Aluminum or inconel downpipe?
08-30-12, 02:46 PM
#28
There is nothing wrong with using aluminum in a street or drag race application. That being said if anyone wants and inconel turbo manifold I have decent about of 1.875 .049 wall inconel 625 to build manifolds with.
Except when you push it aluminum does crack. A crack greatly increases the chance of a fire if you do have an fluid leak onto it.
I know it sounds like if if if, but when you are seriously pushing your car this apparent "perfect storm" of circumstances happens much more than you would expect.
Just something as common as continuous 4th gear pulls tuning a car can easily cause this scenario.
Except when you push it aluminum does crack. A crack greatly increases the chance of a fire if you do have an fluid leak onto it.
I know it sounds like if if if, but when you are seriously pushing your car this apparent "perfect storm" of circumstances happens much more than you would expect.
Just something as common as continuous 4th gear pulls tuning a car can easily cause this scenario.
08-30-12, 04:25 PM
#31
Yield strength of aluminum, SS and titanium vs. temperature:
http://www.burnsstainless.com/yieldstrength.aspx (link also has another handy image with strength to weight)
You can make your exhaust out of silly putty if that floats your boat and maybe even get it to work for a little while. But hot aluminum doesn't even make sense from a strength to weight standpoint. It would make more sense to lighten your exhaust by getting stainless tubing that is dangerously thin. Heck at least that would be stronger.
All metals soften at higher temperature but those with higher melting points soften slower. You can't assume it's good just because it's below melting; it shouldn't even be close.
http://www.burnsstainless.com/yieldstrength.aspx (link also has another handy image with strength to weight)
You can make your exhaust out of silly putty if that floats your boat and maybe even get it to work for a little while. But hot aluminum doesn't even make sense from a strength to weight standpoint. It would make more sense to lighten your exhaust by getting stainless tubing that is dangerously thin. Heck at least that would be stronger.
All metals soften at higher temperature but those with higher melting points soften slower. You can't assume it's good just because it's below melting; it shouldn't even be close.
08-31-12, 03:16 AM
#32
Ah, that chart helps me understand something.
On a run at auto-x when I had dual drivers on a higher speed course I hit a cone with the muffler tip and it put a giant flat spot on the Ti tip like it was made of aluminum.
I pounded on it for hours with a ball peen hammer trying to get it round and finally put a torch on it which really seemed to help.
Now I see on that chart how weak Ti is with heat- it literally was as soft as aluminum when I smacked that cone.
On a run at auto-x when I had dual drivers on a higher speed course I hit a cone with the muffler tip and it put a giant flat spot on the Ti tip like it was made of aluminum.
I pounded on it for hours with a ball peen hammer trying to get it round and finally put a torch on it which really seemed to help.
Now I see on that chart how weak Ti is with heat- it literally was as soft as aluminum when I smacked that cone.
08-31-12, 12:00 PM
#33
Banned. I got OWNED!!!
Yield strength of aluminum, SS and titanium vs. temperature:
Yield Strength (link also has another handy image with strength to weight)
You can make your exhaust out of silly putty if that floats your boat and maybe even get it to work for a little while. But hot aluminum doesn't even make sense from a strength to weight standpoint. It would make more sense to lighten your exhaust by getting stainless tubing that is dangerously thin. Heck at least that would be stronger.
All metals soften at higher temperature but those with higher melting points soften slower. You can't assume it's good just because it's below melting; it shouldn't even be close.
Yield Strength (link also has another handy image with strength to weight)
You can make your exhaust out of silly putty if that floats your boat and maybe even get it to work for a little while. But hot aluminum doesn't even make sense from a strength to weight standpoint. It would make more sense to lighten your exhaust by getting stainless tubing that is dangerously thin. Heck at least that would be stronger.
All metals soften at higher temperature but those with higher melting points soften slower. You can't assume it's good just because it's below melting; it shouldn't even be close.
http://www.flickr.com/photos/74953263@N07/6799374693/http://www.flickr.com/photos/74953263@N07/6799374693/ by http://www.flickr.com/people/74953263@N07/, on Flickr
http://www.flickr.com/photos/74953263@N07/7025378369/http://www.flickr.com/photos/74953263@N07/7025378369/ by http://www.flickr.com/people/74953263@N07/, on Flickr
http://www.flickr.com/photos/74953263@N07/6879294066/http://www.flickr.com/photos/74953263@N07/6879294066/ by http://www.flickr.com/people/74953263@N07/, on Flickr
09-04-12, 06:09 PM
#36
I've been running 4" aluminum exhast for a while with no problems. Just inspected it the other day and still no cracks. That said......I don't drive the car all that much and I used fairly thick aluminum tubing (3mm). The downpipe is ss though. No way the downpipe would last if it was aluminum. Too hot at the first bend. If it is a daily driven street car, I'd go thin wall 316 SS. With aluminum, I'd be worried about going through a puddle after the pipe has heated up. It'd crack out for sure.
09-04-12, 06:49 PM
#37
Wastegate John
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? There are TONS of man hours in that downpipe, a skilled welder's labor is not cheap.
09-13-12, 02:43 PM
#42
Banned. I got OWNED!!!
Didn't meant to hijack the thread by any means, just offering it up as an alternative to using aluminum. Lighter in most cases and will hold up to any heat.
The pie-cuts are used for two reasons.... some people love the way it looks and simply want it. The other is that it makes puting together odd or complex bends very easy. When every piece is a known degree, there isn't any cutting, checking and re-cutting. Most of the time we'll also laser-etch a reference mark at 0 and 180 so we're able to roate them a known degree when snaking through a tight spot.
The pie-cuts are used for two reasons.... some people love the way it looks and simply want it. The other is that it makes puting together odd or complex bends very easy. When every piece is a known degree, there isn't any cutting, checking and re-cutting. Most of the time we'll also laser-etch a reference mark at 0 and 180 so we're able to roate them a known degree when snaking through a tight spot.
09-13-12, 04:00 PM
#43
the implications matter
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Aluminum: bad idea with heat.
Pie cuts: bad idea for flow.
See the last paragraph here:
Burns Stainless LLC - Welding Article Part 2
Pie cuts: bad idea for flow.
See the last paragraph here:
Burns Stainless LLC - Welding Article Part 2
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