Forced Induction / Nitrous
Ok -
Turbocharging
Remember where we talked about VE and how difficult it is to achieve good cylinder filling from atmospheric pressure? What if we were to raise the pressure of the inlet to something well above atmospheric pressure? Obviously we might not only achieve a VE of 100%, we might exceed it by a significant amount and the output power would increase nearly proportionally. Normally we'd use an air pump of some kind, in the case of turbocharging this is a turbine driven by the exhaust gas as it escapes from the engine. Supercharging is a crankshaft driven pump. Both have pros and cons and neither are a perfect solution.
In the case of turbocharging there is an appreciable lag between opening the throttle and the turbo starting to work. Primarily because it's a positive feedback system in which a substantial amount of exhaust needs to flow from the engine to spin the turbine up to speed, which requires a significant throttle opening and engine rpm and a substantial amount of exhaust flow etc. More exotic system have found ways round the problem of maintaining boost during closed throttle but this usually consists of throwing petrol at the exhaust side of the turbo and admitting air from the intake side to keep it spinning. Not very economical. Other than that turbochargers can give good increases in power with increases in efficiency and economy to boot. Engines usually need some modification to cope with higher pressures and heat, reducing CR, injecting water or water methanol mixes are some ways. Substantial amounts of boost usually require substantial modification, but standard V8's will usually run 5lbs of boost as is. Installation and sizing of turbochargers is outside the scope of this document but there are good books around and information is easily available from Garret and other manufacturers.(Eliot's Note: Such as my website!)
Supercharging
Supercharging does not suffer from the lag associated with turbocharging, however it isn’t efficient since a significant amount of engine power is wasted driving the compressor and heating the intake charge as it compresses. In this case the exhaust energy is not recovered, the supercharger (blower) is driven by the crankshaft and may consume at least 15BHP and probably much more. It may well increase output by 75BHP so you still end up with 60BHP more but the economy suffers appallingly.
However, you do get a substantial increase in instant torque, if that is your main concern. Installation and sizing of blowers is also is outside the scope of this FAQ and again there are good resources available with assistance from the likes of Wade, Eaton and other manufacturers. If you take the time to research and understand the techniques you will realise why the EFI systems used on the V8 don't really work with the usual Rootes (lobe type) superchargers although that hasn't stopped people trying and failing (expensively). There are some arrangements which do work extremely well though. Note that it might be easier and cheaper to get a bigger engine.
Nitrous Oxide
In principle this is a very simple way to get vast increases in torque. In practice it’s an easy way to spend large amounts of money very quickly, however, it does work extremely well over short distances. The method is very simple, pour large amounts of petrol and the correct amount of a powerful oxidising agent into an engine and watch it take off. Nitrous Oxide is the preferred oxidiser although Hydrogen Peroxide can be used. Nitrous Oxide has the advantage of being relatively cheap, is a liquid when pressurised meaning it cools rapidly as it expands into the engine, causing a significant charge density increase on top of the extra fuel and oxygen available for combustion. Using it is as simple as turning on metering valve for the Nitrous Oxide and a metering valve for the extra fuel and squirting both directly into the intake ports of the engine. The consequence is a sharp and substantial increase in available power, often in increments of 50 or 100bhp. The only drawbacks are the risk of a serious engine fire, the poor control of the extra power, the considerable rate of usage of Nitrous Oxide and the dangers inherent in applying large step changes in power to an engine. Realistically it belongs in competitions where short bursts of high power are needed, hill/dune climbs and drag racing. Miraculously it is legal but nearly useless on the road. Beware of misfires and hydraulic lock and note that strong oxidising agents will oxidise organic materials like human beings in a similar manner to petrol. You may not just go blond in an accident.