Ford I4 DOHC engine

The Ford I4 DOHC engine was a 4-cylinder inline internal combustion engine with twin overhead camshafts, produced by the Ford Motor Company, at Dagenham Engine Plant. First with 2.0-litre 8-valve version, in later models with 2.0/2.3-litre 16-valve version from 1989 to the end of production of the MK2 Ford Galaxy in 2006. It powered various Ford models during this time, but was most well known in the rear wheel drive "Twin Cam" variants of the Ford Sierra, and Ford Scorpio. Despite being built for the company's larger RWD models, Ford unusually employed the engine in the front wheel drive Galaxy and sport version of Escort named RS 2000 16v.

History

The I4 was originally designed to replace the ageing 2.0L OHC Pinto engine, derivatives of which had powered most of Ford's four-cylinder rear-wheel drive cars since the early 1970s, and which was now lagging badly behind the competition in terms of power output, efficiency and refinement. Equipped with a newly designed twin-cam cylinder head but still only 8 valves, and a "square" 86x86mm bore and stroke, the new I4 unit was launched in the Ford Sierra and Ford Scorpio, mated to the newly designed all-synchromesh MT-75 5-speed manual transmission, or the existing A4LD four-speed automatic. The engine itself received mixed reviews, being seen as an improvement over the Pinto, but not the leap forward one might have expected. With the Sierra in its twilight years by 1989 and the new Mondeo destined to replace it in 1993 powered by the newer 16V Zetec unit, it is probable that Ford considered the I4 would have a relatively short production life and so only put limited investment into the unit, even though it eventually remained in production until 2006.

Transverse installation

Although front wheel drive, and powered by a separate range of transversely mounted engines, the smaller Escort model was to play host to the next major incarnation of the I4. In 1990, the MkV Escort had been launched to disappointing press reviews, and Ford were looking to boost the image of this critically important range and steal sales from arch rivals Vauxhall and VW who were doing very well with big bore GTE/GTI badged versions of their family hatches.

Ford's strategy was to introduce two high-performance versions to steal some of the lucrative hot hatch market, using the well known XR3i and RS2000 badges. The XR3i was to be powered by tweaked versions of the new Zetec 1.8-litre engine from the standard Escort range, but the 2.0 Zetec unit being developed for the new Mondeo was a still a year away. Rather than wait for the new engine to become available, Ford took the unusual decision to take the longitudinally mounted I4, install a highly efficient multivalve cylinder head and tubular exhaust manifold, and mount it transversely in an FWD application. Designated N7A, critics remarked on its similarity in both specification and appearance to the Astra GTE's legendary C20XE "Redtop" unit which itself was widely regarded as the top hot hatch engine of the time. Given the success performance versions of the Astra enjoyed with the C20XE engine, it is perhaps only natural that Ford benchmarked it when developing the 16V I4. The RS2000's engine was well regarded, and is still seen as lively and characterful today.

With the disappearance of the Sierra in 1993, and the fading of the RS2000 in the mid 90's, the I4 engine went on to more workaday applications, later appearing the Ford Galaxy MPV, launched in 1995 as the result of a collaboration with Volkswagen/Seat. By this time, a longer-stroked 2.3-litre 16-valve version of the engine was available alongside the original 2.0 which was still available in both 8-valve and 16-valve versions. This 2.3-litre unit also found its way into the Ford Scorpio and the Ford Transit van. The I4 remained the main petrol unit for the original Galaxy until the all new Ford only car replaced it in 2006, powered by the newer Duratec engine.

8v engine Specifications

N8A

N9A

N9C/N9E/NSE/N9D

16-valve engines

N7A

N3A

Y5A/Y5B

See also

  1. ↑ Maximum continuous engine speed: 5950rpm
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