Optimal Pipe for Exhaust

[Accord2nrz]

So when building an exhaust there are three different metals that I can think of for the piping. Stainless Steel, Iron, and Aluminum. Which metal is better and why?

[Turbineguy]

So when building an exhaust there are three different metals that I can think of for the piping. Stainless Steel, Iron, and Aluminum. Which metal is better and why?

Cast iron is best for heat retention especially upstream of a turbo. T304 or T305 stainless if you want tubular headers which flow better than cast iron and allow different size and length runners to tune the power band on an NA setup. Stainless headers can also allow alot of leeway to optimize the flow into the hotside of a turbo as well. For the rest titanium is my choice but obviously a bit pricey. Don't really think aluminum has much of a place on an exhaust system.

[Dzaster]

Yeah I had a read on something some time ago that kinda made sense.

It was more about piping diameter on exhaust but may still apply. It just mainly stated that oversized exhaust piping bay actually have a negative effect on exhaust flow due to how larger piping will allow the exhaust gases to be cooled and condensed thus slowing the flow of the gases. I took this seriously and fiberglass header wrap my whole 3" pipin from the DP back. Didn't last too long as the 3" piping was sitting a bit lower than the dinky stock 1.25" or whatever it is. Inevitably, the rubbing over time cut through
the fiberglass and so it would be dragging. lol


So basically, the material that would maintain exhaust gas would be best option.