Technical Notes
CHASSIS DYNAMOMETER (PERFORMANCE DYNO)NOTES, REQUIREMENTS, INFORMATION, ETC. For measuring the wheel power, for functional checks, for exhaust-gas measurements under load, for warming up the engine as a substitute for road operation, and for full-load injection volume measurements. Dynamometers listed are suitable for simulating (some require accessories) running resistance (rolling and air resistance plus centrifugal masses). Any such simulation will correspond to the actual conditions prevailing when traveling on a level road (over the entire speed range of the dyno). Purchase of these devices is no longer recommended because of the lack of vehicle adjustment. Future applications and potential uses: Commencing with the A-class vehicles in Germany, the use of chassis dynamometers in connection with diagnosis work is no longer necessary. This is also the aim for future model series. Instead, increasing use is made of the alternatives offered by the vehicle on-board diagnosis system and the capabilities of the STAR DIAGNOSIS system. Specifications and literature references for driving on the chassis dynamometer etc. will no longer be published for the above vehicles series. Warming up the engine, for example is thus the sole remaining purpose of driving on the dynamometer. The purchase of a new dynamometer should be considered especially critically in the light of this situation. Performance test: Any performance test (full load according to engine speed) should be carried out only in the case of explicit performance-related complaints. To prevent tire damage, test wheels/tires must be mounted for speeds in excess of 130 km/h. Winter tires must also be replaced with test tires/wheels. This applies irrespective of the test speed. For an estimative performance test it is sufficient to carry out a function test (partial load according to road speed) in which the test speed is less than 130km/h. Wheel power specifications: the nominal wheel power values specified by MB are minimum outputs. They are approx. 25 - 30% lower than the rated engine outputs due to loss in drive train and tires etc. Other differences may result when the test on the dyno is not performed at exactly the rated engine speed. Dynamometer installation height: With the lifting bar lowered, the vehicle should be standing as level and as horizontal as possible. To this end, the roller top edge should be located 80 or 100mm above the floor level. Dyno room: The dyno today are designed as frontend-type (vehicle is driven onto the dyno in forward direction). The vehicle is then reversed off the dyno. With this arrangement it is not necessary to move the cooling blower when driving in and out, the tail pipe points towards the door and driving in is relatively simple. However it is necessary to provide good illumination in the front section of the room for the engine compartment. Ventilation: Approx. 30 air changes per hour (no full-load continuous test assumed, otherwise a minimum of 60 air changes would be necessary). Ventilation must not cause negative pressure in the test room. Maximum pressure differential from barometric air pressure approx. 30Pa. If a ventilation fan is not present, sufficient supply of air must be ensured by means of appropriate opening in the walls. Exhaust-gas extractor / noise insulation: Exhaust-gas extractor of sufficient capacity (approx. 3000m3/h), sufficient noise insulation, e.g. with suitable soundproofing should be provided. MB standard foundation: The foundation should be constructed according to the plans of the dyno manufacturer. Dimensions of the MB standard foundation: length x width x depth approx. 3675x1140x365mm sloping towards floor drain. Quality assurance and utility value retention:
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