Exhaust Headers - minus all* the noise

Van Pershing

 

*okay, some of the noise!
I've always enjoyed the mellow sound of a Corvair with headers coupled with a nice set of turbo mufflers. I think I enjoyed it more in my youth than I do now because now after a short period of time behind the wheel the sound becomes noise and really gets on my nerves! But the extra power that a good exhaust system gives is truly incredible, and, if truth be known, that's what I really like.
Left: A view of the passenger's side exhaust system. The header is an old Otto Parts unit and the mufflers are Dynaflow Super Turbos
Right: With the rear wheel removed, a good view of the clearance between the piping and the shock absorber can be seen - there ain't much!

The collector on these particular headers is 2½" and so 2½" pipe was used throughout the system along with Dynaflow Super Turbo mufflers with 2½" inlets and outlets. Mandrel bent pipe in 180° sections was purchased from Don's Hot Rod Shop here in Tucson  to avoid trips to the mufflers shop for bending. The bends come in 4" radii only but a tighter radius is needed where the pipe curves back into the inlet side of the muffler. A hack saw and a little welding produced the tighter "radius". Even though it isn't perfect, it flows fine for the street use it will see.

Now, how do we fit all this stuff into the little tiny place that it has to go? There are three spots that really caused problems. The first (and these are in no particular order) is clearance for the shock absorber. The second was clearance for the rear edge of the body. And the third was clearance for the tire. This wouldn't be such a problem if I weren't running 215-60R14s. It was like working one of those Chinese puzzles to get thing to fit with sufficient clearance...

Left: As you can in this view, looking into the wheel well with the wheel removed, there isn't much room. The pipes and the muffler pretty much fill up the entire space.
Right: Looking into the rear of the car with the grill panel removed, you can see there is only about 1/2" clearance between the pipe and the body work.
 

The exhaust piping and muffler pretty much fill all the space available. This is especially true on the driver's side because of the engine off-set. It would be very difficult to adjust the valves on the left back without removing the exhaust system. The passenger's side has plenty of room for adjusting the valves but there are still just as many clearance problems.

One of the things I was told by several people while researching the project was that the exhaust should run straight out the back of the car and the tail pipes should extend beyond the bodywork. This give the noise very little opportunity to find its way back into the passenger's compartment.

What about the noise? Well, I borrowed digital sound meter and took some measurements and compared them on three "regular" cars along with my Corsa with four different exhaust set-ups. Keep in mind that twice as loud is equal to 3 dBA and OSHA required hearing protection when levels average 90 dBA and over. We were able to reduce the noise level quite a bit over a standard header set up, but still twice as loud as a stock set up. Overall, I'm pleased with the results both in noise level and performance. The moral of the story is that if you want a quiet ride you'd better go for something newer like a Cadillac or even a Chevy Blazer. The stock Corsa exhaust system is also another good route, but the extra horses just aren't there.

The Otto headers finally gave up the ghost and were replaced with a set of Clark's Ultimate exhaust system. I added the baffles to reduce the noise a little. The noise levels are much louder than the system with the extra piping as you can see by the table below.

Vehicle Idle*
WOT @ 60mph*
60mph Cruise* Outside car **
'97 Cadillac El Dorado
49 dBA
72 dBA
64 dBA
57 dBA
'96 Chevrolet S 10 Blazer
50 dBA
74 dBA
65 dBA
54 dBA
'04 Cadillac CTS 3.6
43 dBA
77 dBA
68 dBA
51 dBA
Corsa - stock dual exhaust system
61 dBA
81 dBA
70 dBA
62 dBA
Corsa - Otto headers with Turbo Mufflers
66 dBA
85 dBA
82 dBA
76 dBA
Corsa - as above w/ extra piping
65 dBA
82 dBA
74 dBA
75 dBA
Corsa - Clark's Ultimate system w/ baffles
65 dBA
86 dBA
83 dBA
77 dBA
* inside car (driver's seat)
** Outside car approximately 10 feet back from tail pipes at idle.
Heater with headers
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