62, 90, 112 is how many cubic inches per rev the supercharger displaces. If you know the basics, you can do a quick size check.
As a minimum, a postive displacement supercharger must flow as much air as the engine does, before you factor in the boost. The pressure is controlled by the size of the supercharger and the parent engine. If its done right, the supercharger will deliver between 1.2 and 2 times more air than the engine can flow, but the primary requiremnt is going through a calculation like this:-
1.Forget volumetic efficency of the engine or supercharger. Forget that a supercharger heats up air, and looses its efficency. So does an engine.
2. Calculate the peak rpm the engine will run at, and then work out the cfm the engine could ingest without a supercharger.
3.Find the specs on swept volume per revolution of the supercharger you'd like to use.
4.Work out the shaft speed at which the supercharger can be safely driven. The maker has a set rpm level which they don't want exceeded. Its the maximum engine rpm, times a factor.
Example: My friend has a 1988 Holden with a GM 3800 V6. It was supercharged with a Castlemain Rod Shop supercharger kit Normally, the Buick V6 can revs to 5800 rpm before the Memcal computer shuts the engine down.
Before supercharing, it could in theory consume a maximum of 388 cfm using the formula
cubic inch engine displacement X max rpm
.....................3456
The kit uses the Toyota SC14 supercharger, made by Ogura, who make air conditioning pumps for Fords and Mazdas and superchargers for Toyota Celicas, MR2's, and the like . The SC14 displaces 1.4 liters per revolution, or 85 cubic inches per rev.
It revs 1.33 times the maximum shaft speed. That is about 5800 rpm x 1.33, or 7714 rpm. It's peak cfm flow is 379 cfm
cubic inch supercharger displacement X max rpm
.....................1728
That's as far as you need go. As long as the engine flows less than the supercharger, use it.
For those trying to justify themselves further, then calculate the theoretical boost.
In this case, the Holden is also boosted to 9 psi boost. This means that, in addition to the flow of 379 cfm at 5800 rpm, the actual air flow is compressed by the inability of the pressurised engine to flow more. In practice, the 379 cfm increased by
psi boost+14.7
........14.7
or a theoretical boost ratio of times normal air pressure of 1.61
So 379 cfm becomes 610 cfm.
You've now got a 388 cfm engine getting at bit less than 610 cfm right down its throat!
In practice, the car has 176 hp at 5000 rpm in stock form, but 220 hp at 5000 rpm supercharged. This is despite the Ogura SC14 being accepted as smaller than the ideal, and having no intercooler. It gives 9 pounds of boost, and produces stunning acceleration well beyound any XR6 Falcon or factory V8.
For a stock 200 six, that Eaton M62 will not work unless it can spin 1.6 times the maximum engine rpm. Thats only 5000 rpm for a 200, and about 8000 shaft rpm. That's not too much for the M62, but its getting up there for the limits of the supercharger.
M90 or 112 will be much better, but the 200 has only got 80 to 90 hp at 4000 rpm stock, and if you can spin it 1.6 times the crank speed, you'll get 9 pounds of boost. Thats enough for a 40% gain in torque and power, which is like swapping a 200 cube engine for a stock 289. If you can get an M90, I'd be using it.
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