Welcome, brothers and sisters. We are gathered here today to set aside all of our differences and unite as one to genuflect before the Altar of Boost. Now like with any religion, there are different sects and congregations with their own differences and creeds. Whether you follow the Temple of the Turbo or the Shrine of the Supercharger, we are all children of the Patron Saint of Boost (praise be).
So whether you’re wondering what exactly the difference between these two methods of forced induction are, or which is better for any given purpose, we’ll get into the how, the what, and the why of that juicy, glorious boost.
Forced Induction, the Short Story:
The point of a supercharger or turbocharger is to cram as much air into the cylinders as possible. More air allows the ECU to add more fuel, more fuel means more boom, and more boom means more smiles. Who doesn’t like smiles?
The TL;DR on the difference between the two is this:
Superchargers are intake air compressors that are belt driven off the crankshaft.
Turbochargers are intake air compressors that are driven by exhaust gasses.
Now the Long Story:
The amount of power your engine can make effectively comes down to how much fuel it can combust, and how fast it can turn that heat energy into mechanical force. Oxygen needs to be present in order for fuel to burn, and that mixture between air and fuel is a very specific ratio. The most efficient mixture for gasoline engines is 14.7:1 air-fuel, this is called the stoichiometric ratio. At this ratio, the fuel has enough air to burn completely (under ideal conditions).
A lower air-fuel ratio is called running rich, because there is more fuel to be burned than there is oxygen as the accelerant to burn up all the fuel. Running rich is less fuel efficient but in some cases can produce more power, and tend to run cooler. A higher air-fuel ratio is called a lean condition, where there is more air than the fuel needs to burn. Running lean is more efficient, but means the engine tends to run at higher temperatures. There are other side effects of either, but those are for another time.
Compressing the air before it goes into the cylinder allows the ECU to add more fuel to keep up that ideal air-fuel ratio, giving you more power potential. Now let’s get into a few different methods of getting that done.
Pros and Cons of Each:
Though both are common to see, turbochargers are the decided favorite of manufacturers for a few reasons. In the muscle car and old school crowd, superchargers seem to be the favorite. So why is this? Which can make more power? Which is better?
- Linear power delivery with no lag
- Easier to install in the aftermarket
- Less likely to interfere with smog equipment and be street legal
- More power at lower RPMs than a turbo
- Parasitic drag on the engine makes them less efficient
- Less potential for software tuning
- By making use of otherwise wasted exhaust gasses, turbochargers make power more efficiently
- Big power gains can be made with software tweaks alone
- Bigger turbos require time to spool up creating turbo lag before power hits
- Complicated to install in the aftermarket
- Not many bolt-on kits available
I carry the banner of the turbo.
The overwhelming majority of R&D dollars from the auto manufacturers have gone into developing and manufacturing turbochargers. The reason? Well, mainly efficiency. Take Ford’s EcoBoost line of engines as an example of smaller displacement turbo engines edging out the classic V8s of old.
Say what you want about Ford, but if there is one thing they do right, it’s their pickup trucks. Messing with the formula of the best selling vehicle in the country for the past 30+ years is not something that any manufacturer would take lightly. Yet Ford replaced the V8 with a twin turbo V6 for the top-tier engine in the F-150. This allows them to hit higher EPA ratings for mileage while making more power than ever before.
Case in point, you can get a 450hp version of the 3.5 EcoBoost in the Raptor or Limited trims now, making them far more powerful than even the old Lightning models were, and second in the running for most powerful pickup truck ever made (that title goes to the Ram SRT-10 with the engine out of the Viper).
Here’s a more detailed comparison:
Engine: Naturally-aspirated 8.3l V10
Torque: 525 lbs-ft
MPG: 9 city, 15 highway
Ford F-150 Limited
Engine: 3.5l twin-turbo V6
Torque: 510 lbs-ft
MPG: 17 city, 22 highway
Now whether customers will actually see that 22mpg in the real world is another story, but it should be noted that in Doug Demuro’s review of the SRT-10, the MPG readout was displaying 5.7 mpg, so I would take any number with a grain of salt. The point is that turbochargers allow manufacturers to see big power numbers that don’t come with the same mileage penalty that they used to.
You do, of course, still see a few of superchargers on the market still, GM makes good use of these on the Camaro and Corvette, the ever-present Hellcats sport superchargers with more displacement than a Honda Civic’s entire engine, and even the turbo-obsessed Ford threw a supercharger on their new Shelby GT500. Notice, however, that these are all applications where fuel consumption is not exactly a priority.
So now you can tell your grouchy uncle there actually is a replacement for displacement. No matter if you carry your shield in the name of the turbo or the supercharger, we do it in the name of Boost. Praise be.
What do you think? Do you disagree? Drop a comment below!