Alfa Romeo Twin Cam engine

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Alfa Romeo Twin Cam engine
Festival automobile international 2011 - Vente aux enchères - Moteur Alfa Romeo TZ - 1965 02.jpg
Overview
Manufacturer Alfa Romeo
Designer Giuseppe Busso
Also called Nord engine
Production 1954–1994
Layout
Configuration I4
Displacement 1.3 L (1,290 cc (78.7 cu in))
1.3 L (1,357 cc (82.8 cu in))
1.6 L (1,567 cc (95.6 cu in))
1.7 L (1,749 cc (106.7 cu in))
1.8 L (1,773 cc (108.2 cu in))
1.8 L (1,779 cc (108.6 cu in))
2.0 L (1,962 cc (119.7 cu in))
Cylinder block alloy aluminium alloy
Cylinder head alloy aluminium alloy
Valvetrain DOHC 2 valves per cylinder
(some racing heads had 4 valves per cylinder)
Combustion
Fuel type Gasoline
Oil system wet sump
Cooling system Watercooled
Chronology
Predecessor Alfa Romeo 1900 I4
Successor Alfa Romeo TwinSpark

The Alfa Romeo Twin Cam engine is an all-alloy Inline-four engine series produced by Alfa Romeo from 1954 to 1994. In Italian it is known as the "bialbero", and has also been nicknamed the "Nord" (North) engine in reference to its being built in Milan in the North of Italy and to distinguish it from the Alfa Romeo Boxer engine built in the South (Sud) for the Alfasud.

History[edit]

The Twin Cam's predecessor appeared in the 1950 Alfa Romeo 1900 and was an under-square inline four cylinder with a cast-iron block, an aluminium alloy cylinder head with double overhead cams and a 90° included angle between intake and exhaust valves. Development of that engine was overseen by Orazio Satta Puliga who would also helm development of its successor. The 1952 Disco Volante had a 2 litre DOHC four cylinder engine with an aluminium block and sleeves, but this seems to have been a custom version of the 1900 engine rather than a prototype of the forthcoming Twin Cam. While the Twin Cam shared some features with the 1900 engine, it was a new design by Giuseppe Busso.[1]

The Alfa Romeo Twin Cam engine debuted in the 1954 Giulietta. The engine featured:

These features made the Twin Cam an advanced design for a production car engine of the mid-1950s and would, with minor variations, form the basis of all future versions of the engine.

The engine displaced 1290 cc in the 1954 Giulietta.[2] In 1960 another version of the Twin Cam was unveiled along with the Alfa Romeo Tipo 103 small car prototype.[3] This version was noteworthy because, with a bore of 66 mm, a stroke of 65.5 mm and displacing just 896 cc, it was the smallest four-cylinder Twin Cam ever. Power was 38.8 kW (52 hp) at 5500 rpm. In adapting the engine to the transverse front-engine, front-wheel drive application the engine block and transaxle case were built as one unit. Only three of these engines were built.

On June 27, 1962 a larger Twin Cam appeared in the just-released Giulia.[4] The obvious change was that displacement was increased to 1567 cc, but the engine was also now being produced using a different casting method. The diameter of the valve stems had been increased by 1 mm to 9 mm, the bore centre spacing was different, the timing chain longer and the crank had been revised, among other changes.[5]

In 1968 the engine was again enlarged, this time to 1779 cc, for the 1750 GTV and 1750 Berlina.[6] Additional changes to this version included offsetting the big-end bearings on the connecting rods, and adding sodium-filled exhaust valves.[5] In 1971 a 1962 cc version was introduced for the 2000 GTV and 2000 Berlina. This largest production Twin Cam also had fewer teeth in the ring-gear and 6 bolts holding the flywheel instead of 8.[5]

When the engine was adapted for use in the Alfetta in 1972, this necessitated a new oil pump and a change away from the finned sump used in the 105-series cars.[5] While this was an aesthetic loss it may have been beneficial in other ways, as some owners reported that the old sump kept the engine and oil so cool that in cold weather it was sometimes necessary to block off the radiator airflow to raise the coolant temperature enough for the interior heater to be effective. Since the Alfetta also used a rear-mounted transaxle, there was no need for a pilot bearing in the engine.[5]

The Twin Cam was the first production automobile engine to employ a form of Variable Valve Timing (VVT).[7] The system that appeared on the 1980 Spider was an electro-mechanical system employing a variator to alter the phase but not duration of the intake camshaft.

Competition variations and specials[edit]

Alfa Romeo's Autodelta competition arm produced a multiplicity of variations on the Twin Cam for different racing classes and cars including the racing oriented GTA. Displacements ranged from a 1283 cc over-square version with an 84 mm bore and 57.9 mm stroke up to a 2056 cc version with an 86 mm bore and 88.5 mm stroke. Many of these engines used dual ignition systems (see "Twin Spark").

Even though Alfa Romeo never sold a production version of the Twin Cam with more than 8 valves, at least two 16 valve cylinder heads were available. A number of Autodelta engines had them, and another 16-valve head was developed by the tuner Franco Angelini.

Some Autodelta cylinder heads had an included angle between the intake and exhaust valves narrower than the 80° used in the majority of the production engines. These heads are called "testa stretta" (narrow head).

Some engines also had what was called a "monosleeve" liner, where all four cylinder bore liners are cast side-by-side in a single piece.

The 1959 Asardo 1500 AR-S was a one-off non-Alfa prototype that used a custom-built version of the Twin Cam. Starting with a 1290 cc block the bore was increased to 79.5 mm by using custom pistons and wet liners from Mahle so that its final displacement was 1,489 cc (90.9 cu in) and power was 100.7 kW (135 hp).

Forced-induction versions[edit]

In 1967 the Alfa Romeo GTA SA debuted at the Geneva Motor show. Built by Autodelta, the 1567 cc Twin Cam engine was boosted by two superchargers driven by an engine-powered oil pump. Power was reported to be 164.1 kW (220 hp).[8]

In 1979 the Alfa Romeo GTV Turbodelta was released. The 2 litre engine was augmented by a KKK turbocharger blowing through a pair of Dellorto DHLA40H pressurised carburettors and produced 111.9 kW (150 hp) in normal tune[9]. This car was only offered until 1981 when Alfa Romeo left Group 4 to concentrate on Formula 1. 400 were built.[10]

In 1984 Alfa released the Giulietta Turbodelta. Equipped with a 1962 cc Twin Cam, dual carburetors and an Alfa Avio turbocharger the engine produced 125 kW (170.0 PS; 167.6 hp).[11]

In 1986, a turbocharged version of the 1779 cc single-plug engine developing 167 PS (123 kW; 165 bhp) was used to create the Alfa Romeo 75 1.8 Turbo Quadrifoglio.[12] In Group A touring car racing form this engine made up to 223.7 kW (300 bhp).

Twin Spark[edit]

Alfa Romeo Twin Spark engine

Alfa Romeo's Twin Spark technology used dual ignition to fire two spark plugs in the cylinder head of each piston bore and was first used in the A.L.F.A. Grand Prix car of 1914. Racing versions of the Giulia engine, including the engine used in the GTA, featured a cylinder head with two spark plugs per cylinder. Twin Spark versions of the Twin Cam were also developed for 1750 and 2000 models used for racing.

In 1987 the production Alfa 75 2.0 Twin Spark was fitted with a Twin Spark head, which provided improved fuel ignition and allowed an improved combustion chamber shape with narrower angle between intake and exhaust valve. Although developed from the Twin Cam, few if any parts are interchangeable between Twin Spark engines and Twin Cams. For instance, while Twin Cams have six oilways leading to the cylinder head the Twin Sparks only have two, the timing chain cover is narrowed and the included angle between the valves is down to 46°.[5] The Twin Spark engine in the 75 also employed Alfa's variatore di fase VVT system which, when combined with electronic fuel injection, gave a power output of 148 PS (109 kW; 146 bhp).

The last examples of the Alfa Twin Cam were the 1749 cc, 1773 cc and 1995 cc 8V Twin Spark engines featured in the 155 and 164. After 1995 the 155 featured the 16-valve Twin Spark which, although sharing features with the previous engine, is a different design that is a member of Fiat's "Pratola Serra" engine series, while the 164 continued with the 8-valve Twin Spark until the end of production in 1997.

The production of the Alfa Romeo Twin Cam ended in 1997, by which time it had been gradually replaced since 1995 by the newer Fiat-based 16-valve Twin Spark engines.

Production sizes and applications[edit]

Year Bore (mm) Stroke (mm) Displacement Notes Models
1954 74 75 1,290 cc (78.7 cu in) Giulietta, Romeo, Giulia, Spider
1962 78 82 1,567 cc (95.6 cu in) Giulia, Giulia TZ, Gran Sport Quattroruote, Alfetta, Spider, Giulietta, 75
1968 80 88.5 1,779 cc (108.6 cu in) 1750 Berlina, 1750 GTV, Alfetta, Spider, 90, Giulietta, 75
1970 84 88.5 1,962 cc (119.7 cu in) 2000 Berlina, 2000 GTV, Alfetta, Spider, 90, Giulietta, 75
1977 80 67.5 1,357 cc (82.8 cu in) Giulietta
1986 80 88.5 1,779 cc (108.6 cu in) Turbocharged 75
1987 84 88.5 1,962 cc (119.7 cu in) Twin Spark, VVT 75, 164
1992 84 80 1,773 cc (108.2 cu in) Twin Spark, VVT 155
1992 84 88.5 1,995 cc (121.7 cu in) Twin Spark, VVT 164, 155
1993 83.4 80 1,749 cc (106.7 cu in) Twin Spark 155

See also[edit]

References[edit]

  1. ^ "GIUSEPPE BUSSO, 1913-2006: A TRIBUTE TO ALFA ROMEO AND FERRARI'S GREAT ENGINEER". www.italiaspeed.com. 
  2. ^ "Alfa Romeo's Alloy Twin-Cam". www.hemmings.com. 
  3. ^ Tipler, John (June 2000). Alfa Romeo Berlinas. Veloce. ISBN 978-1901295740. 
  4. ^ "Automotive History: Alfa Romeo Twin Cam Four – A Pioneer, And As Beautiful As The Cars It Powered". www.curbsideclassic.com. 
  5. ^ a b c d e f "Alfa Romeo twin cam engine from 1954 until 1997". www.alfaworkshop.co.uk. 
  6. ^ "EVOLUZIONE DELLA SPECIE" (in Italian). Archived from the original on 5 March 2016. Retrieved 2017-07-15. 
  7. ^ "Variable Valve Timing (VVT)". www.autobytel.com. 
  8. ^ "Alfa Romeo Giulia GTA SA". www.alfaworkshop.co.uk. 
  9. ^ Louie, Lane (2013). Alfa Romeo Alfetta Turbodelta Gruppo 4 - Complete Technical Specifications. Loutho. p. 143. ISBN 978-0-9922707-0-4. 
  10. ^ "Alfa Romeo Alfetta GTV Turbodelta (1979-1981)". lautomobileancienne.com (in French). 
  11. ^ "1984 Alfa Romeo Giulietta Turbodelta". www.automobile-catalog.com. 
  12. ^ "Alfa Romeo 75 1.8 Turbo Quadrifoglio". www.carfolio.com. 

Further reading[edit]

  • Owen, David (1979). Alfissimo! The postwar four cylinder twin-overhead camshaft Alfa Romeos: 1900, Giulietta, Giulia, Alfetta, New Giulietta. London: Osprey. ISBN 9780850453270. 
  • Adriaensens, Tony (1994). Alleggerita. Belgium: Corsa Research vzw. ISBN 978-9080119710. 
  • Braden, Pat (1 Jan 1995). Alfa Romeo Owner's Bible 1954 on. Bentley (Robert) Inc., US. ISBN 978-0837607078. 
  • Kartalamakis, Jim (24 November 2002). How To Power Tune Alfa Romeo Twin Cam Engines. Veloce Publishing. ISBN 1-903706-60-2. 
  • Braden, Pat (1 July 2004). Alfa Romeo All-Alloy Twin Cam Companion: 1954-1994: Four Cylinder History, Care and Restoration: Giulietta, Giulia and Alfetta Families. Bentley (Robert) Inc., US. ISBN 978-0837602752. 
  • Busso, Giuseppe (May 2005). Nel cuore dell'Alfa (in Italian). Automobilia. ISBN 9788879601610. 
  • Kartalamakis, Jim (28 Aug 2013). Alfa Romeo DOHC High-performance Manual. Veloce Publishing Ltd. ISBN 978-1845840198. 
  • Louie, Lane (2013). Alfa Romeo Alfetta Turbodelta Gruppo 4 - Complete Technical Specifications. Loutho. ISBN 978-0-9922707-0-4.