Adapted from “Forced Induction: Superchargers, Turbochargers & Related Parts” - July 2009 Fastest Street Car Magazine by Tori Tellem; Adaptation by Nick Gregson
Article link: http://tiny.cc/3fn9t
If you’re playing a drinking game where everyone drinks with each mention of “Make more power”, then the average issue of @Fastest Street Car magazine would have you making friends with the toilet seat in real short order before you made it to the bck page. (The seat’s name is Bemis, apparently.) And that means this story will likely have you on the @Hooniverse Drunkcast before we’re through. Odds are, if you’re reading this, it’s because you want to – surprise of surprises – make more power.
There’s nothing quite like the instant boost-and-pony show that comes with the addition of some manner of forced induction, and their accessory companions. It’s worth noting that intercoolers are a plus for both turbochargers and superchargers- anything that removes heat from the air charge after the compressor is a good thing. Here’s a look at some of the hardware in the aftermarket’s arsenal these days and the basics of how they do what they do.
By definition, a supercharger is an air compressor used for forced induction on an Internal Combustion Engine. The way boost works for both superchargers and turbochargers is the same- they increase power because the added air flow they are forcing into the engine’s intake provides more oxygen to support combustion than a naturally aspirated motor, which in turn allows more fuel to be burned, in turn increasing the engine’s power output. The supercharger’s compressor action is powered mechanically, typically by a belt, gear or shaft connected in some manner to the engine’s crankshaft, the crankshaft being the source of motive energy to turn the compressor.
One key thing to remember is that just because it’s called a supercharger doesn’t mean that we’re always talking about exactly the same type of device. There are four types of positive displacement superchargers, those being Roots, Lysholm Screw, Sliding Vane and Scroll-type superchargers. You’ll notice we didn’t mention centrifugal superchargers in that list- as a centrifugal supercharger is more akin to a turbocharger – but we’ll get into that later. What you do need to know is that the two most common types in use today are Roots and Centrifugal, though it is worth noting that Vortech recently introduced a line of Lysholm Twin-Screw superchargers, but we won’t get into those here.
ROOTS Superchargers (Positive Displacement)
Why Roots supercharge rather than turbocharge? How soon do you want your power is the better question – with a Roots supercharger, peak torque is often acheived by just 2000 rpm, meaning your boost in power is almost instantaneous – there is no “lag” as with a turbocharger. It’s also simple. Superchargers, however, were originally intended to operate at relatively low boost and moderate speeds, so in most cases with a supercharged engine, replacing a smaller blower with a larger one, running it slower to make the same boost will increase compressor efficiency.
ROOTS style superchargers were invented way back in 1860 as an air pump for blast furnaces and the ilk by Philander and Francis Roots, where the name comes from. This means Roots superchargers are the oldest design available. 9 times out of 10 today, when you hear Positive Displacement supercharger, they’re talking about Roots. A roots blower is a positive displacement lobe pump, which pumps air through with a pair of meshing lobes. The lobes mesh together much like a set of gears. Air is trapped in the pockets surrounding the lobes and carried from intake side of the supercharger to the outlet. In most automotive applications, the supercharger is driven by a belt connected to the crankshaft. Typically, a supercharger will have two or three lobes, but recently four lobe designs have come into favor.
We can’t discuss Roots superchargers without bringing up Eaton, probably the number one source for OEM superchargers around, responsible for my personal favorite, the M90. Traditionally, Roots blowers have had the worst thermal efficiency of the existing types of superchargers, recent developments by the Eaton Corporation have developed a more efficient Roots-type supercharger, known as the TVS. While manufacturers like Eaton don’t sell to the public, their distributors on the other hand (such as Roush and Magnuson, just to name a few) do.
TVS is short for Twin Vortices Series, featuring twin four-lobe rotors twisted at 160* (the norm being three lobes twisted 60 degrees). The additional lobe and increased twist coupled with redesigned air inlet and outlet ports increase efficiency of airflow to the engine but also add the perks of reduced noise and vibration. The TVS is also a part of @Edelbrock’s e-Force Supercharger system, shown here for reference (#1598), which on a Camaro, boosts output from 426hp to 599hp/547tq, and upwards of 460tq is available at just 2,500 RPM. If 600hp doesn’t cut the mustard for you, with a few other components and custom calibration, Edelbrock’s e-Force system can support up to 800hp.
Weiand’s Massive 8-71 Supercharger Kits go hand in hand with Big Block Chevys
And of course, we can’t move on without touching briefly on Weiand, who is responsible for the immense 8-71 series. Weiand is well known for its intakes and water pumps, but its healthy line of superchargers are great options. If you’re running a small-block or big-block Chevy motor- and the 8-71 is definitely worth a look, as these Weiand superchargers have been designed to make 10-12 PSI on small block engines and 5-7 PSI on big blocks and 300+ HP increases can be expected with these motors. Weiand also offers supercharger kits for Ford small blocks and the Mopar Hemi, so the boys not wearing a Bow Tie can still join the parade.
Centrifugal Superchargers
Cutaway of a Vortech Supercharger
Now, onto centrifugal superchargers. Like the supercharger, it increases engine output by increasing available oxygen available for combustion–it’s a centrifugal compressor. A centrifugal supercharger is practically identical in operation to a turbocharger, the difference being that that a turbocharger’s compressor is driven by exhaust gases via turbine and the centrifugal supercharger’s compressor is driven from the crankshaft, usually by a belt. This type of supercharger is also the most efficient, but unlike Roots type, it provides little boost at low engine speeds. Because of its design and lack of low-RPM boost, centrifugal superchargers are ideal for a ‘bolt-on’ type application without the need for changing the compression ratio or engine internals.
For intercooled centrifugal superchargers, ProCharger offers a load of products for a range of classes and applications – the company’s knee-deep in developing supercharger kits for high-horsepower EFI engines such as the Hemi, Ford Modular and pushrod LS and LSX, whether that application’s in a car or truck driven at the races or on the street. Vortech also offers a wide selection of centrifugal superchargers and their racing experience has optimized their design. The Vortec Y7i for example took what Vortech learned from the V-4 in racing to develop a supercharger that supports 1,200HP and 36psi of boost. Its exclusive D-port volute and high-speed ceramic ball bearings make it much more efficient than the V-4 that preceded it.
If belt-driven supercharging isn’t your thing, The Supercharger Store offers gear-drive conversions for powering single or dual centrifugal superchargers which puts the supercharger out of side and moved forward for an improvement in aerodynamics, weight distribution, and oh yeah– visibility. Being able to see track is a plus, and the gear drive eliminates the side-load on the engine’s crankshaft and supercharger input shaft completely out of the equation.
Turbochargers
A turbo, by definition, is a centrifugal compressor powered by a turbine. The turbine, in turn, is driven by an engine’s exhaust gases. The benefit is much like that of supercharging because it’s making more power the same way – by forcing more air into the engine, thereby increasing the amount of oxygen available for compression. The term turbocharger is actually a shortened version of turbosupercharger, being a supercharger driven by a turbine.
Why turbocharge? The principle advantage of a turbocharger over supercharging is that it does not use the engine’s mechanical energy to drive it. For instance, on a Rolls Royce Merlin engine, the supercharger alone uses 150hp, but adds an extra 400hp to an engine that would otherwise make 750hp, for a total of 1,000 HP, a net gain of 250hp.
By contrast, the turbocharger does not place a direct mechanical load on the engine, making it more efficient because it converts exhaust gas into horsepower to drive the compressor. The turbocharger does basically does the same thing as a supercharger to increase power, but that power comes without the HP loss a supercharger would incur. The key disadvantage of a turbo is backpressuring of the engine and a delay in response until exhaust gas velocity is sufficient to drive the turbine, that and the fact that controlling a turbocharger is fairly complex.
One of Exile’s ETR Ultra-Light Modular Turbos
Known for its custom race turbocharger systems and compontents, Exile can personalize a turbocharger setup for your specific horsepower and airflow needs. Since turbochargers are turbine-driven, they turn many thousands of revolutions more than your engine will ever see, so it’s only natural that Exile has seen fit to equip some of their turbochargers with their patented dual-ball bearing systems to keep the compressor wheel spinning freely, and their line of custom air-to-air and water-to-air intercoolers and cores are the perfect compliment to a turbo setup. Suitable for high-performance street, diesel and race engines, their intercoolers feature reinforced construction for high boost levels and the bar-and-plate design is both thermally efficient and offers maximum airflow, but with a minimal pressure drop.
Turbonetics TN-400
Turbonetics offers a variety of turbos, intercoolers, wastegates, blow-off valves and more. The TNX-series turbochargers were designed from the ground up with billet parts, and lots of them, says the company. A larger, heavy duty version of the patented ceramic ball bearing is one of the secrets behind the TNX’s 2,600lb thrust capacity. The billet-machined housing has an oil-feed system with its location specifically chosen for superior oil cooling. Now how about some numbers? TNX-series units are capable of up to 2,500HP, 50 PSI and up to 3,500hp and 140PSI when used in compound-format.
Wrap-Up
So that’s more or less the basics of forced induction, which should be enough to get you started looking into your own forced induction setup. Don’t forget, though, the key to making the most of your forced induction and not blowing up your motor is proper tuning and calibration. So, which is better, a turbocharger or a supercharger? The best answer we can give you is that “it depends”. It really is a matter of preference and what you’re trying to do. Whether you decide to go turbo or supercharged, the choice is yours.
Do you think one is better than the other? Which do you think is best: Roots Supercharged, Centrifugal Supercharged or Turbocharged? Why?
SOURCES:
Blower Drive Service
562.693.4302
blowerdriveservice.com
Eaton
eaton.com
Edelbrock Corp
310.781.2222
edelbrock.com
Exile Turbo Systems
805.432.5582
exileturbo.com
ProCharger
913.338.2886
procharger.com
The Supercharger Store
520.456.9706
thesuperchargerstore.com
Turbonetics
805.581.0333
turboneticsinc.com
Vortech Engineering
805.247.0226
vortechsuperchargers.com
Weiand
270.781.9741
weiand.com