pauldan@hou2e.UUCP (P.SAUNDERS) (04/12/85)
Howdy, all you techno-experts! I was recently involved in an argument concerning SUPERcharging versus TURBOcharging. Can I inspire anyone to discuss differences, inherent advantages/disadvantages, which is "better", etc.? Can anyone tell me why all abnormally-aspirated F1 racers are of the turbo-sort, while most "funny cars" are supercharged? Thanks. Dan Masi
genesis@ihu1e.UUCP (R. Sehnoutka) (04/15/85)
> I was recently involved in an argument concerning SUPERcharging versus > TURBOcharging. Can I inspire anyone to discuss differences, inherent > advantages/disadvantages, which is "better", etc.? Can anyone tell me > why all abnormally-aspirated F1 racers are of the turbo-sort, while most > "funny cars" are supercharged? > > Dan Masi I think the main difference between the two is quite simple. SUPERcharging, as in funny cars, is done to achieve the highest horsepower from the engine. Since these engines are NOT water cooled, they have a short life span. Some of the funny car engines and rail engines are supplying 2500 horsepower for a quarter-mile race. TURBOcharging is usually done to normal engines (water cooled), to give the engine more horsepower, without really affecting the life of the engine. -- Russell N. Sehnoutka ------- AT&T Bell Laboratories ihnp4!ihu1e!genesis ------- Naperville, Illinois
davew@shark.UUCP (Dave Williams) (04/15/85)
Turbochargers are a subset of superchargers, but in recent years
it has generally thought of as a different class of unit.
A supercharger is used to stuff air/fuel mixture into the cylinders
at a positive pressure (above atmospheric pressure). A normally
aspirated engine uses the vacuum of the receeding piston to draw
in the mixture. Obviously stuffing for mixture into the cylinders
will result in more HP. Turbochargers are two chambered devices
that use the hot exhaust gases to spin a turbine blade at a very
high velocity. A shaft connects this blade to another blade in
the other chamber that stuffs the mixture into the cylinders. The
turborcharger is an on demand device that only kicks in when
the exhaust flow is sufficient for it to pump out a positive boost.
Turbos have become an easy way of producing added horsepower in
production type cars as they are small, easy to work on, relatively
inexpensive and only put an additional load on the engine when called
on. They cause some restriction in the exhaust system which causes
elevated exhaust temperatures. Early turbochargers suffered from
a hp lagging effect which meant that the boost generated by
the unit started to come on at some point, usually as much as .5
sec after the throotle was opened. Improvements in rotor design
have taken care of this problem.
A supercharger is driven my some mechanical means from the engine
crankshaft. The usual way is to use a geared timing belt with the
supercharger (blower) sitting on top of the intake manifold. Other
variations have the blower siiting in front of the engine with a
duct running back to the manifold. There are several types of
blowers: the centrifugal, as used on the old Mercedes and
Auto Union Grand Prix cars of the 30's and the Novi Indy racer,
this is a fan blowing into a plenum, they produce mucho high end hp
but suffer at low rpm's; the roots type use two interlocking 3 bladed
rotors to produce the boost, this is the type generally seen on drag
racing engines as it produces substantial boost throughout the engines
rpm range, most roots type blowers are variations on the GMC diesel engine
design. There are several other types, such as axial flow, but these
are variations of roots or centrifugal designs. It takes about 35-50 hp
to drive a supercharger and the boost is always there, so engine wear
is considerably faster.
Today turbo's are used on F1 and Indy cars, because of their light weight
and smallness. These are high reving engines and are kept in the power
band by ample use of the gearbox. The drag cars still predominately use
the roots type because of the good low end characteristics. Some
experimentation with some newly designed centrifugal units has been done.
There was some talk in this group several weeks ago about nitromethane
and nitrous oxide. Nitromethane is not a form of TNT as someone stated,
but is a cleaning solvent used in the drycleaning industry. It has less
BTU's per pound than gasoline, but because it has an oxygen bearing
radical more of it can be stuffed into a cylinder without "flooding"
the engine. Nitrous oxide, sometimes called laughing gas, is an
oxydizer. It is injected into the intake manifold under pressure and
allows more fuel to be burned. So there.
wit
--
Dave Williams
Tektronix, Inc.
Engineering Computing Systems
"6000"
"The workstations that made
Wilsonville famous."bhs@siemens.UUCP (04/15/85)
Superchargers are mechanically more complex, what with needing a drive. However, they produce boost without throttle lag, and also are able to produce boost at low rpm, where turbos have difficulties. F1 cars are typically run at high rpm, and thus high exhaust volume, so the low rpm bit is irrelevant. Lancia produce a few cars with supercharging, using a system known as the Volumex compressor. Could it be that superchargers, being based on engine rpm vs. exhaust volume, are not able to develop such high boost pressures? Bernard H. Schwab Siemens RTL, Princeton, NJ
mrl@drutx.UUCP (LongoMR) (04/15/85)
[] My understanding of the difference between the two is that (1) superchargers are belt driven rather than exhaust driven, therefore [here's the biggie] (2) you are able to run headers with a supercharger where you are not able to do so with a turbocharger. Other than that, the two systems accomplish the same thing. (please, if I am wrong about this, someone correct me) Mark Longo Denver
dbp@dataio.UUCP (Dave Pellerin) (04/16/85)
>My understanding of the difference between the two is that >(1) superchargers are belt driven rather than exhaust driven, therefore >[here's the biggie] (2) you are able to run headers with a supercharger >where you are not able to do so with a turbocharger. Other than that, the >two systems accomplish the same thing. >(please, if I am wrong about this, someone correct me) > Mark Longo Denver Well, they sort of do the same thing but the major difference is that a supercharger forces outside air down the engine's throat (in a carburated engine, the supercharger sits above the carb), while a turbocharger increases the manifold pressure by drawing air in through the (carb, throttle, whatever) and then injecting it back into the intake manifold. A turbocharger is more complicated, but allows better throttle control at lower power ranges. - Dave Pellerin
review@drutx.UUCP (Millham) (04/16/85)
Since a supercharger is belt driven, they take engine power to run. A supercharger works well at idle speeds, unlike a turbo. I turbo is driven by exaust gases, using only wasted engine power, not usefull engine power like a supercharger. (there was an article in one of the car mags. this month, I forget which one. If there is enough intrest, I'll post the which one.) -------------------------------------------- Brian Millham AT & T Information Systems Denver, Co. ...!inhp4!drutx!review
klein@ucbcad.UUCP (04/17/85)
> Since a supercharger is belt driven, they take engine power to run. > A supercharger works well at idle speeds, unlike a turbo. I turbo is > driven by exaust gases, using only wasted engine power, not usefull > engine power like a supercharger. (there was an article in one of > the car mags. this month, I forget which one. If there is enough > intrest, I'll post the which one.) > Careful here. A turbocharger, unlike what the above seems to imply, does not get you something for nothing. BOTH take engine power. They just take it from different places. A turbocharger reduces the power by interfering with exhaust flow and increasing exhaust pressure. A supercharger reduces the power by mechanically loading the engine. But in both cases the power is boosted by the action of the charger, so hopefully the benefits outweigh the penalties. -- -Mike Klein ...!ucbvax!ucbmerlin:klein (UUCP) klein%ucbmerlin@berkeley (ARPA)
mike@amdcad.UUCP (Mike Parker) (04/18/85)
> Since a supercharger is belt driven, they take engine power to run. > A supercharger works well at idle speeds, unlike a turbo. I turbo is > driven by exaust gases, using only wasted engine power, not usefull > engine power like a supercharger. (there was an article in one of > the car mags. this month, I forget which one. If there is enough > intrest, I'll post the which one.) > > -------------------------------------------- > > Brian Millham > AT & T Information Systems > Denver, Co. > > ...!inhp4!drutx!review It takes engine power to push exhaust gases out of the cylinder, and I don't think that a turbo charger makes it any easier. Mike @ AMDCAD
allgair@fritz.UUCP (Ed Allgair) (04/18/85)
In article <> davew@shark.UUCP (Dave Williams) writes: >Early turbochargers suffered from >a hp lagging effect which meant that the boost generated by >the unit started to come on at some point, usually as much as .5 >sec after the throotle was opened. Improvements in rotor design >have taken care of this problem. Isn't 'turbo lag' mostly caused by the distance the turbo's compressor is from the intake valves? Also the distance from the exhaust valves to the turbine side? I thought that shortening that path was the point of trying to make the turbo housing a part of the exhaust manifold and keeping the intake as direct as possible. (And a low volume to compress.) Also, my 1985 2.2 turbo has a definite turbo lag of sometimes greater than .5 second. This lag is most noticeable at about 25 mph if I floor the accelerator, but is also quite noticable if I only depress the pedal partway and hold it. In the partway depressed case, the car will immediately accelerate, (no stumbling) then if you listen you can hear a whine as the turbo spins up, accompanied by a power increase beyond what would be expected for the 200 - 300 rpm increase that has happened. (not that I'm dissapointed when the power arrives :-) ) I understand that my car has a wastegate that is 'computer controlled' (as opposed to strictly boost controlled). Could this be playing "economy" games with my turbo, thereby increasing the percieved 'lag'? I'm not on boost continuously until I'm doing about 65 mph, determined by keeping track of whether the last whine was a 'whine-up' or a 'whine-down', so I still can detect lag below that speed. Above 65, I feel no delay from accelerator position to engine action. It's somtimes hard to seperate the auto trans workings from the turbo's at in-between speeds, so these observations are either first-gear or top-gear. On the freeway, the transmission completes its down-shift before the boost surge hits. >...are variations of roots or centrifugal designs. It takes about 35-50 hp >to drive a supercharger and the boost is always there, so engine wear... Does it take that much power to drive any supercharger? I heard about a company in Los Gatos that has come out with a supercharger for the Honda V65 motorcycle. They claim 170 hp instead of stock 112 hp. Does that mean the supercharger takes away 35 hp and gives back 93 hp? Or do some smaller(I assume smaller for the smaller displacement here) superchargers use considerably less power? No contest on the increased engine wear -- you've got to pay for it somehow. :-) What about superchargers and fuel-injected cars? How would a turbo or superchager work on all these new-fangled 'port-injected' or 'cross-fire injected' and other injection systems that have a zillion sensors feeding the control computer? If they weren't designed for it originally,(come from the factory that way) would it be nearly impossible do add one? Hmmm...Yes, let's discuss superchargers! :-) Ed Allgair
gvcormack@watdaisy.UUCP (Gordon V. Cormack) (04/19/85)
> It takes engine power to push exhaust gases out of the > cylinder, and I don't think that a turbo charger makes > it any easier. > > Mike @ AMDCAD This argument was also put forward in a previous round of discussion a year ago. The simple fact is that, by nature of the cycle in the internal combustion engine, the exhaust is released at many atmospheres of pressure. Even if the exhaust were to a total vacuum, the kinetic energy of the exhaust would be wasted. The turbo harnesses this energy. Of course, a turbine is going to increase the back pressure a bit, but it need not do so very much. The bottom line is that the first clause of the above quotation is fallacious; most of the energy pushing exhaust gasses out of the cylinder is waste heat, not useful mechanical energy from the engine. The turbine harnesses much more waste energy than useful energy. -- Gordon V. Cormack CS Department, University of Waterloo gvcormack@watdaisy.uucp gvcormack%watdaisy@waterloo.csnet
lrd@drusd.UUCP (L. R. DuBroff) (04/22/85)
Forget the supercharger vs. turbocharger question. You don't have to make that choice anymore; just get one of each! I glanced through the current issue of "Car and Driver" this weekend and saw a description of a car (I don't remember the manufacturer) intended for rallying to be produced in small quantity (n == 200, for homologation) that will have both a mechanically driven supercharger AND an exhaust driven turbo- charger. The claimed power output was 400 hp from 107 cubic inches.
rex@eneevax.UUCP (Rex Root) (04/23/85)
Headers can also be used with turbochargers. Take a look at a Formula car. A plumber's work of art.
man@bocar.UUCP (M Nevar) (04/23/85)
This is about the "Car & Driver" article about a turbo AND supercharged
ralley car.
It is a Lancia Delta S4, made in Italy.
Vehicle is mid-engine, 4-wheel drive, 2-passanger, 2-door sedan.
Engine type: supercharged, turbocharged, and intercooled 4 in-line,
aluminum block and head, fuel ingected.
Displacement: 107 cu in. 1759 cc
Power (DIN) 400 bhp at 8000 rpm
Transmission: 5 speed
Wheelbase: 96.0 in
Length: 157.0 in
Curb weight: 1950 lb
Summarized from the article:
The S4's 1759cc four-cylinder engine was designed and built by Fiat's Abarth
division. It is the first volume powerplant that features both a crankshaft-
driven positive-displacement compressor (known as Volumex) ans an exhaust-gas-
driven turbocharger. Although the supercharger creates plenty of revs, it
gradually runs out of breath around 3500 rpm--and this is precisely where
the KKK turbocharger cuts in. This combintion provides massive torque
at just above idle speed and completely eliminates turbo lag.
Top speed varies between 109 and 128 depending on final drive ratio.
0-60 time is around 5 seconds.
Mark