Superchargers vs. Turbochargers

By SRT-Tom · Dec 27, 2018 ·
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  1. SRT-Tom
    When designing an engine to pull in more than atmospheric pressure, engineers often turn to forced induction. It’s one of the fastest ways to add significant power to almost any engine, and there are two prevalent ways it can be done: supercharging and turbocharging. But, which is better? Both are different in terms of how they work, performance and cost. Both operate on the principle that the more air you can get into your engine, the more power your car will make.

    Supercharging is old technology. The world's first patent for supercharging an internal combustion engine occurred in 1885. Superchargers have been used in a variety of engines, in fighter planes to Top Fuel dragsters.

    A supercharger is a unit that bolts to your engine and connects with a belt between your crankshaft and the supercharger unit. As the engine spins, it spins the supercharger and makes it force air into the engine. The size of the pulley that spins the supercharger determines how much boost you will make. A smaller pulley means the supercharger will spin faster so it will make more boost. The supercharger is limited by its efficiency, so if you overboost the supercharger, it will blow hot air into your engine and you will not make as much power (among other problems). Since the engine needs to literally spin the supercharger, it is not as efficient as a turbocharger since it needs to use horsepower to make horsepower.

    Kits to retro-fit superchargers on Challengers can be obtained from companies like Vortech, Whipple and Edelbrock.

    A turbo is similar to a supercharger, except it has an exhaust housing instead of a pulley, and runs off of your exhaust gas (i.e., waste energy). As your car produces exhaust, the exhaust gas spins the turbine which causes the compressor to force air into the engine. A turbo is more efficient than a supercharger since your engine does not need to work harder to power the turbo. Because a turbo is not connected directly to the engine, it can spin much faster than a supercharger.

    Here are the pros and cons of turbocharging vs. supercharging.

    Turbochargers

    Pros:
    • Produces a significant increase in horsepower.
    • Better fuel economy- smaller engines use less fuel to idle, and have less rotational and reciprocating mass, which improves fuel economy.
    • Higher efficiency- turbochargers run off energy that is typically lost in naturally-aspirated and supercharged engines (exhaust gases), thus the recovery of this energy improves the overall efficiency of the engine.
    • Supports Engine Displacements- If you have a smaller engine in your vehicle then the turbocharger will support its displacement. That way, you can generate additional power for an engine that is smaller.
    Cons:
    • Turbo lag- turbochargers, especially large turbochargers, take time to spool up and provide useful boost. The power delivered to the turbocharger is not consistent because it depends on the presence of exhaust gasses from the turbine rather than consistent power from the engine’s crankshaft.
    • Boost threshold- for traditional turbochargers, they are often sized for a certain rpm range, where the exhaust gas flow is adequate to provide additional boost for the engine. They typically do not operate across as wide an RPM range as superchargers.
    • Power surge- in some turbocharger applications, especially larger ones, reaching the boost threshold can provide an almost instantaneous surge in power, which could compromise tire traction or cause some instability of the car.
    • Oil requirement- turbochargers get very hot and often tap into the engine’s oil supply. This calls for additional plumbing, and is more demanding on the engine oil. As a result, your engine oil will need to be changed more frequently.
    Superchargers

    Pros:
    • Quick solution to boost horsepower. Compared to a turbocharger, a supercharger will enable an engine to have much more horsepower
    • No lag- the supercharger has power that is consistently and immediately delivered it is driven by the engine’s crankshaft which is always turning.
    • Cost-Effectiveness- a supercharger is the most affordable forced induction system.
    • Power for Low rpm- provides engines with low RPM a useful boost.
    · Less smog altering equipment- while a supercharger can have an intercooler and blow off valve, it does not have a wastegate. These items can make a car fail emissions testing.

    Cons:
    • Less efficient: the biggest disadvantage of superchargers is that they suck engine power simply to produce engine power. They run off an engine belt connected to the crankshaft, so you’re essentially powering an air pump with another air pump. Because of this, superchargers are significantly less efficient than turbochargers.
    • Less Reliability- with all forced induction systems (including turbochargers), the engine internals will be exposed to higher pressures and temperatures, which will of course affect the longevity of the engine and the supercharger.
    Dodge engineers first used turbochargers on the Dodge Neon SRT 4, that was produced from 2003-2005. The small 2.3L 4-cylinder engine produced 208 hp. and 180 lb/ft. of torque. This translated to 13.9 lb/hp. weight to power distribution in a 2,900 lb. car. The Neon was replaced by the Caliber for the 2008-2009 model years. The more powerful 2.4L engine in the 3,052 lb. SRT produced 285 hp. and 265lb/ft of torque. This increased the power-to-weight distribution to an excellent 10.7 lb/hp.

    At this time, rumors are circulating that the 3.6 Pentastar 6-cylinder engine will eventually be replaced by a high-tech, 2.4L twin-scroll turbocharged engine that will produce 240-300 hp. Similarly, the 5.7 Hemi may be replaced by a high tech 3.0-3.6L twin turbo 6-cylinder engine that will produce 400 hp. and 400lb/ft. of torque.

    Superchargers often go hand in hand with big V8s, like Hemis, and they’re certainly capable of providing big boosts of power, like a turbo. Dodge’s most powerful engine, the 6.2L Hemi, makes its horsepower using a supercharger. The first supercharged 6.2L occurred in 2015, with the introduction of the tire-shredding Challenger Hellcat. The engine produced an amazing 707 hp with 650 lb/ft of torque.

    IHI Turbo America (formerly Warner-Ishi) manufactured the entire 80-pound supercharger-aluminum housing, aluminum rotors supported by steel shafts, and the twin air-liquid intercoolers- in a Shelbyville, Illinois, plant. A one-way clutch on the blower’s input shaft prevented the high-inertia rotating components from back-driving the engine during lift-throttle conditions. More potent than a street sweeper, this blower could move 30,000 liters of air per minute. (Note- IHI earned this business in a fly-off against two other supercharger suppliers).

    Spinning the twin-screw IHI supercharger is a substantial engineering feat. Washers securing the 10-rib drive pulley to the crankshaft are infused with industrial diamonds to provide sufficient clamping friction. Driving the blower 2.36 times crankshaft rpm, to deliver 2.4 liters of air per revolution, consumes 80 horsepower. The asymmetrical supercharger rotors spin at different speeds thanks to their interlocking configuration and 3:5-ratio phase gears at the back of the blower. At the 6,000-rpm engine horsepower peak, the rotor spun by the belt from the crankshaft turns at 14,160 rpm while its mate spins at 23,600 rpm. The rotors are coated with a Teflon material that helps maintain the tight clearances needed to prevent airflow leaks. In the event of accidental contact, the soft coating abrades instead of the aluminum rotor material. Gears and rotor bearings are lubricated by a sealed-for-life splash system containing synthetic oil. Durability was proven by canting the blower at 47 degrees from horizontal and running it at different speeds and loads for 300 test hours.

    Dodge “doubled-down,” in 2017 with the debut of the Challenger Demon- a drag race special. This limited production car (3,000 made) came loaded with all of the drag racing “tricks of the trade,” (e.g., higher stall speed torque converter, air-conditioner-powered air cooler, looser front
    suspension, firmer rear springs, two-step ignition timing, trans brake, line lock, massive street-legal drag radials, etc.). Most importantly, the Demon’s 2.7 liter supercharger was larger than the Hellcat’s. It allowed for 8 lbs. of boost during staging and 14.5 lbs. of boost within six feet of the drag strip run.

    It’s mega-power 6.2L supercharged engine cranked out 808 hp. and 770 lb/ft. of torque (840 hp. with the Demon Crate package). In 840 hp. form, the Demon could demolish the quarter-mile in 9.65 seconds at 140 mph! Although the Demon had only a one-year run, for 2019, Dodge is offering the Challenger SRT Hellcat Redeye. This model produces 797 hp. and 707 lb/ft. of torque, thanks to its supercharged 6.2L engine that steals components, like a bigger supercharger, an extra fuel pump, and beefed-up pistons and connecting rods, from the Demon parts bin. All this allows it to rip through the quarter mile in a blazing 10.8 seconds at 131 mph- only .15 sec. slower than the race-ready Demon!

    Although Dodge has been extremely successful with superchargers, it seems that turbochargers will be the preferred choice of forced induction in the future. It’s difficult to argue against efficiency. With the industry focused on fuel economy, CAFE standards and smaller engines, turbochargers simply make more sense.

    SUPERCHARGERS


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    TURBOCHARGERS

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