tohaapanen@watrose.UUCP (Tom Haapanen) (03/03/86)
davidsen@kbsvax.UUCP (Davidsen) writes: > >Some applications in which superchargers are preferred: > 1) large trucks and heavy machinery such as road graders. > 2) off road applications (4x4's) > 3) towing vehicles > >For a given engine, adding a turbocharger feels somewhat like adding a >hotter cam; not much change at low rpm, power building through the >midrange, tons of power at the top end. A supercharger feels more like a >bore and stroke job; just more power everywhere. Having driven both, I >like turbos better on small engines and light cars which encourage sporty >driving, and superchargers on heavier vehicles and all my 4x4's. Now, I can't argue with a personal preference (or can I, Chuck? :-) but having done lots of reading on the new Volkswagen G-supercharger --- which has not yet made an appearance on this continent --- I'd like add some information. Indeed, a supercharger feels the same as a bore and stroke job, but so does a 4-valve-per-cylinder head. These are generally preferred for predictability and low-end power; you can still have an excellent top end with the correct head design, the right cam and the right ignition setup. For an extreme example, imagine that you're driving a Porsche 935 (known for turbo lag) around Watkins Glen. You drive into a tight right-hander, flooring the pedal so that the power will come on as you exit the curve. Now, if you misjudge your timing, the turbo will come on while you're still at the apex. If you're not a professional driver familiar with RWD Porsches, it's goodbye time when the horsepower suddenly doubles in the curve. VW has found that superchargers work better on 2-vpc heads, giving a much more even power curve. With 4-vpc heads, the power curve is already much improved, and apparently a turbocharger is better suited for such an engine than a supercharger. The superchargers vary greatly in any case. There are radical differences between the vane supercharger, Roots blower and the G-supercharger; each has different efficiency and power characteristics. \tom haapanen / watrose!tohaapanen university of waterloo ..!watmath <-- watmum!tohaapanen \ watlion!tohaapanen I am one in ten, a number on a list I am one in ten, even though I don't exist No-body knows me, though I'm always there A statistical reminder of a world that doesn't care (c) UB40, 1981