Exhaust Adaptive Valve

[chuckl1218]

14'SilveradoLT - Is that with the HVAC in Auto, vent only or off?

Edited April 27, 2014 by chuckl1218

[fondupot]

I would get a 5 or 6" from Home Depot, hell you could lock it down with a 2" clamp just wrapped around the two square heads on the valve end, its just a little harder to hold when you do it but not impossible by any means.

 

Found a 3" clamp laying around in my garage. locked open the square heads. I honestly cant tell a difference in sound. But ill leave it like this until I feel like crawling back under the truck to take it off.

[iCryWheniGoPoop]

I'm not sure if that alone will make a lot of difference other than in V4 mode. I never tried it personally so I have no first hand experience

[440hsp]

With the ac on if you meant me. Lol too dang hot here in the south.

 

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[440hsp]

I like the lower rumble it makes now that I've clamped it but when you get on it you dont really hear what a 6.2 is supposed to sound like. Guess it's time to look into exhaust upgrades.

 

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[glcbn]

Clamped it open today. Tomorrow will see if anything is noticeably different.

Edited April 27, 2014 by glc

[chuckl1218]

Yeah I'm 5.3L w/ 3.42's and that was at 65mph. Seems to be about my sweet spot.

Was wondering if you achieved 24 mpg with A/C in Auto or off? Most folks post their mileage, but not whether they are running in Auto or not. I get better mileage when NOT having HVAC set to Auto even in winter.

[cansled]

I have seen a lot of speculation about the purpose of this valve, but why did GM really put it in there? Seems like a lot of work and extra cost only for sound. What are the effects of clamping it open or removing it? Torque, Power, Sound, Drone in V4....anyone know for SURE? I'm Not interested in speculation....

Edited April 27, 2014 by cansled

[14'SilveradoLT]

Was wondering if you achieved 24 mpg with A/C in Auto or off? Most folks post their mileage, but not whether they are running in Auto or not. I get better mileage when NOT having HVAC set to Auto even in winter.

 

It was in auto at 72*....but to be honest I don't how much it's ran----we've been having high 60s-to low 80s. That was with shell premium in the tank. I swapped back to mid-grade today and got 20 mpg over a 72 mile round trip. That was with 3 adults and two kids in the cab...so around 170lb more weight.

 

My lifetime over 1200 miles looked to have been around 17.1.

[fondupot]

I have seen a lot of speculation about the purpose of this valve, but why did GM really put it in there? Seems like a lot of work and extra cost only for sound. What are the effects of clamping it open or removing it? Torque, Power, Sound, Drone in V4....anyone know for SURE? I'm Not interested in speculation....

 

It's meant to reduce drone in V4 mode. Although when I clamped mine open this weekend and took it for a spin without my range unit plugged in, I didn't notice much drone, but I didn't get up to highway speeds. only around 45-50mph. My guess is it really helps at highway speeds when the truck gets into V4 mode. Because the higher RPMs will make it drone more than if it was at lower RPMs.

[cansled]

Did the 07-13 have these valves? I didn't notice any drone in my 2007 when it kicked into v4 mode with the stock exhaust. Why do the 2014's need it?

[chuckl1218]

My '11 did NOT have the adaptive valve. New for '14.

[fondupot]

Did the 07-13 have these valves? I didn't notice any drone in my 2007 when it kicked into v4 mode with the stock exhaust. Why do the 2014's need it?

 

 

The older trucks didnt have them. but these are different motors son.

With these new trucks they are trying to make them as quiet as possible. Adding the valve just makes them that much quieter.

Edited April 28, 2014 by fondupot

[glcbn]

Well, a couple things are definitely different. It stays in V4,and 6th gear a heck of a lot longer. Sometimes never downshifting to 5th where before it would constantly bounce back and forth between 5th and 6th on the roller coaster rural road that's part of my daily commute.

 

Maybe it's just me,but it seems to shift a lot smoother. Not that it didn't before, but even better now. The V4 drone is no better,or worse for that matter. The exhaust does have a much better sound too. No louder, just better.

 

So, to anyone who has been thinking of at least clamping it open, DO IT!!! IMO, these trucks would be better off without it. What were they thinking with this thing anyway.

Edited April 28, 2014 by glc

[Trackermi]

My Ducati has this baffle in there and once you hit a certain rpm it opens up all the way. I was told it was for CA emissions and noise control regulations for the bike to pass as the test is done at idle.

 

But my sierra has a high pitch noise coming from under the engine area in the exhaust when going from 4-8. I don't see this baffle all the way in the back causing this. Are there two baffles. Or one flapper valve and one baffle?

 

Yes the exhaust system has been replaced and second one does it also after a few thousand miles. Just trying to figure out where in the front area would that noise come from.

 

 

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Edited April 30, 2014 by Trackermi