Can a Aluminum downpipe be used on a RX7??????????????????
 

I've got a 5 inch downpipe, but the thing is heavy as hell. Can a Aluminum downpipe withstand the heat of a rotary?

no, the aluminum wont last


whats the wall thickness of ur dp? i bought sections of 5" from a truck supplier, 16g aluminized steel.. see how long it holds up

Mine is 16 gauge as well.

Just thinking, alot of the turbo mustang guys run them without problems. Just thought it might be a possibility for us.

Bump for a good question. I also was wondering the same.

You've been talking to Dan, haven't you? My application's a little different from yours, but I can't imagine it holding up on a rotary, even for drag race use.

I'm going to be running aluminum exhaust, but a stainless downpipe. I don't think the aluminum would stand much of a chance at the first bend after the turbine. Lots of heat and vibration Hell, the aluminum exhaust will probably crack out after a couple thousand miles, but we'll see.

Absolutly not... Typical EGT is above 1600 on a rotary, aluminum melts at 1200...

I know a guy that tried one on a turbo nissan, it didnt last more than 5 minutes of hot laps at the track.

I think hes going to be running corn juice so his EGT's will be much lower. I think you should try it. Besides the cost of the aluminum and your labor what else do you have to lose?

They use them on a lot of drag cars. Aluminum is cheap, give it a shot :)

ceramic coated aluminum :)

I dunno, we'll see............ I've got one hell of a bend after the turbo....... and I'm sure it will get alot of heat there

http://img.photobucket.com/albums/v2...m/DSCN1892.jpg

^^ interesting.

not a chance.

egts w 100% alcohol run at least 1550 and while they lose some heat thru the turbine and aluminum melts at 1200....

the primary point is even if the DP doesn't see 1200 if it is close to that temp the aluminum will have no strength. add to it the major bend and you might be picking up puddled aluminum from under the dyno.

hc

Alright............... well atleast it sounded good :)

Why not titanium..You would be spending about 500 bucks in material but it would be light as hell and stronger than SS. :)

Titanium melts around ~1650 F, that's cutting it a little close for comfort if you ask me. It'd probably work, just big $$$. I'm all for someone that's not me paying to figure it out. :)

Hmmmm, who wants to make me a titanium downpipe for $500? :)

Your average grade of Titanium will not be stronger than 304SS, but will have a higher strength to weight ratio. Titanium also does not melt until 3000F depending on alloy, but will lose strength and corrosion resistance quickly as the temperature goes up. Also, good luck finding a long enough piece of straight 5" titanium tubing for $500 or less, let alone bends.

Thin wall (20 guage) 321SS or Inconel would be your best bet.

Yep, they use inconel for high end exhausts because they can make it really thin/light and it will survive.

Inconel and stainless are less thermally conductive than titanium so you lose less exhaust energy/velocity.

Easier to weld too.

Inconel melts at a pretty high temp, but even better it creates its own protective layer at high temps.

As pointed out, titanium gets significantly weaker at higher temperatures so it would have to be thicker tube.

Nickel and steel :)

Good cast iron exhaust castings are also made of high nickel cast iron (Ni-Resist). Well, Ti is pretty kick ass for exhaust castings for weight savings :) as some lucky Evo owners know...

the only way i can see aluminum as a remotely viable choice would to use water cooling like a boat which would make the weight savings a moot point

No Way

Eric don't be such a weiner......step it up with the big boyzz and get one made out of Inconel :) I thought you were a bawlah :hahaha: ?

-J

shoot, i'm on a budget..........

my mild steel one wouldn't be too heavy................ but my mig welding added probably 20 lbs ! haha

Hahaha :lol: :lol: ......I'm sure it wasn't that bad bruthah. Give your self a little credit!

-J

IIRC aluminum is good up to 370F, then it becomes soft like lead and loses its alloy properties, making it rather soft and weak. Exhaust temps are at least 1000F. Or it might get even hotter and melt like someone said. My point is even if you could get the temps down it'd still be a bad idea. I think steel has the same problem above 800F but heat won't screw up the alloy on mild steel. Unless you make your exhaust out of chrome-moly or some fancy steel alloy.

Ceramic does not block heat. It's snake-oil. It's not that it isn't an okay material, it's that a thin coating of anything simply cannot insulate. You need a thick mat. Likewise the thermal conductivity of other materials is entirely moot: your exhaust will be almost exactly the same temp on the inner wall as the outer wall due to the huge area to thickness ratio. The main barrier to heat leaving the exhaust is air.

Inconel would work well b/c it's a super high temp material; I doubt it'd even soften like steel does. That's fancy aerospace stuff there. Also costs a fortune. Titanium both melts and softens at a higher point than steel, so while it softens at high temps I would think that steel softens just as much or more. A quick google confirmed its use in exhausts. It's expensive though.