Now, time for a little history lesson. IMP built its first car in 1927. The car in question was a large six cylinder luxury car simply called "L6". At the time IMP only had experience in building trucks and engines, so a very conventional approach was chosen, using a 5.1L side valve engine and three-speed gearbox from one of IMPs bread and butter vehicles. Overall, this first effort was rather lackluster, thus sales were abysmal, a fact not at all helped by the depression of 1929. Production ended in 1930 after only 53 vehicles including rolling chassis had been sold. For a long time it was thought that none of the original L6 have survived, but in 2003 a bodyless frame and engine were found in a garage in Slovakia, and are now on display in IMPs Grevenbroich headquarter.
Following WW2 IMPs efforts began to shift towards cars again, and as early as 1948 began developing a completely new, advanced line of large sedans. The results were the 1950 IMP 2 and the 1952 IMP L6.
The L6 nameplate had been revived to suggest that this time IMP were being serious, and indeed they were. The car was built around a monocoque chassis powered by the all new 3.8L A-series straight six engine. With 155hp, it was in fact the most powerful german post-war car up to that point, yet sales were low at first due to poor built quality, unharmonic ride and a lack of rear headroom. The design meanwhile also drew a lot of criticism from the conservative german public, with its weird grille mounted main headlights and top mounted fog lamps:
But IMP remained persistent and gave the L6 a heavy facelift for the 1955 model year, including a completely redesigned front end, raised roof line, retuned suspension, increased compression ratio and a 2-speed GM Hydramatic transmission that replaced the old 3-speed manual.
This "L6 Super" remained in production until 1960 with steadily improving sales, which gave IMP the confidence to produce a successor.
The second generation was built on the same platform, but exchanged the live rear axle for a DeDion tube and was now also available with front disk brakes. The engine was the proven 3.8L straight six which had been revised with new, forged internals and a new carburettor which increased power to 190hp. The bodywork meanwhile was completely redone with a new, angular appearance and oval shaped headlights which were to become a main design element on all IMP vehicles of the next 15 years.
The new body had unfortunately also increased weight significantly, and the engine was beginning to struggle with it. At the time IMP lacked the funds to develop a new engine, so in 1961 the engine was fitted with a twin carburettor setup that increased the output to 205hp, at the expense of noticeable reliability issues. Thus for 1962 a different approach was chosen, with the engine now reverted to a single carburettor, but bored out to 4.1L. Power meanwhile remained the same. In this form it continued until 1966. The last batch of cars before the third generation made between February 1966 and April 1967 received the then-new F-3800 engine with the same power, but less weight and better fuel consumption as well as some visual updates from a stillborn 1963 prototype with a V12 engine.
The 1967 third generation L6 once again stuck with the old platform, which was reengineered with an increased wheelbase and new fully independent suspension as well as four-wheel disk brakes.
The first model year retained the carbureted 3.8L engine, which was upgraded with Bosch D-Jetronic fuel injection for 1968. At the same time, out of nowhere IMP released an all new 285hp, all aluminium 4.7L dual overhead cam V8 that finally gave the car a much needed increase in performance.
The straight six models were mated to a Chrysler TorqueFlite A-904 transmission, while the V8 transmitted its considerably higher power through the stronger A-727. An optional limited slip-differential became available in 1970. For 1973 all engines were switched to run on unleaded fuel in order to comply with north american emissions regulations. To combat the loss in power both engines were bored out to 4.0 and 5.0L respectively.
In those later years sales were steadily falling, with only 818 cars sold in 1974. Production of the L6 ended in 1976 with no immediate replacement.
Despite being well received by the motoring press, both the second and third generation L6 often tend to be forgotten in classic car circles, and as a result both demand and prices on the classic car market have remained low thus far. Only pre-1973 V8 models have something of a following, with prices of well preserved examples reaching upwards of $35,000.