Opel CIH

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Photo of the 1.9 L CIH engine (19S) of a Manta-B . The valve chamber cover has been removed, the valve drive is exposed

The Camshaft in Head engines from Adam Opel AG are an engine series used in Opel cars from 1965 to 1995 .

history

The CIH engine family was developed by General Motors (GM) USA in Detroit ( Michigan ) in the early 1960s . At the GM subsidiary Opel, the CIH engines with their overhead camshaft (CIH in German camshaft in the cylinder head ) replaced the OHV engines with a side (underneath) camshaft that had been used until then ; these were still based on the engines of the Opel Super 6 and Admiral from 1937 and no longer met the requirements - especially in terms of speed and smoothness.

CIH the motor technology was introduced in 1965 with the record B and 2.8 liter engines of the captain A / A Admiral . Until 12/1993 with the end of the Omega / Senator series, it was used in various displacement variants for almost 30 years.

As the successor to the CIH engine, OHC engines with a cross-flow cylinder head made of light metal and an overhead camshaft with a toothed belt drive were used in the Opel Kadett D and Ascona B. The new engines were more revving, more economical and had better emissions. Modifications of this were then offered in the Opel Rekord E 1.8N, 1.8S and 1.8i models. With the new Omega , the "real" OHC engines with light metal cylinder heads based on the CIH engine design finally prevailed at Opel.

The last Opel models with CIH engines were the Frontera 2.4i, the Opel Omega A 2.4i, 2.6i and 3.0i and the Senator B 2.6i and 3.0i.

The following displacement variants have been built over the years:

  • 4 cylinders:
1.5 liters of regular gasoline
1.6 liters of regular and premium petrol
Calls:
1.7 liters of regular and premium petrol
1.9 liters of regular and premium gasoline ( carburetor and injection variants )
2.0 liters of regular and premium gasoline (carburetor and injection variants)
2.2 liters of premium gasoline (injection)
2.4 liters of premium gasoline (injection)
  • 6 cylinders:
2.2 liters of regular gasoline (only carburettor version)
2.5 liters of regular and premium gasoline (carburetor and injection variants)
2.6 liters of premium gasoline (injection)
2.8 liters of regular and premium gasoline (carburetor and injector)
3.0 liters of premium gasoline (carburetor and injector)
3.6 liters of premium petrol (injection)> Irmscher
3.9 liters of premium gasoline (injection)> Mantzel (including Bitter SC 3.9)

technology

The camshaft of the CIH engines is next to the valves in the cylinder head and is driven by a duplex roller chain with a hydraulic chain tensioner . It operates the hanging valves in a row via the tappet and rocker arm . The overhead camshafts of many other OHC designs , on the other hand, enable even higher speeds because their valve trains only use rocker arms or tappets, i.e. have fewer moving parts.

Adjusting the valve clearance

To adjust the valve clearance , the rocker arm pivot point is moved up or down on an adjustable tie rod. The threads of the tie-rod nuts are self-locking and can be adjusted without a lock nut . With the CIH engines (without hydraulic valve lifters) the valves can be adjusted while the engine is running due to the camshaft that is largely covered at the top and the low-lying rocker arm pivot point. Hydraulic valve lifters with automatic valve clearance compensation were later used, meaning that valve clearance did not need to be adjusted. Opel was one of the first manufacturers to introduce this simplified maintenance in the mass market.

Further features of the CIH motors are short-stroke and greater freedom of rotation along with a favorable torque curve . In later versions, so-called “ rotocaps ” ensured a small rotation with each valve stroke, which was intended to prevent the valves from striking their seats. The cylinder head and the engine block are made of gray cast iron .

The disadvantage of the design was the continued use of the counterflow cylinder head : the inlet and outlet sides were both arranged on the right in the direction of travel, which in principle causes higher fuel consumption due to the poorer flushing of the combustion chamber .

Since the fuel supply was directly above the exhaust manifold in the CIH engine, the fuel hoses quickly became porous as a result of its heat radiation . These leaks could result in an engine fire. Another known weak point of the series was the water pump , which seldom lasted more than 60,000 km and sometimes failed after barely more than 30,000 km. It essentially suffered from a too small bearing on the belt side and a sealing problem on the impeller side. A low delivery rate and the poor arrangement in the air flow (installed lengthways) caused a poor cooling effect. The motor could overheat at high loads. In particular, the S and H engines (engines with high (super) and particularly high compression), the 1.7 liter (83 hp), the 1.9 liter (90 and 106 hp) and 2.0 liter (100 HP) were affected by cooling problems to a noticeably greater extent than the weaker N engines (regular gasoline). In later years there was a remedy in the form of modified water pumps from third-party suppliers with improved bearings for the pump shaft, the installation of which made damage to the cooling circuit a thing of the past. Opel and the factory representatives, however, never admitted to this problem, but participated economically in the flourishing market for replacing the notoriously weak water pumps and in repairs. For Opel customers, this was an expensive and annoying point over the entire construction period of the CIH engines.

source

  • Hans-Jürgen Schneider: 125 years of Opel, cars and technology , Verlag Schneider + Repschläger 1987 (without ISBN)

literature

  • Helmut Hütten: vehicle engines. Structure and mode of operation. (= Series of Adam-Opel-AG, No. 40) [Editor: Adam Opel Aktiengesellschaft, PR Program]