Combustion chamber deposits increase compression and absorb heat during combustion. Later, they release that heat during the intake cycle. In some engines deposits can cause the piston to actually hit the cylinder head – a process known as "carbon rap".The deposits can also flake off and become trapped between the valves and valve seat, resulting in compression loss.
Higher compression and stored heat increase the likelihoodof pre-ignition “knock” when the fuel spontaneously combustsprior to spark ignition. This increases emissions and may causeengine damage. Most vehicles have sensors that adjust sparktiming to prevent knock. Although audible “knock” is controlled, power is lost from retarded timing and engine efficiency suffers.Higher octane fuels can be used to help prevent the phenomenon. As a vehicle ages, more-expensive, higher-octane fuel is needed to keep it operating at peak performance.
Combustion chamber deposits:
• Increase the possibility of “carbon rap”
• Contribute to compression loss, difficult starting and rough idling
• Increase the possibility of pre-ignition “knock” or “pinging”
P.I. fightscombustionchamberdeposits which helps restore power, control knock, increase fuel economy and reduce the need for higher-octane fuels.