Exhaust Experience

[cobrastang]

Hello all! I have discussed this matter on a different forum, but since i see that there is a lot of exhaust discussion here as well, i thought i would post my db and dyno results here also. I have a ffr, which comes iwth 2.5" ID diameter pipes, so my experience and results will vary from other kits that have more restrictive or different exhaust systems. However, my results should help some of you to chose what will sound best and create the most positive results according to your goals. I am running a 306 with a mass-flo fuel injection system from www.massfloefi.com with afr 165cc heads, and 9:1 compression.
4 into 4 header vs. shorty headers and J pipes
Only a small loss in hp over the 4 into 4s-j-pipes and shorties helped reduce noise.

cc inserts installed in j-pipes with packing(absolutely killed power) However, i never tested them without the packing material, but i could still feel a significant seat of the pants difference.


Classic Chambered cobrapacks vs. FFR pipes

DB comparison


FFR pipes with CC inserts in J-pipes

Results-while sitting in the car at idle 900rpm

Before-101db
After-98dbs

3 feet away from pipes
Before 102db
After 99db

While cruising at 2000rpm
Before 105db
After 102db

2200RPM
Before-107db
After 104db

Classic chambered Cobrapacks were the same as FFR pipes except were more mellow at idle by 2 dbs. However, at other tested rpms they were the same as the ffr mufflers regardless of their 6 inch extra length. With that said, they did sound more mellow at cruising speed, but sounded the same going up hill and while at full throttle.

FFR vs Sweet-thunder
sitting still in the car before 101 after 98dbs
standing 3 feet away from the car-either side
Before 102 After 96dbs
Behind the car-93dbs

2000rpm in 4th before 105 After 102dbs
2200rpm in 4th Before 107 After 104dbs
2500rpm in 4th Before(never tested)After 106dbs


2.5" internal diameter Classic Chambered mufflers(26" long)
NO difference over ffr exhaust.
<img src="http://i20.photobucket.com/albums/b218/corbrastang/cobrapackdyno.jpg">

And my final exhaust data is inconclusive till tomorrow, but i do have videos of a much improved sound. The inserts were made and installed by www.sweet-thunder.com and they truly replicate that of the mid-year vettes while quieting down the db level.
Video 1
http://s20.photobucket.com/albums/b2...ravideo003.flv

http://s20.photobucket.com/albums/b2...ravideo002.flv

I also tested the gas-n stainless pipes. They were just as loud if not louder than the stock FFR pipes, but were much prettier. The baffles were faced in the opposite direction so they did produce a flappy sound while coasting or downshifting. The same flappy sound was evident with all of the mufflers that had the louvers facing the direction in which the catch air, yet the db levels were only minimally reduced if any.