[Herr-Kuhn]

http://209.85.165.104/search?q=cache:c8-dTKye5GAJ:media.gm.com/division/powertrain/products/engine/carengines/2004/lsj_final.doc+SUPERCHARGED+SODIUM+FILLED+EXHAUST+V ALVES&hl=en&ct=clnk&cd=1&gl=us

Since we were debating the "need" for sodium filled exhaust valves on a turbocharged car and some were saying they were not needed on a supercharged car, well please see above. GM seems to have fitted sodium filled exhaust valves to their supercharged Ecotec engine.

Does this mean I think that sodium filled valves are a must to bolt a turbo on a 928? No, but the point here is all forms of forced induction place higher thermal loads on the exhaust valves. The thought that one system needs these while another can get off scott-free is another myth. The statement that OEMs do not install sodium filled exhaust valves on a supercharged car is false. Race a twin turbo or a supercharged car and you want the extra insurance?, then go ahead and install them. Is it better? Of course it is.

Do I think all owners of supercharged 928s should be worried of exhaust valve melt-down? Of course not!...but please let's stop throwing things the turbocharger's way about this sodium filled exhaust valve topic. Here we have a simple 2.0 liter GM powerplant with a positive displacement pump that has the sodium filled exhaust valves fitted by the OEM. One should consider how much more time this engine stays on boost compared to a supercharged or turbocharged V8. I'll go on a limb here and say the valves in a boosted 4 cylinder see way more thermal load than they would in a V8 turbo or supercharged car. You just don't need to hold your foot into it that long with the big V8.