Aluminum pipe.. anybody using it? drag car? street car? Anyone?

[Rrider]

Anybody using aluminum pipe? What wall thickness.. what alloy?

Like this car..
http://www.gtrblog.com/wp-content/uploads/2008/09/ma-motorsports-exhaust-proto-001.jpg

[GLHNSLHT2]

that's the crappiest looking exhaust I think I've ever seen.

[zin]

It works, but won't last long, especially if a cat is used. I definitely wouldn't use it for a downpipe, unless it was drag only and I had some kind of disorder that compelled me to lighten things excessively. Lol

Mike

[shayne]

aluminum isnt designed to last in an application like that. it would corrode badly and look like crud real quick on a street car.

[RoadWarrior222]

Order a chinese stainless catback, that will be light as hell :D

[Rrider]

Maybe that guys from Columbia can shed some light, I've heard it works great, it doesnt work at all.. everything in between. On the googles it looks like mostly race cars, but there are also some street cars.

[RoadWarrior222]

Apart from worrying about it burning through on a turbo car, the first thing that comes to mind for it not being a good idea is fatigue resistance from vibration in thin aluminum alloy*. The second thing is that road fuels have ethanol which tends to make some acids which aluminum might not agree with too well, aside from any nitric acids. I would imagine for example that any race vehicles using it are running something more like leaded high octane, than anything with ethanol or methanol. I would suspect for example, longer life on premium fuel which supposedly does not have ethanol here, than with regular, and a short life with e85... it ain't so much what happens when a well tuned motor is running I would think, as what it sneezes out briefly when it first fires up... so alky injection since it's fired when the motor is warmed up and running, might not be so bad.

(*Cast intakes are shorter and chunkier than exhaust pipes.)

A duralumin type of alloy might be best for vibration and general ding resistance, and some kind of anodisation or oxide coat enhancing process may inhibit corrosion.

[turbovanman²]

IIRC, BSX and Reeves are both using aluminum downpipes and exhaust, it works, I thought the same that it would belt but aparantly, it doesn't.

[zin]

With good ceramic coatings, on the inside at a minimum, the durability would go up, but I'd still be concerned about 1400*F exhaust coming off the turbo... Not saying it's not doable, heck the Super Duty Pontiacs back in the early 60s had AL "headers" provided by the factory, but there was the occasional silver drip...

I'd consider a lightweight stainless down pipe, with a ceramic coating, with the remainder, from where the cat would have been to the tailpipe AL, IF weight was my main enemy... As in primarily drag race, for a track car or street duty, some form of steel would be the choice material, unless I hit the lottery, in which case I'd be doing some coated Ti!

Mike

Mike

[RoadWarrior222]

Possibly there's a magic point for ally, where the wall thickness is enough, such that it's high thermal conductivity can dissipate heat away from it fast enough that it won't burn through. But at beer can kind of thickness, the cross sectional area isn't enough.... obviously, piston and head thickness is great enough and it dissipates to oil or coolant.

[rx2mazda]

I have aluminum exhaust on my GLH. The DP is SS and then it V-bands into aluminum all the way back to the aluminum muffler. It split at the welds on me twice on the street. Both times I had severe wheel hop during accel which caused it. After that its been fine.

[Rrider]

16 gage??

[rx2mazda]

yes sir

[Reaper1]

^^This is the man I immediately thought of when I saw the title to the thread. It's possible and it works! I would have it ceramic coated, though.

[Ondonti]

I thought of the fact that probably everyone is running it in FWD racing these days. 4" pipe is heavy. Probably save a lot of headaches putting a larger diameter flex section into the end of your non aluminum downpipe.

[shayne]

the big thing is aluminum's lack of strength when heated to more than 400 degrees f, and fatigue strength in general. after reading a bunch more about this it seems as though most folk dont actually use it on a vehicle they use everyday, year round. i have doubts about it lasting 25,000miles. looking into prices for aluminum it would be a bunch cheaper than ss and a 2/3rds lighter, so it is very tempting, and from a fabricating point of view it would be a bunch easier to fab.

[turbovanman²]

Maybe I'll switch and save a few lbs...........................


















Not bloody likely, :lol:

[GLHNSLHT2]

unless I hit the lottery, in which case I'd be doing some coated Ti!

Inconel would be a better choice at that point :)

[RoadWarrior222]

What's that pipe they use for furnace and water heater exhausts now, maybe you can use that from the muffler back :D

[Ondonti]

Does it help at all to have 4" pipe on a 2 liter motor or is it going to get just as hot and beaten up as a 2" exhaust? (talking aluminum of course). Not sure how the increased volume/surface area will affect things.

[RoadWarrior222]

Well remember it all goes up with the square of the diameter so 4" is four times as cool as a 2". ;-)

But actually, the bigger you go with the same gauge the more dent prone it becomes, and probably the more you have to worry about the vibration fatigue at the welds.

[shayne]

no, you have to worry less about a weld fatigue failure with a larger diameter pipe/tube weld. the weld on a larger diameter pipe/tube has a greater mechanical advantage against forces acting against it.

[turbovanman²]

Does it help at all to have 4" pipe on a 2 liter motor or is it going to get just as hot and beaten up as a 2" exhaust? (talking aluminum of course). Not sure how the increased volume/surface area will affect things.

Depends on turbo or n/a, why choke up a turbo motor with 2" exhaust but 4" on an n/a motor unless 1000 whp etc, is useless, :eyebrows:

[RoadWarrior222]

no, you have to worry less about a weld fatigue failure with a larger diameter pipe/tube weld. the weld on a larger diameter pipe/tube has a greater mechanical advantage against forces acting against it.But is that when gauge increases with diameter? ... and the fact that if you can't weld worth crap you're better off trying to weld something thicker than thinner?

---------- Post added at 10:25 PM ---------- Previous post was at 10:23 PM ----------

Oh crap, I see what you're saying, when you have say 1 meter of pipe held at a 90* mitre weld and whack it on the end with a hammer, the same blow is spread over more area of weld on a larger diameter pipe than a smaller diameter pipe.

[shayne]

the gauge of a tube does not increase with diameter, 16ga is always the same thickness no matter what diameter.
i think your thinking of pipe "schedule" and that can change with diameter, but the schedule of a pipe is always measured or rated at an amount to hold a certain static pressure or spike pressure.
the greater the distance the weld is spread over will always require more effort to create a failure or permanent elongation.
if you cant weld worth a crap your better off welding something thinner and run less of a chance of lack of penetration than weld something thick and do a poor job, the unfused root is a breeding ground for stress risers and is usually the source of critical weld failure.

[tkelly27]

I wouldn't weld tabs to an Al pipe, I would support it in some sort of hanging fashion. Then there is only cyclical fatigue on the pipe itself, which has a shape that is naturally fairly strong in bending.

I would run Al on the street if it was supported properly. Not in the down pipe, but after the cat. I like side exit pipes, so I don't normally have much more than a down pipe anyway.