Hey all,

I realize some of my mods are "going against the grain" as far as "Corvette tradition," so let's please move past that from the get-go. I ended up removing my stock Ti rear section in favor of a freer-flowing muffler design with a more aggressive note, and to save cost, I went with the Chinese DNA Motoring setup. Overall I'm SUPER happy with the purchase, as it sounds fantastic and does seem to give a bit more punch. However, I have the same common issue with it - the tips on the right side don't line up well.

I was looking at having a chop cut/weld/bend to get them straightened on the right side, but I saw a picture of a C5 that I really liked and I was wondering if anyone else had pictures of a similar setup. The bullet-style mufflers point straight out behind the rear tires, but then there's extraneous piping making a 180-degree turn to head back toward the center of the car, and then another 90-degree turn to exit through the tips. My idea was to simply go straight out the side with a 6" cut of 2.5" pipe, below the rear bumper and immediately behind the rear tires, as illustrated below.

This would ALSO give me more room to add a rear diffuser, as I am slowly addressing aero issues with the car (front feed, vented hood, slick bottom front belly pan, front splitter, rear diffuser is the plan after reading several dozen aero threads).

...yes, I realize I'm going to get a TON of graphic design job offers after the forum sees my masterful MS Paint skills.

Thoughts/opinions/more pictures of a setup like the one I'm imagining? Seems like it would save maybe 3-5 lbs as an added bonus, and they'd be so far in from the rear end of the car that I don't think departure angles would be an issue with the 2.5" pipe tucked very close to the rear tire.


This is essentially what the system looks like now (not my car, just a similar system)...

This is sort of what I was thinking...the yellow would be the new exits (just plain 2.5" pipe, no decorative tips)...

This is *kind of* what I was thinking, but straight out instead of at an angle...and much closer to the rear tire.

 

I think ground clearance will be a huge issue.

 

what if you had it exit out on the sides of the rear bumper and use an exhaust finisher like lots of turbo cars do?... I think that would look pretty sweet but it would leave the center section wide open and personally I think that area looks weird with nothing there

 

Well, that was my first and primary concern...but with just a 2.5" pipe, if you draw a straight line from the rear apron to the rear tire, it really doesn't seem like it would hit anything. If anything was going to hit in that area, it would certainly hit the front lip first...and I don't even scratch in my sloped driveway in the front anymore.


That's a little too "ricky racer" for me...not to mention a LOT more work and expense! My car isn't turbo, and I don't want to call *that* much attention to myself unless it's more than fast enough to offset routing my exhaust through holes in body panels. haha. I just thought I'd have better options with rear aero/diffuser without the quad tailpipes there, and less exhaust piping in that back area to worry about. The extra 270 degrees of bends at the back of the car is akin to reducing the pipe diameter by about an inch, flow wise.

 

yeah it isn't for everyone, I get that... what if you just used a turn down off the end of the muffler so it's pointing straight at the ground instead of trying to get it under the bumper like that blue car posted above... aside from the ground clearance it doesn't look good in my opinion

 

Well if the new system added any small amount of drone, you'd then be adding more drone by placing the exhaust right under the rear bumper. You'd then be sending pressure waves through that area, and it will resonate up through the fiber glass tub, trunk, and bumper more. Not to mention possible heat degradation of some of those parts. Also as mentioned, you'd have that huge center gap that even aftermarket diffusers do not fill in. At least none that I'm aware of. You'd also have to find a way to secure the outlets, because the hangers that attach near the tips would be cut off if you went that route. They would bounce around and vibrate quite alot.

 

Quick reply to all comments thus far, lol...no resonance really, but I wouldn't want a dump underneath the car for that reason. Finding a place to secure the over-axle pipe is easy enough (saw 2 options when I was under the car...probably about a 15 minute job with a lift and a MIG). No, there aren't any off the shelf diffusers that would work, but I have some ideas sketched out after seeing a few wind tunnel test threads on C5's...most people build their own anyway. I was going to take some measurements and see if there are some cheap off the shelf options for other cars that might come close to filling the gap, and then piecemeal the setup together...or just make it from scratch.

Not in a huge hurry to get this done, but if/when I do I'll post my shitbox. Thank you for playing devil's advocate with me!

I meant to attach this pic earlier, just my thinking on the breakover angle. Mine has a bit more rake front to rear, so I don't think I'd be able to hit them on anything in the back unless I took it off-roading!

 

My comments respond to your exhaust question but in an indirect manner. My comments are based on actual experience finessing and fabricating underbody aerodynamics on a Lotus Exige that I used on the track (2,500 miles logged...doubled as seat time to evaluate aero) and for canyon carving over a 12 year period. Aero is a never ending chase and often involves compromises based on physical (chassis design) limitations.

The placement of the exhaust outlets will be totally dependent on your under body aero package. Designing, fabricating and retrofitting underbody functional aerodynamics for a C5 could be a challenging, lengthy, and likely expensive process. It will involve a lot of trial and error and testing at high speeds. A C5 with fully functional underbody aero would be stealth; it would look almost factory stock from the topside and would be wonderful to drive at speed (80 mph+). Depending on how you use your car that could be good; it wouldn't score many looks at Cars & Coffee...but a big wing and carbon fiber bling would.

There are two types of rear diffusers: functional, and; adornment (this is a nice word for the candy-*** tack-on do-dads that do nothing...zippo...nada).

If you intend to create a functional rear diffuser, the underside of the car must have a continuous flat surface that allows laminar air flow from the nose of the car to the entrance of the rear diffuser. Air flows under a properly prepped car much in the same way that water flows down a slightly sloped driveway surface (smooth and uninterrupted is good for flow; diversions, level changes and surface interruptions are not good).

The design of the rear diffuser will depend greatly on physical limitations of the chassis; this is especially the case when done as a retrofit. At minimum, the rear diffuser will have a pretty large surface area (lengthwise, and it will be as wide/maybe wider than the body's rear-end), it will have be angled upward to create a vacuum and pull air outward, and it will have long strakes for air flow separation (packaging and routing of car mechanical systems and ground clearance are the compromises).

So, once you have done a mock-up of or fabricated your flush under body panels and rear diffuser, you'll know how much space is left to retrofit your exhaust outlets. There will not likely be enough room between your flush underbody panels and chassis for your exhaust outlets be routed cross-ways. Most obvious choices are: integrate the exhaust outlets into the diffuser design exiting rearward (check out some Ferraris); integrate the exhausts so they dump downward through the diffuser (F1 cars circa 2017 as well as the Lotus Exige OEM design); exit above the diffuser (check out a Ferrari 360, Pagani, new Ford GT). For my Lotus Exige, I rerouted the OEM exhaust to exit above the diffuser in the cavity located between the underside of the trunk floor and topside of the diffuser (great for aero management, but the trunk would become very warm...the compromise).

Plan accordingly.