MikeBergy
Blah blah blah....
In response to your first paragraph, "ive still yet to see any car loose power from open header", I don't think you are looking at the whole picture. From a purely balls out racing performace perspective, yes, your top end will see gains from running open header, or with a larger exhaust. But think of it in terms of energy: In order to operate efficiently across the entire rev range, you need to keep the exhaust gas verlocity up in order to help smooth out the pressure distribution of the exhaust pulses. If you run a larger exhaust, you lower the kinetic energy of the exhaust gas that is effectively smoothing out the pulses by an exponential amount (remember KE = 1/2m(V^2) ), thus decreasing the smoothing effect the exhaust has. Running open header decreases the energy by eliminating the mass in the exhaust system (the "m" in the equation, lol) While it's true that this is an open system, a snapshot in time will show how much mass is contributing to the overall system.
This is somewhat similar to the flywheel debate. A light flywheel allows you to rev faster, because less energy is spent in spinning the flywheel mass. But you trade performance for comfort, i.e. It requires more effort on the part of the engine to get the car moving with a lighter flywheel because there is less overall momentum. You get performance advantages with a larger exhaust system, but the system is more "peaky". That's good for racing, because the engine spends most of it's time at the top end, but driveability on the street is compromised. A larger exhaust is also heavier, so keep in mind that with a minor increase in engine performance, you may have negated it by adding 25-50 lb to your car.
That said, my car will have a 3 in exhaust with a burns stainless ultralight muffler. It will sound like a can of bees, but who cares?
Just make sure that you actually need 3" piping before you go out spending the cash. It's unlikely that any 1.6 liter will ever push enough air to need anything that large, and a 1.8 liter is probably not going to benefit that much from it, unless the engine is fully built. Most limitations are in the head anyway, so get a good valve job and port work done before considering a large exhaust. My engine is definitely restricted, but I am using a bone stock LS exhaust, with the exception of the usdm type r manifold.
Oh yeah, racers also run open header because it's an easy way to lose 50-60 lb. That steel is heavy! Aluminum all the way!
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