Turbochargers vs. Superchargers

Announcer: Go behind the wheel, under the hood, and beyond with Car Stuff from www.HowStuffWorks.com.

Ben: Hello everybody, thanks for tuning in. Welcome to - Don't call it a comeback, but were changing the name to Car Stuff, right Scott? Scott: The first official Car Stuff podcast.

Ben: Whoa, that's us. Okay, and don't worry. We haven't changed too much. My name is still Ben Bowlin, and this week I am in charge of metric conversions, which we are not doing on this podcast, just around the office.

Scott: Very good, very good. My name is Scott Benjamin, and I am the Auto Editor here at www.HowStuffWorks.com. Today we have an interesting topic. I think a lot of people have some curiosity about this.

Ben: Yeah, and not just people in the wide world of the internet, but we have a couple of enthusiasts here in the office, and they would probably - actually one of our guys I think asked me about this a couple months back.

Scott: Oh, no kidding? Okay, well hopefully we can get an answer for him today.

Ben: Now what question are we trying to answer?

Scott: Turbo versus supercharger, which is better, what are the benefits of each one, what's the difference between each one really is the main concern because what does each one do, and how do they differ. That's really it.

Ben: And you know, we should let you guys know getting into it that you're not gonna get a definitive answer from either Scott or myself.

Scott: Man, that's fair to say because I mean you can't say what is gonna work best in every situation. Everybody is gonna have their own favorite, and as you hear - you know, as we get down to the advantages, disadvantages, those play better for one person versus another one, depending on what type of vehicle you are using, what you're using it for, the intended purpose, so you'll find out which one is best for you.

Ben: Oh, and before we get into the shocks and jolts, and the nuts and bolts, Scott, I have to tell you - our buddy Tyler in the production department, came up with a pretty good nickname for you -

Scott: For me?

Ben: Scott, the tiger, Benjamin.

Scott: The tiger.

Ben: Actually he didn't do it on purpose. He used the word tiger earlier today, but that would be cool. How do you feel about that?

Scott: Scott, the tiger, or Scott tiger?

Ben: You know, either or, I feel like the proper noun adds a little something.

Scott: Tiger is somewhat fitting. I'm from Detroit, from the Detroit area.

Ben: Yeah, tiger has the whole Mary Jane-Spiderman thing going on, too.

Scott: True, true. Boy, now I am at a loss. I don't have anything for you.

Ben: You better not stick me with a lame animal.

Scott: Maybe by the end of this we'll have something for you.

Ben: So let's get down to it.

Scott: Okay, where do you want to start, do you want to start - well, basically I guess we can describe them as this - Both turbo and superchargers are both really, when you boil it right down to bare minimum, they're both air compressors.

Ben: Yeah, which are forced induction systems. They compress the air flowing into the engine.

Scott: Exactly. Yeah, so you know the advantage of more air, or do you want me to -

Ben: We should break it down.

Scott: Okay, all right good. So the advantage of more air - You induce more air into the engine, you introduce more air into the engine, and you can also introduce more fuel into the engine, so you get a more powerful explosion every time that the combustion happens. So you know, you might have to play with this a little bit with your computer or with - you know, if you're still running the carbureted systems, you'll be able to adjust more fuel into the mix, too, so you know, obviously more fuel, more fire.

Ben: More Ben fear -

Scott: Exactly, more fuel, more air. You need more air to do that as well. You can't just up the fuel and expect the same thing to happen. So this idea of compressing the air that goes into the cylinder, that's really basically all turbo is, and all a supercharger is, they just go about it in different ways.

Ben: Leading to some different advantages and disadvantages.

Scott: Exactly, yeah, there are some advantages and disadvantages of each one. I guess we'll just quickly talk about what the difference is between the two, really so that there's just a general understanding of this, really. I'll do it super fast, but supercharger is really just a belt-driven system. It runs just like any other engine accessory would run via the engine, via belt I guess. The belt exactly matches the engine speed, so you know, so this thing is constantly running. There is no variation in that at all other than, you know, it matches the engine speed exactly, and it continuously causes air.

Ben: So that's pretty cool, actually.

Scott: It just continually brings air in a compressed format I guess, and allows it to achieve greater power through the entire power band from the beginning to end. Now turbo is exhaust gas-driven, so that means that the faster the engine runs - well it runs off the wasted energy that would be otherwise the exhaust gas. That spins the turbine, which then compresses air, which feeds into the intake system, so really, it also works in the same way through the power bands, but there's gonna be some lag because you're waiting for the exhaust system to kick out the exhaust in order to power the turbines to feed the induction system, so there's a time gap, and that's what you hear about when you hear turbo lag, and that's all it is really, the time between when you stop on the gas, and when you really feel that turbo kick in. Supercharge is more instantaneous. It's like I said, it's continually running at optimum speed, and it matches the engine speed exactly.

Ben: Right, so a supercharger is a 1 to 1 match with the engine, and then turbocharger on the other hand comes in at the fourth stage of the cycle.

Scott: Yeah, so just so I'm not muddying this up, which I think I am, the turbo is more of a reactive system, I guess. It's reacting to the exhaust, you know, the exiting gas, and then that causes the air to be compressed on the other side, so there's just that short little bit of lag, but it's enough to both people enough so they say I don't prefer this, I prefer a supercharger.

Ben: Well, Scott, in their defense, my friend, there are some people who can't afford a turbo lag.

Scott: True.

Ben: I'm glad that my life is laid back enough to where it doesn't make too much of a difference for me.

Scott: Yeah, you're not racing, and you don't have a hot rod, or something like that because another thing is that superchargers are the cool-looking things that stick out of the tops of the hot rods. They've got a belt that's driving them. It's usual ly a wide belt, probably like a 3-inch belt or something. It has the big butterfly valves that you see opening sometimes. That's called - they call them blowers. They're also known as blowers. Really it's just a supercharger, but they make a distinctive sound, and they're really cool-looking, but they are functional.

Ben: They absolutely do -

Scott: Yeah, they do serve a purpose.

Ben: A lot of people wondered that. I wondered that before. I looked it up here, but I know they weren't just ornamentation, but I'll be honest with you man, at first I thought maybe they were just there for the look, especially in some of the more showy, more ostentatious racing vehicles.

Scott: Yeah, I think so. I mean they're not definitely very aerodynamic in design, you know, unless you cover them with some type of body apparatus, like a scoop or something like that, but you do have to have air flow into these things. If you're talking about the type that you're talking about, the big blowers with the intake valve.

Ben: Yeah, true.

Scott: You need to have airflow to them, of course, and it's kind of cool-looking, so you want to see it anyway.

Ben: You got a -

Scott: A lot of other superchargers you know, they don't really necessarily need this big air intake on the top, and they're under the hood, and you wouldn't even know that the car had it really. Typically they fit under the hood, either off to the side or right on the center on the top, and that's two different types. There's another type that's called a centrifugal supercharger, and that can be mounted right in the very front of the engine, and that one looks more like a turbo, only it's truly a supercharger.

Ben: Okay, so it still has that 1 to 1 match.

Scott: Exactly, yeah. It's running all the time.

Ben: So I think I can maybe read the mind of some of our listeners here, and they're out there, and they're thinking okay, fine, that's the difference, I get it. Turbocharger at the end of the cycle, supercharger, the whole time, which one do I want?

Scott: Well, see that's the tricky part here. Now, the supercharger creates the most boost, I guess, or actually an equal amount of boost all the way through the power band. To say equal, you know what I mean, it's matching the engine speed, so it's lower, lower, lower, then gets higher and higher as the engine gets faster and faster. However, a turbo has that lag, but eventually it does catch up to it, so it's running at the same speed. So you just have to wait for it with the turbo, but with the supercharger, it's instantaneous, so if you are going for low RPM boost, you probably want a supercharger. If you're going for slight lag, but you still want the same amount of boost you can go with a turbocharger, but that's if you don't mind the lag at the beginning.

Ben: Well, now also a good question to ask here, is one about efficiency right?

Scott: Efficiency, sure. We can talk about that.

Ben: Okay, so from what I understand, logically, actually with some help from a little website you may have heard of, www.HowStuffWorks.com, I got hooked to the notion that some people would say a turbo charger is actually more efficient.

Scott: Correct, and that's because it is using wasted energy. It would just be the exhaust gas flow that leaves the vehicle, and that's it, but this is reclaiming that energy in order to drive the motor a little faster, allow it to compress more air. It's turning a turbine wheel then it runs the air compressor that runs the air compressor that adds the air to the cylinder, so it's just using the wasted energy that would be exhaust gas in order to create something that is beneficial for the engine.

Ben: Where does the energy for the supercharger come from?

Scott: The supercharger is belt driven, so it's all from t he engine itself.

Ben: So from whatever the engine power source is, whether it's like electric battery or most likely, gasoline.

Scott: Exactly. Now there are three types of superchargers. There's the roots type, the twin screw type, and then there's centrifugal. I don't know why that was hard for me to say, but it was.

Ben: It's tricky.

Scott: So roots, twin screw, and centrifugal, and they all have their own benefits and downsides as well. Actually we should just say that the roots type is the oldest.

Ben: Is it the most common as well?

Scott: It is probably the most common. I can't say at this point if it is the most common or not, but I know that a while back it was the most common.

Ben: Okay.

Scott: It's the simplest type. It was - now get this - this idea goes way back, so it was patented in 1860. So it goes far, far back.

Ben: Really?

Scott: The idea was that it would ventilate mine shafts. It was an idea to compress air, you know, draw air into a mine shaft that otherwise needed air.

Ben: I see.

Scott: Simple as, I guess a fan would also work, but this is a way to get more air into the mine shaft, and then as early as 1900, Daimler added a root supercharger to a car engine, so that was the first automobile application. So you know, like I said, this is going way, way back, and that was a roots type as well. Now that's the type that we call blowers, you know, the typical hot rod type favorite, but they're also the least efficient because they don't have a continuous flow. These operate in bursts. They operate in very distinctive, discrete, bursts. When you hit the fuel, it operates. It's not a continuous simple - continuous operation I should say. Now the twin-screw type is a little bit more efficient, but not the most efficient, and that one is probably the most expensive one. This one is the most costly to produce because it requires such a tight machining process. It requires the most, I guess, precision in the build.

Ben: A lot more precision.Scott: Because the twin-screws are fitted together in a way that as the air is drawn in, as it moves down these screws, it's slowly compressed, or quickly compressed I should say, and that's where it is drawn into the engine, and then the last type is the centrifugal supercharger, which is the most efficient design.

Ben: That's the one at the front, right?Scott: Exactly. It's the one at the front, not the one that attaches to the top like we typically think of really.Ben: Like the blowers and stuff.

Scott: Yeah, we usually think of the top-mounted ones. So that's the three types of superchargers. Now they do add horsepower, they don't have any lag. They're easier to install typically because they're a bolt-on system, you know -

Ben: Go on.

Scott: It's a supercharger, but they are expensive, and that's the downside. They're easy to install, easy to maintain, easy to service, a simple operation, but again, more expensive. Now, turbos, when you talk about - oh, one other thing -

Ben: What's that?

Scott: Now before we're talking about turbos - they do have another disadvantage that I should mention - I'm sorry - Another advantage that they have.

Ben: Oh, okay, okay.Scott: Another advantage - They don't have any shutdown procedure like a turbo does, and mo st people don't do this, but turbo requires you to allow the engine, or the turbo rather, to cool down after operation. Like if you're out doing a lot of fast driving, a little spirited driving, it's a good idea to allow this thing to idle down, and cool down before you shut off the key. The reason is because they're oil cooled - air-cooled, oil-cooled, and you need to let the oil fully circulate and cool the entire system before just shutting it down cold.

Ben: That makes sense.

Scott: For longevity, you know, it works a little better.

Ben: Probably no one does that though.

Scott: Exactly. No, not many people do.

Ben: People just stop their cars.

Scott: People who are extremely serious about it do it, but I had a turbo car one time, and I was routinely guilty of just shutting it off.

Ben: Which one?

Scott: It was an Audi.

Ben: Oh, those are nice cars.

Scott: Yeah, it was. Well I mean, I just didn't really think about it. It wasn't that I was always out flogging it either. I was just driving it normally, and I think it was fine. I never had any trouble with it.

Ben: Sure. In the middle of a car chase. Scott: Let's get to the disadvantages, and then we'll move on, I promise.

Ben: Disadvantages.

Scott: Disadvantages of superchargers is that they can consume a lot of horsepower from the engine because it's another - think about it like a giant accessory that you're running. You know, when you turn on the AC, and you've got something else running off of the engine, it's gonna draw power. This can take as much as about 20 percent of your horsepower away from your engine.

Ben: Wow!

Scott: Because it takes a lot of energy to run this thing.

Ben: And it's running the whole time.

Scott: Yeah, exactly. Now, so why would anybody ever consider putting one of these on? Well because you can gain 46 percent of what the car is capable of because of the increased combustion.

Ben: So you're netting 26 percent in theory.

Scott: And of course, you got to talk about like reduction of that a little bit because of mechanical efficiencies, things like that, where that goes away, but you do see a lot of benefit from a supercharger, don't get me wrong, but it does rob a lot of power. So does the turbo. They both do the same thing, but the benefits outweigh the downside, as far as I'm concerned, on the supercharger.

Ben: Theoretically.

Scott: Theoretically?

Ben: I'm just saying, right?

Scott: Yeah.

Ben: Because you know one thing that is true, and a very good point that you're making is that when we say it sucks up an average of 20 percent, but increases output by 46 percent -

Scott: 46 percent, yeah.

Ben: Then, we have to permit, or we have to assume some give there, some margin of error for road conditions, driver style, which is huge, like the way you ride the gas pedal, it does make a big difference.

Scott: Yeah, exactly, and there's a lot more to it than just that. I mean, it's your altitude, I mean where you are -

Ben: Oh, good one, good one.

Scott: In the world, if you're at sea level or if you're in the mountains, that matters dramatically, I mean just the atmospheric pressure. That matters for turbos as well. There's a variety of things that can come into play at this point. Now it could be installation issues as well. Maybe it wasn't installed right. Maybe it's not matched to your engine. Maybe it's not the one that you should have. Maybe you're trying to overdo it, and you're not getting the full benefit out of it, but it's taking more power than it should. There's a lot to -

Ben: Maybe it's on a geometro, in which case, why did you do that?

Scott: That's strange.

Ben: That's one of those things -

Scott: You know, we shouldn't criticize for anybody wanting to put a supercharger on anything. I'd put it on my lawnmower if I could.

Ben: Really?

Scott: Yeah, I don't see why not.

Ben: Do you have a push mower?

Scott: I did.

Ben: You're fooling yourself, buddy.

Scott: I do, so I would have to run.

Ben: You have a jog mower now.

Scott: I would. I would have a sprint mower.

Ben: Dude, before we get too far in, it just occurred to me, and I have to apologize to this guy when we get his name, but we had a listener suggest this, and you know, I am sorry sir from the internet. Your name escapes me right now, but we're gonna get back to you. We didn't forget about you.

Scott: No, no, we'll pick it up later. We'll figure out who it was, and give you credit later.

Ben: A shout out.

Scott: Yeah, exactly, exactly. Now I guess we should talk about turbochargers a little bit.

Ben: Yes, yes, yes, sir.

Scott: Some of the upsides and downsides of those.

Ben: More efficient.

Scott: More efficient, yeah that's right. Well, it's arguably more efficient.

Ben: It's theoretically more efficient.

Scott: Yeah, it's theoretically more efficient. All right, okay because, as we talked about before, it uses the exhaust gas. Now these things spin at an incredible rate of speed. The superchargers, I think they spin at around 50 or 60,000 RPMs, something like that.

Ben: Yes, really correct.

Scott: Now a turbo can spin somewhere in the neighborhood of 150,000 RPMs. Like I said, that little wheel that is compressing the air before it enters your engine - 150,000 RPMs, so as you can imagine, that requires some pretty intense bearings, and cooling. So the bearings are really - there's a fluid bearing, which is something kind of interesting.

Ben: A little different.

Scott: Yeah, it supports the turbine shaft on a thin layer of oil, and of course, that not only helps reduce friction, but it also cools the shaft, as well, so that this thing is spinning out of control, I men it's ridiculous. That's why you need to cool these things down, which I didn't do. There's also - and you can get some that have ball bearings. The ball bearing systems are very expensive because they are extremely precise, and they apparently provide less friction than even the fluid bearings do.

Ben: Really?

Scott: Yeah, which you wouldn't think.

Ben: Wow, that's some high tech engineering right there.

Scott: Exactly, I don't have any idea what the materials are, the cost of them versus the fluid bearing, but I can't imagine the cost. It's got to be a race application.

Ben: I'm gonna make a totally unfounded prediction, and say that those kind of bearings are either coming from Germany, Japan or Italy.

Scott: Really?

Ben: I would - Maybe the U.S., maybe the U.S.

Scott: I don't know, I don't know, I just don't know where the big ball bearing manufacturers are because you'd be surprised where some of these little components crop up.

Ben: True, you know what, fair enough, but I'm saying just as far as track record for high end automotive, or just precision engineering -

Scott: You're feeding the stereotypes.

Ben: Am I feeding - are they stereotypes?

Scott: I think you are.

Ben: Really?

Scott: I think so.

Ben: Oh man, I'm sorry if I've offended anybody.

Scott: It's okay. You may be exactly right, and then I'll have to eat my words, but -

Ben: I would never want you to have to eat your words, man. I'm totally o n your team. We'll just forget it ever happened.

Scott: Okay. Fair enough, fair enough. We'll look into it.

Ben: So seriously, the physical ball bearings would be better than the fluid bearings?

Scott: In some situations yes because - Now I'm sure there are some lousy ones out there, that happens. You know, someone makes cheap turbo. Now we're talking about the extreme high end very, very expensive turbos that they use the ball bearings versus the fluid bearings, and the fluid bearings are more typical, believe it or not, and it sounds like something kind of exotic, but it's not.

Ben: Yeah, it's kind of counterintuitive really.Scott: Yeah, yeah. I mean they're expensive systems, anyway. They're not cheap. Let's see, I guess we can talk about - There's a wastegate on a turbo, which the supercharger does not have. A wastegate, all it does really is release excess pressure that's built up, so if the turbine blades aren't spinning fast enough, and the gas pressure builds up too much, the wastegate pops open. You've probably heard it on a turbo care before. You hear it kind of accelerate away. It wines, and then you hear it kind of like an exhale almost. It's like a (sound effect).

Ben: Oh!

Scott: Yeah, and you'll hear it between each gear. If they get to the very top end of the revs, you hear that sound. That's the wastegate opening up. That's adjustable on some turbos, and that's, I don't know, that's kind of an interesting thing, that - if you pay attention, you'll hear that often in some of the sport import tuner type cars that you'll see on the road.

Ben: And for some people this is gonna be like one of those, once you've heard it you can't unhear it things.

Scott: Yeah because I hear it all the time now. I guess I'm paying attention or just listening for it because once you hear it, you know exactly what it is, and you'll hear it all the time.

Ben: I've got one for you.

Scott: Sure.

Ben: I don't want to blind side you with this.

Scott: Yeah, go ahead.

Ben: All right. I ask this as a representative of some interested parties at the office. What's the best thing for someone to put on their car after market?

Scott: Really, a bolt on horsepower adding type accessory? I'm gonna go with supercharger.

Ben: You're gonna go with supercharger?

Scott: I'm gonna go with supercharger, now I mean, with what we have said here today, you know, the benefits, the downsides, and everything, I'm gonna go with supercharger, yeah. It's expensive, but it's a bolt on accessory that you can do yourself. If you have basic knowledge, if you feel you can tackle something like this.

Ben: Basics, patience and some free time.

Scott: Well, I don't even mean basic - I guess maybe a little bit more than basic. If you feel pretty confident with the tools, I think you should do it. Yeah, that's probably one of the best things, and then from there, you know, intake and then exhaust of course is the next thing to kind of free that flow up past the engine. So I think those two things are probably the best thing you can do. It depends on the engine, though, like I drive a Honda, and I know that my car benefits greatly from adding air. A lot of air is the best thing for it. It doesn't get enough right now.

Ben: Hondas can get some zip when they -

Scott: Exactly, exactl y, a lot of air, and of course, free flow and exhaust, and that is one of the biggest modifications that people do usually, intake and exhaust, but if you add a supercharger to that, why not?

Ben: Why not?

Scott: Why not? Do you have a preference on this? Are you gonna say like spinning rooms or something?

Ben: I'm gonna go - I'm gonna do something -

Scott: Neon highlights.

Ben: I'm gonna do something a little bit different from my usual MO, and I am going to agree with you, and I think that the up front costs in the beginning is worth all of the headaches you're saving yourself as far as the maintenance goes, as far as installation, all the time you're saving if you're one of those people who would shut down the turbocharger properly. No offense.

Scott: None taken.

Ben: You know what I'm saying. I'm saying the initial cost at the beginning, you can make a very easy argument that it pays you back later on.

Scott: Yeah, now you're talking about several thousand dollars, so it takes a long time, but if you truly enjoy it, it's worth it to you. I mean, if you enjoy the feel of your car performing better, it's definitely worth it.

Ben: You know what I want to hear, man? I want to hear some listener's opinions on both sides of this debate.

Scott: Yeah, sure because there's no real right answer. I guess maybe for each vehicle, and each style of driving, like if you're gonna be at the drag strip, you don't want this, if you're gonna be at the Auto Cross Event, you're gonna want this, and it depends on the car too, and it depends on the driver, and what they want. There's no one definitive right answer that you have to have this or you have to have that. I don't know, it's just pure opinion.

Ben: So you heard it here guys, our first Car Stuff Listener Mail request is for you guys to let us know which you prefer, turbocharger or supercharger, and why, sound reasonable Scott?

Scott: Yeah, sounds reasonable, yeah, yeah, I think so, as long as the why is there because there should be some reasoning behind why it would be a good idea.

Ben: Don't just put turbocharger, lull.

Scott: Okay, fair enough, fair enough, but yeah, I think that's a reasonable request. Oh you know what, one quick thing before we wrap up. Combining the two systems together.

Ben: Blow my mind, man, give me the elevator speech.

Scott: It's possible, but not very common at all. It's really not common at all, but what it does, is if you combine a turbocharger and a supercharger together, it's very rare, but I've heard of a couple of instances of it. In our article, we mention a VW Golf GTT. I've also heard of a Skyline GTR that has this, a Nissan, but twin turbo, twin supercharge as well, so extreme amount of power for these cars no matter what, but - what?

Ben: Is it more than the sum of its parts then?

Scott: What do you mean?

Ben: In the application?

Scott: Oh, sure, yeah because when you - usually twin turbo or quad-turbo engines have extremely high output. You can imagine if it's twin supercharged and twin turbocharged, I don't know about the numbers here because I don't have them in front of me, but incredible gains in horsepower. So the idea is that the turbo is feeding the supercharger with the boosted air, so you're starting with boosted air, and then the boosted air is then force fed into the en gine with the superchargers, and then that drives the turbos even faster, and it's a big -

Ben: Positive fed back loop.

Scott: Exactly, yeah, and now it virtually eliminates any lag as well because you're starting with two system. You get the benefits of the supercharger, which are instant to the engine power, and then the turbo, which is feeding compressed air to the supercharger, so you can imagine the amount of air and fuel that this thing is burning.

Ben: Yeah, can you imagine the mileage on that?

Scott: I know, it's unbelievable.

Ben: One mile per gallon.

Scott: I don't think that really comes into it, but what it does - it's just a way to balance this power curve that you've got the, I guess, disadvantages of each one are kind of negated by other one.

Ben: Nice.

Scott: Yeah, it's a good system, but it's very costly I'm sure, and to get everything to work out exactly right because a turbo set up requires exhaust work whereas a supercharger is a bolt on accessory, but if you're gonna add a turbo to your car, it's a lot more extensive than if you were just to add a supercharger. Now these we're talking about of course, they're made at the factory, or probably not a factory, but more of a speed shop, where this is what they do all day, and of course, they can do it quickly.

Ben: Yeah, this is not DIY stuff.

Scott: No exactly, I don't think so, I'm sure somebody has done it, but it requires a lot of skill.

Ben: Right, okay, you're right, you're right. Let's unoffend that listener - For most people, this is DIY.

Scott: Sure, that one listener because there might be one out there.

Ben: You, sir are extraordinary. Congratulations.

Scott: Correct.

Ben: I guess we've done - I don't know Scott, I think we did a pretty good job breaking this down.

Scott: We've done a job of it.

Ben: We've done a job of it. Okay, all right, what about you guys? Tell us what you think. Send us an E-mail at -

Scott: CarStuff@HowStuffWorks.com.

Ben: We'll see you next time.

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