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Discussion Starter #1
What is the maximum pressure that is produced by an unmodified cooper s and at what rpm does this occur? Does this boost pressure stay constant to redline as long as the throttle is fully open, or is it that the boost increases as the rpms increase? i.e: at redline there is the most boost?

Does changing the size of the pulley reduce the point at which maximum boost occurs and the rpm at which it occurs?

Cheers

Rob
 

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The supercharger is driven directly by the engine so as rpm's increase, the boost increases. Maximum boost hits at the highest possible rpm. When you put a reduction pulley in, the boost will have the same curve, but just a higher boost (i.e. ~15% lower rpm with a 15% reduction pulley). The stock SC will produce a max boost between 11 and 12 lbs while a 15% red. pulley has been seen to give up to 15 lbs and 19, up to 19 lbs. A 19% reduction pulley runs the SC very close to redline and the heat generated is massive so most installers don't recommend a 19% reduction..
 

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Discussion Starter #3
So with the supercharger, the more you push it the better. But i guess the fact that the 11 - 12 lbs boost is seen at max rpm (redline) isn't the best system. Most driving on the street would be in the 2000 - 4500 rpm range, i'm guessing that in this range the boost will go from 5lbs to 8-9lbs. There fore in order to have a quick burst of acceleration, you need to drop a gear or two, depending on your speed.

Would it be better to be able just to push the throttle down and have instant acceleration rather than having to shift down. Less fun i admit but more practical in a way.

I wonder if it would be helpful to place a electronically controlled gearbox that sits on the pulley drive that keeps the speed of the supercharger constant through the entire rev range.
 

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Mini Mod
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AMUSE COOPER S said:
So with the supercharger, the more you push it the better. But i guess the fact that the 11 - 12 lbs boost is seen at max rpm (redline) isn't the best system. Most driving on the street would be in the 2000 - 4500 rpm range, i'm guessing that in this range the boost will go from 5lbs to 8-9lbs. There fore in order to have a quick burst of acceleration, you need to drop a gear or two, depending on your speed.

Would it be better to be able just to push the throttle down and have instant acceleration rather than having to shift down. Less fun i admit but more practical in a way.

I wonder if it would be helpful to place a electronically controlled gearbox that sits on the pulley drive that keeps the speed of the supercharger constant through the entire rev range.
The more the better up to a point. After the design max an SC becomes very inefficient.
A 19% running over around 6200RPM is past the designed max of the SC, Not a good thing.
The 19% does have the advantage of bringing in boost at lower RPMs.


Read post # 12 on this thread
Andy is chock full of good info and data.
 

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Boy who made the wolf cry
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Ahhh, a along way away!! Im in Geelong, Victoria!!

Get in contact witht he Sydney guys, they will show you some great roads to have fun on!!

Todd
 
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