Originally Posted by varsis

get a cherry bomb turbo. they sounded good on my friends 3.9

Originally Posted by wink2873

for the love of god dont do that. you'll sound like a civic, trust me. i was bored one time and cut off my stock muffler and clamped in a cherry bomb, it was terrible. a couple months later i got a dynomax 3" superturbo catback, and in all honesty i dont think my truck could sound better. it sounds better than my friend's 4.7 at idle and decent until about 3k rpms, but by then the engine is so loud i cant hear the exhaust anyway. someday i'll post a video of my exhaust.

Originally Posted by 95_318SLT

I'd like to take the opportunity to break this myth. There isn't a motor in the world that needs backpressure. If the exhaust has backpressure, the engine is having to work harder to push the gas out and that work is robbing performance. Think about how much backpressure there is in the open headers on a top fuel dragster that pushes thousands of horsepower...not much.

The reason for this common misconception is that most people don't think about how the exhaust flows through a pipe. At the walls of the pipe there is friction, causing the exhaust gas at the walls to flow slower than the gas in the middle of the pipe. Thinking about one "segment" of exhaust gas when the gas in the middle overcomes the gas at the walls (since it is flowing faster), it expands and rolls back on itself. This is what causes backpressure. The way to stop backpressure at low rpms where there is less exhaust gas is to use a smaller pipe that has less surface area and therefore less friction. However, a small diameter exhaust pipe does an engine no good at high rpms where there is a lot more gas. At high rpms an engine needs a larger pipe to allow the extra exhaust room to get out. This is the most important thing to consider when choosing an exhaust system. If you drive you vehicle at lower rpms you will want a smaller diameter pipe to reduce backpressure. If you like to run your motor up into its higher range you will want a larger pipe so you don't "choke" the engine.

Originally Posted by minirdr

hmmmm...what to do, what to do.

Originally Posted by 95_318SLT

Some backpressure was neccessary back in the days of carberators. The reason for this was that an extra vaccum was created by a lack of backpressure, which leaned out the engine and burned the valves. Modern computers can better compensate the lean mixture and therefore are not in need of backpressure. And my source on this is that I'm a mechanical engineering student who understands thermodynamics.

Originally Posted by f0x672

i understand where youre coming from but thats pretty muc hthe theory behind it.. theory is 100% true in a perfect world.. too bad we dont live in one. i want to convert my exhaust back to single outlet cause my loss of backpressure kills me on hills. even so, my dynomax exhaust had a smaller diameter exhaust tubing versus my magnaflow. did better on hills with the dynomax. go figure right?

Originally Posted by 95_318SLT

I think we're close to on the same page here but for different reasons. I'm fairly confident in saying the reason your dynomax exhaust system worked better was because it had less back pressure. Most people associate smaller pipes with more backpressure, I was simply trying to explain how thats not the case.