HIGHER COMPRESSION

One quick way of increasing power while keeping to the same capacity is to raise the engine compression. For example, a high compression ratio of 10:1 means that the air-fuel mixture taken into the cylinder is compressed to one tenth of its original volume (and of course ignited along the way by the spark). Higher compression could be achieved in a few ways where legal:

1. by changing the flat-top pistons to high compression ones that curve upward to result in a higher compression ratio. However, since the air and fuel are both more highly compressed, the fuel will start burning spontaneously (before the spark plug ignites) at some point and this causes knocking (by a spontaneous flame front coming down at the piston trying to go upwards), which will reduce engine power. It is for this reason that only higher octanes are usable in modern engines, because lower octanes like 92 are even more prone to knocking.

2. turbocharging. This gives maximum power when the turbocharger is spooled up beyond 3000 rpm, but below that engine speed the turbo will slow the engine down as it is exhaust driven. This is called turbo lag. Furthermore, to be prepared for the very high effective net engine compression that results when the turbo comes on fully (air is pre-compressed through the turbo and forced into the engine), the engine must have an inherently low compression ratio such as 8:1, which further takes away power before the turbo is up. This in all causes higher fuel consumption in turbocharged cars.

3. supercharging. This gives an increased charge proportional to rpm, but loads the engine straightaway like an aircon pulley, whenever. At low rpm the boost effect is also noticeably absent.

4. using a Surbo. The Surbo gives higher air pre-compression in the air intake, outside of the cylinder so it does not affect the fuel compression in the cylinder (like in 1.) and does not cause knocking. It achieves the desired higher compression and thus increased power safely. Among the four, the Surbo is also the least costly and most fuel-efficient.

The Surbo can also be used in
1. very high compression engines to lessen the fuel input and prevent knocking, or enable usage of lower octane fuel (this is because with a Surbo, less of the accelerator is used and fuel put in is less).
2. turbocharged engines, to cut the turbo lag. The surbo's precompression from low rpm before the turbo is up increases the engine's inherent compression, and the increased air flow moves faster through the exhaust, thus spooling the turbo sooner (at a lower rpm) so cutting the lag and consumption, and improving overall response. Surbo-fitted turbo vehicles include the Volvo T6 (250 bhp) and Daihatsu Charade, and turbodiesels like the VW Caddy and Opel Combo and Mercedes Vito 110 and automatic 112, amongst others.
3. supercharged engines (as in Mercedes Kompressor C180) to increase the low rpm power, especially if it is automatic and normally limited to the lower rpm range.