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, Tue, 23 Mar 2004 09:21:16
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From basic priciples the mount does not generate any forces, it only transfers STATIC forces from one location to another and the mounting points are not changed.
With an elastic element, higher frequency vibrations are absorbed to some extent, just as with the stock element. So some changes in vibration from the engine may be noticeable.
Another issue, is that when an engine is moving around on a stock mount, the engine and trany assy will building up momentum with its large excursions and the mount then will see and transmit some of the forces required to halt such motion. A mount that does not allow the engine/trany to be in such motion, will not see the dynamic forces required to reverse such motion. The new mount is taking care of this issue.
But these are all secondary effects. The primary static loads from engine torque will not be any different. The major effect seems to be when you go from full boost to nothing when shifting. With the stock mount the motion allowed can be excessive. From what I read, this new mount controls these large movements resulting from extreme torque changes. With high boost, the stock mounts, especially when tired out, are not controlling the engine. The torque on the engine/trany assy is the reaction force of the torque delivered to the wheels. So full boost in 1st & 2nd gear probably creates the worse dynamics when shifting out.
Sadly, Saab seems to have gone through a phase of mounting everything in rubber/blubber to an extreme. The result has been rubbery steering that really sucks for the intended vehicle service and peoples expectations. So it would be no surprise if the engine mounts were too blubbery all along. There simply has been no alternative to evaluate before this.
All of that mounting in rubber seems to have been a total waste of time. When folks have hard mounted the steering rack and replaced the rubber bushings with poly and steel, everything just gets better and there are no road vibration problems at all. The problems with wheel shake that sometimes drives folks crazy, and the prolems that were very often found woth the 1994 suspension, were obviously, in 20-20 hindsite, largely a result of too much rubber. Elastometric mechanisms with heavy componets (tire, wheel ,hub, knuckle, rotor, caliper, strut, spring, control arms) are subject to large amplitude low frequency harmonic vibrations: AKA shaking. So wheel imbalances can create extremes of motion. And the steering geometry is sloppy and load variable (read indeterminant).
Maybe Saab should have made a front lower wishone out of one piece of rubber and they could have reduce the part count!
posted by 65.68.10...
, Mon, 22 Mar 2004 18:51:39, Tue, 23 Mar 2004 09:21:16, Tue, 23 Mar 2004 06:35:38
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