Helmer Petterson
The P1800 project started in
1957. There was a previous Volvo sports coupe, the P1900, but it was a disaster, with only 68 cars sold. The man behind the project was engineering consultant Helmer Petterson, who in the 1940s was responsible for the
Volvo PV444. The design work was done by Helmer's son Pelle Petterson, who worked at
Pietro Frua at that time.
Volvo insisted it was an Italian design by Frua and only officially recognized that Pelle Petterson designed it in 2009. The Italian Carrozzeria Pietro Frua design firm (then a recently acquired subsidiary of Ghia) built from September
1957 to spring
1958 the first three prototypes, later designated by Volvo in September
1958 : P958-X1, P958-X2 and P958-X3, (P:Project 9:September 58:Year 1958 = P958).
P1800
The engine was the B18 (B for the Swedish word for gasoline: Bensin; 18 for 1800 cc displacement) with dual
SU carburettors, producing 100 hp (75 kW). This variant (named B18B) had a higher compression ratio than the slightly less powerful twin-carb B18D used in the contemporary Amazon 122S, as well as a different camshaft. The 'new' B18 was actually developed from the existing B36 V8 engine used in Volvo trucks at the time. This cut production costs, as well as furnishing the P1800 with a strong engine boasting five main crankshaft bearings. The B18 was matched with the new and more robust M40 manual gearbox through
1963.
From
1963 to
1972 the M41 gearbox with electrically actuated overdrive was a popular option. Two overdrive types were used, the D-Type through
1969, and the J-type through
1973. The J-type had a slightly shorter ratio of 0.797:1 as opposed to 0.756:1 for the D-type. The overdrive effectively gave the 1800 series a fifth gear, for improved fuel efficiency and decreased drivetrain wear.
Cars without overdrive had a numerically lower-ratio differential, which had the interesting effect of giving them a somewhat higher top speed (just under 120 mph) than the more popular overdrive models. This was because the non-overdrive cars could reach the engine's redline in top gear, while the overdrive-equipped cars could not, giving them a top speed of roughly 110 mph (177 km/h).
1800S
As time progressed, Jensen had problems with quality control, so the contract was ended early at 6,000 cars. In
1963 production was moved to Volvo's Lundby Plant in Gothenburg and the car's name was changed to 1800S (the 'S' indicating Swedish assembly). The engine was improved with an additional 8 hp (6 kW). In
1966 the four-cylinder engine was updated to 115 hp (86 kW). Top speed was 175 km/h (109 mph). In
1969 the B18 engine was replaced with the 2-litre B20B variant of the B20 giving 118 bhp (89 kW), though it kept the designation 1800S.
1800E
For
1970 numerous changes came with the fuel-injected 1800E, which had the B20E engine with Bosch D-Jetronic fuel injection and a revised camshaft, and produced 130 bhp (97 kW) without sacrificing fuel economy. Top speed was around 190 km/h (120 mph) and acceleration from 0–100 km/h (0-62.1 mph) took 9.5 seconds. In addition, the 1970 model was the first 1800 with four-wheel disc brakes; till then the 1800 series had front discs and rear drums.
1800ES
In
1972 came the last model, the 1800ES, a coupé station wagon with an all-glass tailgate, sometimes described as a shooting-brake. The final design was chosen after two prototypes had been built by Sergio Coggiola and Pietro Frua. Frua's very unusual looking prototype, Raketen ("the Rocket", on the right), currently resides in the Volvo Museum. Both Italian prototypes were considered too futuristic, and instead in-house designer Jan Wilsgaard's proposal was accepted.
The ES engine was downgraded to 125 bhp (92 kW) by reducing the compression ratio with a thicker head gasket (engine variant B20F); although maximum power was slightly down the engine was less "peaky" and the car's on-the-road performance was actually improved.
The ES's rear backrest folded down to create a long flat loading area. As an alternative to the usual four-speed plus overdrive manual transmission, a Borg-Warner three-speed automatic was vailable in the 1800ES. With stricter American safety and emissions standards looming for
1974, Volvo did not see fit to spend the considerable amount that would be necessary to redesign the small-volume 1800 ES. Only 8,077 examples of the ES were built in its two model years.
Also see:
The History of Volvo (USA Edition) 
