My latest mod. idle hands are the devil's playground
 

I'm going to prefice this by saying i am in NO WAY going to reproduce, market, sell, give away, rent, lend or condone this.

Here is the latest from my twisted mind. you're saying to yourself " so what? you put a new exhaust on your 930", then you say, "is that a coating on the pipe? looks silver". Well aluminum is silvery in color

http://forums.pelicanparts.com/uploa...1269807981.jpg

yes, it's aluminum. from the flange to the tailpipe tip.
http://forums.pelicanparts.com/uploa...1269808210.jpg

http://forums.pelicanparts.com/uploa...1269808233.jpg

http://forums.pelicanparts.com/uploa...1269808249.jpg


yes, i am aware aluminum melts in the 800* area. Yes, i am aware for road racing this would NOT hold up AT ALL. But it's all in fun and thats what hor rodding is all about.

Sounds pretty good as well.

Yup, idle hands. Nice work.

Nothing wrong with experimenting and trying something different, keep at it!

You may see temperatures 1000*F higher than the melting point of aluminum in the neck area. Please show pictures of what the looks like as I can't quite imagine it.

the flange off the turbo is 1/2" thick aluminum. The tubing going to the muffler is .120" wall but the muffler is only .083" (we'll see how that holds up). The real unknown is how well the "U" turn will hold up. It's a "donut" we sell and it's really for intercooler piping and .065" wall. It provided me with the tightest radius in one piece but if it blows out i'll replace it with 2 90*'s in the thick wall. The car sounds good, i'll video it and post for all to hear.

Mad doctor at work! Love it.
Drag racers have been doing it for years. Why not try on a Porsche? What's the worst that'll happen -- it'll melt at the turbo and get loud?
Go for it!

I wish I could Tig like that!

true.

funny thing is i had just a 24" long straight pipe with no muffler on it before. It weighs 5.75 pounds. This whole contraption weighs 5 pounds and the car sounds much better

Nothing ventured nothing gained. As a one-off in a specific lower-than-tyical heat application it may last for a little while. That design is pretty much how my mufflers look and they weigh 12 pounds in 321 stainless. I would love to use aluminum as it is less expensive and lighter but it is nowhere near as durable as 321. You have seen those pictures of cherry red glowing turbos yes? That would turn your muffler into a vulcano.
Is your muffler packed or a perforated chamber?

Maybe you could give the inside ceramic coating if there is a process like powdercoating using ceramic. I guess that would require a "firing" that would melt Aluminum. Maybe a liquid dip?

I thought about some sort of coating on the inside but not sure what it would do to the muffler packing. We made the muffler out of perforated aluminum rolled into a tube shape then stuffed into the 4" tube with stainless packing material.

Brian, I did use your design for this set-up as it looks to give a bit quieter exhaust note due to the longer tubing. I'm going to the drag strip Wed night so we'll see if it stays on.

If your engine is in good tune with propper AFRs you should not see crazy heat like some of my mufflers have been exposed to. I would LOVE to use aluminum but it just isn't practical for all the various applications and range (or lack of) of tune.
Please do report back as I have never personally seen aluminum used in a turbo application. N/A typically produces a lot less localized heat.

As an FYI tidbit,

Inconel (Nickel alloy of ~30% Chrome and about ~5% Iron) is used for headers to save weight. It is actually similar density to Stainless Steels but it has a much higher resistance to heat. It is stronger (by weight) than SS at high temperatures. Therefore, F1 teams or high-budget racers can use paper-thin Inconel tubing to save on materials and weight. The problem is that it work hardens quickly and is very easy to fold/bend with tube walls than thin.

alot of my drag racing customers use aluminum exhaut on their turbo cars. They are after light weight and low price. Even if they have to replace the pipes at the end of the season it's still a whole lot cheaper than exotic materials. I keep my a/f on the fat side (10.5 @ WOT) so we'll see how well it holds up.

I would never recommend aluminum for road racing or any kind of extended WOT situations

That is a great application for this material, short term high performance.

We worked up a set of headers in inconel. Cost for materials alone was going to be $5000. Wow!

yikes

Brian, did your customer actually go ahead with the inconel system? Bragging rights or to save 2 oz? Where can I find customers like this.

A friend used aluminum for the rear half of the exhaust on a turbo road race car. To my surprise it lived.

The inconel headers were bagged by the client due to a personal issue that affected financing. He did pay for all the R&D work and some fixturing costs which was very nice.
LOVE the ditty under your screen name.

Well, I went to the dragstrip last night. Not that I was trying to compare this exhaust to the old "straight pipe" but hey why not see. With a bit less boost (now 15psi) compared to last time (17psi), 2 * more timing from 4500-6000rpm and a slightly better launch (2.03 60') she ran 12.18 @ 118MPH.

But now the clutch is slipping in 4th at WOT

oh, and the exhaust still looks brand new, no discoloring, cracking or any other signs of extreme heat. Maybe the E85 lowers the EGT's

Fun!

Make it a right side exit and you might almost cut the weight in half.

Aluminum dose not catch on fire right?

One last thought. Cooling is the enemy of exhaust performance and aluminum I believe cools faster than SS. Probably not an issue is a short run. Coating seems a good idea.

E85? That should run much cooler than high octane gasoline. That's a game changer. Have you measured EGT's?

Aluminum will not burn at these temperatures. Exhaust cooling is not such an issue once the exhaust leaves the turbo. The ID of this system should be sufficient to compensate for any expansion I would think.

Also, aluminum will not discolor. It will however oxidize.

i considered dumping on the right side but wanted the longer run to lower the noise level. I don't believe cooling is bad for performance after the turbo.

I wasn't sure if it would discolor or not. I kind of expected there to be some sign of heat right at the turbo outlet but it looked perfectly fine. I have not checked EGT but with the rich a/f i figure it's gotta be low.

Aluminum has some interesting properties. It will not discolor with heat but rather plasiticise when approaching the melting point. I wouldn't expect a total meltdown or "vulcano" as I breviously joked but I would expect a lot of warping or distortion over time if this were used in a regular gasoline powered 930. Your challenge likely may be oxidation. EtOH has some corrosive properties and moisure is of course one of the exhaust bi-products. I don't know off hand what you could treat the outside with to keep it looking nice.
Please keep us informed on how this works for your application. Pretty neat.

We have a local anodizer we use for some of our products, that would look cool

Yes, probably not an issue for this application.

However, in principle cooling at the exhaust slows down flow and adds to back pressure. Builders often go to the effort to minimize this like using coatings, going to a shorter exhaust pipe (like side exits), and or use different diameter pipe along the run (i.e. stepped headers).

One of the attributes of aluminum is it dissipates heat faster than steel. Its light weight is a definite advantage. I am just guessing that the reason it is not used in exhausts is mostly the temp issue but the second reason might be the cooling issue.

Brian, how about a right side exit titanium muffler system for the 930? Could be a must have to go with your wonderful headers.

Still, this alloy system is a very fun project.

I'd love to make my systems out of titanium but I don't think anyone would pay for it, ha!
One limiting fact of mass production is the product must be durable. I couldn't maintain my warranty program using such a fragile material as aluminum. Sure great to see what is possible though! An E85 fueled 930 with an aluminum muffler; that's pretty neat.

I guess I was thinking there were Ti mufflers already and that makes up much of the exhaust with a passenger side exit. Just add a flange and about 15" of tubing.

If it only saved 2 lbs or so it probably would not be worth the effort or cost. Still, it would be sexy.

How is your exhaust and E85 setup holding up?

funny you should ask.

E85 is working great. no problems there. But the aluminum exhaust has not faired as well. Actually the piping held up great, the perforated aluminum inside the muffler deteriorated and the packing came out of the muffler and wadded itself up in the next bend. That caused a huge restriction which resulted in the pipe bursting. All this happened over the weekend... thanks for asking ;)

What about a spool piece in Stainless from the turbo to the muffler and alu. from there out?

the tubing held up fine, even the flange bolted to the turbo outlet showed no signs of failure. The muffler's inner perforated tube may have to be made of something stronger however.

We've had to look at changing our sound deadening material due to a few failures caused by extreme heat.
I've toyed with the idea of aluminum tailpipes. Leave the muffler 321 stainless and make the 180 bend and tailpipe out of aluminum. I guess it comes down to how important that last 5 pounds of weight loss is to the customer. Darin's muffler in 321, which is the same as mine, would weigh 12 pounds.

My whole system weighed right at 5 pounds.

I considered making billet aluminum end pieces with a receiver groove that the stainless perforated tube would nest into. Then weld the ends to the aluminum muffler body sandwiching (sp?) the stainless. Shouldn't add much weight and will hopefully keep this from happening again. Here we go again :)

No, that's a great idea!
I had misunderstood what you said about the failure. If the perforated tube is what failed then your solution should be the fix. That area sees the most heat and by being perforated it has more surface area, which will in turn becomes more vulnerable to the heat. The 321 stainless perforated core in the mufflers I have received back with melted sound deadening meterial were turned blue from excess heat. They most certainly would have failed if aluminum.