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Lotus Service Notes
Exige S/C Page 8 Air is drawn from the standard air cleaner through the throttle body and adaptor and into the supercharger axial intake port. From the outlet port on the compressor top surface, the air is directed through a 'U' bend duct to the LH end of an air/air chargecooler rubber mounted above the engine, where airflow gathered from the roof duct is used to cool the compressed intake charge. The chargecooler uses four rubber bobbins attached to two mounting brackets themselves secured to the inlet manifold and cam cover. A charge air temperature sensor is mounted in the outlet tank of the chargecooler. The cooled air exiting from the RH end of the chargecooler flows via another 'U' bend duct into a cast alloy intake plenum/manifold. The whole intake tract has been kept as short as possible, and uses large diameter ducting and generously radiused bends to optimise airflow and efficiency to the particular benefit of throttle response and fuel economy. A re-shaped breather pipe is used to connect the crankcase breather spigot to the cam cover and circum- navigate the supercharger. On the 240R and Cup cars, a stainless steel 'level one' sports exhaust muffler (LOTAC05334) is fitted to provide an acoustic enhancement and features enlarged, slash cut tailpipes and a near 20% weight saving over the standard system. Exige S models use a stainless muffler with a single, oval shaped, tailpipe design. 240R models use 4 standard port fuel injectors together with an additional 5th injector mounted in the intake end of the inlet manifold. Cup cars use 4 special high-flow port injectors, and Exige S cars retain stand- ard injectors. The Lotus engine management system is reprogrammed to suit each engine specification and incorporates additional functions to control the fifth injector (240R) and supercharger by-pass valve. The boost characteristics have allowed the switching point from low to high lift cam profile to be reduced from 6,000 to 4,000 rpm (at normal running temperature). 240R models use a mechanical cable operated throttle body, whereas the Cup and Exige S cars use '06 model electronic throttle. Twin front mounted oil/air coolers are fitted to all supercharged Exige. Accusump - 240R & Cup 240 To provide protection against the possibility of oil starvation caused by the extreme g-forces possible with track use on slick tyres, the 240R and Cup cars are fitted with an Accusump oil storage system. A 2-litre Accusump reservoir is mounted in the rear luggage compartment, plumbed into the LH oil cooler return hose at the front of the engine bay, with the connecting hose routed over the RH rear wheelarch. The device comprises an alloy cylinder divided by a sliding piston, one side of which is connected to the engine oil supply, with the other containing pressurised air. With the engine running, the cylinder is charged with oil provided by the engine oil pump, but if the pressure should drop for a short period due to oil pump pick up pipe exposure during extreme braking or cornering events, the accumulator air pressure forces the stored oil into the engine lubrication system to maintain continuity of oil supply until normal conditions are resumed. A one-way valve at the oil cooler connection of the 'T'- piece ensures that the oil discharged from the Accusump is directed into the oil pump and not the cooler. An Electric Pressure Control (EPC) valve fitted at the connection to the Accusump cylinder, allows cylinder charging when oil pressure is above 35 - 40 psi, and cylinder discharging at engine oil pressures below 35 - 40 psi. The EPC is also linked to the ignition switch such that with the ignition switched on the valve is open to allow oil flow, and with ignition off the valve is closed to retain oil within the reservoir. Normal Operation When the ignition is turned on, the EPC valve on the Accusump is opened, allowing the pressurised oil stored in the reservoir to flow out into the engine and prime the oil galleries and bearings ready for start up. When the reservoir has been emptied, the pressure gauge on the end of the reservoir will indicate the pre- charge pressure which should be 7 - 15 psi. When the engine is started, engine oil pressure will force the reservoir piston back, such that the reservoir air pressure gauge will indicate engine oil pressure, with the quantity of stored oil dependent on this pressure at any one time. With cold oil, 80 psi may be seen, but idling at normal running temperature should produce around 30 - 40 psi. When the engine is stopped, the EPC valve closes and a quantity of oil pertaining to that oil pressure will be retained in the Accusump, ready for re-starting. Routine Checks Be aware that the indicated oil level on the dipstick will depend on the amount of oil stored in the Accu- sump, which itself is dependent on the both the Accusump pre-charge air pressure and the engine oil pressure when the ignition was switched off. sn_Exige Supercharged supplement.indd 8 03/03/2006 11:32:37 |