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I had a question come up after reading Twoliters post about FI cams, but did not want to hijack.

How would cams designed for SC applications differ from Turbo applications? Im assuming both need a low overlap, but other than that, what specs would dictate a better cam selection for a turbo car vs a SC one?
 

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That is a good question...

I assume you want something less aggressive for turbos or roots type blowers where you get boost early. Whereas for a centrifugal blower, you'll want something that makes power at the top end?

Mebbe I'm wrong... its pure speculation
 

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From my understanding, you can afford to be more aggressive with the supercharger cams because their airflow is solely based off the RPM you are spinning. Put in a cam with a 4000-7000RPM power range and you will still get the same airflow you had before with the stock cam at all RPM's (However boost will vary, but boost is just a measure of backpressure, not airflow or power potential). Your power down in the lower RPM ranges (and even some midrange) will suffer but you should pick up power in the range of the cam.

Turbo cars are much more sensative to cam timing, change the RPM range of the cam, or even alter the cam timing and you have changed the attitude of the engine because the turbo spool time will increase or decrease based on your change. To give you an example of how sensative turbo's can be to cam timing, my friend has an SVO mustang (turbo old school 2.3L) and advancing or retarding his cam just 1 degree will move his spool time ~200RPM. Keep in mind that is just changing the cam timing with a stock cam, if he were to put in a more aggressive cam it would most likely aggressively alter his spool time as well. Too much cam and the turbo might be hard to even spool up to full boost.

Another thing is with NA you want wide lobe seperation between the intake and exhaust, this allows more time to fill and empty the combustion chamber. On a supercharged car you can accept a little seperation between the intake and exhaust depending on what your going for. With a turbo however you want the seperation tight. The wider the lobe seperation the less low RPM power you will have and the longer it will take to get "into the powerband" (conversly it will perform better then a narrow cam at upper RPM's when the valves have much less time to fill the chamber in between cycles).

That's my basic understanding, someone correct me if I am wrong.
 
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