopter sound in V4 mode, but that will be eliminated soon enough

juscuzram · October 31, 2018

That's what I did with mine. It sounds too good that way to spend more on a new muffler haha. Nice growl, not too crazy. About as loud as the Magnaflow I had on my last truck, maybe a little quieter at idle.

Ozer · October 31, 2018

Arent mufflers required emission item for yearly inspections? Im in NY and i believe they are required

Mileguru · November 1, 2018

For those that welded/clamped open the flapper or cut it out completely, did you notice a performance difference or a stumble in the engine and exhaust when starting it up or revving it a little at idle?

I have a 6.2L with a supercharger and tied mine open for a few days. The performance (mainly throttle response) took a hit and there was a stumble while giving it a slight rev at idle. Maybe a back-pressure issue...?

markt111 · November 1, 2018

21 hours ago, Ozer said:

Arent mufflers required emission item for yearly inspections? Im in NY and i believe they are required

cats would be required, not mufflers, stock it had 3 cats and two mufflers. Mufflers are for sound reduction only.

markt111 · November 1, 2018

7 hours ago, Mileguru said:

For those that welded/clamped open the flapper or cut it out completely, did you notice a performance difference or a stumble in the engine and exhaust when starting it up or revving it a little at idle?

I have a 6.2L with a supercharger and tied mine open for a few days. The performance (mainly throttle response) took a hit and there was a stumble while giving it a slight rev at idle. Maybe a back-pressure issue...?

I removed mine all together, now that I can see what it looks like it is a definite bottleneck in exhaust flow. I have the 5.3 and have no stumble with it removed. You with the larger 6.2 and a blower would need all the flow you can get out of the exhaust, maybe it's in your tune? maybe it is the large chunk of metal on the flapper blade in your exhaust creating turbulence and restricting flow?

Centex14 · November 1, 2018

Only way that flapper would hinder performance is if it’s locked in the closed position. Otherwise it’s just a small piece of metal that’s running parallel to the air flow, just like your throttle body.

2014 z71 LTZ
Volant Intake
Borla Exhaust
Diablo
Bilstein 5100
Rough Country Level

Mileguru · November 2, 2018

13 hours ago, Centex14 said:

Only way that flapper would hinder performance is if it’s locked in the closed position. Otherwise it’s just a small piece of metal that’s running parallel to the air flow, just like your throttle body.

2014 z71 LTZ
Volant Intake
Borla Exhaust
Diablo
Bilstein 5100
Rough Country Level

It seems as logical as this, but there was absolutely a difference when I had it open. I wonder if low-end torque is hindered by having it open because of a lack of pressure, albeit a momentary lack of back-pressure because the flapper does open about two seconds after you get into the throttle.

Centex14 · November 2, 2018

It’s not back pressure.

2014 z71 LTZ
Volant Intake
Borla Exhaust
Diablo

Ozer · November 2, 2018

Lots of talk about back pressure and what it does and so on...

By the time exhaust reaches the cats and into the system, the power has already been made, exhaust is the waste exiting... Im i missing something?

The more open, more free flowing your exhaust to get as much waste out the better it is, No? Holding in exhaust gasses in the exhaust pipe to make more TQ doesnt make sense to me.

Feeel free to explain otherwise, im all ears.