Straight pipes

5.0 Mustang magazine did a test of the most popular mufflers on the market. At the same time they tested open pipes. The straight pipes made the least power, and were of course the loudest. So there was no advantage for that setup to run without mufflers.
There are engine setups where straight pipes would be an advantage. Most likely you are not running this kind of setup.
Straight pipes are not bad for the motor, they just might not promote optimum cylinder filling with the intake and cam setup that is run on the motor.
Make sense?
Not all motors need backpressure.

Edit: can't spell

Something about not giving it equal backpressure, I;m not totally sure? Plus you don't want it b/c it sounds terrible!!!

Jakob

Exaust is alot more complex than many people think.

Backpressure is never good. No car needs even a single bit of it. It's about flow and velosity, and pipe size and length can greatly effect these factors. The size of the tube effects the volume it can handle. If you go to a smaller tube, the exaust gasses will flow faster, which will help low end alot, but because of the lower volume it can handle, it will not be benificail at higher rpm's where the volume is much higher. A large tube will fow better up top, but because of the larger volume, it will be harder for exaust gasses to be pushed through. A longer tube will have more exaust gas in it, but if that volume is moving faster, it will actually cause suction. This is called scavaging. It's hard to explain.

A muffler will often not just deaden sound, but the different chambers and passages actually increase power by maintaing the flow to a steady rate, which increases velosity.

I can attest to the real world power differences while running my car with strait pipes vs running it with the magnaflow kit. My car was stock at this point. Not only does it sound like utter crap (imagine a 70s pos rusty chevy falling apart truck sound) it takes a little longer to get moving..

A stock motor may actually run better with a tad of backpressure. High compression, big cammed motors need less back pressure.

Look at the way different drag race headers are designed, you have prostock running headers and a short exhaust, and things like alcohol funny car running zoomies. If you put zoomies on a stock stang engine, it would run like crap and sound the same.

Stock motors sound like dump trucks with straight pipes. Check out my link to hear my car with open headers. With my tune, I slowed 3 tenths with 10 inch header extensions! The car was probably way too rich at the time.