a couple friends of mine use exhaust pipe crush bent on their 240sx turbos. they're boosting pretty well and havent really had any problems that i know of.

 

Those look like Mandrels to me. Crush Tubing usually
has "ripples" in it. Even Mandrels sometimes have a little mark where the tool came in contact

BTW - I recommend Aluminum. It has much better heat dissipating qualities, as well as weight savings, and can be polished quite nicely.

If you need to make it out of something - Aluminized Exhaust tubing would be the next best thing. (What my Exhaust is made out of)

 

$10 = 7 foot of 2 1-1/2" piping
$5 = Blue anodized pray paint (Advanced auto parts)
Hanger = measure where to make the bends.

My frend works at a muffler shop, so he made the bends on his lunch break. Since we did'nt have the car at the muffler shop, we used hanger to get an idea of the angles. One of the pipes came out perfect on the first try. The other we had to go back and bend a bit more.

 

Most newer die benders don't leave ripples anymore, but they still create more a restriction than mandrel bent tubes. Still, on the cheap you can't really go wrong with them, its just not going to make as much power. The larger the turbo the more effect the restriction will have.

I agree in theory, however in most applications the higher heat transfer rate works against you at stop lights, when parked or moving slowly due to heat soak. I recently had my steel IC pipes ceramic coated for looks, as well as decreased heat transfer. I noticed that my intake temps are generally cooler by several degrees, even more so at long traffic lights, or when starting the car hot. I can only imagine that the alluminum would soak even more than my steel pipes before I coated them.

The other benifits of Aluminium, weight savings and good looks, are still quite valid though.