Aluminum exhaust questions

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A friend of mine wants to make an aluminum exhaust for his car so we were talking about it. He is really good at welding, but I have some questions that confused us both.Can you use aluminum for a downpipe close to a turbo or are the EGT too hot? Maybe that's why I've only seen cat back exhausts. (and what about for an NA car)Would a 2bolt, 3bolt, or vband exhaust flange (aluminum) warp over time with the heat and not seal any more?Piping would be about .0060 thick and the flanges I'm seeing are thick. So do you set the amperage to the thinner material and just wait for a long time for the flange to heat up?Here is a pic of the flangehttp://www.ebay.com/itm/OBX-3-V-Band...#ht_1656wt_952Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Your friend is seriously under-educated on this subject. Aluminum melts around 1200F.....think about it.
Reply:Not sure the EGT is coming out of a manifold or a header.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Originally Posted by makoman1860Your friend is seriously under-educated on this subject. Aluminum melts around 1200F.....think about it.
Reply:heat turns aluminum into butter, any heat treatment it had will be long gone anywhere near the manifold or turbo. I'd look into stainless,
Reply:Originally Posted by zapsterGood point!As soon as I read the title I knew there was something drastically wrong..Aluminum EXHAUST?..Near the turbo no less???Think about this and think really HARD...WHEN is the last time you actually saw one?? ...zap!
Reply:Originally Posted by ironmangqheat turns aluminum into butter, any heat treatment it had will be long gone anywhere near the manifold or turbo. I'd look into stainless,
Reply:Originally Posted by rlitmanNo, I have not seen an aluminum exhaust.
Reply:I've seen quite a few of themhere is 1 of themhttp://tab-fabrication.com/Store.htmlTorchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Well then go right ahead and make it and see how long it lasts.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by GambleI've seen quite a few of themhere is 1 of themhttp://tab-fabrication.com/Store.html
Reply:Originally Posted by zapsterWell then go right ahead and make it and see how long it lasts.....zap!
Reply:Hello Gamble, as the others have advised, look at your link closely. All of the components that are in contact with the head(s), turbo, or near proximity to the engine are of stainless construction. Only the resonator, muffler, or other remote items are of aluminum construction. That is not to say that there isn't heat back there, but to simply point out that by the time that the exhaust gases have reached that portion of the system the temperature and the dissapation ability of the aluminum components alllows for those components to survive. Some boats do use aluminum manifolds, but they also use a jacketing system that flows water around them to deal with heat dissapation issues. Plan for stainless steel and you won't get any undue surprises. Good luck and best regards, Allanaevald
Reply:So you wouldn't even do a cat back or axle back as aluminum then huh. Thanks.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Turbos, manifolds and downpipes in steel are well known to glow red after a while on full throttle. You would be spraying aluminum all over the place long before it got that hot if you had an aluminum exhaust.I HAVE seen aluminum exhaust pieces actually - made for low powered twostroke engines.
Reply:Originally Posted by GambleSo you wouldn't even do a cat back or axle back as aluminum then huh. Thanks.
Reply:Originally Posted by rlitmanNo, I have not seen an aluminum exhaust.  Just wondering now . . .
Reply:http://www.yellowbullet.com/forum/sh...um+for+exhaust
Reply:Originally Posted by MikeGyverActually..... it's not unheard of in the racing world.If it's used right It won't melt. and 'just using' titanium is by far the dumbest thing I've heard all day. I don't even think they make Ti tubing that big and it would be unf-ingbelievable expensive, and a huge pita the make..
Reply:Pistons = aluminumCylinder heads (most cars nowadays, aluminum)Engine blocks (lots nowadays, aluminum).Granted, material thickness on these guys is a good bit thicker than what is used for exhaust systems (except for sch 40 turbo manifolds some guys build), but aluminum does work on exhaust systems.  No, I'm not going to build one that comes right off the head or turbo, but if I was a fiend for being light weight, I'd run it under the car.Someone asked why OEMs don't use it for their exhaust systems.  My guess is that its cost prohibitive, both in material and labor costs (unless that robot is using a spool gun).  Bottom line is, if someone wants to do it, what skin is it off your back?-AaronJet 17.5" Drill Press1942 South Bend 16x84 Lathe1980s Miller 320A / BP --- 2013 Power Mig 2562012 Jet 7x12 Horizontal BandsawVictor O/A Setup
Reply:Maybe the question needs to be asked, is this for a race car or a daily driver?? Race guys ( especially drag ) can get away with things that wont last under normal conditions. GM uses a Ti system on some of the newer vettes, as does chrysler on the viper. Ti exhaust systems for aviation piston engines are not uncommon. You dont see aluminum in OEM applications because it is a poor choice for anything but a race application ( however some powersports mufflers are a composite of stainless, aluminum and non metallics ). So by the OP asking what they did, I will go out on a limb and assume that the application is a street car ( vs a professional race setup ), and for that I stand by my thoughts on aluminum being a poor choice at any place in the system
Reply:It's been done in the racing world, yes. And some of those guys have made a pass and come back to find their aluminum pipes sagging. If it's for a race car, you could probably make it work. If the car expects to see ANY street driving, I wouldn'tAs far as the actual welding, it's not bad at all. Puddle on the pipe itself, since it is a big flat area relative to the edge of the flange. Puddle on the flat of the pipe, then dab some filler into the puddle and work it up to the flange. Once you've got them connected, ramp up the heat to wet the added metal adequately into the flange and pipe. Start from there and weld it up like normal. The arc will chew away some of the material from the flange, but that's okay, you just fill it back in. You must keep consistent heat, though, or the puddle will slowly walk into the flange as the heat builds up.
Reply:Mick120, you're right about the AL heads / blocks being cooled.  I was thinking about that on my drive back to work last night to finish building the non-aluminum cat-back Jeep Wrangler exhaust I started yesterday.-AaronJet 17.5" Drill Press1942 South Bend 16x84 Lathe1980s Miller 320A / BP --- 2013 Power Mig 2562012 Jet 7x12 Horizontal BandsawVictor O/A Setup
Reply:Aluminum exhausts? Why yes! I build them all the time for ALL applications.This car has more aluminum in it than anything else.
Reply:Any applications besides powersports and racing?The one car is a street driven car.  What other "exhaust" applications are there besides cars and powersports? RC cars have aluminum exhaust, jet engines are almost half aluminum, ummm dryer vents can be aluminum, ladders, plates, toilet paper holders...
Reply:Originally Posted by VPTThe one car is a street driven car.  What other "exhaust" applications are there besides cars and powersports? RC cars have aluminum exhaust, jet engines are almost half aluminum, ummm dryer vents can be aluminum, ladders, plates, toilet paper holders...
Reply:VPT - how thick of aluminum do you use? Never had any warping or melting or any issues at all on a turbo application?Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Originally Posted by BCTimberwolfAre you serious? Have you ever seen a jet engine up close?
Reply:Yes that black car has a stainless header. Aluminum from turbo back has been done plenty though.
Reply:Mountain-o-welds intake?Welding/Fab Pics: www.UtahWeld.com
Reply:Originally Posted by MikeGyverMountain-o-welds intake?
Reply:This is how an intake should look.and the only way the aluminum DP's are surviving is because of the turbo. It's essentially using the excess heat and expanding gasses to drive the turbine. Therefore cooling the exhaust charge. Put those pipes on the other side of the turbine and it would be a whole different outcome.
Reply:A header may be able to take the heat, I am not sure. I haven't seen a NA car with an aluminum header yet. I was just saying aluminum off a turbo is fine, and aluminum header back is fine.And a turbo doesn't soak up all the heat. The downpipes see nearly just as much heat as pre turbo piping.If you look back at the pics you will see the blue car isn't on a strait track for 1/4". The black car has been all over the state.Your just reaching Mick. If I found a daily driven car with an aluminum header you'll probably just move on to say "Well I bet it doesn't have aluminum bolts in the header".http://www.hotrod.com/techarticles/e.../photo_23.htmlBlack car being driven:
Reply:I never said it would soak up all of the heat. But put an egt probe pre and post turbo and you will notice a 400*-500* difference on a DD. All dependent of course on load, A/F ratios, etc. Look at the clear difference in your last picture between the headers and the DP's. There's a tremendous amount of energy being consumed by the turbos, dramatically reducing EGT's. It's simple thermodynamics
Reply:No I didn't read the link. If the egt's stay where they should aluminum would be fine.
Reply:Funny thing, On a marine boosted engine, if cooling water  is lost in the aluminum exhaust manifold it fails within seconds. But I guess if the system has the lazy life of a car........
Reply:Funny things:http://www.pontiacparadise.com/parts...-manifolds.phphttp://www.edsindianbolts.com/Indianfourparts.htm
Reply:cast aluminum manifolds for extremely low HP N/A engines from the 30's and 60's? You're losing the battle here. Plus, the OP is talking about using .060 tubing...not 5/8" wall castings.
Reply:Originally Posted by BCTimberwolfcast aluminum manifolds for extremely low HP N/A engines from the 30's and 60's? You're losing the battle here. Plus, the OP is talking about using .060 tubing...not 5/8" wall castings.
Reply:Originally Posted by Mick120I still say no....no matter what's been done in the past.....
Reply:Originally Posted by er3456dfSo even though it's been done.... it can't be done?
Reply:Think I would just use a thin wall stainless and call it a day.  I have seen this done on road race cars who go at for 30 minutes at a time of 90% WOT throttle and high heat, but have not seen it done on many turbo apps.  Seems from the above pics it has and can be done, but with stainless I don't have to worry if my exhaust is going to melt.
Reply:Originally Posted by sargThink I would just use a thin wall stainless and call it a day.  I have seen this done on road race cars who go at for 30 minutes at a time of 90% WOT throttle and high heat, but have not seen it done on many turbo apps.  Seems from the above pics it has and can be done, but with stainless I don't have to worry if my exhaust is going to melt.
Reply:Eh, $30 t and a ebay $30 regulator and you are ready to go on purging!  I just did it a month ago or so.
Reply:Pffft. I have $10 in my whole backpurge system. A T after the regulator, a valve, and a brake line.You can kind of see it in the background in this pic.
Reply:Ti exhausts are actually preferred on modern race cars, below are pics of my exhaust on my 750whp 4 cylinder.With turbo cars aluminum exhaust is fine post cat, pre cat you want cast preferably or 340 / 304 stainless. EGT's are typically 1400 to 1650* so anything that bolts directly to the turbine housing will get heat stressed. This is why the turbine wheels are typically inconel or gama Ti.