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, Fri, 13 Jun 2014 16:51:13
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Hi Terry,
Good question!
The first Saabs had two stroke motors. These get their lubrication from oil added to the gas similar to a chain saw or weed wacker. When you step on the gas, the car accelerates and more fuel/oil mixture is drawn in and there is good lubrication for the rings and crank bearings. However, when the car decelerates, there is little fuel/oil mixture so there is alot less lubrication. Think of a long downhill- as the car goes down the hill, there is no foot on the gas and not much lubrication, and the engine compression is holding the car back- engine braking. With little lubrication, the engine wears greatly. Saab solved this problem by putting in a freewheel. When the car is in freewheel mode, if you let off the gas, the car freewheels- its essentially coasting with no engine braking at all, so no wear on the engine. But more wear on the brakes. The freewheel is a centrifugal clutch, just like in a chainsaw. As the rev's come up, little rollers press against a hub and lock the transmission in.
This design was carried over to the four stroke V4 motor. There's not the same need for one with the four stroke- this motor has an oil sump and pump and gets pressurized lubrication. Freewheel use on the V4 will increase your fuel mileage a bit and most of us think it's pretty cool to let your foot off the gas and coast. You can shift without the clutch as well.
As I said, they tend to be fragile and many people lock them out with a special sleeve. My two Sonett's have the freewheel locked, but my 3 96's have operating freewheels. I enjoy using them, but they must be treated with some respect. IE, gradually apply the throttle and be gentle with them.
Hope that helps explain.
eric in vermont
posted by 69.54.2...
, Wed, 11 Jun 2014 13:31:39, Fri, 13 Jun 2014 16:51:13
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