The realm of boost can be a wonderful place. It’s a place where one can reach far beyond the power output of a similar naturally aspirated engine. This land of PSI, horsepower and torque can make your wildest dreams come true. This is the land of superchargers and turbochargers. This, friends, is the land of forced induction.
The real question, though, is what’s the best way to boost an engine? Sure, let’s go down THAT road. Put on your helmets kids, because it could be a bumpy ride, the eternal debate of Supercharger vs Turbocharger ends here! Or does it?
Table of Contents
Forced Induction and You
An engine needs air to burn with the fuel. Engines are limited in how much air they can get in naturally, but some use contraptions to forcefully shove even more air in. With more air, you can burn more fuel. This makes a bigger bang and therefore more power. But how do we get there?
Enter, the turbocharger, or turbo. Essentially this is an extremely powerful fan (yep, I just called it a fan). When I say extremely powerful, I really mean efficient. See, there are actually TWO fans on a turbo, directly connected to each other so they spin at the same time. One side is connected to the exhaust (the turbine) and the other connected to the intake (the compressor).
The exhaust gasses that your car is already blowing out cause the turbine to spin. This causes the compressor to spin (or spool up) as well, pressurizing the intake side of the engine and forcing air in. Pressures can reach 30 psi or even higher, making the charged air very dense and great for making more power.
What’s very cool about turbos is the use of otherwise wasted exhaust gasses to spool the turbo. Remember me calling it efficient? Don’t forget, efficiency and fuel economy are not the same! The “restriction” of the turbine in the exhaust is far outweighed by the power produced by the compressor.
Superchargers operate differently. They still use a compressor “fan” (of sorts) to cram more air into the engine, but there’s no turbine. In fact, the exhaust is out of the equation entirely. Superchargers are belt driven, just like your alternator or AC compressor. The belt spins a pulley, which is attached to the supercharger and voila! You have boost!
You may be saying, “OK, cool… So it doesn’t really matter which one you use.”
WRONG!
There are some huge differences between the two. This includes the complexity, the type of power delivery, and the reliability of each system. Furthermore, there are different methods of turbocharging and supercharging within their own realms. Then there are a few strange ones that are both supercharged AND turbocharged… But that’s for another time. A lot of times, the method of boost comes down to the specific goals to be achieved or cost effectiveness.
My main goal here is to discuss which of these is better for making power, but there are a lot of other interesting differences we can talk about.
Attainability
To be perfectly blunt, superchargers are far simpler (and usually cheaper) to install and set up. If your car was not boosted from the factory, the easiest way to go is a supercharger, hands down. Dozens of great companies sell whole kits that come with everything you need, even the ECU reflash in some cases! You can slap everything right on and instantly get an extra 50% on top of your stock power. Some of them even come with warranties!
To be fair, in recent years a lot more “everything included” turbo kits have been popping up, and these are great too. But overall, they still won’t be as simple to install. Turbocharging a car without a full kit can be a serious headache. In some ways you almost have to engineer your own kit. Sometimes parts will need to be measured or fabricated, and you’ll need to decide if the fuel injectors should be upgraded, which turbo you want, etc etc. The edge here for installing an aftermarket set up definitely goes to the supercharger.
Reliability
I have to make this point clear, both systems can be extremely reliable if they are properly set up. Especially if it came from the factory with a turbo or blower. Provided you don’t start messing with the boost levels without appropriate supporting upgrades, there’s no reason it shouldn’t last a very long time.
HOWEVER, I’m going to give a slight edge to the turbocharger. Assuming of course that the set ups are well done and all things being equal, the turbo will usually be gentler on your engine. Superchargers can generate a lot more heat than a turbo, and their boost generally (but not always) comes on all at once and builds from there. This can put a big strain on your bottom end. Turbocharger boost generally builds up a little slower and so there is less of a “shock” to your internals. Modern turbos are having less and less lag, however, so the difference may be negligible at this point.
Power Delivery
As I already pointed out, turbo lag is something that was, largely, left way back in the 90s. I think it’s still worth talking about though, so go grab a 1990s turbocharged car (go ahead, I’ll wait) and take it for a spin. Notice how the car feels pretty slow till the turbo really kicks in? This is called turbo lag. It’s what happens when it takes a little time for the turbo to build pressure. Supras, RX-7s and even 300ZXs are all great examples. All fantastic cars, but turbo technology wasn’t quite advanced enough to provide lots of lag free boost at the time.
Superchargers never had this issue. You want torque? Here it is! And it’s there ALL the time. Even when you don’t want it. In most situations,the supercharger is always working, always spinning, always boosting. Yes, there’s usually still some kind of pressure relief or “blow off” valve, but as soon as you open the throttle your engine is getting all the PSI it could ever want.
The Ultimate Power
Alright, so which is better overall for power? It’s not a hard question to answer, really. But let’s take a look at some examples to help demonstrate the kind of power you can expect from each. All of these examples will be four-cylinders for simplicity, but the rules apply to V6 and V8 engines as well. The only difference is cost, as a supercharger is almost always the cheaper option for V type engines.
The Toyota MR-2
The first two generations of the mid-engined MR-2 offered forced induction as an option. First gen came with a supercharged four banger, and the second gen could be equipped with a turbocharger instead. The engines were of different displacements and different designs, so this won’t be as direct a comparison as the next set of cars. We can still break down horsepower per liter, however, to give us an idea of which method works best.
The AW11 (first gen) supercharged MR-2 made 145 horsepower and 140-lb-ft of torque. It may not sound like much, but in the early 80s this was a very powerful four cylinder at only 1.6 liters of displacement. The car itself was feather light, too. All together it was a worthy mid-engined sports car, very well suited for curvy back roads. Per liter, these engines made about 90 horsepower. Not bad!
The SW20 (second gen), however, was a new animal. The engine was newer and larger, so it had a power and technology advantage from the get go. Once you factor in the turbocharger it’s the clear winner. The JDM version put out a whopping 218 horsepower from a 2.0 liter engine in 1990. Four years later the same engine jumped up to 242 hp.
Take notice as well, this isn’t like the high revving Honda engines we recently discussed where torque figures were more modest. The more powerful version of this engine put out 224-lb-ft of torque. These were BIG numbers even for some V6 engines of the day. All in all, the turbo engine here made between 109 to 121 horsepower per liter. A significant jump up from the earlier supercharged MR-2, regardless of the increased displacement.
The Chevy Cobalt SS
To many, this car is a bit of an unsung hero. Although not without a few quirks, it was an excellent, affordable and fun car that was cut down before its time. During one generation the Cobalt SS had three different power plants, NA, supercharged and finally turbocharged. This is a more direct comparison than the MR-2, as these engines all came from the same family. The boosted engines shared the same displacement (2.0 liters) and the only major technological difference was the turbocharged cars direct fuel injection system.
The supercharged Cobalt was a bit of a surprise from Chevy, but it was well received all the same. While not setting any records for four cylinder power, it made a respectable 205 horsepower. That’s about 102.5 per liter, but Chevy wanted to up their game. After a short break for 2008, they launched the 2009 Cobalt SS Turbocharged.
As with the two versions of the MR-2, this version of the Cobalt SS was an absolute monster by comparison. With the same 2.0 liters its supercharged brother had, it made an astounding 260 horsepower, or 130 per liter. That’s more than any other engine we’ve talked about in this article. Was it the most powerful four-cylinder at the time? No, but hopefully it’s becoming clear that there is simply more potential power to be gained from a turbocharger. Mechanically speaking, the exhaust gasses can provide more energy to a turbo than a belt and pulley can to a supercharger.
The Final Word
There, I said it. And it’s on the internet, so it must be true. If the sky is the limit, you’re not going to be disappointed with what a turbo can provide in terms of power. Then again, a supercharger can bring an awful lot of grunt to the table, too, and have it all on tap and ready whenever you are. So really, the final word is that there IS no final word.
There’s a lot of food for thought available, and not just in this article. This is a largely (sometimes heated) opinion-based topic. It will be up to you to decide what kind of personality you want your car to have, and how much work it will take to get there. One thing is for sure: whether you have a supercharger or a turbo, chances are it’s going to put a smile on your face.
So tell me, how do YOU boost?
