Tech: Superchargers, Turbochargers, & Induction
Adding Boost? Compression, cams, and installation headaches.
By Fergus Ogilvy: The two most common uncertainties about the prospects of supercharging are fitment and engine tune. Will the supercharger fit under the hood and will it operate with all its accessories: alternator, power steering pump, and air conditioning compressor? The second relates to tuning in general and the preferred compression ratio and camshaft specification in particular. For the most part, a supercharger that doesn’t fit under the hood is undesirable in most quarters. So, woe betides the manufacturer that requires a hood hole to accommodate it, for he will most likely perish in obscurity. Owners desperately seeking attention may relish the thought of a monstrous supercharger towering above, but for the average Muscle car owner, hardly. With regard to the configuration of alternators, steering pumps and compressors, the approach taken by most manufacturers is determined by first identifying the vehicle. These are briefly explored below under the headings Chevrolet or Chrysler or Ford. Select the one that is relevant. Installations Chevrolet: Considering TorqStorm Superchargers, their units for small-block Chevrolets are available in right- or left-hand options, whatever works best. Better still, to avoid unknown complications, they provide a supercharger option that includes all accessories. Similar options are available for Chevrolet big-blocks. Of the most sought-after kits, it is the LS model that raises most questions. These engines (4.8L, 5.3L, and 6.0L) are favored because of their notable power output and value for money; truck engines are inexpensive. But the supercharger maker must be notified that the engine is, in fact, from a truck as their dimensions differ. TorqStorm’s LS truck supercharger kit is designed to operate with...
To intercool or not to intercool?
But first an amusing, brief story involving a big-block Chevrolet, an intercooler, and freon. By Sam Logan “I’m no authority on intercoolers,” admits performance carburetor specialist Dale Cubic of CFM, “but I do recall a memorable moment five years ago that involved one. Nothing too scientific,” he adds; nonetheless, it seemed an anecdote worth telling. The noted carburetor specialist had visited an engine builder’s shop with a carburetor for a 1600hp 565ci supercharged big-block Chevrolet. The engine was already installed on the dyno and suspended above it an intercooler. Unsurprisingly, with the intercooler connected, the engine improved by 50–80hp. But then the engine builder unexpectedly produced a can of freon, purchased from a local parts store, and reached up and sprayed some of its contents over and around the intercooler. He then hastened to the dyno room and made a pull. “It gained a further 40hp! Spraying freon on that intercooler was like feeding it with nitrous oxide,” remembers Cubic. But the mischief didn’t end there, to further mark the occasion it blew the plumbing off the supercharger! The engine was powered by a small Dominator and a Stage II ProCharger and the freon had condensed the charge sufficiently to pack in more air than anticipated. Intercool or not to intercool? Racers, by instinct, explore every avenue that might lead them to more power. They know that the introduction of compressed air to the cylinders generates heat and excessive heat provokes early detonation. The common solution for expelling excessive heat is to install an intercooler. And similarly with designers of modern turbochargers, who believe that no serious person would...
Comparison: Testing a TorqStorm
But the best part was the TorqStorm’s ability to generate 400lb ft torque at 2000rpm; its rival reached 400lb ft at 2500rpm. At 3000rpm the ‘Storm generated 484lb ft compared to the Vortech at 436.
The anatomy of the supercharger or what makes it tick
By Titus Bloom: Superchargers are magical devices. They increase the oxygen supply to the engine by compressing the air, thus increasing its density. Accordingly, the engine burns more air-fuel mixture and produces more power. In a centrifugal supercharger, the air is propelled through the compressor wheel and compressed in the diffuser—the thin passage formed between the compressor cover and the bearing housing—and in the volute or scroll where its kinetic energy is converted to pressure. All of the dimensions, including the diameter of the diffuser, diffuser gap distance, size and diameter of the volute, contribute to the degree of compression. In a turbocharger—exhaust-driven forced induction—the compressor wheel is powered by exhaust flow, but in the supercharger the compressor wheel is driven via a gearbox that takes its power from a crankshaft pulley by way of a drive belt. The gearbox accelerates the compressor wheel from engine speed to a point where the compressor operates efficiently. Here below is the assembly process: Source: TorqStorm Superchargers Rick Lewis (616) 706-5580 Sales@TorqStorm.com...
Mistakes that weaken a supercharger’s performance
Bertie S. Brown: TorqStorm Superchargers’s product manager, Chris Beardsley, has dealt with thousands of incoming queries in the first decade of the firm’s history. Here are five of the most common: 1) Compression ratios and intercoolers “The compression ratio for pump-gas engines is crucial,” says Chris Beardsley. “TorqStorm recommends ratios of 9.1 to 9.5:1.” Higher ratios usually require an intercooler. “But if you are running less than 12psi of boost and under 10:1 compression ratio with aluminum cylinder heads, and a blow-through carburetor or venturi-style throttle body fuel injection,” insists Beardsley, “ you can still achieve significant power increases without an intercooler, even on pump gas. Blow-through carburetors do a very good job of controlling intake charge temperatures.” 2) What increases in power can I expect? “Our single centrifugal supercharger, which supports 700+hp and generates boost of 6-8psi., increases engine power by about 40 percent over stock performance,” claims Beardsley. “Add a second unit, which collectively generate 12-15psi., and the engine’s power output potentially doubles.” Note that the fuel pump must support 21psi of fuel pressure and it relies on a return line to the tank. 3) Carburetors and regulators The fuel delivered to a carburetor on a normally aspirated engine operates at 6 or 7psi. But the blow-through carburetor is designed to operate from 5psi to boosted pressures that can reach 18psi on a forced-induction engine. This task is achieved by the introduction of a boost-referenced fuel pressure regulator. Via a small-bore hose, the regulator is connected to a port on the intake manifold below the carburetor throttle plates. In this way it reads boost and increases the...