Super Confused?

Q & A: Five things to know before you install a supercharger system

Words: Bertie S. Brown; Photos: Torqstorm

Superchargers require different care and handling than normally aspirated engines. For one, they live in a pressure-packed world where external environments have little to do with their ability to intake, compress, and kick out fuel and air. TorqStorm Product Manager Rick Lewis and Rob Walden of LWA Engines know what it takes to achieve proper supercharger operation. Here are some of the most misunderstood things when it comes to generating the most power from your supercharger.

What camshaft spec is best?

Installing a camshaft designed specifically for a supercharged engine is best. But, often the existing camshaft works surprisingly well, and those with lobe separation angles between 112 to 116 degrees are ideal. Of course, when cruising down the road, and thus not building boost, nothing more than a normal camshaft is required. However, to realize maximum power with narrow lobe separation angles, there is a sound argument for installing a more suitable cam.

“Your aim is to trap as much boost in the cylinder as possible,” says Rob Walden of LWA, an Atlanta tuning house. “The success or failure in achieving this is affected by the camshaft’s lobe separation angles and valve overlap. Too much overlap and you’ll blow your boost out the exhaust.”
In general, naturally aspirated engines run narrower lobe separation angles of around 106 to 108, whereas supercharged, turbo, or nitrous engines operate with 112 to 114 and higher. On larger displacement supercharger units, 116 to 118 degrees of separation are common.

Compression ratios and intercoolers

“The compression ratio for pump-gas engines is crucial,” Lewis says. “TorqStorm recommends ratios of 9.1 to 9.5:1.” Higher ratios usually require an intercooler.

“But if you are running less than 12 psi of boost and under 10:1 compression ratio with a blow-through carburetor or venturi-style throttle body fuel injection, you do not need to run an intercooler, even on pump gas,” he continues. “Blow-through carburetors do a very good job of controlling intake charge temps.”

What increases in power can I expect?

“Our single centrifugal supercharger, which supports 700-plus hp and generates boost of 6-8 psi, increases engine power by about 40 percent over stock performance,” Lewis claims. “Add a second unit which collectively generates 12-15 psi and the engine’s power output potentially doubles.”
Note that the fuel pump must support 21 psi of fuel pressure, and it requires a return line to the tank.

Carburetors and regulators

The fuel delivered to a carburetor on a normally aspirated engine operates at 6 or 7 psi. But the blow-through carburetor is designed to operate from 5 psi to boosted pressures up to 18 psi on a forced-induction engine. This task is achieved by the introduction of a boost-referenced fuel pressure regulator.

The fuel delivered to a carburetor on a normally aspirated engine operates at 6 or 7 psi. But the blow-through carburetor is designed to operate from 5 psi to boosted pressures up to 18 psi on a forced-induction engine. This task is achieved by the introduction of a boost-referenced fuel pressure regulator.
Through 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 fuel pressure by 1 psi for each additional 1 psi of boost. Blow-through carburetors also possess more robust floats to deter crushing under pressure. In addition, their jetting is different, and they operate with sealed throttle shafts to prevent leaking under pressure.

EFI, injectors, pumps, and tuning

A large number of supercharger kits, especially when using EFI induction, are installed by specialty shops that use a chassis dynamometer and a laptop computer to obtain the correct tune.
“So most tuning would be conducted by someone with the expertise and a chassis dynamometer,” Walden, who uses HP Tuners software, says.

On all late-model EFI vehicles, TorqStorm offers their superchargers as Tuner Kits only, which means they don’t include ECU or fuel management.

Torqstormconfused-03 (1200x939)

Correct belt tension is critical to maximizing power output. Belt slippage is the biggest killer of boost.

“Often, an EFI supercharger kit does require an upgraded fuel pump or a booster pump,” Walden says.
Booster pumps increase their fuel delivery by increasing their voltage output — higher voltage spins the pump faster. Also, they are boost-referenced, which means that as the boost increases, so too does the fuel pump pressure. Thus, the pump’s volume keeps pace with the demand at a corresponding rate. Alternatively, should greater delivery be required, a larger in-tank pump could suffice.
Fuel injector sizes are determined by the engine’s power output. They are calculated in pounds per hour of fuel dispersed. For example, 25 lbs/hr is sufficient to support 350 hp, 45 lbs /hr is sufficient for 500 hp, and so on.

Lastly, hot air expands and cold air condenses — the colder the air, the better the cylinder-filling, to say nothing of its deterrent to detonation. Thus, adding an intercooler when costs permit is never wasteful.

Bonus explanation: Clearances

Clearance questions around the alternator and above the carburetor seem to be the chief concerns.
“We provide chassis drawings,” Lewis says. “With regard to alternator relocation on the small-block Ford and big-block Mopar — both A-body and B-body — we have mocked up all those components and, though the clearances appear to be close to the engine, they are adequate.”

Nevertheless, the most prominent clearance question involves the carburetor hat. TorqStorm’s previous “two-can-style” hat measured 3.5 inches deep. Their latest free-flowing innovation, however, measures 3.25 inches. Though usually regarded as more restrictive, low-rise carburetor hats, measuring 2.400 inches are still available.

Sources: Torqstorm Superchargers, torqstorm.com; Lamar Walden Automotive, lwaengines.com

About the author

PPN Editor

Power & Performance News is the source for news, tech and products that help you get more performance from your vehicle. If powertrain performance projects and hardcore technical content are your interest, Power & Performance News is the publication designed for you. Our acclaimed editorial staff covers all aspects of engine and driveline upgrades with a mission of presenting information that is both interesting and achievable for the “average car guy”.
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