![]() ![]() If the haldex clutch is fully closed, torque goes wherever there is grip, front (100:0) or rear (0:100), and everything inbetween depending on grip. Haldex isn't as bad as it may seem as they are also electrically governed and can very much close the clutch before traction is lost in front. Up to this point, this is the same layout as what is commonly referred to as 'Haldex'. This clutch is a slippy clutch, so it can transfers varying amount of power back depending on the pressure on the clutchpack. Rear differential is driven also by a shaft directly on the gearbox, but with a multi-plate clutch in between. The GR Yaris has a transverse engine, the gearbox directly drives the front differential. Torque distribution is instead induced by loss of grip of the other end (= 'passive') or difference in rotation speed (='active' or 'vectoring'). Brace yourselves, it is not very short…įirst off, forget the idea that all awd systems 'distribute' torque just like as one reads in marketing material. This is that, I'll try to explain how the GFY system works in the light of other awd systems present on hot hatches and rally oriented road cars of the past. The GR Yaris Circuit Pack is additionally equipped with front and rear Torsen limited-slip differentials which offer enhanced cornering performance and grip with control of left and right-hand drive torque distribution on the front and rear axles."Īwd systems is a rather big subject, and not very often I meet correct explanation on the workings as they often stop short, so I tend to dig deeper myself as I'm keen to understand what's actually going on. ![]() Electronic control of the multi-plate clutch uses information from the wheel speed and G sensors and the clutch's temperature sensor. The system's ECU controls the drive torque distribution to suit the driving situation, according to data gathered on vehicle performance such as speed, acceleration, braking and steering. The two units are connected by a three-joint, two-axis propeller shaft. Lightweight aluminium is also used for the rear differential, which is integrated with an electronically controlled multi-plate clutch. The transfer case is constructed in aluminium and contains a hypoid gear, with bearing support optimised for rigidity. The mode options are: 50:50 Track mode, suitable for fast driving in any road conditions, from dry to snow 30:70 Sport mode, to prioritise rear-wheel drive characteristics and 60:40 Normal mode (the default mode), suitable for day-to-day performance. ![]() Slightly different gear ratios are used in the high-response coupling and rear differential, allowing greater drive force to be directed to the rear wheels even when there is no slip at the front wheels. Operation is electronically controlled with three modes the driver can select to suit their preference or the driving scenario. "The full-time system is simple in design and light in weight - lighter than alternative twin- coupling or centre differential systems. Goes deeper than the quoted press pack and compares to other systems. Wrote this on PH, took some time so thought I share it here too. ![]()
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