Exhaust help, I'm so lost!!!

tim5779 · December 30, 2018

Alright, so I've literally spent probably 8 hours or so researching on this forum about exhaust and intake upgrades. (I have a '17 Sierra 5.3) Obviously the CAI horse has been beaten to death on pretty much every forum immaginable. I'm a Mechanical Engineer by trade so data goes a long way with me. From what I've seen, on this new Ecotec engine, you don't really gain a whole lot with a CIA, many have just resorted to the Airaid MIT, but even that only see's minimal improvements and only around 5,500 rpm. So I just opted to go with the AEM dry filter for a bit more flow, and call it a day. I've even thought about doing the airbox mod, but when I got everything apart, the cross sectional area of the square hole in the airbox looks to be about the same as the cross sectional area of the intake tube diameter...So whats the point? (unless I'm missing something). So I just left it at the new AEM filter and called it a day. I have the level and 33's on this truck, so I'm not looking to drag race it. Just get it to breath as well as possible. Any input or opinions on this setup would be appreciated. Now on to the exhaust. I plan to just do a muffler swap, so I bought a new Borla Pro XS. I've seen a TON of debate on "leave the resonator, remove the resonator, leave the flapper, remove the flapper". I dont want this thing to be loud. I just want it to sound good and "natural". So as I said, I just opted to leave everything stock and replace the muffler. HOWEVER, I scooted under the truck this morning just to take a look, and now I'm completely baffled (pun intended). It looks to me like the resonator on this truck is AFTER the muffler!?!? You have the giant oil barrel shaped muffler with the flapper just in front of it, then downstream you have a (roughly) 8" diameter round barrel which I can only assume is the resonator? So my question is, is that correct, or am I missing something? ...maybe I have it backwards? Also, is leaving the flapper and resonator the correct thing to do if I just want a slight sound upgrade? Thanks guys!

KARNUT · December 30, 2018

Alright, so I've literally spent probably 8 hours or so researching on this forum about exhaust and intake upgrades. (I have a '17 Sierra 5.3) Obviously the CAI horse has been beaten to death on pretty much every forum immaginable. I'm a Mechanical Engineer by trade so data goes a long way with me. From what I've seen, on this new Ecotec engine, you don't really gain a whole lot with a CIA, many have just resorted to the Airaid MIT, but even that only see's minimal improvements and only around 5,500 rpm. So I just opted to go with the AEM dry filter for a bit more flow, and call it a day. I've even thought about doing the airbox mod, but when I got everything apart, the cross sectional area of the square hole in the airbox looks to be about the same as the cross sectional area of the intake tube diameter...So whats the point? (unless I'm missing something). So I just left it at the new AEM filter and called it a day. I have the level and 33's on this truck, so I'm not looking to drag race it. Just get it to breath as well as possible. Any input or opinions on this setup would be appreciated. Now on to the exhaust. I plan to just do a muffler swap, so I bought a new Borla Pro XS. I've seen a TON of debate on "leave the resonator, remove the resonator, leave the flapper, remove the flapper". I dont want this thing to be loud. I just want it to sound good and "natural". So as I said, I just opted to leave everything stock and replace the muffler. HOWEVER, I scooted under the truck this morning just to take a look, and now I'm completely baffled (pun intended). It looks to me like the resonator on this truck is AFTER the muffler!?!? You have the giant oil barrel shaped muffler with the flapper just in front of it, then downstream you have a (roughly) 8" diameter round barrel which I can only assume is the resonator? So my question is, is that correct, or am I missing something? ...maybe I have it backwards? Also, is leaving the flapper and resonator the correct thing to do if I just want a slight sound upgrade? Thanks guys!

The exhaust is designed with flow and noise reduction in mind. The resonator is always after the muffler and is a muffler, all high flow. Anything to increase sound will give you the V4 chopper sound, be prepared for that. I did a muffler delete and later added a mega flow type muffler. In my younger days the muffler delete would have been enough. I grew to appreciate just how quiet the interior of the truck was. I didn't need to drown out rattles or wind noise. I tuned out the V4.

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Fishtail8 · December 30, 2018

On my 2015 5.3 I did a muffler delete, keeping the flapper and resonator in. I found by leaving the flapper and resonator in when V4 kicked in on the highway the drone and chop from V4 was not that noticable. When I did the same mod on my 2017 6.2 they cut the flapper out with the muffler and the drone and sound of the truck was louder then I wanted. They put the flapper back in and the sound around town is great and on the highway it's almost as quiet as stock. I would try just the muffler delete, keeping the flapper and resonator. It's a cheap start and if you don't like the sound then you go back and put a muffler on it. Unfortunately one person's quiet exhaust is too loud for others, just do a little mod at a time till you find the sound.

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tim5779 · December 30, 2018

52 minutes ago, Fishtail8 said:

On my 2015 5.3 I did a muffler delete, keeping the flapper and resonator in. I found by leaving the flapper and resonator in when V4 kicked in on the highway the drone and chop from V4 was not that noticable. When I did the same mod on my 2017 6.2 they cut the flapper out with the muffler and the drone and sound of the truck was louder then I wanted. They put the flapper back in and the sound around town is great and on the highway it's almost as quiet as stock. I would try just the muffler delete, keeping the flapper and resonator. It's a cheap start and if you don't like the sound then you go back and put a muffler on it. Unfortunately one person's quiet exhaust is too loud for others, just do a little mod at a time till you find the sound.

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When you say muffler delete, are you saying you just welded in a straight pipe, or did you do a muffler "swap" with a high performance muffler like the Borla I purchased?

tim5779 · December 30, 2018

Nevermind, I just re-read what you said. Sounds like a logical plan.

Fishtail8 · December 30, 2018

When you say muffler delete, are you saying you just welded in a straight pipe, or did you do a muffler "swap" with a high performance muffler like the Borla I purchased?

Just welded in a straight pipe. I was figuring if I didn't like that sound then go and put a muffler back in. Only cost $75 to try it out. Just make sure they keep flapper and resonator.

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Mikebtte · December 30, 2018

Chiming in on the CAI.

You can only get as much air as your throttle body has a CFM rating for, I want the MIT with the dry filter. Airaid has a chart showing the CFM of the MIT being higher than stock and getting maximum air flow with the factory CAI set up. If you want more you should upgrade a lot more than the intake. Tune, cam, throttle body bore size and possibly an intake manifold.

On the exhaust. If your putting more air in, you will need to get more out, you will have "drone" and here the V4 mode. This never bothered me as my whole life people have run load exhaust and never talked of drone cause it was expected of the new exhaust.

You can have the V4 mod turned off. My fuel use is the same with V4 off as it was on and I don't here the V4 sound.

Hope this helps

tim5779 · December 30, 2018

44 minutes ago, Mikebtte said:

Chiming in on the CAI.

You can only get as much air as your throttle body has a CFM rating for, I want the MIT with the dry filter. Airaid has a chart showing the CFM of the MIT being higher than stock and getting maximum air flow with the factory CAI set up. If you want more you should upgrade a lot more than the intake. Tune, cam, throttle body bore size and possibly an intake manifold.

On the exhaust. If your putting more air in, you will need to get more out, you will have "drone" and here the V4 mode. This never bothered me as my whole life people have run load exhaust and never talked of drone cause it was expected of the new exhaust.

You can have the V4 mod turned off. My fuel use is the same with V4 off as it was on and I don't here the V4 sound.

Hope this helps

Hey Mike,

Check out the independant study (very important) that Black Bear performance did on multiple CAI's on our truck. The MIP actually performed better than the other full CAI systems. If I remember correctly it was absolutely no improvement, until 5,500 rpm, where they saw like a 1-2 horse gain. To me thats not worth it. I agree with what was said above. If you're looking for that much performance do the entire intake/exhaust system with a tune. OR...if you have the EcoTec3 flex fuel, simply run E85 for a 10% gain across the board. Having said all that, the only reason I want more air is because in my experience, if youbwant the best sound out of your muffler, you should at least put in a high flow filter. But I've always had older vehicles and used flowmaster exhaust. Maybe the newer tech engines with Borla exhaust has obsoleted that concept and I'm wasting my time. All I'm looking for here is a nice throaty/smooth/non obnoxious sound. I'm dead set on Borla, my confusion came from keeping or removing the resonator/flapper. I think I'll just have the muffler welded on and go from there.

Jacoby · December 31, 2018

MBRP Installer series

high flow filter

a tune

in that order

you need a tune to bring it all together. Without it the other mods are just a waste of money

tim5779 · December 31, 2018

11 hours ago, Fishtail8 said:

Just welded in a straight pipe. I was figuring if I didn't like that sound then go and put a muffler back in. Only cost $75 to try it out. Just make sure they keep flapper and resonator.

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So heres a dumb question. Would the straight pipe be louder than the Borla XS Pro muffler I purchased? I guess my conflict is, I already purchased the Borla, so if its going to sound better, I may as well put it in. If the straight pipe sounds better, I may as well send the Borla back. Ha ha...I told you I was lost :-P

Jacoby · December 31, 2018

Of course it will be louder. There is no muffler

Mikebtte · December 31, 2018

10 hours ago, tim5779 said:

So heres a dumb question. Would the straight pipe be louder than the Borla XS Pro muffler I purchased? I guess my conflict is, I already purchased the Borla, so if its going to sound better, I may as well put it in. If the straight pipe sounds better, I may as well send the Borla back. Ha ha...I told you I was lost :-P

Most defiantly, IMHO you will be thrilled with the Borla. They make a great muffler and the flow is as close as you can get to that of a strait pipe. Make sure you post a sound clip if you can, be nice he here what it sounds like.

tim5779 · December 31, 2018

1 hour ago, Jacoby said:

Of course it will be louder. There is no muffler

Well no shit Sherlock ;-)

OK "louder" was a poor choice if words. Does it sound BETTER? Which I realize is a double dumb question because that is a matter of opinion. What we need here fellas, is a good ol' fashioned D.O.E. 5 different mufflers or so, then start throwing them on one after the other in different configurations. Muffler with no resonator, resonator on with no flapper, muffler resonator and flapper...and so on. You get the picture. Thats why I came here though. I bet with all the members on here combined, pretty much every configuration imaginable has been tried...hence my post.

tim5779 · December 31, 2018

7 minutes ago, Mikebtte said:

Most defiantly, IMHO you will be thrilled with the Borla. They make a great muffler and the flow is as close as you can get to that of a strait pipe. Make sure you post a sound clip if you can, be nice he here what it sounds like.

I think the obviouse course of action here is to just have the muffler shop clamp on a straight pipe, listen...clamp on the Borla, listen. Thanks for all the input.

Ozer · December 31, 2018

I did Carven TR muffler and removed the flapper. Sound is great and deep but V4 chop sounds like a military helicopter when on highway speeds in V4.

I had turned V4 off anyways (truck drives and shifts better) but i wanted to try it with the muffler on. It hurt my ears after a while so it hasnt been turned on again.

Leave the flapper on, you can always clamp it open if you need to.