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Supercharger vs Turbo

Posted on: 06/03/2014

For almost the entire time that both of them have been in existence, it has been a constant source of discussion as to which is better, the supercharger or the turbo.

Both of them seek to achieve the same enhancement in engine performance, by greatly increasing the amount of air going into the cylinder, thereby increasing the amount of fuel that can be burned, resulting in a higher power output. It’s the manner that both of these devices manage to do so where they differ.

The supercharger draws its power directly from the crankshaft by use of a belt, whilst the turbo utilizes otherwise wasted power, in the form of the exhaust gasses being thrust out of the engine operating the mechanism to pump more clean air in.

The immediate drawback to the supercharger is the use of power that would otherwise go to the drive being used up operating the supercharger impeller. A turbo doesn’t tax the engine at all, deriving all of its impetus from superheated exhaust being pushed out naturally. Game, Set, Match to the turbo then, you might think.

However, because the supercharger is attached to the crankshaft, its impact on the engine is far more immediate and predictable when the throttle is applied, meaning a much faster response when applying the accelerator. As you can imagine, in a racing environment for instance, this immediacy has definite advantages for the driver.

With a turbo, as it’s activated by the exhaust, there is a pause or ‘lag’ which in the past has made the turbo harder to manage in the fast moving world of racing, as the power comes on with a delay, when the pedal is pressed.

Turbos are also much more complicated to attach to an existing engine and require some pretty impressive engineering to ensure that the serious temperatures involved in the exhaust aren’t transferred to the air inlet. There is also an extensive modification needed to any existing exhaust system, with the amount of expansion in the manifold meaning the use of expensive, heat resistant materials.

In comparison, a supercharger can be bolted on relatively simply and at far less cost, without the need to deal with such high temperatures, or interfering with existing mechanisms unduly. Accordingly, this also makes them easier to maintain.

Superchargers do need a little warming up initially, however turbochargers need a quite comprehensive shutdown procedure. This is because, unlike superchargers, turbos are oil cooled and will overheat of they are simply shut down with the engine.

Blowers in the past tended to work very well at lower speeds, where turbos came into their own at higher rpm. There have been occasions where designers have actually employed both on an engine to take advantage of this disparity, however the cost and indeed weight disadvantage to doing so has prevented a bigger uptake of this idea.

Superchargers can rob an engine of as much as 20% of their efficiency, however, they can supply an additional 46% horsepower, so the trade-off is usually considered worthwhile. However, as they operate directly off the engine, they also require a robust driving mechanism to cope with the additional strain, whereas the turbo avoids this engine strain entirely. Superchargers also work best with higher octane fuel, again adding to costs.

When all is said and done, the complexity and overall cost of a turbo combined with the lag tends to give the win to superchargers, which can after all, still increase the power by between 50-100%.

For those of you unafraid of the extra complication, the ultimate solution is Twincharging. This is where both a turbo and a supercharger are used on the same engine, no decision needed! While it sounds like something reserved for race cars it's actually ridiculously practical, helping everyday cars meet new EU emissions tests whilst matching the power of previous engines. 

In the battle of Supercharger versus Turbo its Twincharging that wins.