m42 stock manifold material and thickness

[KyleTaylor]

What is the stock exhaust manifold made of and what thickness?

I want to modify a stock manifold for a bottom mounting turbo that can be used with the stock exhaust.  I am looking at the Mosselman system for direction as the turbo I have from a 2.0L Saab with internal wastegate is rather small.  Think 5 or 6 psi, no more.

This is my daily driver and the goal is added fuel efficiency.  The plan is to have about 5 psi to make up for using a 3.25 LSD in place of the current 4.10.  If I do not see a fuel economy increase it will all go back to stock.

I currently get 30 mpg city/highway average.  The differential ratio difference is about 20%... not sure if there will be a direct correlation to fuel economy but 20% increase would be 6 mpg, I would settle for 3 which would just be 10%.

Just a science experiment, not looking to make a race car!

[E36Al]

Ummm, thats a no no on fuel economy mate.
These engines are great on fuel anyway.
Fit a turbo for the power increase.
Why are you fitting an lsd and lower ratio if you're more concerned with economy than performance?
The standard exhaust headers are mild steel so are easy to work with, but where i come from they're too expensive to hack up.
Low mount setups in the bmw generally require a lift pump for oil return to sump-keep this in mind.

[crazzy_hippo]

I don't think you will get better fuel economy by fitting a turbo though. If you are thinking of improving the economy, you need to improve the efficiency of the engine.

This means higher compression..... 10:1 is rather low.....

[E36Al]

Actually just read that the material is stainless steel.
Mine are definately mild steel, perhaps an australian spec thing, they look factory?

Though the info i read is from an australian site link below
http://http://www.motortraders.net.au/groups/group.asp?group=1&menu=89

[nuvolarossa]

I like too experiments, but every time you are in boost you need to add fuel...
If you want to save fuel all the Otto cycle is wrong only 25-30% of energy produced from combustion goes to the wheels, the other is heat and pollution
 
PS: it can be a pricey experiment