Hey guys I have a strange question... I was wondering if it were possible to run an aluminum cat back? I know the exhaust gases would be substantially cooled after it exits the y-pipe so the risk of melting would be none existant. I know some of us, much like my self are weight ****'s so I thought I'd ask. I'm thinking of a 3.5 single set up with my LT383. So the question stands...can it be done????? lol

 

Do you have a source for aluminum thin wall tubing?

 

I do actually, there's a welding shop here in town that has good access to some.Also I've found that ebay has a ton of Mandrel bent stuff in aluminum thin wall tubing.

 

Cool, I guess it would work.

Any idea what the weight difference is?

Like you said, heat should not be a real issue, probably the only issue would be strength. I would think aluminum would get dented up pretty quickly.

 

Titanium is the thing for lightweight exhaust.

 

What about carbon nano tubes?

 

True but trying to build one of those I could buy another car lol. I know that the aluminum could take a beating over time but it would be easy to patch up if needed.

 

You underestimate the availability of titanium tubing on the surplus market.

 

who needs exhaust anyway?

 

Aluminum will take the heat no problem after the cat. Just no exhaust manifolds

 

Maybe so but aluminum tubing is still far easier to obtain than titanium and much cheaper.

 

Again, I'd be interested to see what the weight savings would be.

 

True, but it doesn't work-harden under vibration and fall off... or corrode under all the acids that condense out of the exhaust gasses.

 

Probably not alot of weight savings, few pounds, If you have access to free or really cheap tubing and can weld/join it, go for it, I wouldn't spend much money on it, the bang for buck ratio is probably not good, but adding lightness is always good

 

Titanium exhaust tubing is actually quite cheap on the market these days. No where near as cheap as steel but definitively do able. I have seen 3" x 4' lengths of thin wall tubing for less than 200$.

Problem is its extremely difficult to weld correctly, is reactive to air and oxygen at temps over 800º. Need specific shielding gas, as well as you need to weld in an untraditional way when compared to alum and steel. I have seen titanium welded in a vacuum for these reasons. I have also seen TIG torches liquid and water cooled for welding Ti.

Aluminum is perfectly fine as an exhaust, I have seen many systems done out of aluminum. Its sounds killer too compared to steel.

Just an FYI alum is more brittle than steel and even more so at high temps. You can not use weld on hangers. You will need to use special hangers band clamped to the exhaust.

Also due to oxidation issues you will need to coat it.


@danclemts: How do you add lightness? If you add something you are almost always adding weight. And It is quite a bit of weight savings, We weighed a Aluminum cat back exhaust and it was under 20lbs including the stainless muffler. When a OEM system can weigh up to 70lbs.

 

Wow a 50lb weight savings! as I'm building my 88 to be a road race car the cost per weight ratio for me wouldn't be that much of a factor. Coating the tubing wouldn't be that big of an issus either as a friend of mine works at a powdercoating/ceramic coating place here in town and could do it for me on the cheap. Or since it doesn't get that hot I figure high temp header paint would probably work just fine.

 

Thats compared to a stock cat back.

If its a road race car, are you even required to run a full exhuast and mufflers?

 

The question is can you weld aluminum or have your exhaust welded. A bunch of clamps or a couple of 4' true dual straight pipes with mufflers on the end are not cool, and tasteless.

 

Aluminum isnt cheap but very light weight. I could easily see 20-50 lbs depending on type of system.

My dual 3" is off the car at the moment. Let me weigh it and by looking at what alumium weighs i could estimate the difference. My 3" steel is extremely heavy.

 

Adding lightness is an old car guy thing, i think it was Colin Chapman who coined it (Lotus) 50 lbs is substantial, I'm in the middle, got 2 -2 1/4 pipes going into a single 3" into a flowmaster

 

Yes I can have it welded in large sections. I want it to be a full catback as I would still like to reuse my Aerochamber muffler. The only major clamps I could see would be the one from the y-pipe to the I-pipe then from the end of the I-pipe just before the bend over the axle. My only concern after that would be having a flange made to bolt the muffler to the pipe.

 

Well my quest continues for the aluminum catback...I found a pretty nice kit on ebay today that comes with all the bends needed to create the catback and then some. It's a good price too. I'm going to write the seller to see if he has 3.5 straight tubing in a 36 inch length for the I pipe. Here's the kit in question...

http://www.ebay.com/itm/3-5-mandrel-...d6a249&vxp=mtr

Actually I just found another seller that sells 36inch staright tubing for a fairly decent price too..
http://www.ebay.com/itm/3-5-Aluminum...item53f50a303c

 

whats is the min gauge also the recommended this sounds like an awesome idea, and also you cant get it pretty cheap at metal yard.

 

I dont think there is any issue with aluminum exhaust pipes - other than the temperature of manifolds excluding them from that use.

Titanium is really light, but very hard to weld as other have mentioned - Arapovic sells them for imports, some systems top $8k.

The one material I haven't heard mentioned is inconel steel tubing, like NASCAR teams use for their headers - really thin wall, light, and pretty easy to weld (definitely not as hard as Ti). Just don't know if you can get it in 3" or larger. Don't forget that you will need a muffler - that is a heavy chunk of metal.

 

Inconel would be way expensive. Aluminum is ok, i just learned some guys use that for downpipes on turbo cars! Yikes that is very hot service