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A 1981 Ford Econoline E150, which I have converted to exclusive operation on compressed natural gas (CNG).

Below are a few pictures of the installation. The motor is a Ford 351 Windsor small block, rebuilt with various optimizations for CNG: domed pistons for 11:1 compression ratio, stainless steel exhaust valves, hardened valve seat inserts, and heavy-duty head gasket. The intent was to re-create the stock engine's performance without using gasoline, with low-end torque taking precedence over high-rpm horsepower. The stock cast-iron exhaust was retained, and a Ford 2-barrel aluminum intake was used for better heat transfer.

Twin aluminum tanks are fueled to 3,000psi through a filler next to the driver's seat. Gas is delivered through a series of safety valves to a high-pressure regulator with integrated lockoff solenoid under the hood, which reduces the pressure to 150psi. Engine coolant circulates through the regulator to prevent it from freezing. The gas is further reduced to just a few psi by an OHG X2 low-pressure regulator controlled by intake vacuum, and supplied to an OHG 450 gas mixer sitting on a 2-barrel throttle body.

Under the hood on the driver's side is mounted an OHG Air Fuel Mixture Control module. This device reads an oxygen sensor mounted in the exhaust pipe and continuously adjusts the low-pressure mixer to approximate an optimal fuel-air ratio. At least, that's the theory. The van is currently tuned manually.

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Installation instructions for the O2 Air Fuel Mixture Control:

[Hookup diagram]

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