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.
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 OEM accessories.
In fact, this configuration but with different brackets also accommodates F-body vehicles Gen 1, 2, and 3 (Camaro, Firebird 1967-92) and yet a further kit with slightly different brackets still, fits the 2010 to 2015 Camaro.
Chrysler: Concerning their big-block engines, TorqStorm’s supercharger is offered in one configuration. This kit mounts the charger on the passenger side and relocates the alternator to a lower position. Similar to the Chevrolet, a complete kit that includes alternator, power steering pump and air conditioning compressor is also available.
The small-block Chrysler is similar, except the supercharger mounts on the driver’s side. The alternator remains on the passenger side and the power steering pump is located under the supercharger. On both small- and big-block Chrysler supercharger kits, the accessory drive and the supercharger drive are combined on one pulley; that is, one part of the pulley runs a V-belt to drive the accessories and the other part runs an eight-rib serpentine belt to drive the supercharger.
Ford kits operate in a similar manner to Chrysler.
Fan blades: Sometimes the radiator fan blades can get in the way of the supercharger belt. This is usually overcome in Chevrolet engines by specifying the water pump length: long or short. Beyond this, fan spacers are readily available. Fan spacers extend the fan blades closer to the radiator. That said engine-driven water pumps are often replaced by electric fans, which conveniently don’t rob power from the engine.
To see how simple a TorqStorm supercharger is to install, click here.
Compression ratios and other useful information
Forced induction engines run higher combustion temperatures than their naturally aspirated counterparts. Higher combustion temperatures increase the risk of detonation. Therefore, use spark plugs that are rated one or two steps colder to deter detonation, a destructive condition induced by extreme heat. Also, use a boost-retard ignition system, if not already integrated in the engine’s control system. The ignition should be retarded by 1 to 1.5 degrees for each pound of force per square inch of boost.
When boosted to 8psi, it’s wise not to exceed a compression ratio of 9:1 when using cast iron cylinder heads, and no higher than 10:1 with aluminum heads. Add 8psi of boost to a static compression ratio of 10:1 and your overall compression ratio increases to 15.4:1. By adding 8psi of boost to a static compression ratio of 9:1, your overall compression ratio increases to 13.9:1. Of course, light throttle cruising doesn’t generate boost.
Generally, naturally aspirated engines run camshafts with narrower lobe separation angles, typically around 106 to 108. On the other hand, supercharged, turbo or nitrous engines operate with 112 to 114 and higher. On larger displacement units 116 to 118 degrees of separation are common.
Your aim is to trap as much boost in the cylinders as possible. The success or failure in achieving this is affected by the camshaft’s lobe separation angles and the resulting valve overlap. Too much overlap and your cherished boost pressure escapes out the exhaust.
Lastly, what kind of power increase might you expect from supercharging? It depends on the quality of airflow reaching the cylinders. A TorqStorm unit, however, delivers around 40 percent over base at 7psi on most engines.