View Single Post
Flieger Flieger is offline
Max Sluiter
 
Flieger's Avatar
 
Join Date: Mar 2006
Location: So Cal
Posts: 19,573
Garage
The Valvetronic BMW system is the variable-lift. It uses an intermediate rocker shaft between the camshaft and the valve tappet. This intermediate shaft is positioned by another cam lobe and as its position changes, so does the pivot point for the rocker arm. This changes the rocker arm ratio and therefore valve lift. I did a case study on it in my intro to metalcasting class. They investment cast the intermediate arms.

Double-VANOS is the BMW variable valve timing system which phases the camshaft relative to crankshaft. Many issues with hydraulic seals as these BMW engines age.

What is wrong with casting? I have seen jet turbine blades which are investment cast. They have tiny micro features like little ribs and holes to allow cooling airflow around and through them, as these blades work at or above the melting temperature of the Nickel Titanium Chrome etc. Superalloys in the jet turbine combustion chambers.

I would like to see a machinist machine ribs and holes on the inside of a turbine blade which is about 5cm long, 2cm wide, and 5mm thick.
__________________
911S
1971 chassis, 2.7RS spec MFI engine, suspension mods, lightened

Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance
http://www.flickr.com/photos/max_911_fahrer/

Last edited by Flieger; 06-11-2010 at 11:40 AM..
Old 06-11-2010, 11:38 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #22 (permalink)