I've been talking with someone about thermal conductivity of material in car exhaust system. If you compare the aluminium to the stainless steel, the aluminium has around 200 W/m.K and stainless steel is around 20 W/m.K.
I think the aluminium pipe will lose more heat to the surrouding, resulting in a decrease of internal temperature as opposed to the stainless steel...is this right?

 

Internal temperature of what?

 

Temperature of the exhaust gas. From what i said, the exhaust gas velocity in aluminium pipe would be lower (because of a lower temperature) compared to a higher exhaust gas velocity in stainless steel pipe (because of the higher temperature). Is everything right?

 

Yes, but it's not going to be a night and day difference.

 

Also aluminum has 2 distinct advantages to steel. it weighs less and it will not rust. BUT it will crack before it bends and will need to be mig welded i believe. sorry if thats wrong but i call a mig a tig and a tig a mig all damn day long. Im sure theres a reason why we dont use aluminum though i just dont know why...

 

i thought of it probably because it gets hot and aluminum becomes kind of maliable and brittle.

 

Yeah but aluminium can dissipate heat way better than stainless steel, so stainless steel will get hotter. So i don't think the aluminium will get to the temperature where it gets maliable and brittle.

 

I guess I have to ask, in the the real world, what difference does it make?

 

I think aluminum sounds like **** that's why its not used from the manufacture. And its exspensive.

 

you don't want exhaust to dissipate heat. you want to get as much of that heat out and away from the underside of the car.

closer to the engine, the manifold.. could get hot enough to deform and likely blow out. Also aluminum doesn't rust but it does "oxidize." it can also be susceptible to some of the more corrosive components of exhaust, especially in the presence of moisture.

if you want to do better than stainless, Ti or Iconel. both high dollar but totally up to the task.

 

It has a measurable impact on baller status.