so i was just thinking, since everyone is all over the lightweight exhaust components, ie titanium, why dont manufacturers make aluminum manifolds and exhausts? i know that basic aluminum is not the best at taking heat, but seeing as how there are engine blocks and pistons that are made of aluminum it must be possible.

could some experts chime in on this? aluminum is very easy to work with, and im thinking that some of the higher grades should be comparable to steel.

 

turbo manifolds see temps easily hundreds of degrees higher than an engine block will, and most aluminum engine blocks have iron sleeves as it is.

No aluminum tubing would ever withstand the heat and pressure from a turbo manifold, besides, you want a metal like steel or iron to keep in as much heat as possible instead of dissipating it like aluminum does.

one of the biggest things that spools a turbo is thermal expansion from heat. The more heat stays in, the better the spool.


also, aluminum pistons are usually forged for strength, which really increases the density of the metal. And the temps in a turbo manifold are sustained for long periods....I'm talking anywhere from 1200* and higher.

 

ya egts on a turbo car can easily see 800-900*C. i was just curious if this was a possibility. as aluminum is comparable in weight to titanium, but much cheaper and easier to work with.

so there are no grades that can take the heat?

 

I like to think, at this point in the aftermarket industry, that if it was a viable, good option, it would have already been done by now

 

exhaust gas temps are the hottest thing involved in an engine. the exhaust temps in a turbocharged engine are over 1000 degrees F hotter then your water cooled engine block gets.

While the melting point of Ti is over 3000 degrees F, the melting point of aluminum is around 1200 degrees F. I suppose if you water cooled the header, such as a boat header, maybe then you could use aluminum... but of course that complication wouldn't be worth it.

As for Titanium manifolds... I am not sure if you could do that or not. I think that the melting point is definatly high enough, but perhaps it has insane expansion rates, i am not sure. i have never personally seen anything cast Titanium before, and I hear the mandrel bending Ti pipe will eat up the bending machine... so I am not sure how you would make a nice one, even if you could afford its expense, or if it was even a reliable material for such application.

 

Couple of reasons come to mind in regards to your question.

1) The rate of heat expansion on aluminum parts, especially thin walled components when compared to a block or head, is much greater than stainless or mild steel. You'd probably need something along the lines of heavy schedule 80 pipe (not tubing) to avoid excessive expansion. Because of that, you've just defeated the purpose of using aluminum for weight savings.

2) Aluminum conducts a tremendous amount of heat, when again, compared to SS or mild steel. This will also effect turbo performance as it relies on that heat to drive the turbine. The only way to combat that would be, you guessed it, to use large heavy pipe.