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, Wed, 29 Sep 2004 08:32:46
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I'm a bit late to the party, and the thread DougM suggested is excellent... here are another two cents...
A couple of handy metaphors for 'freewheeling' can be found in a simple ratchet, and/or the freewheel hub of a bicycle. When power is applied in one direction, useful work is done... in the other direction, nothing much happens.
On a SAAB, it has to do with the relative rotational speeds of the engine and the primary shaft of the transmission. When the engine revs match or exceed that of the primary shaft, engine power is 'passed' to the transmission. Conversely, when engine revs fall below that of the primary shaft, the input shaft (situated between the two) is allowed to slip or 'freewheel' with respect to the primary shaft. Effectively, it has much the same result as stepping on the clutch.
As I understand it, this feature was necessary for 'mixer' two-strokers. Since the only engine lubrication is in the fuel/oil mix, there is little oil available when the throttle is closed, making any extended engine braking problematic. So, instead of braking the engine on deceleration, the transmission quietly disengages via the freewheel... and the engine idles down on its own. Good for engine, gas mileage and transmission; hard on brakes.
The feature was probably retained throughout the V4 years owing to 'tradition'. V4's, with their higher torque, routinely tore up input shaft and primary shaft cup teeth. Many owners simply locked out the freewheel. It really wasn't necessary for the V4.
Peter B.
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PS - I'm new here, so shouldn't complain, but several quite innocuous posts have been deleted since I 'arrived'. I've read the FAQ, but still don't see any reason for the deletions.
Also... it would be good to see the 'Parts For Sale' and 'Wanted' sections broken up into more model-specific areas.
(Okay, so I'll buy some ad space next time I whine.)
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posted by 216.180.20...
, Wed, 29 Sep 2004 08:32:46
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