Engine sizes for several 911 variants have increased in the latest model year to a whopping 3.8 liters. This includes the Carrera S, Carrera 4S, GT3, GT3 RS and most recently the Turbo. While this transition may seem like a natural progression for Porsche in the great “size and horsepower race” that many manufacturers have engaged in over the past decade, the move to 3.8 liters was not always a sure thing. For some it’s hard to remember that it all started 45 years ago with a 2.0 liter flat 6 engine that was “originally designed to be stretched to 2.7 liters”. Then came the 3.3 liter Turbo motor of the late 70’s and later the 3.6 liter 964 motor of the early 90’s. All of these air cooled engines were based on the same cylinder spacing (bore centers) with ever increasing cylinder bore diameters.

Contrary to the expectations of many, in 1992 Porsche was looking to upgrade the 3.6 liter Carrera RS with a more powerful engine. Again the cylinder bore was increased from 100 mm to 102 mm which, coupled with the standard 76.4 mm stroke, increased the overall displacement to 3746cc. This got upsized to 3.8 liters for marketing purposes. The question was how reliable would the new engine be given the minimal cylinder wall spacing in air cooled form. Porsche put the engine to the test and entered it at Le Mans and at Spa, both 24 hour races, where it won both GT classes and proved its reliability.

The 3.8 liter engines on today are no longer air cooled and are technically far advanced over the earlier versions. With the new 9A1 type engine we see other fundamental changes that will doubtless lead to more horsepower and fuel efficiency. Will we see a production version of a 4.0 liter flat 6 for a road going Porsche in the near future? Only time will tell but we know it’s on somebody’s wish list.

(The Porsche 911 Story by Paul Frere was a resource for this article.)