backpressure you have?...im not sure about the piping size in my car i think its straight piping ill have to measure and take a pic but i think its 2.25 not sure...maybe 2.5...but anyway how do u measure backpressure?...i read the sticky but im still confused..i know that turbo NEEDS 3inch piping...and what does mendral bending mean?...im sure press bending means pressing the metal to make it look like a pipe in different measurements by hand?...idk i feel retarded..

 

mandrel bent piping is a way the piping is bent so that there is no restriction at all, the piping stays the original diameter the entire way around the bends, which is the best since the exhaust can flow the best. Press bent is 2nd best, just a slight restrcition through the bends, and crush bent is the worst. Are far as back pressure goes, there is a balance that you should try for between horsepower and exhaust size, i can't remember it exactly, but an N/A engine like between 100 and 150 hp is good with 2.25" or 2.5", low boost that is maybe near 200 hp is good with like 3", and some major boost can be like 3.5" or 4". Sorry i don't know specifics, but if you're keeping your car with some bolt-ons, 2.5" would be just fine.

 

so what is the main difference between 2.25 and 2.5

 

well just slightly bigger exhaust flow. More horsepower needs a bigger exhaust to let more exhaust flow out, and the slightly larger exhaust will give you a slightly larger exhaust flow, less backpressure, and at the same time maybe some less torque is 2.5" is too big for your horsepower.

 

You could measure backflow by plumbing a pressure gauge into the exhaust manifold, should that manifold or header have a fitting for it. The higher the flow, out the tailpipe, the lower the backpressure. Some backpressure is essential to keeping valves working efficiently and as you may have heard, the engine's torque peak will shift upward as backpressure decreases. At some point (very low backpressure), the torque peak is essentially unattainable and your car would feel very weak at any rpm. Honda shoots for decent torque around town at the expense of higher horsepower numbers. The S2000's torque peak is way up there and the HP peak of 240 from such a small engine, shows how it was obtained.

 

^ to add, think about a garden hose. When you put your finger over the opening, water shoots out really fast, but the hole is small, so the flow is small. Now imagine if it was like a 6" hose. Water would just be pouring out of it at a very slow rate. You need to find the perfect balance between high velocity of exhaust flow, and a large amount of exhuast being able to flow out. ^ Good info though conceptual

 

^^ yea i like that...so lets say if i get a Greddy EVO2 exhaust, i can get them to tune it with the right backpressure and everything?...does anyone know some info about the EVO2's?