You just want to keep me posting all night...
Direct Drive would allow a low boost configuration or using an existing pulley configuration to drive the supercharger.
Countershaft introduces a ratio.
For example:
Ratio from Crank to Counter Shaft(CS) 2:1
Ratio from CS to SC primary 2:1
Ratio from SC primary to drive shaft 2:1
Result (2x2)x2 = 8:1 final drive
So at 5k engine RPM - your SC is spinning at 40K
Depending on Compressor wheel thats typically good for atleast 8 PSI, most of my units that would be coming up on 12 PSI. Even on a lower effeciency unit:
A Little of the science:
I can increase effeciency by increasing the ratio between the compressor wheel's inducer and exducer (minor and major)diamters, this also modifies max CFM. So the wheel can be modified to fit and application and still supply the PSI desired.
Now:
Need more boost change the ratios, need less, change the ratios.
Keep in mind that a Centrifugal SC makes boost similar to any turbo, its belt driven not exhaust driven, but other wise they both spool up.
Difference with the SC, you are not depending on exhaust pressure and velocity, you are building boost directly related to engine RPM.
That means Boost climbs through the RPM range till it reaches its max rpm.
I build/design the SC to the application based on your Redline, if you post the engine past redline, you could make more boost becuase as engine RPM increases so does compressor RPM.
Dont get hung up on the direct drive "name" it doesnt get driven off the crank directly or something like that. It just doenst come with a counter shaft on the plate. Allowing more unique configurations and less overal speed.
Beauty of a Centrifugal SC --- cant really over boost, long as MAX boost is a product of max rpm.
You can however use say a 12 PSI Max unit and dump excess pressure above a give limit - think dump valve or waste gate in principal and operation.
Why do that? Simple - you can get more boost faster/sooner in the RPM range and then hold that boost level across the rest of the rpm range.
This is the part where tayloring it to your needs comes in. You tell me what you want and when I will tell you whats possible and for how much.
In my eventual BOOST 101 thread I will get into max boost, differences in operation and yield from various SC and Turbo systems.