Originally Posted by bfsgross

I can't imagine anyone here not aware of exhaust mods performed on STR's. Those interested in an exhaust mod and those who have already implemented re-pipeing may recieve some insight from this thread prior to cutting up and welding in their masterpiece of pipes or re-pipe: Obviously when coupled to a 112 cu. in. Eaton design positive displacement supercharger (PDS), the little 4.2 DOHC 32 valve belts out power (400 hp @ 410 lb/ft torque). The PDS effectively increases engine displacement to nearly 6 litres but with a much more dense air and fuel mixture forced down her gullet...creating power rivaling the 6+ litre GM metal. Some of us would love to enhance this process and the most common methods that may come to mind is increasing air intake and out-take (exhaust) that compliment the areas of the power curve that matters the most in street or track competition. The STR can definitely handle improvement in both air in and and air-out departments...we installed low restriction air filters and smaller blower pulleys, and await Mafioso's "Big Suck" air intake tube. My recent experience with my 03 STR's air-in-air-out modding has taught me the lesson of: "Don't over do it" in the air-out department. The Magnaflow hi-flow cats? Wow! Definitely do this...huge improvement in throttle response and cylinder scavenging, allows the motor to suck more air in (this likely lowers block temperatures too +++). Magnaflow X-pipe? Wow! again...the engine loves this; as it evens out and smooths exhaust impulses, again allowing much improved cylinder scavenging. Continue with either 2 1/4 or 2 1/2" pipe to the muffler. Your choice of muffler is what I believe to be critical at this juncture. If not using a pulley smaller than 1.5 lb., you may make the mistake of welding on a flow through muffler and lose noticeable and mucho needed low end torque. I wouldn't be writing this if the STR was blessed with an LSD differential sporting 3:25:1 or lower cogs. At the present I have the above full exhaust mod but with 12" Dynomax glass packed tube (flow through) pre-mufflers leading to Dynomax Super Turbos (14", glass packed, two-chamber with full throttle by-pass tube), low temperature thermostat, K&N filter, and a 1.5 lb pulley. IMO this combo is perfect because it: breaths, maintains low end trq., and emits a combo of rasp and growl without filling the cabin with annoying resonance while at cruise. From a stop my STR launches harder than when it was stock and with flow through mufflers. The balance of exhaust noise to blower whine is perfect. The launch growl is just "Right" and when "off it" cruise noise is comfortable with just a little more than subtle deep exhaust groan. Without pre-mufflers the Dynomax Super Turbos emit annoying interior resonance, most notable when climbing a hill in high gear. When I had the Magnaflow mufflers there was a noticeable loss of low end torque (trq.)...sounded real mean but definitely some low end trq. missing. With a 3 lb. pulley (which i'm still hedging on) and Mafioso's air intake tube perhaps some or all of that missing torque will come home with a flow through muffler. Otherwise, the s/c 4.2 is a good breather out of the box but stands to be improved. "Over-improving" the air-out dept. may emit impressive sounds albeit at the cost of "another" showin ya his butt whilst ya wondering "Where have all the low end grunt gone". Happy to answer questions and Happy Holidays.

Originally Posted by bfsgross

Hi jag79. Close...use aluminized steel 18" Walker glasspacked tube mufflers ($45/pair?). I'll sift through the Summitt Racing site for the mufflers and will get back soon.