ted@imsvax.UUCP (Ted Holden) (02/11/86)
The turbocharger, despite any increase in backpressure it may cause, is still the most efficient kind of supercharger. The only reason anyone uses belt-driven superchargers at all has to do with the requirements of drag-racing, in which split seconds mean winning or losing. This is the one situation in which the turbocharger doesn't quite get it, due to the fact that it only comes on at (relatively) higher rpms, whereas the boast from the belt-driven supercharger is there from jump. Drag-racer motors still lose more power from driving the belt-driven supercharger than they would from driving a turbo but, all things considered, it doesn't matter to them. Turbochargers are the superior technology for any other application requiring monstrous amounts of power, although most hot-rodders still prefer more ordinary technology.
hsu@eneevax.UUCP (Dave Hsu) (02/12/86)
In article <511@imsvax.UUCP> ted@imsvax.UUCP writes: > >.... This is the >one situation in which the turbocharger doesn't quite get it, due to the >fact that it only comes on at (relatively) higher rpms, whereas the boast >from the belt-driven supercharger is there from jump. Although I don't think we'll ever see even a remotely successful turbomotor for drag-racing, the high-revs problem is slowly changing as a number of automakers are developing movable `scrolls' to change the intake parameters on their turbos. (wow, mom, a one-sentence posting. Oops, I just blew it) -dave -- David Hsu Communication & Signal Processing Lab, EE Department <disclaimer> University of Maryland, College Park, MD 20742 hsu@eneevax.umd.edu {seismo,allegra}!umcp-cs!eneevax!hsu "They were the elite, the vanguard of progress. They would take mankind to the heights...and perhaps beyond." -Arthur C. Clarke, Childhood's End
svirsky@ttidcb.UUCP (William Svirsky) (02/13/86)
In article <511@imsvax.UUCP> ted@imsvax.UUCP (Ted Holden) writes: > >The turbocharger, despite any increase in backpressure it may cause, is >still the most efficient kind of supercharger. The only reason anyone >uses belt-driven superchargers at all has to do with the requirements of >drag-racing, in which split seconds mean winning or losing.... >........ Turbochargers are the superior technology for any other application >requiring monstrous amounts of power, Some companies, specifically Lancia, Toyota, and Volkswagen, are looking into belt-driven superchargers for production cars. VW has already installed one on a Europe-only Polo Coupe GT G40. The belt-driven supercharger boosts the 1.3 liter four cylinders' output from 55 hp to 115 hp. VW claims it does 0-62 in 9 seconds and top speed is 120 mph. The type of belt-driven supercharger they are using produces higher efficiency, lower noise, and is smoother running - 3 of big problems with belt-driven superchargers. The article I read stated early that another problem with belt-driven superchargers was that they gulped fuel, but then never mentioned any mileage statistics for the VW Polo. -- Bill Svirsky Citicorp/TTI 3100 Ocean Park Blvd. Santa Monica, CA 90405 Work phone: 213-450-9111 x2597 {philabs,randvax,trwrb,vortex}!ttidca!ttidcb!svirsky
cuda@ihuxf.UUCP (Mike Nelson) (02/14/86)
> > The turbocharger, despite any increase in backpressure it may cause, is > still the most efficient kind of supercharger. The only reason anyone > uses belt-driven superchargers at all has to do with the requirements of > drag-racing, in which split seconds mean winning or losing. This is the > one situation in which the turbocharger doesn't quite get it, due to the > fact that it only comes on at (relatively) higher rpms, whereas the boast > from the belt-driven supercharger is there from jump. Drag-racer motors > still lose more power from driving the belt-driven supercharger than they > would from driving a turbo but, all things considered, it doesn't matter > to them. Turbochargers are the superior technology for any other application > requiring monstrous amounts of power, although most hot-rodders still prefer > more ordinary technology. While the comment of instant boost for superchargers in drag racing is in all practical purposes correct, the most important reason for using a supercharger over turbo is the amount of horse power the units can add. When was the last time you saw a V-8 (approx 600) cubes producing 2800 HP with turbos? It is very easy to change the gearing on a supercharger to control the boost. How could a turbo user modify the amount of boost in a few minutes? When the superior technology for turbos causes their net gain in HP to be greater than can be gained by superchargers then you can be sure more drag racers will be using them. I think the writer of the referenced note might be confusing the need for monstrous amounts of power with reliability and versitility where turbos are superior. Mike Nelson ihuxf!cuda
king@kestrel.ARPA (Dick King) (02/20/86)
From: cuda@ihuxf.UUCP (Mike Nelson) Newsgroups: net.auto Date: 14 Feb 86 13:38:15 GMT While the comment of instant boost for superchargers in drag racing is in all practical purposes correct, the most important reason for using a supercharger over turbo is the amount of horse power the units can add. When was the last time you saw a V-8 (approx 600) cubes producing 2800 HP with turbos? It is very easy to change the gearing on a supercharger to control the boost. How could a turbo user modify the amount of boost in a few minutes? Well, turbos have "dump servos" or "waste gates" that bypass a proportion of the exhaust past the turbine that depends on the compressor's output pressure. Couldn't the setpoint of the waste gate be changed much more easily than changing the gear of a supercharger? Seems to me that it could be changed while the car was running, continuously variable, by a choke-knob-like adjuster! -dick
davidsen@steinmetz.UUCP (Davidsen) (02/20/86)
In article <511@imsvax.UUCP> ted@imsvax.UUCP (Ted Holden) writes: > >The turbocharger, despite any increase in backpressure it may cause, is >still the most efficient kind of supercharger. The only reason anyone >uses belt-driven superchargers at all has to do with the requirements of >drag-racing, in which split seconds mean winning or losing. This is not the complete truth... The area in which positive displacement superchargers (like GMC or Paxton) shine is low rpm boost and throttle response. Since the boost is imediate and volume is proportional to the engine rpm, there is a big gain under those conditions. 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. Note that I have not quoted or disagreed with the balance of the original posting, there is no need to repeat those points if you disagree. -- -bill davidsen seismo!rochester!steinmetz!--\ / \ ihnp4! unirot ------------->---> crdos1!davidsen \ / chinet! ---------------------/ (davidsen@ge-crd.ARPA) "It seemed like a good idea at the time..."
tohaapanen@watrose.UUCP (Tom Haapanen) (02/22/86)
In article <5004@kestrel.ARPA> king@kestrel.ARPA (Dick King) writes: > >> It is very easy to change the gearing on a supercharger to control >> the boost. >> How could a turbo user modify the amount of boost in a few minutes? > >Well, turbos have "dump servos" or "waste gates" that bypass a >proportion of the exhaust past the turbine that depends on the >compressor's output pressure. Couldn't the setpoint of the waste gate >be changed much more easily than changing the gear of a supercharger? >Seems to me that it could be changed while the car was running, >continuously variable, by a choke-knob-like adjuster! Dick is right; this is in fact what practically all turbo'd race cars have. (At least WEC, IMSA, F1 and WRC). During qualifying, the driver 'cranks up the boost' to provide better lap times; during the race he'll keep it at a lower boost to conserve the engine and gasoline (critical in WEC and F1), and turn it up for passing other cars when necessary. \tom haapanen watmath!watrose!haapanen I'm all lost in the Supermarket I can no longer shop happily I came in here for that special offer Guaranteed personality (c) The Clash, 1979
jon@msunix.UUCP (Jonathan Hue) (02/24/86)
In article <2802@ihuxf.UUCP>, cuda@ihuxf.UUCP (Mike Nelson) writes: > > While the comment of instant boost for superchargers in drag racing is in all > practical purposes correct, the most important reason for using a supercharger > over turbo is the amount of horse power the units can add. When was the > last time you saw a V-8 (approx 600) cubes producing 2800 HP with turbos? > It is very easy to change the gearing on a supercharger to control the boost. > How could a turbo user modify the amount of boost in a few minutes? When > the superior technology for turbos causes their net gain in HP to be greater > than can be gained by superchargers then you can be sure more drag racers > will be using them. I think the writer of the referenced note might be > confusing the need for monstrous amounts of power with reliability and > versitility where turbos are superior. I don't agree. The BMW 1.5-liter turbocharged engine used in the Brabham Formula 1 car produces 1150hp during qualifying, which is 12.78hp/inch^3, and it can hold together for a few laps while it's doing that. In a 90 minute race, the engine produces 818hp (9.62hp/inch^3) and, well, sometimes will last the whole race. TAG-Porsche Formula 1 engines produce more power in race configuration and are more reliable. I think 818hp from 1.5 liters for 90 minutes of acceleration, braking, and a couple thousand shifts is a heck of a lot more impressive than 2800hp from a blown, Keith Black Chrysler Hemi engine burning nitromethane (nitromethanol?) and methanol which lasts six seconds, whereupon it needs a rebuild. Bitchin' Camaro! Jonathan Hue Bitchin' Camaro! LMSC-Mechanisms & Servos Tire Tracks Across your Lawn! (c) The Dead Milkmen, 1985 {amdcad!cae780,sun!sunncal}!leadsv!msunix!jon
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