General LSX Automobile Discussion - catalytic converters and exhaust noise levels
04-01-2012, 08:14 PM
I recently completed an engine conversion using the drive train from an 99 ws6, The car use ARH 1-7/8 headers, with 3 in collectors, to dual 2.5 with an x pipe out a single magnaflow muffler. I would like to both quiet the car down some and add catalytic converters. I know is a tough question as the engine noise varies with cam selection..etc. But roughly how much should the addition of catalytic converters reduce the exhaust noise? I am thinking about using the magnaflow spun cats. They are close to a 300 cell count if i remember right. Should i expect much of a noise level drop with these? The car currently idles at 108db and hit around 120 at wot
04-01-2012, 08:58 PM
I was suprised at how much the cats quieted down my car. I had long tubes with a TSP catted y pipe but then changed it to and ory cause the catted one fit like shit. I have a loudmouth 1 cat back and with the cats the exhaust level was tolerable but with the off road y it was soo much louder
04-01-2012, 09:51 PM
I just went from a catted to off road y pipe with long tubes and lm1. Id say the volume went up from a 7 / 10 to a 10 / 10:devil:
04-02-2012, 12:50 PM
My friend has this db app thing on his phone, so IDK how accurate it is... but we compared our cars from inside the car keeping the phone above the center arm rest. Both of our cars are bolt on only, he has an ORY and I have a catted Y. We both have magnaflow cat-backs. Hes auto im m6. I went in 5th so that I could more accurately match his RPMs at highway speeds. The cruising difference @ 70mph was only about 3 db. He was at 89 and I was at about 86. We did not test WOT though...
04-02-2012, 11:22 PM
When I went from stock manifolds to ebay 1 3/4 headers and a 3" the loudness of the exhaust was night and day. I'm running a Borla cat-back with no adjustment plates so the car is super loud when at WOT but actually pretty tame sounding at idle and crusing. If you want to quiet the car down some another option would be to keep the off road X and get some quieter mufflers. You may find a happy medium there.
04-02-2012, 11:37 PM
Have KOOKs LT headers and Corsa exhaust on my G8 GT with a camshaft. Recently removed the KOOKs catted connecting pipes and KOOKs made off-road connecting pipes for it. After putting them on and driving maybe 500 miles and playing around a little - it will be on for a short time before the cats go back on. It is very loud, even at low RPMs (under 3000) it screams and it gets to a point to where it is just a scream with out a note chance - maybe it is too loud for my ears (i'm 22) and I am not picking up on the sound change. With the cats is was a cleaner sound and I have noticed less of a gas smell of course.
04-03-2012, 07:03 AM
i have KOOKS with gutted cats but through an SLP dd IT wasnt much LoUDER BUT IT SOUNDS awesome imo.
04-04-2012, 07:08 AM
I've got the dB app on my phone, again, not sure how accurate it is. I just put thunderbolt metallics on mine and it may have dropped the sound 10%, if even that much. I'm very pleased, but I've got midlengths, flowmaster merge, and a hooker catback, so mine wasn't exactly obnoxious to begin with. I'm sure they'd make a little more difference with alot louder setup, but I'm happy.
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