SEMA show update

Ford displayed cutaway views of their new Ecoboost 4 and 6-cylinder engines at this year’s SEMA (Specialty Equipment Manufacturer’s Association). The new engines include a turbo and gasoline direct injection (GDI).

In traditional engine, the injectors are located above the valves and inject gasoline slightly before the valve opens. The injectors really don’t “inject” like a doctor’s syringe. Instead, the fuel rail is pressurized by the fuel pump and the injectors act like a kitchen faucet—they just open and close. In other word’s they’re solenoids. They have power going to the solenoid coils at all times the key is in the run position and the computer pulses the ground connection on and off. Gasoline pressure in these systems usually runs about 40-50-psi. Once the injector opens, the heat of the valve helps the gasoline droplets vaporize (remember, the engine burns gas vapors, not liquid gasoline.)

In a GDI engine, the inject is located at the top of the combustion chamber. The computer starts injecting gas when the piston is starting on the compression stroke. At first, there’s little pressure pushback against the gasoline injection. But as compression increases, so does fuel pressure—up to 3,000 psi. That extremely high pressure, and the heat caused by compression causes the fuel to vaporize rapidly. Also, keep in mind that the compression caused by the turbo heats up the incoming air. So a side benefit of the GDI is that the rapid vaporization helps cool combustion temperatures—sometimes to the point where the engine no longer needs an EGR valve to reduce oxides of Nitrogen emissions.

The end result is more power and better fuel economy. GDI is the latest in innovations.

I’ll follow up with more news from SEMA and AAPEX

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© 2007 Rick Muscoplat

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