why is it that some cams do not work well with certain turbos, and certain turbos do not work well with certain cams? I would just like to understand the mechanical part of this...

The concept is quite simple really . . .

The profile of any given cam is such that it maximizes efficiency around a certain rpm range.

The size of a turbo is such that it runs most efficiently at a well defined range of mass air flow, which corresponds to a certain rpm range with an engine of given displacement.

The idea is to select both so they match. If the cam is too small for the turbo, the motor will run well, but will lose a bit of power in the upper rpm ranges. If the cam is too large for the turbo, the turbo will run out of steam just as the cam is hitting its sweet spot. The result in both cases is less average hp for any given gear, which results in slower acceleration.

When one matches ALL parts to emphasize power in a specific rpm range, the end result is far better than a case that contains a hodgepodge of mismatched parts.

Cams control the air coming into and going out of the cylinders. Cams have a sweet spot or area. Normally stock cams are built for lower RPMs where 90% of you daily driving occurs. When you up grade cams normally they have larger lift and longer duration. These affect idle and lower rpms quailty, but add HP and sometimes Tq at higher rpms. When they say a cam is not good for a stockish turbo the sweet spot is higher in the rpm range than the turbo can handle. The biggest cams are not always best.

thanks a lot, thanks for telling me not to search, u really know ur stuff, i understand a lot better now...someday i hope to be as knowledgeable as u...

+1

Teb B is good people.

ted is a personal friend i wish i knew half of the stuff he forgot.