The engine can be easily upgraded because it is separated in modules.

Both engines were upgraded over the prior 5 Series generation.

Around the same time, the 800 engine was upgraded, adding three extra horsepower.

In August 1969 the engine was upgraded to 1166 cc.

During this time her engines were upgraded and interiors refurbished.

The engines were upgraded and the equipment list made longer.

The engines are upgraded too, with more power and better economy.

In April 1971, the engine was upgraded so as to make it more quiet.

The engine was upgraded over the course of its production.

He said that at some point the Porsche's engine had been upgraded to make it more powerful.