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| Ford I4 DOHC | |
|---|---|
 2-litre 16 valve DOHC in Ford Scorpio | |
| Overview | |
| Manufacturer | Ford Motor Company |
| Production | 1989–2006 |
| Layout | |
| Configuration | Naturally aspiratedI4 |
| Displacement | 2.0 L (1,998 cc) 2.3 L (2,295 cc) |
| Cylinder bore | 86 mm (3.39 in) 89.6 mm (3.53 in) |
| Piston stroke | 86 mm (3.39 in) 91 mm (3.58 in) |
| Cylinder block material | Cast iron |
| Cylinder head material | Aluminium |
| Valvetrain | DOHC, 2 or4 valves × cyl. |
| Compression ratio | 9.8:1, 10.0:1, 10.3:1 |
| Combustion | |
| Fuel system | Carburettor (N8x only) Multi-point fuel injection |
| Management | FordEEC-IV,EEC-V |
| Fuel type | Petrol |
| Oil system | Wet sump |
| Cooling system | Water-cooled |
| Output | |
| Power output | 107–150 hp (80–112 kW) |
| Torque output | 171–210 N⋅m (126–155 lb⋅ft) |
| Emissions | |
| Emissions control systems | Catalytic converter (N9C/N9D/N9E/NSD/NSE) |
| Chronology | |
| Predecessor | Ford Pinto engine |
| Successor | Ford Duratec engine |
TheFord DOHC engine is aninline 4-cylinder (I4) automotiveinternal combustion engine withdual overhead camshafts (DOHC), produced by theFord Motor Company. Offered from 1989 until 2006, it was initially available as a 2.0-litre 8-valve engine, and later in 2.0 and 2.3-litre 16-valve versions. It powered various Ford models in bothfront wheel drive andrear wheel drive applications. It was Ford's first in-housetwincam engine design to reach volume production.[1]
In Ford's technical reference the engine is given the somewhat anonymous designation of "DOHC".[2] Some sources call it the Sierra engine, but only when used in that car, and in some enthusiast forums it is known informally as the "twincam", or the "twink". Its lack of recognition extends to the aftermarket, as few tuning shops offer options for the engine, and it does not appear in Ford's own list of four-cylinder racing engines.[3][4]
The engine was designed to replace the 2.0-litre OHCPinto engine, which by the late 1980s was lagging behind the competition in terms of power output, efficiency and refinement. Apart from the inline configuration and approximate displacement, the DOHC shares nothing with the Pinto engine, and is described as a "clean sheet" design.[5][6]
The DOHC was produced at Ford'sDagenham Engine Plant inLondon.[1]
In late 1989, the DOHC was launched in 8-valve form in the rear-wheel driveFord Sierra, Sierra Sapphire, andScorpio (in the United Kingdom and Ireland, the MkI Scorpio retained the previous model's name and was sold as theFord Granada MkIII). In these cars it was mated to either the new all-synchromeshMT-75 5-speedmanual transmission or the existingA4LD four-speedautomatic. The engine received mixed reviews, being seen as an improvement over the Pinto, but not the leap forward expected.[1]
The MkV Escort had been launched in 1990 to disappointing reviews, and Ford were looking to boost the image of this critically important range. To that end they introduced two high-performance Escorts to compete in thehot hatch market, using the well knownRS2000 andXR3i badges. The RS2000 debuted in 1991, with the DOHC mounted transversely in a FWD application using a revised block with different mount locations.[7] Engines in these cars also received a newmultivalve cylinder head and tubular exhaust manifold. In the Escort RS2000 16V, the 2.0-litre DOHC developed 150 PS (110 kW; 148 bhp).[8] The XR3i followed in 1992 with the choice of two 1.8-litre versions of the newZeta engine.[7]
The Sierra was discontinued in 1993 and the RS2000 in 1996, but the DOHC continued in use in theFord GalaxyMPV launched in 1995. By this time, a 2.3-litre 16-valve version of the engine was offered alongside the original 2.0-litre in both 8-valve and 16-valve versions. The 2.3-litre also appeared in theFord Scorpio and theFord Transit van. The DOHC remained the main petrol engine for the original Galaxy until its 2006 redesign, after which production of the DOHC ended.
All DOHC engines have acast iron block and an aluminium cylinder head.[9][6] Thesump is also of cast aluminium with built-in webs and serves to stiffen the whole engine assembly. The block has five main bearings for the crankshaft.[2]
The two overhead camshafts are driven by atiming chain. Each camshaft has five bearings.[2] The camshafts operate the valves and dual valve springs throughhydraulic tappets.
The oil pump is driven off the crankshaft by a single roller chain.[2]
The 8-valve, 2.0 L DOHC is a "square" engine, with bore and stroke measuring the same at 86 mm (3.39 in). There are twovalves per cylinder. The compression ratio is 10.3:1 in early engines, and was reduced to 9.8:1 in some later applications. The intake camshaft profiles for carburettor and injection engines are different, while the exhaust camshafts are the same.
The 16-valve 2-litre engines replaced the 8-valve cylinder head with a new 16-valve assembly.Bore and stroke are unchanged from the 8-valve engine.
An enlarged, slightlyundersquare version of the engine was developed with bore × stroke increased to 89.6 mm × 91 mm (3.53 in × 3.58 in), for a total displacement of 2.3 L (2,295 cc). The 2.3-litre engine also received a cylinder block stiffened by additional webbing, a split-mass flywheel, and a revised intake system.[10]
Another change for the 2.3-litre was the addition of two enginebalance shafts located in an enclosure bolted to the bottom of the cylinder block, with a revised sump below that. The shafts were driven from the oil pump drive chain, made longer for the purpose. The system was developed jointly by Ford of Europe,Cosworth Engineering, andFEV Motorentechnik [de].[11][12] With rubber-coated teeth on the balance shafts and the other changes to the engine, interior noise was reduced by 6 decibels.[10]
The DOHC is reported to exhibit certain weaknesses or be prone to particular types of failures, without specifying whether they are the result of design flaws or poor maintenance.[13][5][9] These issues may include:
