911 2.2-litre / C and D series (1969–1971) & 911 2.4-litre / E and F series (1971–1973)

911 2.2-litre / C and D series (1969–1971)

For MY 1970 the engines of all 911s were increased to 2195 cc. Power outputs were uprated to 125 PS (92 kW) in the 911T, 155 PS (114 kW) in the 911E, and 180 PS (118 kW) in the 911S. The 912 was discontinued, thanks to the introduction of the Porsche 911T as an entry model.

The 2.2 L 911E was called "The secret weapon from Zuffenhausen"^{[citation needed]}. Despite the lower power output of the 911E (155 PS, 114 kW) compared to the 911S (180 PS, 132 kW) the 911E was quicker in acceleration up to 160 km/h (100 mph).

911 2.4-litre / E and F series (1971–1973)

The 1972–1973 model years consisted of the same models of 911— the entry level T, the midrange E and the top of the line S. However, all models got a new, larger 2341 cc (142 in³) engine. This is universally known as the "2.4 L" engine, despite its displacement being closer to 2.3 litres— perhaps to emphasize the increase over the 2.2 L. The new power ratings were 130 hp (97 kW), or 140 hp (104 kW) in the U.S., for the T, 165 hp (123 kW) for the E and 190 hp (142 kW) for the S.

The 911E and 911S used mechanical fuel injection (MFI) in all markets. The 911T was carbureted, except in the US where it also used MFI, which accounts for the 7 kW (9 hp) power difference between the two. In January, 1973, US 911Ts were switched to the new K-Jetronic CIS (Continuous Fuel Injection) system from Bosch. These CIS-powered cars are usually referred to as "1973.5" models by enthusiasts.

With the power and torque increases, the 2.4 L cars also got a newer, stronger transmission, identified by its Porsche type number 915. Derived from the transmission in the Porsche 908 race car, the 915 did away with the 901/911 transmission's "dog-leg" style first gear arrangement, opting for a traditional H pattern with first gear up to the left, second gear underneath first, etc. Some say this was because the dog-leg shift to second gear was inconvenient for city driving, other say it was due to Porsche’s desire to put 5th gear outside the main transmission housing where it could easily be changed for different races. The Sportomatic transmission was still available but only as a special order.

In 1972 a tremendous effort was made to improve the handling of the 911. Due to the 911's unusual engine placement (rear-mounted, with most of the vehicle's weight concentrated over the rear axle) early 911's were prone to oversteer when driven at the limit, and could easily spin in the hands of an inexperienced driver. In an attempt to remedy this, Porsche relocated the oil tank from its position behind the right rear wheel to in front of it. This had the effect of moving the weight of almost 9 quarts (8.5 L) of oil from outside the wheelbase to inside, improving weight distribution and thus, handling. To facilitate filling of the oil tank, Porsche installed an oil filler door (much like the fuel filler door on the left front fender) on the right rear quarter panel. Unfortunately, this unique design was scrapped after only one year, some say because inattentive gas station attendants were putting gas in the oil tank. The oil tank was subsequently moved back to its original position for model year 1973, and remained there until it was moved back within the wheelbase for the 964 models.

911S models also gained a discreet spoiler under the front bumper to improve high-speed stability. With the car's weight only 1050 kg (2315 lb), these are often regarded as the best classic mainstream 911s. For racing at this time, the 911 ST was produced in limited numbers (the production run for the ST only lasted from 1970 to 1971.) The cars were available with engines of either 2466 cc or 2492 cc, producing 270 PS (199 kW) at 8000 rpm. Weight was down to 960 kg (2166 lb). The cars had success at the Daytona 6 Hours, the Sebring 12 Hours, the 1000 km Nürburgring and the Targa Florio.