C6 cam vs RSR sprint, why?

[tadd]

Does anyone care to comment on why porsche decided to dump the C6 profile between the 2.8 and 3.0?

Could one speculate that the 'less than optimal' 2.0L combustion chamber needed more overlap to lower the dynamic CR at low rpm when flow would be lazy with minimal turbulance? Then with the flatter 3.0 chamber they were more detonation resistant, so why not get some of the bottom end back at low rpm by widing the lobe center....

Just some extra man behind the knoll thinking.

[Steve@Rennsport]

Originally Posted by tadd

Does anyone care to comment on why porsche decided to dump the C6 profile between the 2.8 and 3.0?

Could one speculate that the 'less than optimal' 2.0L combustion chamber needed more overlap to lower the dynamic CR at low rpm when flow would be lazy with minimal turbulance? Then with the flatter 3.0 chamber they were more detonation resistant, so why not get some of the bottom end back at low rpm by widing the lobe center....

A more useful powerband and a little more power.

[tadd]

Ok, that begs the question why they stayed with it from, what, 64 to 72 1/2 ish?

That seems like a long time. Clearly they were trying other profiles such as in the 2.0 twin cam. Frere says it wasn't liked, but it does show alternate development.

[BURN-BROS]

The 906 cam was developed for a 66mm stroke. As the stroke changed, they started to look for, as Steve stated, a better powerband. The lobe centerline is a big step up from Porsche's earlier thought process. Quite possibly the most important change.