When it comes to the different forms of forced induction, the differences between turbo vs supercharger have always been debated. There are many factors to consider when you are thinking about forced induction. Want to figure out what to weigh between turbo vs supercharger? This guide is here to help you navigate through the differences.
Today we’ll be going over turbo vs supercharger and explaining what considerations you need to think about in your project build. Of course if you are planning a normally aspirated engine build, this article is not for you. However if you want to build a forced induction vehicle or increase the horsepower in your supercharged or turbocharged application, let’s get started.
Why Turbo or Supercharger?
Planning a engine build or a project around forced induction is never an easy choice. However if you want to turn to forced induction, you do know that you don’t want to be limited by a naturally aspirated engine. Although there’s no inherent disadvantage to this style of performance engine, there is a fundamental limitation to how much air is being processed by your naturally aspirated engine.
The concept behind the limitations of a normally aspirated vehicle are simple.
Because there’s no way to increase pressure in your engine beyond atmospheric pressure, you are essentially limited by the displacement and compression of your engine. Because any engine is basically an air pump, the way to create more horsepower is to force more air into the engine.
When you increase the fuel supply and deliver the right amount of spark, you will create more kinetic energy and thus more horsepower.
The basics of supercharger operation are easy to understand. Mechanically driven by your belt or your crank, superchargers act like a air pump that forces greater quantities of air into the engine.
Although superchargers do create positive pressure and boost, they don’t technically compress air.
Instead they move greater quantities of air into your engine. By increasing the volumetric efficiency past 100%, the supercharger can create more horsepower when you deliver the matching amounts of increased fuel.
Some of the most common styles of supercharger is known as the roots style blower, as shown in our Pro Street Mustang above. This supercharger style uses a pair of helical rotors that drive air directly into the intake manifold.
There are different types of supercharger as well, like compressor style superchargers which we’ll get into later. The bonuses of a roots style supercharger are that boost is instantaneous, there is no turbo lag.
Roots style Supercharger Pros
- No Turbo Lag – Instantaneous power
- Easy to install
- Simple to maintain
- Predictable power delivery – Because the curve of the boost never changes it’s easy to tune and predict how the car will act.
Cons or drawbacks of a roots style supercharger
- Raising boost is not easy
- Boost is created through parasitic drag
- Heat can become an issue – Because there’s no mechanism to keep the air charge cool, air intake temperatures can quickly sky rocket.
Much like the supercharger the turbocharger is made to increase air pressure in your engine. However turbos are powered by your exhaust gases, which in theory is a far more superior means of creating boost. Because it’s not belt driven, boost does not cost you horsepower and torque due to parasitic loss.
Turbochargers use a unique blend of innovation and design to increase performance efficiently.
Unlike superchargers a turbocharger is driven by exhaust gases exiting the engine. In essence the turbocharger is using “free” kinetic energy to generate more power.
As your engine runs the exhaust gases exit your exhaust manifold and into the turbine housing. This turbine spins the wheel, which in turn rotates a compressor wheel or impeller that’s located on the cold side of the turbo. These two wheels are designed and connected through a shaft that runs through a water cooled or oil cooled jacket.
The turbine housing section shown above features a specialized wheel that’s sized to perform in a specific manner. The size of the wheel, angle of the fins, and the size of either compressor and turbine housings all play roles in how the turbo reacts and performs.
As your compressor wheel spins up to speed, the turbocharger draws air into itself axially. The compressor housing is designed in such a manner that the compressed air exits centrifugally and into the intake manifold.
This increase in compressed air is known as boost pressure and it exceeds atmospheric pressure.
Turbochargers require a means to regulate this pressure, or there’s a real risk of overboost. The device that does this is called the turbo wastegate, and it’s usually mounted to the exhaust manifold to “bleed off” pressure.
Turbocharged engines can in theory create large amounts of power with just a few tweaks. Because boost is controlled by the wastegate, as long as you can increase fuel safely the engine will generate more power in theory.
- Easy to increase boost – Installing a simple boost controller can usually do the trick
- “Free Power” – Driven by exhaust gases the turbocharger is much more efficient than a supercharger
- Lots of Support – There are many aftermarket tuners and piggyback computers that can make dyno tuning your turbocharged vehicle easy.
Cons or drawbacks of turbocharger
- Turbo Lag – Exhaust gases take time to spool or spin the compressor wheel
- Harder to install – More components, piping and oil lines can complicate the install
- Harder to maintain – Because there are so many components and pieces to a turbocharger kit, you need to stay on top of things to avoid catastrophe.
Without the right amount of maintenance your turbocharged vehicle could become unreliable or even lose the ability to regulate boost.
Boost must be regulated for a variety of reasons. First, if your turbo boost spikes or gets too high the pressure within your combustion chamber could become too great. This will cause physical damage that could cause your pistons to lose a ring land, or your piston rings to break. The result is a loss of compression and your engine becoming nothing more than a heavy lawn ornament.
Secondly if your turbo is too small and there’s too much boost being run through it, this can cause your turbo to fail. This is called overboosting or overspinning your turbocharger, which can cause damage to the center cartridge or the wheels of your turbo.
Turbo vs Supercharger – What is turbo Lag?
To put it in simplest terms, turbo lag is the time between you pressing the gas pedal down and the turbo actually creating positive pressure. To the uninitiated, turbo lag is a detriment while people who have owned turbocharged vehicles before understand that lag is part of the process.
Exhaust gas is the main driving force behind turbo boost, so there’s always going to be some aspect of turbo lag. This lag is caused by the time it takes for the compressor wheel to create positive pressure. There are several factors that go into the amount of turbo lag your car will have.
The size of your turbocharger is one of the most obvious factors that can increase turbo lag.
Some of these sizing factors range from the diameter and depth of the turbine and the compressor wheels, to the air ratios or A/R of the housings.
Turbocharger A/R, the size of the compressor, design of the manifold and your engine displacement are just some of the deciding factors. This is one of the biggest advantages that superchargers can have in the turbo vs supercharger argument. Superchargers lack any turbo lag because they are mechanically driven.
Why is Turbo Lag Good?
It’s not necessarily a good thing to have too much turbo lag, but it’s a essential part of your turbo equation. The larger your turbo and compressor wheel are, the greater amont of rotational inertia. This will create a longer time for your turbo to spool up to speed and spin up, which is why so many people opt for a smaller turbine and turbo.
While smaller turbos will spool up quicker, they will also run out of breath faster. Small turbochargers respond quickly to throttle and create boost in a short amount of time. This results in excellent low to mid-range performance. However this isn’t where the technology of turbocharging shines.
Smaller turbos cannot move the large quantities of air at higher engine speeds to produce high power outputs. Attempting to raise the boost past the turbo’s efficiency level will create a overspin situation, and can lead to your turbo dying a quick death.
Larger turbos will produce more power at higher engine speeds, but will take longer to reach operating speeds. This is why many people believe that turbo lag is a good thing, however it’s possible to go too far in the wrong direction.
Simply slapping an oversized turbocharger on the front of a small engine could lead to an poor build. When there’s more turbo lag than usable powerband, this makes for an unpleasant experience. If your project goals are for low or mid range performance, this is a consideration you will have to take into account when weighing the turbo vs supercharger.
Whatever style of forced induction you decide on, you’ll need supporting mods and a proper tune to avoid detonation or engine knock. Given the higher pressures in your combustion chamber, the margin of error becomes smaller as your turbo boost pressures rise.
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