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Old 05-21-2012, 05:02 PM   #107
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Originally Posted by AZfocus2012 View Post
Are you saying the fuel injectors are downstream of the valves or in the cylinders?
Direct Fuel injection uses high pressure fuel injectors directly inserted inside the combustion chamber, instead of the low pressure port fuel injectors which injected fuel into the intake plenum where it had a chance to vaporize and mix with the incoming air before being drawn into the combustion chamber.

With direct injection you can run higher compression ratios for greater efficiency and since you're injecting liquid fuel after drawing the air into the combustion chamber you can get away with 12:1 compression on 87 octane where as in the past it was viewed with carburetors or port fuel injection that anything over 10.5:1 compression demanded higher octane fuels to prevent detonation (ping/knock/ pre-ignition) of the air fuel mixture ahead of the flame front from the spark plug.
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