It seems to me that putting turbo chargers on all car engines would be a worthwhile prospect as you seem to get (somewhat) free energy for nothing.
A car with a turbo charger has a greater power output than a car with the same engine sans a turbo charger. Essentially you could shrink the size of the engine for the same power output thus increasing efficiency.
The only reason against it I can see is you are making the engine more complex and thus increasing costs of production but wouldn’t that be mitigated by being able to make smaller engines for the same amount of power? If you’re going for a bare-bones, inexpensive car then I can understand the reasoning not to bother but otherwise it would seemt that most cars would benefit from such an addition.
Obviously there must be more to this equation as most cars don’t have turbo chargers. I’m just wondering why not?
[sub]I suppose you’d also need higher octane gas to run such an engine which may make it less desirable to some people (higher operating cost).[/sub]
Actually, turbo engines make more power per liter as soon as you slap one on.
But more power per <b> buck <b/> comes from making the engine bigger via a bigger bore or stroke, or adding a more aggressive cam or better internal valvetrain, exhaust, etc.
SIMPLY STATED: a turbor is an ADD-ON, while other engine improvements are substitutions. Add on = add on costs…complexity and wear.
Is the added cost and complexity of a turbo that significant when compared to the overall cost of the car? Also, as I mentioned earlier, you can theoretically make a smaller engine with a turbo to get the same power output as a car with a bigger engine (I’m using ‘bigger’ and ‘smaller’ here loosely…I know there is more to the power equation than mere size). Wouldn’t that mitigate the overall added cost of the turbo?
I know a turbo engine with a power output of (say) 200hp isn’t as desirable as a bigger engine (sanas turbo) also with a power output of 200hp. Turbo lag for one thing as well as a power curve issue for turbo (as I understand it turbos can be tweaked for providing more power at the lower speed end or the higher end but they can’t do both equally well). Still, turbo chargers are a well established technology and it seems a relatively simple add-on to get more performance.
Yeah, what Philster said. Doesn’t a turbo basically work by have an engine’s exhaust gases spin a turbine, which in turn further compresses the intake gasses coming in, enabling more power from the same air/fuel mix (non-turbo-compressed) or the equivalent amount of power from a leaner air/fuel mix?
That being the case, adding a turbo: a) adds complexity; and b) adds stress on the system in the form of greater compression. It strikes me that either of these, if not designed in, could lead to problems. So aftermarket turbos, if not done right, appear like they could be problematic.
I don’t know how much it costs to design in turbos - perhaps the car companies can only cost-justify the extra parts and design fees for premium priced, and not value-priced, cars…
Turbos can be used for greater economy but this is usually done for this purpose on diesel engines, especially if they are epected to run at near constant revs such as on a ship or a generator.
The faster you go, the greater the aerodynamic losses which increase in a logarithmic way, so if you use the turbo merely to go faster then you will reduce your mpg.
The cost of adding a turbo is usually in excess of adding extra cubes so there has to be some extra reason to fit one, such as increasing power density with minimal increase in weight, like on sports cars.
I am surprised that superchargers are not used more, since you get the extra power right the way through the rev range rather than the relatively narrow band that the turbos provides.
There are still the same issues of cost and there is increased complexity, though less than a turbo, but superchargers are very good at delivering the extra torque instantly such as might be required whne overtaking.
Cost more to make.
Cost more to fix.
Add stress to the engine (pistons, rods, crank), shortening its life.
Aren’t being clamored for by the general public–they do have their quirks, and not everyone appreciates them.
Permit to chime in here, having owned several turbocharged cars.
As a general question, asking why all cars don’t have turbos is like asking why all cars don’t have 4 doors. Turbocharging comes with a specific set of advantages and disadvantages that make it unsuitable or undesirable in all cases.
Fist, permit me to clear up some misconceptions:
Wordmans assertion about running leaner is not true. In order to get more power from the added air a turbo pushes into the cylinder, more fuel must be added as well. There is only 1 “ideal” ratio of air:gas in an IC gas engine (14.7:1 IIRC). So if you add air, you must add gas to maintain the stoichiometric ratio.
The reason a turbo allows increased power is not so much that it pushes more air into the cylinder, it’s that it allows you to inject more gas (because you need to maintain the right ratio) More gas = more power.
The advantages of all this are that:
A turbo uses the movement of the exhaust gas to pressurize the intake air, so parasitic loss is low as there is no mechanical connection to the engine output (as with a supercharger)
(as mole mentioned) since it allows an engine to produce more power, the engine can be downsized so that it is more efficient when not on boost.
The primary disadvantages of a turbo are:
Intense heat created by the turbo as it pressurizes the air(remember PV=nRT) can shorten life of engine parts
That same heat means that the air it pumps is less dense, removing some of the advantage. To get around this, most turbo cars are also equipped with an intercooler to cool the air, adding more cost and complexity.
Turbos operate at EXTREMELY high RPMS (100,000 is not unsual), requiring sophisticated oiling mechanisms
The well known turbo lag
So all this adds up the fact that there are situations where the advantages clearly outweigh the disadvantages. Premium passenger cars are a good fit, because people are willing to pay for the added development cost, as well increased warrantee costs (more parts to cover) in exchange for more power.
Places where you might not find a gas turbo to be a good fit could include trucks. Towing would probably put the turbo under too much stress (operating on boost for extended periods).
casadave: superchargers aren’t used as often because a) they are much larger physically, and b) the parasitic power loss is much more significant as they are connected directly to the output shaft of the engine.
Turbo chargers do not improve low-end torque either. For city driving a turbo is almost useless. They ARE also expensive to repair. Considering some are intercooled, requiring to and fro coolant lines, the impellar bearings, etc. I would think people who drive turbos probably don`t get better gas mileage because they are always on the gas(lets kick the turbo in!!).
CASDAVE is right, superchargers get more bang for the buck and are easier to install and maintain. I think the initial cost is roughly the same.
“The Motor Man” (has a weekly radio show), says he installs a supercharger an all his vehicles, for whatever that`s worth.
As far as installing turbos as standard equip., the dealers could then not be able to charge “extra” for the turbo models. This would also raise the price of the base model $1500 bucks.