Obviously a larger diameter exhaust will reduce back pressure. I'm curious how the larger volume of gas behind the turbo affects egt in the pipe, and consequently radiated heat from the pipe. Any comments? I'm assuming that the timing advance gained from the reduction in back pressure would reduce egt significantly enough to overshadow any changes in the amount of heat energy in the exhaust system.

My take is less backpressure means less time gases spent in exhaust and more heat would escape through tip of the exhaust. Also when gases expand they cool down based on thermodynamics. Of course if we add more volume of those heated gases then they start to reduce that gain, but if we have same everything but bigger downpipe and exhaust, the pipes should actually run cooler.

Can the timing be advanced with the change to bigger exhaust?

hrk (stuck in Honda Mall of GA :( )

What does that mean?
I'm 1 exit north of the MoG

The bigger tube translates into an increase in volume and decrease in velocity. So you have a larger quantity of heat energy moving through the tube at a slower rate, which would give more opportunity for heat to transfer from the gas to the pipe.

I would have to agree with hrk on this one, I would think a larger diameter exhaust would run cooler mainly due to allowing the gasses to expand more rather than being compressed. Expansion of gasses absorbs tons of heat ... ever sprayed compressed butane onto your hand?

I know, that's why I had to add it. I was having wifes car serviced there and took laptop to pass some time there.

hrk

yeah, since you said "stuck" I wanted to know if you needed help or a ride or wanting to grab lunch or whatever.

bigger diameter will let the gases expand, but also when you turn off your car, MORE of that gas will stay in those pipes, when you start your car don't be surprised if you see a sweet fireball, lol... poof!