Why are turbos more popular than superchargers?
Discussion
Very few new cars are fitted with superchargers as standard while very many (possibly most) new cars are fitted with turbos.
Can anyone explain why the turbo has won the battle so conclusively?
Superchargers - AFAIK - provide much more linear power delivery but I imagine they require more input of force to actuate them.
Turbos - AFAIK - provide far less linear power delivery but they require less input of force to actuate them. In fact, is it true to say that as they are powered by exhaust gases, they require zero effort from the engine to turn them? Or is that overly simplistic?
Turbos are getting far more smooth in their delivery through the application of technology; would superchargers have improved similarly if they'd won the technology race some years back, or is there only so much you could do to improve them? For example, turbos now have various technologies like twin scroll/variable vane to try and eliminate lag and delayed response - could anything by done with a supercharger, or is it a turbine on a chain, with which very little can be done?
Finally, I only ever see SCs on large engines, presumably smaller engines would lose to much power turning them (?). So for the record, what's the smallest engine on a production car to have come out of the factory supercharged? I know MX5s have them as an aftermarket kit, but let's stick to production cars for this thread.
Can anyone explain why the turbo has won the battle so conclusively?
Superchargers - AFAIK - provide much more linear power delivery but I imagine they require more input of force to actuate them.
Turbos - AFAIK - provide far less linear power delivery but they require less input of force to actuate them. In fact, is it true to say that as they are powered by exhaust gases, they require zero effort from the engine to turn them? Or is that overly simplistic?
Turbos are getting far more smooth in their delivery through the application of technology; would superchargers have improved similarly if they'd won the technology race some years back, or is there only so much you could do to improve them? For example, turbos now have various technologies like twin scroll/variable vane to try and eliminate lag and delayed response - could anything by done with a supercharger, or is it a turbine on a chain, with which very little can be done?
Finally, I only ever see SCs on large engines, presumably smaller engines would lose to much power turning them (?). So for the record, what's the smallest engine on a production car to have come out of the factory supercharged? I know MX5s have them as an aftermarket kit, but let's stick to production cars for this thread.
The primary reason is fuel economy - turbochargers have lower parasitic losses.
ETA: It's would be misleading to say that turbochargers introduce no parasitic losses to the engine. They don't directly induce drag on the engine, but they do introduce exhaust back-pressure and seriously limit exhaust gas scavenging, which has much the same effect.
There is no fundamental reason not to supercharge small engines, but they tend to be tuned more aggressively for economy than larger ones.
ETA: It's would be misleading to say that turbochargers introduce no parasitic losses to the engine. They don't directly induce drag on the engine, but they do introduce exhaust back-pressure and seriously limit exhaust gas scavenging, which has much the same effect.
There is no fundamental reason not to supercharge small engines, but they tend to be tuned more aggressively for economy than larger ones.
Edited by kambites on Monday 25th February 09:08
Johnnytheboy said:
Finally, I only ever see SCs on large engines, presumably smaller engines would lose to much power turning them (?). So for the record, what's the smallest engine on a production car to have come out of the factory supercharged? I know MX5s have them as an aftermarket kit, but let's stick to production cars for this thread.
My Elise is supercharged, and it's only a 1.8 engine.The difference in use, iirc, is down to the parasitic losses of a supercharger - out there in the real world they're too costly for efficiency over a turbo. Definitely prefer a supercharger though, lovely. 
ETA: Sniped! Not sure I like that Wiki page's definition of where a turbo's energy comes from though - I can't see any PE component in an exhaust gas that a turbo harvests.
ETA: Sniped! Not sure I like that Wiki page's definition of where a turbo's energy comes from though - I can't see any PE component in an exhaust gas that a turbo harvests.
Edited by Krikkit on Monday 25th February 09:09
Johnnytheboy said:
Superchargers - AFAIK - provide much more linear power delivery but I imagine they require more input of force to actuate them.
Turbos - AFAIK - provide far less linear power delivery but they require less input of force to actuate them. In fact, is it true to say that as they are powered by exhaust gases, they require zero effort from the engine to turn them? Or is that overly simplistic?
That's my understanding of the matter as well - superchargers are less efficient overall due to sapping power from the crank to turn it. As a lot of the current focus by manufacturers is to make engines more efficient, I think turbos make more sense.Turbos - AFAIK - provide far less linear power delivery but they require less input of force to actuate them. In fact, is it true to say that as they are powered by exhaust gases, they require zero effort from the engine to turn them? Or is that overly simplistic?
I don't think it's 100% accurate to say zero engine effort is required to spin a turbo - energy is never completely 'free' - exhaust design affects scavenging, and the turbo is effectively a blockage in the system.
Honestherbert said:
Polo G40 are supercharged iirc and they are only 1300cc
Turbo's are more commonly used due to economy I believe,both on the side of fuel consumption overall and the costs of producing them.
I can't imagine why turbos would be cheaper to produce (other than economies of scale). Belt driven superchargers are inherently simpler things. Turbo's are more commonly used due to economy I believe,both on the side of fuel consumption overall and the costs of producing them.Basically I agree with the general drift - that turbochargers offer more for less. Over the years, I have not only owned many turbocharged cars - from Ford RS200s to my current Jaguar XF 3.0D - but been involved in the development and marketing of several others.
As far as engineers are concerned, the supercharger has two major disadvantages - one being that it has to be physically close to the engine, and the spinning axis in line with the crankshaft (which sometimes makes it difficult to 'package'), the other being that it has to be driven, by chain, belt, gears or whatever.
The turbocharger, on the other hand, doesn't have to be driven (which is one less thing to go wrong, break or wear out), and the other is that it can be placed in many different points between the engine and the exhaust pipe.
As far as engineers are concerned, the supercharger has two major disadvantages - one being that it has to be physically close to the engine, and the spinning axis in line with the crankshaft (which sometimes makes it difficult to 'package'), the other being that it has to be driven, by chain, belt, gears or whatever.
The turbocharger, on the other hand, doesn't have to be driven (which is one less thing to go wrong, break or wear out), and the other is that it can be placed in many different points between the engine and the exhaust pipe.
The key benefit of a turbo is that it's speed can be varied independently of the engine speed efficiently and reliably, where as with a super charger that is directly driven it's not feasible.
In an ideal situation with a turbo engine you could design all the components in the bottom end to be rated to a specific torque and then the software could take care of of managing the amount of boost you need at achieve that maximum torque giving you a perfectly smooth torque curve from the lowest rpm where you have enough boost up until the point the turbo speed is maxed out. If you ever see a turbo torque curve with a perfectly flat peak section that is what is happening and it means at those rpms the engine produces the maximum amount of power it possibly could do without starting to ripping it's self apart (according to the design strength of the bottom end).
It is essentially impossible to efficiently achieve this kind of long flat peak with a super a charger or NA
In an ideal situation with a turbo engine you could design all the components in the bottom end to be rated to a specific torque and then the software could take care of of managing the amount of boost you need at achieve that maximum torque giving you a perfectly smooth torque curve from the lowest rpm where you have enough boost up until the point the turbo speed is maxed out. If you ever see a turbo torque curve with a perfectly flat peak section that is what is happening and it means at those rpms the engine produces the maximum amount of power it possibly could do without starting to ripping it's self apart (according to the design strength of the bottom end).
It is essentially impossible to efficiently achieve this kind of long flat peak with a super a charger or NA
ging84 said:
The key benefit of a turbo is that it's speed can be varied independently of the engine speed efficiently and reliably, where as with a super charger that is directly driven it's not feasible.
I see no reason you shouldn't use some sort of crude CVT setup on a supercharger?Out of interest, how does a turbocharged engine actually vary the boost?
Honestherbert said:
Polo G40 are supercharged iirc and they are only 1300cc Turbo's are more commonly used due to economy I believe,both on the side of fuel consumption overall and the costs of producing them.
Oooh, that's a small SC engine I had forgotten! Turbo's are more commonly used due to economy I believe,both on the side of fuel consumption overall and the costs of producing them.AAGR said:
As far as engineers are concerned, the supercharger has two major disadvantages - one being that it has to be physically close to the engine, and the spinning axis in line with the crankshaft (which sometimes makes it difficult to 'package'), the other being that it has to be driven, by chain, belt, gears or whatever.
The turbocharger, on the other hand, doesn't have to be driven (which is one less thing to go wrong, break or wear out), and the other is that it can be placed in many different points between the engine and the exhaust pipe.
The packaging/alignment argument is one I hadn't thought of. So on a modern transverse engine it would have to be in line with the engine effectively. The turbocharger, on the other hand, doesn't have to be driven (which is one less thing to go wrong, break or wear out), and the other is that it can be placed in many different points between the engine and the exhaust pipe.
kambites said:
ging84 said:
The key benefit of a turbo is that it's speed can be varied independently of the engine speed efficiently and reliably, where as with a super charger that is directly driven it's not feasible.
I see no reason you shouldn't use some sort of crude CVT setup on a supercharger?Now, if you really want to consider cost and complication, think of Cosworth's first attempt in the 1980s to produce F1 power from a 1.5-litre engine, which was on the basis of a very very modified BD block, etc - but with a turbo compound arrangement that I don't even attempt to understand or describe. It needed only a handful of test bed explosions (one caught on TV cameras ...) for it to be abandoned.
Gassing Station | General Gassing | Top of Page | What's New | My Stuff