The C20XE came into production as an evolution of the 1987 C20NE engine. The 20XE (Bosch Motronic 2.5) first saw the light of day in 1987 with the launch of the Opel Kadett GSI 16v, introducing 16-valve technology and Knock Sensors Opel/Vauxhall lineup. In 1988 the C20XE was introduced, with a 150 PS (110 kW) output compared to the earlier 20XE's 156 PS (115 kW). The C20XE was fitted with a catalyst and oxygen sensor in the exhaust. This was due to new emission standards, which forced manufacturers to specify their cars with a catalytic converter and a lambda sensor - this requirement permitted the fitment of a new generation of Engine Management Systems (Bosch Motronic 2.5).
The C20XE engine featured in many Opel/Vauxhall vehicles including some models of the Opel Astra/Kadett E and the Opel Calibra/Vectra. Enthusiasts commonly refer to this engine as the 'Red Top' (or just 'XE') because of the appearance of the red L-shaped spark plug cover.(This was red, but black colours are available, and the rocker cover was only available in silver). At the time of its launch, this engine was something of a milestone unit in Europe and was widely used in motorsport in many specialist race versions. It is still revered and sought after by enthusiasts today, nearly two decades later. A version of the engine also appeared in Lada cars in the late 1990s.
The C20XE served as the base for the turbocharged C20LET, which appeared in versions of the Vauxhall Cavalier/Opel Vectra and the Vauxhall/Opel Calibra. The C20LET was identical on the surface, apart from a black plastic plenum/'top hat' shroud with a 'turbo' script. This version features forged, lower compression Mahle pistons, and offers a 34% increase of power over the C20XE (204 PS (150 kW; 201 hp)).
Some versions of the engine implemented switchable Traction Control (commonly included in the early Astra GSi models). The inlet had a secondary throttle valve sandwiched underneath the primary throttle body. This is closed by a motor/arm assembly when the traction control ECU senses loss of grip/spin at the wheels. The engine was also equipped with a different throttle position sensor (six pin, as opposed to three), and a different coolant temperature sensor (which was black, as opposed to the normal light blue colour).
In its last version before production ended, the C20XE came with a new engine management system which included a distributorless ignition system, namely Bosch Motronic 2.8. The last version was called C20LN (Low Noise) and has a stronger engine block. The engines that appeared in the early 90's also swapped the cast metal spark plug cover for a cheaper (and less regarded) plastic version.
The 20XE has now evolved into a large family of GM 16v engines, one of which is a 2.2 l (134.3 cu in) 16v chain driven engine found in many GM brands, including Saab, Pontiac, Saturn, Chevrolet and Oldsmobile. It was borrowed by Fiat and Alfa Romeo, for the Croma and the 159, respectively.
All of the 2-litre engines of this era share the same cast-iron engine block, with the exception of the oil return for the turbo on the C20LET.
The engine was designed by Dr Fritz Indra, who was head of Advanced Engine Development for Opel in Germany from 1985 to 1989. The engine was originally intended for race application, hence Cosworth's involvement.
'COSCAST' (Early) and GM (Later) head differences
The C20XE's cylinder heads came in two notable forms. The original version, which first appeared in the Astra GTE, Calibra and Vauxhall Cavalier/Opel Vectra between 1988 and 1991, was cast by Cosworth and was marketed under the name 'Coscast'. In 1991, the Coscast items were replaced by GM manufactured heads, which first appeared in the Astra GSi. One of the most prominently recognised qualities of the 'COSCAST' head is its inherent lack of porosity; this was achieved by pumping the liquid metal into the mold rather than pouring it, hence, minimizing the presence of tiny air bubbles that usually form during the standard casting process. The Coscast head can be identified by a 'Coscast' logo which is stamped under the 3rd exhaust port and a ridge on the head under the distributor. The GM head was manufactured by Kolben-Schmidt  and featured a slightly different oil/water gallery design. These design changes required that a pair of welsch plugs be pressed in at either end of the head. In situations where a complete C20XE is still fitted to a vehicle, the presence of welsch plugs (or lack of) has proven to be the sole means of differentiating between GM and Coscast heads. A reinforced version of the GM head became available in the later years of the C20XE; however, these reinforcements meant that it had smaller inlet/exhaust channels than the other two.
Since an engine's oil circulates at much higher pressures than its coolant, oil in a porous head has a tendency to gradually seep into the coolant galleries. A typical symptom of a porous head is usually a 'mayonnaise'-like substance forming somewhere inside the cooling system (usually, this can be found residing on the coolant reservoir cap). However, depending on the degree of porosity, symptoms of a porous head have a tendency to vary. Many C20XE operators have described the symptom as a curry-like residue or in more severe cases, a thick brown sludge which may overcome the entire cooling system. In such instances, engine oil will readily react with the sulfur in rubber components, hence quickly degrading coolant pipes and hoses to the point of failure. During the porous head debacle, GM faced bankruptcy - therefore dealers failed to recall affected models. Due in part, to the engine's immense prominence and demand, many businesses now specialise in the repair of porous GM C20XE/LET heads - by either sleeving the affected gallery or by injecting a polymer based substance into the porous region. Reportedly, a small number of total GM C20XE cylinder heads ever exhibited significant symptoms of porosity.
The early engines used round tooth cambelts while the later used square (with a plastic pre-tensioner). There are also subtle differences between the crankshaft, and visible difference in the pattern of the SFi airbox.
The C20XE has seen extensive use in motorsport. Typical uses for the engine have ranged from hillclimb events, to open wheel racing categories. Despite its age, it remains the powerplant of choice for many Formula 3 teams and has most recently found acclaim in the Australian F3 scene where Tim Macrow, the 2007 Australian F3 champion, drove an Opel-Spiess powered car to claim victory. Tuned by Spiess, an F3 grade C20XE is easily capable of producing 250 bhp (190 kW) in its naturally aspirated form.
Many aftermarket tuners have further developed the C20XE for racing purposes. SBD Motorsport, an aftermarket tuning company based in the UK, developed a C20XE unit with a power output in excess of 290 bhp (220 kW). QED Motorsport is another such company that have had a huge involvement with the C20XE. They developed the first aluminium block for the engine giving a massive 19 kg weight saving over the standard block and the potential for 2.3 litres of capacity! QED also developed the first direct-to-head throttle bodies, allowing for greater performance in highly tuned motorsport applications as well as other enhancements. Typically, both QED Motorsport and SBD built engines have seen use in Westfield and Caterham vehicles competing in various hillclimb events.
The C20XE was used by the Chevrolet WTCC (World Touring Car Championship) team and the Lada WTCC team. The engine was also an option in Westfield kitcars.
The C20XE and C20LET variation have been retro fitted into many other Opels including the Corsa, Tigra, Omega, Ascona, Manta, Vectra and others. The majority of these conversions/transplants are made possible by the extensive range of products offered by various motorsport manufacturers.
The C20XE is also a popular choice for many people that want a 16v engine in their mini, due to its relatively compact arrangement (with gearbox) and its cost effectiveness. The C20XE engine can also be fitted to the MkI and MkII Ford Escort models using Sierra 2litre "Pinto" gearbox and running gear, this is a popular modification for the race enthusiast. This is also a popular powerplant in hot rods and kit cars.
The breakdown of the engine name is as follows:
- C - Exhaust Emissions Level: ECE R 83 A
- 20 - Displacement: 2 litres
- X - Compression Ratio Threshold: X = 10.0-11.5:1
- E - Mixture System: Electronic Fuel Injection
The engine produces 150 bhp (112 kW; 152 PS) at 6,000 rpm, with a low optimum specific fuel consumption of 232 g/kWh which is equivalent to a maximum efficiency of 37%; a better efficiency than some of the diesel engines that were available at the time of its release. The valves are set at 46° and are accompanied by pistons with shallow valve pockets - thereby eliminating the need for a shorter connecting rod hence, allowing a suitable compression ratio to be achieved. Long spark plugs are used and positioned concentric to the cylinder. The later engine were suffixed C20XELN to indicate 'Low Noise' revisions (smaller cylinder head port, cast pistons, and different crank bearing size) in line with EU regulations. The engine has a square bore/stroke and shares piston dimensions with the Bugatti Veyron (86 x 86 mm).
|Number Of Cylinders||4|
|Displacement||1,998 cc (121.93 cu in)|
|Bore||86 mm (3.386 in)|
|Stroke||86 mm (3.386 in)|
|Power||150 bhp (111.9 kW; 152.1 PS) @ 6,000 rpm|
|Torque||196 N·m (145 lb·ft) @ 4,800 rpm|
|Engine management||Bosch Motronic 2.5/Bosch Motronic 2.8|
|Idle speed||800-900 rpm|
List of cars fitted with C20XE
|Opel Calibra 16V||1989–1994||Europe, Australia, Brazil, South Africa|
|Opel Kadett E, GSI/GTE||1988–1992||Europe - Germany, Ireland, South Africa|
|Opel Vectra A, GTE||1988–1995||Europe, New Zealand|
|Opel Astra F||1991–1996||Europe, Australia, South Africa|
|Vauxhall Calibra 16V||1989–1994||UK|
|Vauxhall Astra Mk 2, GTE||1988–1992||UK|
|Vauxhall Cavalier Mk 3, GSi, SRi||1988–1995||UK|
|Vauxhall Astra Mk 3, GSi||1991–1994||UK|
|Lada 110||1996 -||Europe, Russia|
|Chevrolet Vectra GSi||1993–1996||Brazil|
- "C20XE conversion list". Robbie's Manta Site. Archived from the original on 2007-10-08. Retrieved 2007-07-05.
- "Interview with Dr Fritz indra" (PDF). www.CalibraWiki.com. Retrieved 2008-04-13.
- "Benefits of Coscast head". Retrieved 2010-11-15.
- "What engines are affected with porous heads". Retrieved 2010-11-15.
- "Detailed GM & Cosworth difference photos". Vauxsport. Retrieved 2008-04-13.
- "Porous GM Head Info". Scoobler. Retrieved 2008-04-22.
- "SBD Website". 290+ Taper Throttle Kit. Retrieved 2008-05-25.
- "QED Motorsport Aluminium Block". 'qedmotorsport.co.uk'. Retrieved 2009-04-07.
- "QED Motorsport Direct-To-Head Throttle Bodies". 'qedmotorsport.co.uk'. Retrieved 2009-04-07.
- "QED Motorsport - C20XE". 'qedmotorsport.co.uk'. Retrieved 2009-04-07.
- "Engine Codes Explained". Topbuzz Website. 2002. Retrieved 2007-07-05.