How do you supercharge an engine?

Answer 1

Supercharging an engine is done through increasing the Oxygen content in the cylinders during engine operation. Since the air contains a relatively fixed ratio of Oxygen, Nitrogen and other gases the only way to increase the Oxygen content is to increase the total air volume. This is done through compression of the air.

Most engines fail to burn 100% of the fuel that passes through the engine due to efficiency issues including the balance of air to fuel (air/fuel ratio) simply increasing the Oxygen content is not enough because the small increase in power burning 100% of the fuel may yield is not nearly enough to make it a viable solution. Even small levels of compression (commonly called boost pressure) will yield more Oxygen than you actually need for a complete fuel burn. This results in a "lean" air/fuel ratio (meaning there is too much air for the given fuel amount) resulting in engine damage. Lean air/fuel ratios can cause pistons, valves and etc. to become hard and brittle.

The solution then is to add more fuel. So, the greater the boost (compression of air) the more fuel that needs to be delivered. Proper air/fuel ratio must be maintained. The rest is simple physics, the more air and fuel you can pack into a given space the more pressure will be created upon detonation which results in more power from the engine. Compression of air will increase air temp a great deal. This can cause pre-detonation (early detonation of the air/fuel mixture) which can damage the engine. High octane fuels resist pre-detonation. Also increasing fuel % in the air fuel ratio can help reduce pre-detonation but results in a "rich" air/fuel ration.

Retarding spark can also help. The "art" of supercharging is balancing desired use/drivability with desired performance characteristics. High boost will require specialty fuels and specialty tuning but will yield a massive power potential. Low boost requires less engine modifications and may run on high octane pump fuel. Medium boost may require some engine modifications and may/may not run on high octane pump fuel.

Engine mods can include fuel delivery system improvements to supply more fuel; air/fuel ratio gauges for tuning and safety; crank shaft, piston and cam changes. Specifically for ANY medium to high boost condition you must get stronger engine components such as the pistons and crank shaft. These items which are typically made of cast steel should be forged. Forged aluminum pistons come in different types which need to be balanced with desired usage also but that is another topic.

Intercoolers can be used to reduce the air temp prior to mixing with fuel which will allow running higher boost levels before having to retard timing or using expensive specialty fuels. The cooler air will be denser thus actually having higher oxygen content at lower pressure levels so intercooling a supercharger is a highly recommended solution. Intercooling will also reduce the boost pressure slightly so there is an art, again, in balancing the pressure at the compressor with the actual boost pressure at the manifold after running through an intercooler. There are many type and sizes of intercoolers but selection of the right one is another topic.

There are also many different types and styles of superchargers but the selection of the right one is another topic. I prefer ProCharger systems and you cal learn a great deal from their website and support staff.