ahh a critic!
No, not all factory exhaust manifolds are cast iron.
Eg.. many toyota 4cyls including some celicas, all SW20 MR2s.. come with factory mild steel extractors/headers.
the aforementioned 3000GT twin turbo has one cast manifold and one mild steel manifold (V6 twin turbo). Why? the mild steel manifold is placed at the rear turbo (east/west engine) as that area receives much less cooling... and cast manifolds would fail/crack/warp too quickly. yes - a mild steel manifold.. while not retaining as much heat energy as a chunky cast iron manifold for any given change in temperature... is actually more reliable under heat stress. And no, the rear manifold is not at all prone to failure on these cars.
I could list on but theres no point, and to be honest I dont really pay a lot of attention to which N/A cars have mild headers.
Most, yes. All, definately not!
I am -not- forgetting the fact that 800+ degree gas is passing through the pipes at high pressure and velocity. Which is exactly why I stated that an unground manifold with bits hanging off will most definately flake. Yes, I have a magical die grinder. With the right flexible extensions and cleverly shaped tips.. and sometimes a bit of manual filing, it is not difficult to ensure all surfaces are well ground. And with proper preparation of the steam bends and careful welding, the actual grinding necessary is very minimal. However, I do not go so far as to call it magical.. its just intelligent.
Whats more.. the manifold I have been running on the MR2 was created by another company. It is unground internally.. but is there any evidence of flaking, despite the excessive heat it has seen and the fact Im pushing 1.5bar of boost (= very hot and high pressure exhaust gas)? no. all edges are still rough and sharp.
is there any damage to my turbine? no.
No, I do not heat treat my manifolds. It is an innecessary cost. A well designed and welded manifold will last a long time.
My question. who does? and what makes you think heat treating a manifold is a good thing?
If someone wishes to heat treat one of my manifolds after buying it.. then they're welcome to. If someone wishes me to include it in an already bloody cheap $600 price, they can wake up now and stop dreaming.
Do you really even believe that a small amount of tiny metal flakes will actually damage a turbine?
Why is steam pipe a different matter?
And what are you suggesting? That I make my manifolds out of thin, crack prone stainless? Or set up a large iron casting factory? Oh I know! I'll invent a new metal! And I'll call it Trisobium. Designed specifically for exhaust manifolds.
Yes, I know, Mild steel isnt perfect.. but its the best option out there especially for those budget conscious modifiers. Do you disagree???
If you dont disagree .. then why the hell are you hassling me?
If you do disagree then please enlighten me! Im yet to hear what you think would be better.
I honestly have no idea whatsoever of why you are being so critial of my work.. and the materials I use.. you have yet to offer any suggestions in regards to what would be better... so please, get to the point.
-Tristan