Project Viper GTS: Part 6 - Corsa Exhaust and Kooks HFC

Project VIPER GTS: Part 6 - Corsa Performance Exhaust and Kooks Green Cats

by Billy Johnson

After some impressive gains from intake work in Part 4, we now turn our attention to the opposite side of the engine to improve the evacuation of exhaust gasses as well as reduce the cabin temperature of our notoriously hot viper.  For as outlandish and attention grabbing the Viper’s style was, the exhaust note did not have the same head-turning appeal.  To remedy this we reached out to our friends at Corsa Performance for their 3” cat-back exhaust to give our viper a more sporty and refined tone.  To further boost the volume and greatly knock down the calf-burning side sill heat, we installed a pair of compact Kooks Green Cats which are both environmentally and power friendly. 

The Viper’s odd-firing 90-degree V-10 is not an inherently balanced design like an I-6, V12, Flat-6, or V8.  This combined with separated side exhaust made the Gen 1 Viper sound far from ‘exotic’, with a 5-cylinder exhaust note that some described as sounding like UPS trucks (which are usually powered by Ford “300” inline 6-cylinders and sound nothing like a Viper to me).  The 2nd Gen Vipers had the exhaust routed to the back of the car which resulted in a slightly smoother sound by having the exhaust pulses of all 10 cylinders coming from the same place. 

When it comes to a performance exhaust for the Viper, there are a variety of options which they vary greatly in terms of price, quality, and sound.  The Corsa Performance exhaust really seems to stand out with its smoother and more refined pitch while delivering one of the quietest cabins with virtually zero drone; a notorious problem for the Gen 2 coupes. 


Viper GTS Corsa Exhaust RearMade of T304 stainless, the Corsa Performance exhaust looks great and will be extremely durable.
Corsa Viper GTS Exhaust TipsNot to mention they have some of the best exhaust tips around, which is always important.
Viper GTS Stock RearOur Viper already had an aftermarket rear exhaust that deletes the rear muffler and did not come with a flashy exhaust tip.  I personally didn’t mind the utilitarian look since racecars don’t have shiny exhaust tips, but most people love chrome and I admit it’s hard to dislike a quality exhaust tip like the ones Corsa uses.
Viper GTS Cat Delete UnderThe only modification on the car when we acquired it was the rear muffler delete.  The pipes were nicely made and TIG welded, but despite giving our car a louder than stock sound, it was still too quiet and left something to be desired as far as its pitch.
Viper GTS Dyno K&N Smooth TubesIn Part 4, our Viper made an impressive 451.83 hp and 493.17 lb-ft of torque from K&N filters, smooth tubes, and this aftermarket rear muffler delete exhaust.  We were anxious to see how much more power the Corsa Performance exhaust and Kooks Green Cats would make since there are not a ton of A-B comparisons in the Viper community.

The installation of the cats was going to require some welding and fabrication to connect to the off the shelf cat-back exhaust, so we headed back over to our friends at RareFab in Boynton Beach, Florida - where the majority of Project Viper is worked on. 

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Monday, April 11, 2016 11:36 PM
Have I mentioned the 2nd Gen GTS is my first automotive love? I may not be able to resist the call of temptation much longer. That Corsa exhaust is just perfection!
Tuesday, April 12, 2016 10:22 AM
...and what about the EPA test with the new CATs and tune? Did the car passed it? Is it street legal again?
Tuesday, April 12, 2016 11:44 AM
^doesn't matter. to be actually street legal to the letter of the law, all emissions control equipment must be OEM.
Tuesday, April 12, 2016 12:59 PM
cause the viper totally needs more off idle torque... haha

this is a joke...
Tuesday, April 12, 2016 1:31 PM
@IVO - The car resides in FL, which has no smog check or emission standards and as it says in the article:

“Green Cats” do not rob power ...are OBD-2 compliant, and meets EPA Federal emission standards and are 49-state certified (due to the California Vehicle Code Section 27156 and 38391)."
Tuesday, April 12, 2016 3:15 PM
Great article!
I might check the guys @ Rarefab to get my stock muffler modified!
Mike Kojima
Mike Kojimalink
Wednesday, April 13, 2016 12:17 AM
Us do an EPA 4 bag FTP test? Thats thousands of dollars.
Colorado S14
Colorado S14link
Friday, April 15, 2016 12:16 PM
It looks like Vibrant Performance is making the same cat using the GESI core. Hopefully some good old fashioned business competition drops these down in price a bit.
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