Ford I4 DOHC engine

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1 Summary
2 History
3 Transverse installation
4 8v engine Specifications
5 16 valve engines
6 Gallery
7 See also

[edit] Summary

The Ford I4 DOHC engine was a 4-cylinder inline internal combustion engine with twin overhead camshafts, produced by the Ford Motor Company. 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 first generation Ford Galaxy in 2000. 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 RS2000.

[edit] History

The I4 was originally designed to replace the ageing US-designed 2.0L OHC Ford Pinto engine, derivatives of which had powered most of Ford's four cylinder rear-wheel drive cars since the 1960's, 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. However with the Sierra in its twilight years, and the new bigger Mondeo ultimately destined to replace both Sierra and Scorpio, and with the forthcoming Mondeo having been developed around the new Zetec unit, it is conceivable that Ford knew the engine would have a relatively short production life, and chose to keep investment costs low.

[edit] 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. How much of this similarity was intentional is hard to say, but Ford would have to have been aware of the huge success enjoyed by the Astra, and the amount of credit its engine was given for that success. Certainly 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 bored out 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.

[edit] 8v engine Specifications

Two valves per cylinder with hydraulic valve lifters
Twin camshafts driving by a timing chain
Stroke and bore were both 86 mm (3.4 in)
Compression was 10.3:1
Five main crankshaft bearings

[edit] N8A

Carbureted
Power: 107 hp (80 kW) at 5600 rpm.
Torque: 174 N·m (128 ft·lbf) at 3000 rpm.
Redline: 6050 rpm

[edit] N9A

Electronic fuel injection (Batched multi-point)
Power: 123 hp (92 kW) at 5500 rpm.
Torque: 174 N·m (128 ft·lbf) at 2500 rpm.
Redline: 5950 rpm

[edit] N9C/N9E/NSE

Electronic fuel injection (Batched multi-point)
Catalytic converter
Power: 118 hp (88 kW) at 5500 rpm
Torque: 171 N·m (126 ft·lbf) at 2500 rpm.
Redline: 5950 rpm

[edit] 16 valve engines

[edit] N7A

Capacity: 1998 cc
Bore: 86.0 mm
Stroke: 86.0 mm
Compression: 10.3:1
Valvegear: Chain driven twin OHC. 16 valves. Hydraulic tappets.
Fuelling: EEC-IV controlled multi-point fuel injection
Power: 150 hp (110 kW) @ 6000 rpm
Torque: 190 N·m (140 ft·lbf) @ 4500 rpm

[edit] N3A

Capacity: 1998 cc
Bore: 86.0 mm
Stroke: 86.0 mm
Compression: 9.8:1
Valvegear: Chain driven twin OHC. 16 valves. Hydraulic tappets.
Fuelling: EEC-V controlled multi-point fuel injection
Power: 136 hp (101 kW) @ 6300 rpm
Torque: 175 N·m (129 ft·lbf) @ 4200 rpm

[edit] Y5A/Y5B

Capacity: 2295 cc
Bore: 89.6 mm
Stroke: 91.0 mm
Compression: 10:1
Valvegear: Chain driven twin OHC. 16 valves. Hydraulic tappets.
Fuelling: EEC-V controlled multi-point fuel injection
Power: 145 hp (108 kW) @ 5600 rpm
Torque: 202 N·m (149 ft·lbf) @ 4500 rpm

[edit] Gallery

Cylinder head without cam drive or valve lifters	Close-up of cam profile and valve lifter	The camshafts unmounted from the engine	The engine block with the cylinder head removed
The cylinder head, seen from its bottom side	The cylinder head with camshafts