The now Defunct Saab brand is remembered for many things, but their break through in variable compressions engines is not one of them. The plucky Swedish brand refused to conform to conventional engineering, even when it was controlled by GM, which lead to its eventual demise. However, before Saab bowed out, they built a variable compression engine known as the SVC, featuring a variable compression ratio thanks to a movable head design.
The benefits of varying an engines compression ratio with a simple engineering solution offers a huge reward for very little engineering risk. Saab’s SVC engine was built just like a normal engine with the inclusion of one new part known as the Monohead. This device acted like a normal head on any engine, but it could be raised and lowered by a hydraulic crank to vary the volume of the combustion camber, therefore changing the compression ratio.The SVC engine was a supercharged 1.6 liter 5-cylinder that could vary its compression from 14:1 to 8:1 depending on the driving situation. This culmination of technology allowed the 1.6L to produce an impressive 225 horsepower while reducing fuel consumption by 30%. The high compression ratio would be used during low load situations, while during high loads the low compression ratio would be used to account for the boost of the supercharger. This engine’s adaptability meant it could tailor its output to perfectly suit the driving situation without impacting performance.
This promising technology would have allowed Saab to leapfrog the competition in efficiency and power, but unfortunately it never went into production. GM did not see it as a worthy investment of their capital, and the engine remained a concept. One could only imagine how effective this technology would be if GM had funded it 16 years ago. Now that Nissan is bringing variable compression back remember, the third greatest Swedish car maker did it first.
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