Question about superchargers.

Why is it superchargers are frowned upon because they use power directly from the engine to compress the air/fuel mixture. I’ve read in different car magazines that people have used turbochargers instead of superchargers when customizing a car because of this. Is it merely because a turbocharger gives more power, I thought the s’charger would be better because you don’t have to have the engine reving so high for it to start working. But then again as I have demonstrated before I know very little about car mechanics.

Well, I am not an expert but just a semi-knowledgeble back yard grease monkey. Here are my thoughts.

  1. They require more drastic changes to the engine than a turbo charger, hence more money. At the least, they require:

Different intake manifold
Different crank pulley
A lot of room under the hood
A whole lot of plumbing
A whole lot of $$$

  1. Since power is taken directly from the engine to drive it, you are getting a smaller “boost” than you would like. (This is a guess, since I think this is really quite minimal…probably something like an air conditioner compressor)

A Turbo on the otherhand requires (at a minimum):

A different exhaust manifold
Some plumbing (air ducting and at least oil lines)

Thats about it. They are generally a little cheaper too. That probably has a lot to do with it.

I will say this though, a lot of serious racers (especially drag) will ONLY use superchargers. They give an instantanious boost, whereas Turbos (depending on the size, of course) usually come on line around 3000RPM.

I have not really heard Superchargers getting a “bad rap” before this post, and many hard core racers swear by them. So, these are only possible answers to your question. I Hope it makes a bit of sense!

Hmm, I am not sure ‘frowned upon’ is the correct phrase.
Turbochargers and superchargers are simply two different ways of getting more power out of an engine.
However, to answer the question I think you’re posing let’s restate it as “what’s the difference between turbocharging and supercharging and which one is better?”

Both systems basically work on the principal of cramming more fuel and air into the cylinders of an internal combustion engine. More fuel/air mix = more power.

Turbochargers do this by using normally wasted exhaust gas pressure to spin an impeller, which does the ‘cramming’.

Superchargers do the same thing but use a belt driven off the crankshaft to spin the impeller(s). Here is probably the ‘frowned upon’ part you’ve alluded to. Due to the fact that the supercharger is using engine power to spin, it is not as efficient as the turbo which essentially uses ‘free’(normally wasted) energy. This is probably why there are more production cars with turbos than with superchargers.

Which is better? Difficult to say and depends greatly on the application. As you mentioned, superchargers (often called ‘blowers’) tend to produce their power more evenly across the rev range, while turbos do need quite a bit of rpm to spin up (if they’re large, smaller one’s spin up faster at lower revs, but are limited in the power they help generate. Modern technology has narrowed the differences between the two systems and saying that one or the other is preferred is not a position I am going to defend. They’re simply different.

Perhaps you mean “frowned upon” in that they are frequently described as being “parasitic”, and there have been many more production cars sent out with turbos than with superchargers.

Superchargers can be somewhat more expensive than turbos, and hood clearance, which is important as automakers try to cram more and more into less space, is limited. Superchargers have a belt which needs replacing, and which causes unholy Hell if it breaks. Superchargers tend to have a lower life expectancy than a turbo does. They also have a clutch, which can be problematic with age.

Overall efficiency wise, a supercharger produces less power per power consumed. This is not to say that the turbo does not limit power somewhat by increasing backpressure, but it still ends up being more efficient than a supercharger.

Another reason blowers are “frowned upon” is due to the lack of performance potential.
A blower’s performance is fixed, that is, directly dependent to the engine crankshaft’s RPM. Since the blower is run off the crancshaft via belt, chain, or shaft, it’s maximum boost is also fixed, unless you change the belt/chain pulleys.
A turbo operates independently of RPM. Many professional race cars have a dial in the cockpit which allows the racer to choose the boost he wants…often while he’s already going round the track.

Before you argue the point of the turbo being independent of RPM, I state that it is dependent upon exhaust gas flow.
That is, units of volume of exhaust per units of time
(ie. CFM/Min)
Thats why turbos dont kick in until a certain RPM is reached. The engine simply isn’t flowing enough exhaust yet. This is called turbo lag.

Now, certain strides have been made in order to minimize lag, using ceramic turbines and composite impellers(to reduce inertia), ball bearings (to reduce friction),
and variable geometry (Nozzles which sqweeze the flow of exhaust, like putting your thumb on a garden hose, to increase the pressure at lower RPMs)

Furthermore, turbos generally incorporate an intercooler (air-to-air heat exchanger) which removes the heat from the boost (Remember…compressing a gas raises its temperature).
This allows for a denser intake charge of air/fuel mixture, as well as reducing engine knock and detonation.
Blowers usually bolt directly to the intake manifold, without using an intercooler (a notable exception is the 3.8 liter Thunderbird SC)

Superchargers can use wastegates too - and thus end up with some adjustment in maximum boost.

And many of the aftermarket ones now use intercoolers - this is becoming much more common.

Superchargers are popular with drag racers for one reason: The Big Boys (and Girls) use them (NHRA Top Fuel Dragster/Funny Car, etc). Why do these big-time racers use them? Because turbochargers are illegal in NHRA and IHRA competition. Professional racing rules are not set up to make the cars go as fast as possible; they are set up to keep the speeds down yet fast enough to thrill the crowds.

Case in point: Most racing series engine development (including NHRA Top Fuel) is all about specific output. Specific output is horsepower/displacement. Back in the early 1980’s, NHRA cars were making maybe 3500hp (pretty generous estimate, 3000 is more likely). Those are 500 cubic inch engines (8.2L). These engines are supercharged and use very exotic fuel. At the same time, FIA Formula one cars were restricted to 1.5L displacement yet were making about 1000hp (some say as much as 1200hp) using turbocharging with moderately modified gasoline formulations. Specific power ratios: 427hp/L for NHRA and a whopping 667 for FIA.

Turbochargers are much more effecient and have a higher power potential. They also tend to be more reliable. In the heyday of piston-engined aviation, both methods of boost were known. Every successful boosted engine design used turbocharging. Power and reliability were both important factors in that trend.

Oops, I forgot the other half of debunking the supposed limitations of turbos in drag racing: Supposed turbo lag.

What drag racer stages his car and leaves the engine at a slow idle? Everyone revs up in anticipation of the green light. I’ve been in a turbo car at an import drag meet and watched the boost guage all the way down the track. It never dipped between staging and whistling through the traps. The wastegate was open the whole time, limiting boost to the specified max (12psi in this case).

Yes, there’s lag when going from idle to WOT but serious racers never start at idle.

Are you serious? A larger engine will generally produce fewer horsepower per liter. The Honda S2000 gets 120hp out of each of it’s 2 liters. The Dodge Viper only gets about 70hp out of each of its 8 liters. With that in mind, your figures aren’t very convincing. In addition, Formula One cars have much higher redlines and much more money is pumped into their engine development.

Boost is boost. 14psi from a blower is exactly the same as 14psi from a turbo. Superchargers have instant boost but the pulley system sucks up some engine power.

The supercharger in my MR2 has made it through 120,000 miles without needing any repairs. Most turbo MR2s usually require a rebuild after about 50,000 miles. If the MR2’s forced induction reliability is similar to that of most cars, I think it’d be far to say that a supercharger is more reliable.

FWIW, Formula One engines are all now 3.0 liter V-10’s with normal aspiration, burning essentially normal gasoline, and produce on the order of 800 HP at around 18,000 RPM. Turbos were banned in the late '70’s because it was too easy to skirt the boost-limit rules. IRL cars are similar but with less displacement, while CART allows (and therefore essentially requires) turbos.

Wrong decade.

From The Formula One World Championship Timeline, under “1987”,