I have always thought it was a bit on the loud side. Even though my neighbors have never shown up with pitchforks and court orders, it still bothered me. I started with the specified short pipe with one Speedway auger each side, which was deafeningly loud while driving it. I then lengthened the pipes and added another auger. This was in the right direction but still too loud. While trolling through car magazines I noticed an ad for Car Chemistry exhaust inserts claiming to allow an “open header look with muffler noise levels”. Intrigued, I started searching for information. There was quite a bit of good feedback in various hot rod forums, so I took the plunge.
The exhaust insert is formed from a perforated center tube with three perforated disks that match the ID of the exhaust collector. There are two end caps provided with each insert. The advice on the website conflicts with the instructions provide with the product regarding the use of the solid end cap. I welded the cap with the hole on the upstream end of the insert (the end with the longer tube extension) for the first tests. I ended up welding both end caps on and leaving the solid cap completely closed. I only used spot welds, so it would not be hard to remove for experimentation.
Yesterday I installed them. I gathered some data to see how much, if any, difference there really was. I didn’t have a helper so I elected just to do some quick SPL measurements for trends. With the car in the garage with completely open pipes at idle I walked my dB meter back to where I measured less than 100dB and marked that spot. I then tried different configurations of exhaust and measured at the same spot. I would prefer to have someone else take measurements while I drive by at different speeds, but I don’t have any friends nearby that loyal! Not too mention driving by with open headers probably would bring out the pitchforks and court orders…
Here are the measurements:
Open Headers: 97dB
CC Inserts with upstream plug (0.87″ diameter): 87dB
CC Inserts with upstream and downstream plug (closed): 83 dB
Complete long pipes with CC inserts and speedway augers: 73dB
24dB decrease is HUGE. It is quiet enough that I don’t think I will suffer irreparable hearing damage if I drive to the gas station without ear plugs and the tone is much nicer. The previous exhaust sounded flatulent. The CC Inserts have cut down the high frequency and made it more of a roar than a howl. My butt dyno thinks the engine is running stronger, but that could be placebo…overall I am very happy with them.