Saturn Sky Redline Combustion Chamber

A look at the combustion chamber shows a fairly standard four-valve setup with centrally-mounted spark plug, but peeking through on the left is the tip of the SIDI system's fuel injector: a breakthrough in more than one way. "SIDI is effective in cooling the charge because the energy to evaporate the fuel comes from the gas phase in the cylinder. With port fuel injection, the energy to evaporate the fuel is coming from the port walls, so the heat is coming out of the metal. But with SIDI, we are injecting during the intake stroke into the gas phase so we are taking the heat out of the air. This helps cool the charge, which lets you up the compression ratio roughly 1 unit. A PFI engine at this level of boost would normally be in the 8s for compression," says GM's Groff.

Red-Hot Roadster - 2007 Saturn Sky Red Line

A look at the combustion chamber shows a fairly standard four-valve setup with centrally-mounted spark plug, but peeking through on the left is the tip of the SIDI system's fuel injector: a breakthrough in more than one way. "SIDI is effective in cooling the charge because the energy to evaporate the fuel comes from the gas phase in the cylinder. With port fuel injection, the energy to evaporate the fuel is coming from the port walls, so the heat is coming out of the metal. But with SIDI, we are injecting during the intake stroke into the gas phase so we are taking the heat out of the air. This helps cool the charge, which lets you up the compression ratio roughly 1 unit. A PFI engine at this level of boost would normally be in the 8s for compression," says GM's Groff. View Related Article

Saturn Sky Redline Combustion Chamber

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