Factory Crossover Restriction

[dennisfly]

 I have a new 2021 LT, 5.3, crew cab, 4wd, Z71.  The picture of the crossover shows it was severely crimped during manufacture.  This appears to be by design and if it hadn't been done it would extend below the frame/skid plates.  It has to be disastrous for flow rate.  Why such large pipes downstream from this?

[eppieguy]

They’re all that way and it’s been discussed a lot and most say you aren’t going to gain anything with a round tube vs. the flattened tube. 

[redwngr]

It's that way by design.

There was even a bulletin...which  is likely in at least some of the other threads about this.

 

https://gm-techlink.com/?p=13456

 

Exhaust Pipe Shaped to Avoid Low Contact

July 30, 2020

A quick look at the exhaust pipe crossover section on 2019-2020 Silverado and Sierra models equipped with a V6 or V8 engine shows that it is not a completely round shape as other parts of the pipe. (Fig. 27) The unique shape of the exhaust pipe is by design. The kinks or shape of the pipe does not indicate the pipe is damaged.

 

Fig. 27

 

The exhaust pipe is distinctly formed in order to make it higher from the ground than the adjacent frame members. (Fig. 28) Due to its unique shape, it is not the lowest part on the vehicle and is protected by the frame from contact while traversing over areas with low ground clearance, which helps prevent it from being struck by objects passing under the vehicle. While driving off road, for example, an object would strike the frame first.

 

Fig. 28

 

The design of the crossover section of the exhaust pipe is hydroformed, or shaped by hydraulic pressure, to an ovate shape that has the same cross-section as a round part of the pipe.

There is no flow restriction from the shape and it does not affect engine performance in any way. (Fig. 29)

 

Fig. 29

 

 

 

[dennisfly]

Good info.  Thanks