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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
Old 04-01-2010, 07:19 AM
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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
Old 04-01-2010, 07:22 AM
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Quote:
Originally Posted by drmatera View Post
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

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.

Last edited by 911st; 04-01-2010 at 08:11 AM..
Old 04-01-2010, 08:09 AM
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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.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 04-01-2010, 09:33 AM
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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.
Old 04-01-2010, 09:38 AM
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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.
Old 04-01-2010, 10:12 AM
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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.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 04-01-2010, 10:33 AM
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We have a local anodizer we use for some of our products, that would look cool
Old 04-01-2010, 11:51 AM
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Quote:
Originally Posted by RarlyL8 View Post
E85? ... Exhaust cooling is not such an issue once the exhaust leaves the turbo...
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.
Old 04-01-2010, 03:20 PM
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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.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 04-01-2010, 06:30 PM
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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.
Old 04-01-2010, 08:17 PM
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How is your exhaust and E85 setup holding up?
Old 07-05-2010, 07:08 PM
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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
Old 07-06-2010, 06:25 AM
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Quote:
Originally Posted by RarlyL8 View Post
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.
What about a spool piece in Stainless from the turbo to the muffler and alu. from there out?
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Old 07-06-2010, 07:31 AM
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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.
Old 07-06-2010, 10:10 AM
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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.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 07-06-2010, 08:03 PM
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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
Old 07-07-2010, 06:31 AM
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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.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 07-07-2010, 07:42 AM
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