Anybody tried an aluminum exhaust?

I just finished fabbing a (partially) aluminum exhaust and I'm wondering if anyone here has done anything similar.

I'm well aware of aluminum's low strength at high temperatures and limited fatigue life (all discussed in detail at the link below) but I think I've taken those issues into account with the design of the system.

Has anyone here seen or tried aluminum exhausts, and if so, how did they hold up?

http://www.motoiq.com/magazine_articles/articletype/articleview/articleid/2224/project-miatabusa-part-12--why-you-cant-make-aluminum-exhausts-and-why-i-did-it-anyway.aspx

-Dave

Wow, that was a great read. I didn't expect to be there for all 9 pages, but you held my attention right to the end. Love all the ad hoc bracket ingenuity .

How much weight do you estimate was saved over a typical steel system? (That's the primary advantage, right?)

how's it sound compared to a steel system?

Aluminum exhausts are all the rage with turbocharged "street" cars....

Ranger50 wrote: Aluminum exhausts are all the rage with turbocharged "street" cars....

I've never heard much about them in the subaru community, which is a big chunk of those "turbocharged street tuners".....polished stainless steel still seems to be the popular choice.

irish44j wrote:

Ranger50 wrote: Aluminum exhausts are all the rage with turbocharged "street" cars....

I've never heard much about them in the subaru community, which is a big chunk of those "turbocharged street tuners".....polished stainless steel still seems to be the popular choice.

This is the kind of "street" car I am talking about:

I just saw a car with an aluminum exhaust this past weekend.

It was an 800hp Civic he drove on the street. He used a 4" alum exhaust and a flowmaster muffler to get a nice street sound, although the noise level did wake up under full throttle.

I don't remember the exact numbers but he saved quite a surprising amount of weight with the alum over stainless steel. At least it amazed me.

The sound did have a little "tink" to it over what it would have had with steel. And also there was more exhaust sound coming from the pipes themselves when he goosed it, but overall it was quite pleasant sounding.

I would be more concerned with the rapid cooling of the gasses slowing the flow and causing back-pressure than strength or sound. I suppose if you keep it short and use a turbo to force the gasses out it makes less difference though.

Pontiac tried aluminum exhaust manifolds in the early 60s, might have been on the Swiss Cheese cars. Worked for drag racing but they would start melting if you drove it on the street. Not one of the better ideas.

Since they make heads out of aluminum, it should be possible to make aluminum exhaust that will hold up. I guess the next rage is titanium exhaust?

"Don't start with that "you need backpressure" horseE36 M3. It isn't true."

You and me baby. One of these days we will correct this myth.

DILYSI Dave wrote: "Don't start with that "you need backpressure" horseE36 M3. It isn't true." You and me baby. One of these days we will correct this myth.

One of the best myths! Right along side "torque wins races" and the hub-centric wheel myth.

I know a few "real street" drag racing guys who run aluminum exhausts, mostly huge 4 inch sewer pipe stuff after the header.. Durability is less of an issue for those guys. I'll talk to them and see what they say about the pros/ cons.

Really like your website, BTW.

I had a ceramic coated aluminum exhaust from autotech back ten years ago on my MKI GTI. it sounded wild.

81cpcamaro wrote: Pontiac tried aluminum exhaust manifolds in the early 60s, might have been on the Swiss Cheese cars. Worked for drag racing but they would start melting if you drove it on the street. Not one of the better ideas.

Those original SD exhaust manifolds were designed to be used for only a quarter mile at a time, and the exhaust heat would blow holes in them if they were used any longer. However, you can get reproductions of them today that have been coated by Jet Hot or similar, and they will work on the street - I have a friend who has them on his '63 Catalina.

DILYSI Dave wrote: "Don't start with that "you need backpressure" horseE36 M3. It isn't true." You and me baby. One of these days we will correct this myth.

+1

The name of the game is "pump more air". You only need backpressure if your engine tuning was designed for a restrictive exhaust - and even then what you need is better flow and new tuning

Isn't exhaust pulse savaging important and effected by back pressure hence the need for some?

Not once you get past the collector.

The word from the drag racing guys is to use a billet flange for the join between the headers/ turbo outlet and the initial aluminum downpipe, and 11ga thickness aluminum for the first bend. The mandrel bends run a larger diameter which might affect fitment, but that's the only downside.

Keith wrote: Not once you get past the collector.

And certainly not with a turbo. The less restriction, the better. There is no scavenging with a turbo so the bigger the better.

curtis73 wrote:

Keith wrote: Not once you get past the collector.

And certainly not with a turbo. The less restriction, the better. There is no scavenging with a turbo so the bigger the better.

With a turbo you also want the air pressure drop - high pressure before the the turbo, low pressure after.

Pressure differential in other words

Well, yes. But this car is naturally aspirated (at the moment) so I was commenting as if it were naturally aspirated. I don't think anyone believes backpressure is good for turbos.

I think I may be more excited over the fact that there is finally another installment of Project Miatabusa. Though after clicking over there I realize I just haven't checked in a while. There was that 8 month gap between part 7 and part 8. You do have to like Dave Coleman though.

81cpcamaro wrote: Pontiac tried aluminum exhaust manifolds in the early 60s, might have been on the Swiss Cheese cars. Worked for drag racing but they would start melting if you drove it on the street. Not one of the better ideas. Since they make heads out of aluminum, it should be possible to make aluminum exhaust that will hold up. I guess the next rage is titanium exhaust?

That's why my aluminum starts halfway down the car. Back half of the exhaust is much cooler.

I've had titanium exhaust before. It was incredibly light, but titanium prices are insane. It was a $1300 exhaust when I had it, and they cost $2000 now. Not worth it. Aluminum is relatively cheap, so the cost per pound saved is reasonable, if the exhaust will survive.

chandlerGTi wrote: I had a ceramic coated aluminum exhaust from autotech back ten years ago on my MKI GTI. it sounded wild.

Really? I had no idea that existed! So no problems with it? How long did you have it?