Mitsubishi Evo's FAQ's Pt3
If I fit the ACD monitoring kit can I tell what activity is happening while I drive?
No, the software strategies and the reaction time of the differential are so fast a log system is ultimately the only way to truly check and analyse the performance of the centre differential. Virtually all physical dashboard gauges of the VDO type are internally damped to stop the needles falling off during periods of intense activity. The pressure in the ACD system is altering in milliseconds so a manual gauge cannot reflect true activity within the system. BTR is working on production of a simple ACD analysis tool comprising an LED string, which will show the result of slip differentials between the front and rear axles. This will be in the form of a kit, the wiring for which will be “piggybacked” to the production wiring on the ACD controller wiring to receive and analyse wheelspeed information from all 4 wheels. Each LED will be to a % of slip value, so the more slip (error) the more LED’s will light. Monitoring will only be of value while full throttle is being used. As the 3 differentials lose efficiency through wear and tear more LEDS will light more regularly.
How critical is bleeding the ACD system?
Very critical. As the system has a single hydraulic line from the pump/control unit to the ACD differential there is no oil flow as such. Bleeding the system correctly and thoroughly is key to the systems correct operation
How do I bleed the ACD system?
A dealer would use the previously mentioned MUT2 service computer to conduct a service routine, which “fools the system” and operates the pump and proportion valve in the ACD system while the car is standing still. This develops an oil pressure, which passes to the ACD differential, opening a bleed nipple allows oil to flow freely until the technician can see the oil supply clear of air, similar to a brake bleeding exercise. As stated before the MUT2 service computer is not available to non-Mitsubishi dealers and is an extremely high cost item. Some optional ACD electronic control units allow a small pressure to pass to the differential unit to allow the differential to be bled if a 30kph wheel speed is achieved and use of the handbrake forces a slip scenario. Pressures achieve via this method are very low and care must be taken to ensure the system is fully bled out. I can only recommend driving the car for a short road test and re-bleeding immediately to ensure the system is clear of air.
Alternatively BTR has developed an on-board bleeding system in the form of a secondary control unit which overrides the production ACD ECU and manually runs the pump and controls the proportion valve. Via this method, pressures of up to the 11 bar maximum can be passed to the ACD differential without the car running and ignition on thus ensuring reliable bleeding
If I lose hydraulic pressure in the ACD system what are the effects?
Traction will be severely compromised, as there will be high levels of slip between the front and rear axles. The handling will be unpredictable due to the excessive slip, and braking distances will increase