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Discussion Starter #1
Anybody make track specific side pipes for low DB days? After trying my best to find a set of the Flowmaster slimlines (discontinued) I am now looking to alternatives. I know there are some good pipes from vendors that fit the bill, but most are pretty pricey and will drop power (always a trade off). I have not found a cheap muffle that looks “right” on the cobra, but was thinking I could get some cheap steel side pipes and add a big not so attractive muffler that might bring the noise level down without killing power. My end goal is running Laguna Seca or similar tracks a couple times a year and then toss my “pretty” pipes back on for normal cruising or tracks that are not as strict.


I am also considering the auger inserts many have talked about. I feel the jury is still out for DB reduction and power loss though. Little power loss is probably fine, but I would be concerned the added restriction would trow the tune out of wack.
 

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Discussion Starter #3
Ya, I was looking at some posts with the super trapps as well. From what I gather most use the 3” inlet 5” outlet and weld to a short 3” tube that can slide into the side pipe. Did you do any dyno or DB reads with / without the supertrapps? Oh and were you able to meet 92dB? That seems pretty good. I figured I would only be able to reach for high dB days at Laguna.
 

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Too Cheap to paint!
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I tried all sorts of stuff to make it to 86dB at Lime Rock, never made it.
 

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Ya, I was looking at some posts with the super trapps as well. From what I gather most use the 3” inlet 5” outlet and weld to a short 3” tube that can slide into the side pipe. Did you do any dyno or DB reads with / without the supertrapps? Oh and were you able to meet 92dB? That seems pretty good. I figured I would only be able to reach for high dB days at Laguna.
I only did sound tests at various distances. Did not have time to get to a dyno to figure out the best configuration (tune to noise ratio).
I just wanted to make sure I was not sent home so I used 90 db as my target. I probably lowered my horsepower with the set up I used.
 

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Not a waxer
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I got nailed with a >95 db reading on the roadcourse at Indy's Lucas Oil Raceway (Ironicly the site of the US Nationals where top fuelers and funny cars run like a bazillion db!). The meter was set up 50 feet off of a full throttle area of the track about a foot off the ground. Our pipes being turned out the sides blew sound waves right at it. Turning the ends 90 degrees down blew the waves at the track surface rather than directly into the meter---result was no more noise warnings! Easy change that might get you below the limit.

Jeff
 

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FFCobra Craftsman
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I put augers in mine 4-5 yrs ago. May have lost some power but I couldn't feel it. I cut the turn down off leaving the pipe as long as possible. I got slip over turndowns to add on. The augers kept getting loose as vibration cracked my spot welds so I pulled the turn down off. Figured where on the bottom of the pipe I could drill through the outer pipe and into the auger center tube. Welded a 1/4 inch nut to the auger. Found a 1/4 in fine thread machine screw w/ phillips head. Put the auger in, ran the screw in and put the turndown back on. Now maybe once every year I have to tighten the screw a 1/4 turn to quiet a rattle. The turn down is secured w/ an 1/8 in hole drilled through it and the main pipe. I drop a small thin head nail through the hole and cover it w/ a hose clamp. The clamp also tightens the shrink section of the turndown but doesn't deform it so it's easy to remove if needed. I have the turn down aimed about 45 degrees downward the road. BTW I have no idea how this would measure but it is significantly quieter.
 

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Discussion Starter #9
Thanks for all the replys. I picked up a cheap db meter and some of the auger inserts. Figured I will try this first and see how if I gett the needed db reduction. IF it gets me there I'll see about dyno testing, but probably a ways off from that.
 

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I also installed augers and turned down the outlet to reduce the noise. To secure the auger I welded a steel plug in the end and drilled and tapped it for a stainless steel hex head bolt. The plug stops the straight through shot down the centre of the auger. To prevent too much restriction and thus significant power loss I drilled a number of holes through the auger tube in front of the plug. This area coincides with the expansion in the inside of the side pipe after the muffler section. The first two auger sections are trimmed to fit inside the glass pack area and the last fits in the turn down. I had a local welding shop weld the turn downs back on. Here’s a couple of picture. I might be able to find more if you want.
415A5736-55EF-4E93-BABA-0D1D7E857684.jpeg
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