A turbocharger converts wasted heat energy into usable mechanical energy, increasing engine output. And since turbochargers rely on waste energy, a turbocharger must reach a minimum speed before it converts enough of this exhaust energy to produce positive pressure in the intake manifold.
This is known as turbocharger lag, the time in which it takes for a turbocharger to reach the point when it builds positive pressure. The pressure that a turbocharger creates is relative to engine load and not engine speed. A turbocharger's characteristics, including responsiveness and maximum airflow, depend on a number of variables.
Turbocharger compressor and turbine wheel sizes, compressor and turbine housing sizes, and the geometry of the compressor wheel all play a considerable role in performance characteristics. This is how turbochargers are produced in such variety - from small, quick spooling turbochargers to large, high flow models and everything in between. Superchargers feature a compressor or rotors that are driven off the engine crankshaft via a belt drive - anytime the crankshaft is spinning, the supercharger is rotating proportional to engine speed.
The supercharger draws in ambient air and compresses it, creating positive manifold pressure. Unlike a turbocharger, a supercharger uses energy directly from the engine to increase the total engine output. The pressure that a supercharger creates is relative to engine speed - as long as the engine is spinning, the supercharger is compressing air. This pressure increases with engine speed, but peaks well before the engine reaches redline for most street superchargers, peak pressure is reached shortly off idle.
A superchargers characteristics tend to be less about geometry and more about displacement. Getting more pressure boost from a supercharger can be as simple as changing the size of the drive pulley so that it spins either faster or slower relative to engine speed. Instant boost - no lag since system operates relative to engine speed. A supercharger will create positive pressure directly off -idle. Turbo lag - manifold pressure is dependent on engine load, not engine speed, and turbochargers are much slower in creating boost off-idle than superchargers.
Some of the present-day superchargers are discussed, including the Roots, vane, centrifugal, and exhaust turbo-type blowers, and the advantages and disadvantages of each are given. Before closing his paper, Mr. Knudsen emphasizes the need for more compact and efficient accessories.
Subscribers can view annotate, and download all of SAE's content. Learn More ». View Details. Search My Stuff What's New 3 12 24 Why dont we get Supercharged Diesel car engines? Prev of 2 2 Next. I have seen supercharged marine deisels, and even better, supercharged two stroke deisels. We have them on some oil rigs for generators. V12's and their pistons are about 8 inches in diameter! A very old supercharged two stroke deisel was the rather odd Commer TS3, which was the only true boxer engine I have ever come across, 3 cylinders, 6 pistons!
The con rods were attached to a large rocker to another con rod, and then onto a common crank. Very odd set up, but very powerful. GavinPearson 5, posts months. Turbochargers are powered by energy that would otherwise be wasted so they are providing power for free. Given that diesels are there to save fuel it makes sense to not waste it by powering a supercharger and let the energy of exhaust gas go down the pipe without driving anything. It is certainly a feasible project to build a supercharged diesel, response off the line would be stunning.
Slightly off thread, and wayyyyyy too big for cars, but what about Napier's Deltic for a supercharged two stroke diesel?? Three cranks, 18 cylinders, opposed pistons Mazda make one on the , it's not very fast though compared to a Tdi. FourWheelDrift 83, posts months.
Pigeon 18, posts months.
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