I have been searching for this and searching for this i am started to think iam loosing it in my old age or something but i cant for the life of me find a comparison in weight for aluminized steel and stainless steel. i know this isnt really tech for the rx8 in general but it is for mine. i am considering having a custom exhaust made for my car buyt they use aluminized steel here in alaska to fend off weather. from the research i have done i found out that aluminized steel dissipaets heat like 33% more than stainless steel. but i cant find out an actual weight for it. i am assuming it weighs less but i wanna know how much less. also i have found that the wall for the piping is gonna be a lot thicker than if i used stainless steel, i am just trying to figure out if i go with this aluminized stuff am i gonna be getting a 75lb catback exhaust that adds 2 hp. i have talked to the ppl that are gonna do it and they wont give me a straight answer. they say if u are worried about weight go ti. yet in alaska there is no one to work with that. any info on this would be great guys thanks.

 

The difference in steel types is generally minimal with a density of about .284 lbs/cu in. Aluminized steel is usually low carbon (maybe some 1018) with a protective "aluminized" coating. Aluminum oxidizes quickly, but aluminum oxide looks like a hazing of the surface and is mostly inert. It will protect the steel from rusting. If you scratch it or wear through it, the pipes will rust. Stainless steel of different grades is pretty resistant to rusting. 302, a common stainless used, is kind of low grade. Something like 406 (I think) is a finer steel.

So, it's more important how much steel is used (gage of the piping) than what type of steel when it comes to weight.

 

Here is a link for all stainless steels:

http://www.alleghenyludlum.com/pages...s/products.asp

A 400 grade stainless will rust because it is a ferritic grade. 400 grades exist because they are cheaper (than 300's) and perform better than carbon steel. If you are into appearance over time choose a 300 grade stainless (304 is common). 300 grades are usually not OEM due the high price of the alloy. Its the nickel content in 304 that provides the corrosion resistance, and nickel is getting expensive. The cheaper alternative is aluminized 409, but I am not too sure there are any aftermarket applications.

 

Don't base your decisions around "cooling" the exhaust - it is not a function of an exhaust to cool the gases, in fact it may be counter productive - by slowing your gas velocity through the system.

....a big heavy system that actually subtracts 2 or 3 horsepower is surely not your goal.

S

 

the difference is nil, every place you cut and weld aluminized steel will result in an exposed corrosion area because the base steel will be exposed. The readily available wall gauge for stainless tubing is 16 Ga., if you build it from that it will could possibly end up heavier than OE depending on the muffler design/weight, etc. You really need 18 or 20 Ga. wall thickness, which is usually harder to obtain locally and is also a bit more difficult to fabricate & weld. If you don't have a mandrel bender (as opposed to the crush-style std muffler shop bender) you'll have to buy mandrel fittings and trim/weld them in as needed; more cost in parts & fabrication labor.

Unless you're a serious competitor my advice is to skip custom and just buy an aftermarket exhaust. Used stainless exhausts come up for sale regularly if cost is a concern. For the ultimate corrsoion resistance and lightest weight you can put out for a full Ti exhaust if money is not a concern.

 

Aluminized steel can't handle as much heat as stainless- the rotary runs hot enough that it may bake off the aluminum and rust out quicly.

 

In Alaska........... Go Racing Beat you won't regret it.

Sure it's heavier than stock but you won't have it rust out. It's solid.

If you must make it your self go high grade stainless.

Forget about weight. most important thing is longivity because of the enviroment you live in.

 

I have also heard that Aluminized or mild steel can't take the rotary exhaust gas heat and you should go with Stainless steel.

 

Alloy was right if I was going to go custom exhaust I would go 301 or 304 stainless they will last longer and hold up better.