|
Ok the Rotrex im using is big C30-94. Its rated at 200 - 400 horses.
The Rotrex C30-94 charger has a maximum impellor speed of 100,000 RPM. My car is geared so the charger is spinning at this speed at the redline, so the charger is being used to its full potential. This gives about 20 PSI of boost on redline, so plenty of top end power. Lower down the rev range, say at 3000 RPM, the charger is giving about 3 PSI, so its just starting to give useable boost. And remember, this is with the charger geared so its spinning as fast as possible.
Now the problem - im using a standard engine, and only want 7-8 PSI of peak boost (ie, at redline), which will give approx 230 - 250 BHP. To get this, you need a much bigger pulley in order to rotate the supercharger more slowly. The problem with this is, the low and mid-range performance will really suffer - and it wont be giving usable boost until 5-6000 RPM - not ideal.
The solution. Wouldn't it be good if you could have the low and midrange punch of a high boost conversion, but with a sensible peak boost for a standard engine? Well now you can. My maintaining the same pulley size, but restricting the inlet, we achieve this. At low speeds, the inlet restrictor ring does not hamper the air flow, as there is simply not enough air flow for it to become restrictive. As air velocity increases past the restrictor ring, it becomes restrictive and limits the volume of air that can flow past it.
So basically what you achieve is the dream powergraph... Power and torque will progressively increase, until about 5-6000 RPM, then it will level out (it will still rise very slowly). The best thing is, the power will NEVER tail off.
This gives MUCH more area 'under the graph' than limiting boost by using a bigger pulley. And, if you speak to anyone who knows what they're talking about, its the are under the graph the determines how quick a car is.
For those of you ever contiplating doing high boost, ( or change internals ) the restrictor ring can be left out .
|