Manta 2.4
Introduction
This engine is being built for David Jackson, from England. It is to be installed in a modified 1979 Opel Manta B, and used for Hillclimb and Sprint events, as well as being driven on the road. The UK RAC Motorsports Association class rules, for Modified Production Saloon Cars, require that the car must use an engine block as originally specified by the manufacturer. In the case of this car, this is the Opel 2.0l CIH block. In fact, the Manta 400 16 valve engine would also be acceptable, since it was homolgated, but far outside my price range.
Short Engine Specification
The block is a 2.0l unit, which has been used for about 50,000 miles. This very important as the stress in the block, from manufacturing, will have been relieved. The block was bored and honed to allow installation of 0.50mm oversize pistons. The steel billet crankshaft was manufactured by Farndon Engineering Ltd, and has an 85mm stroke, and has two dowel pins as well as six bolts to hold the flywheel in place. The I-beam con rods are also manufactured by Farndon, having 55mm big ends, 22mm little ends, and are 137.1mm between centres. The pistons are modified 95.5mm Mahle pistons, used in the 2.4i Fronterra and 1988 Omega. As you have probably guessed, there is very little room left within the block. The crankshaft, flywheel and clutch cover have been balanced to race standard. the con rods and pistons have all been weight matched. The sump is baffled to keep the oil where it's needed.
We require an 11-1 static compression ratio for the engine, which will run Super Unleaded (98 Octane) petrol. The engine is designed around the work done by Peter Fisher, at SP Performance Centre, on the cylinder head. Therefore, the inlet valve pockets in the piston tops had to be enlarged, the exhaust valve pockets are unchanged. This also meant that the block, timing cover and piston tops needed to be skimmed to give the correct combustion chamber size. At this compression it is often a good idea to have the cylinder bore tops machined for copper wire rings, to enhance cylinder head gasket seal performance. The oil pump delivery pressure will be increased as required by the new configuration.
Cylinder Head Specification
The cylinder head originally came from a Vauxhall Carlton 2.2l engine. This head is very similar to the Manta head, except that the inlet ports sit higher in the head and has larger valves, so giving better airflow as standard. The design requirement for the head was that it should run on Super Unleaded Petrol, and should maximise the torque to be delivered by the engine throughout the rev range. With this requirement in mind, the head was given to Peter Fisher at SP Performance Centre. Peter is well known for his work on many different cylinder heads, but especially for his work in dramatically increasing the torque available from Ford Pinto engines. The "Manta SP1" special profile camshaft was manufactured by Kent from one of their OP camshaft blanks, this means that this camshaft is made from the same blank as say, a Kent OP234 camshaft. The camshaft profile and the cylinder head work comes as a complete package developed using the patented "Flow Passage Control" technology.
The final specification for the 2.2l head is as follows:
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Fuel System and Exhaust
The inlet manifold is a Ray West Racing 2.2L racing manifold, on which a pair of Weber 50DCOE are fitted. The tubular 4-2-1 exhaust manifold and two box system is 2.5" diameter, supplied by Ashley Performance Exhausts. When money allows the Weber carbs will be replaced by a set of 48mm Jenvey injection throttle bodies. I have no details about the injectors that will be used, at this time.
Timing, Ignition and Engine Management
The timing system uses the crankshaft pulley and timing sensor from the 2.4l Fronterra. An Emerald Distributorless Ignition Engine Management Unit is used to control the engine operation. This system uses a throttle potentiometer, coolant temperature sensor and air temperature sensor, together with the timing sensor data to provide a map with 8 load sites and 24 speed sites, which are altered for air and coolant temperature. The speed sites are in 500rpm steps up to 12,500rpm, and the load sites are evenly spaced between idle and full throttle. This management system has both a soft and hard rev limiter. The distributor has been cut down, so removing the distributor head, and plated over. What remains of the distributor unit is only used to drive the oil pump
Cooling System
The cooling uses the thermostat housing from the Carlton 2.2l, which is connected to a modified 2.0l 8V Vauxhall Astra radiator with a 4 row staggered core. The water pump pulley diameter has been reduced, due to the bigger diameter of the Fronterra crankshaft pulley. This will mean that the pump will run slightly faster, but hopefully not too fast to cause cavitation. The oil is cooled by a 13 row oil cooler, which has thermostatic control. The radiator air intake has been made bigger and boxed in, and the oil cooler sits directly in the airflow to the radiator.
Conclusions
This engine is not yet been complete, but will be installed and running before the new season starts in March 2000. I have no figures yet, but this engine is expected to give BIG torque, over a wide rev band, with good driveability at low rpm. The quality of the components used should easily allow the engine to rev to 7000 rpm, but this should not be necessary. However, since this is a development project, there are no guarantees, and expectations mean nothing until the engine is completed, and tested.
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