5.3 squashed y-pipe

[code-man26]

While I was admiring the underside of my bran new 19 Silverado I noticed the exhaust pipe, immediately after the cat, is squished, like super flat... Has anyone replaced that section with a normal round piece of tubing? Did it make any improvements in sound/mpg? Seems like it must! 

[eppieguy]

That's the way they are supposed to be, even the Camaros are that way, tests have been done with changing out the pipe and there were no changes. 

[Donstar]

Maybe "history can inform the present"!

 

 

[Wheelguy]

I know for a fact that the dents are a byproduct of the bending or flat area tube forming process.  It's not easy to manufacture a pipe with a flat so close to a bend or even bends close to insertion joints (connections) - it's the nature of the beast.  Sometimes the material doesn't cooperate or small mistakes are made during the manufacturing process and missed by human eyes (in the case of the dents) during visual inspection.  Often, GM will overlook small "shortcomings" like this because while visually not appealing or causing possible end owner concern, they are of little impact to how the full emissions system ends up working and the name of the game is to continue pumping out trucks from the assembly plants.  Both GM and the exhaust supplier work out the kinks (no pun intended) in the meantime.  That's why the dents (pictured in the older thread) will more than likely or should I say hopefully slowly start to disappear as more trucks (and exhaust systems) are built.

Edited July 24, 2019 by Wheelguy

[Cohocarl]

I noticed how the exhaust on my 5.3 is "clearanced" where it crosses over.  

I'm not an engineer, and I'm sure it's not as constrictive as it looks...but being pinched off like that looks painful.  Seems to me there would be reduced flow due to the turbulence it would make.  

[code-man26]

Yes, once my MBRP cat back gets here I'll take the truck down to the muffler shop to get a proper round tube fitted. The squished one just annoys my OCD.

[Wheelguy]

The design of that crossover pipe is absolutely nothing with which you should be concerned to the point you start removing stock tubing in favor of round tubes.

 

Pipes are formed in specific shapes for good reasons - typically for either access (getting a tool to a fastener behind a pipe) or clearance.  The simplest form of a pipe is round and straight - they don't deviate from that shape for sh!ts & giggles.  Once the emission gasses pass through the converters, it's all about acoustics (sound) and volume (inside the tubes, collector, adaptive valves, muffler and any resonators, etc.).  The volume in that area of the crossover pipe is pretty much the same as the round tube portion would be.  When making pipes with these types of features and using the cheaper manufacturing methods for high volumes (quantity), material is typically moved around, not removed or reduced (or that is at least the goal) during the forming process.

 

There are GM requirements for clearing both vehicle undercarriage, surrounding components as well as ground clearance.  That's what GM ends up with given those requirements.  The previous generation (K2XX) crossover pipe was also formed in a similar fashion but has a different cross sectional shape in that general area.  The design of that area of the crossover pipe takes into consideration the starting tube diameter/circumference, so putting a round tube in there will change nothing other than possibly start causing interference which can lead to undesirable noises or taking damage under certain conditions.  The entire system is tested both virtually (simulated on a computer using 3D models) and physically literally years before these trucks are built.  The entire exhaust system performs the way GM desires it to perform, even with that flattened tubing.  If there were any deviations from expected flow behavior, there is absolutely no way GM would allow those pipes on production intent vehicles and the supplier wouldn't be too keen on spending money on tooling to produce parts that ended up being a detriment somehow (of course, that all depends on how GM desires the system functions as a whole, too).

 

However weird anything with the exhaust systems look, there's usually a very good reason GM didn't want that pipe to be round on either side or have a bash here or there.  They don't make manufacturing a pipe more difficult, time consuming and costly just for looks or their own amusement.  That costs GM money.  The suppliers of the exhaust systems don't deform, flatten, bash, etc. tubing for looks or wasting machine production time either - that stuff costs money and they want it out of the plant as soon as possible in terms of processing time.

 

But hey, it's your time and money you're wasting and it's your truck - you do what you want with it.

 

Finally, I wouldn't waste my time responding to any of this if I didn't have intimate and first hand knowledge about the above, whatever that may be worth to you.

Edited August 1, 2019 by Wheelguy

[code-man26]

Wow, you put a lot of effort into that post to say the same thing over and over. I bet you also agree with GM on the whole Auto Start/Stop function too...?

There is absolutely no other reason for that squished pipe other than for clearance and maybe to quiet the exhaust down to Denali owner desires. I desire 'some' noise from my truck and rather than spending $800 on a full exhaust system (where you remove EVERY stock tubing), I'll just tune the stock system and this is a super easy/simple way of achieving 'some' noise. My last truck (05 LLY Duramax) had a similar squished downtube that was for clearance also. After I replaced it with a true 3" round downtube I gained better throttle response, lower EGT's and better sound so, I'm speaking from intimate and first hand experience.

[Wheelguy]

Wow, you put a lot of effort into being more or less a dick. Sorry but, my crystal ball was in the shop, ace. Hope you get the sound you’re after.

Edited August 2, 2019 by Wheelguy

[fieldsend]

I would rather get a quality catback instead of hacking up my factory y pipe for "more sound". It will do virtually nothing on this truck without removal of the cats and I bet cutting that y pipe will void your warranty. 

[fatwhiteboy]

On ‎8‎/‎1‎/‎2019 at 10:58 AM, Wheelguy said:

The design of that crossover pipe is absolutely nothing with which you should be concerned to the point you start removing stock tubing in favor of round tubes.

 

Pipes are formed in specific shapes for good reasons - typically for either access (getting a tool to a fastener behind a pipe) or clearance.  The simplest form of a pipe is round and straight - they don't deviate from that shape for sh!ts & giggles.  Once the emission gasses pass through the converters, it's all about acoustics (sound) and volume (inside the tubes, collector, adaptive valves, muffler and any resonators, etc.).  The volume in that area of the crossover pipe is pretty much the same as the round tube portion would be.  When making pipes with these types of features and using the cheaper manufacturing methods for high volumes (quantity), material is typically moved around, not removed or reduced (or that is at least the goal) during the forming process.

 

There are GM requirements for clearing both vehicle undercarriage, surrounding components as well as ground clearance.  That's what GM ends up with given those requirements.  The previous generation (K2XX) crossover pipe was also formed in a similar fashion but has a different cross sectional shape in that general area.  The design of that area of the crossover pipe takes into consideration the starting tube diameter/circumference, so putting a round tube in there will change nothing other than possibly start causing interference which can lead to undesirable noises or taking damage under certain conditions.  The entire system is tested both virtually (simulated on a computer using 3D models) and physically literally years before these trucks are built.  The entire exhaust system performs the way GM desires it to perform, even with that flattened tubing.  If there were any deviations from expected flow behavior, there is absolutely no way GM would allow those pipes on production intent vehicles and the supplier wouldn't be too keen on spending money on tooling to produce parts that ended up being a detriment somehow (of course, that all depends on how GM desires the system functions as a whole, too).

 

However weird anything with the exhaust systems look, there's usually a very good reason GM didn't want that pipe to be round on either side or have a bash here or there.  They don't make manufacturing a pipe more difficult, time consuming and costly just for looks or their own amusement.  That costs GM money.  The suppliers of the exhaust systems don't deform, flatten, bash, etc. tubing for looks or wasting machine production time either - that stuff costs money and they want it out of the plant as soon as possible in terms of processing time.

 

But hey, it's your time and money you're wasting and it's your truck - you do what you want with it.

 

Finally, I wouldn't waste my time responding to any of this if I didn't have intimate and first hand knowledge about the above, whatever that may be worth to you.

As much as I enjoyed the read, unless you calculated the CFM of the cross section of the crushed area this is all BS.  Cost overrides quality at GM and most OEM's.  The machine to crush this tube is much cheaper the fabricating a nice oval or hydroforming the tube to keep the size consistent.  When I get the time to cut mine off, I will calculate the CFM of the crushed area and I'd bet a  C note that the left bank is running richer than the right due to flow restriction on that side.  The flappers are a bigger joke.  When I took my exhaust off to put the Borla cat back on, at only 4000 mile they already had carbon build up.  These are probably why GM extended warrantee does not cover the exhaust, they know these valves will fail. 

 

I have been in automotive engineering for 30 years, 10 at GM and I build race cars and trucks for fun.  Think of your engine as a simple air pump, fast smooth in and fast smooth out makes for more efficiency.

[Saul Cruz]

I just changed out that squashed pipe on my 2021 Silverado 4.3 v6. Also had the tech weld open that silly muffler flap. These are the results:

*sounds a bit louder when I accelerate 
*the engine doesn’t sound like it’s struggling, in fact - the shifting in gears is much smoother for some reason

*maybe a mile or two increase in mpg

 

[Thisisfuckingretarded]

On 7/24/2019 at 6:25 AM, code-man26 said:

While I was admiring the underside of my bran new 19 Silverado I noticed the exhaust pipe, immediately after the cat, is squished, like super flat... Has anyone replaced that section with a normal round piece of tubing? Did it make any improvements in sound/mpg? Seems like it must! 

i noticed the same thing on mine as well as a dent in the passenger side s pipe coming off the manifold just before the cats, the in between piece. i'm considering doing a forced induction setup on mine