IMS solution,or Pedro's DOF

[JFP in PA]

Originally Posted by Homeoboxter

It’s actually the opposite, since the bearing wear is twice as fast in the single row because of the double load compared to the dual row. So the single row starts pitting much sooner. DOF would make sense if the failure was the result of lack of lubrication. But that’s not the case in a bearing that’s swimming in oil all the time.

The theory on the DOF is the lack of lubrication causes heat build up, leading to galling and failure. As the dual row has twice the contact area, the heat build up in the bearing should be both faster and to a higher temp, which should be leading to its failure sooner than the single row. But that is not what happens in the real world, were single rows fail at a rate near ten times that of dual rows.

[Homeoboxter]

Originally Posted by JFP in PA

The theory on the DOF is the lack of lubrication causes heat build up, leading to galling and failure. As the dual row has twice the contact area, the heat build up in the bearing should be both faster and to a higher temp, which should be leading to its failure sooner than the single row. But that is not what happens in the real world, were single rows fail at a rate near ten times that of dual rows.

I don`t think the contact area really matters here. The axial force on each ball is double in a single-row bearing as compared to a dual-row. The contact surface from the bearing ball`s point of view is identical in both single-row and dual-row. Heat dissipation is similar too, as it`s like putting two bearings next to each other. What is different, is the load. If the bearing was running completely dry, the dual row would still last longer.

[jaykay]

Originally Posted by JFP in PA

The theory on the DOF is the lack of lubrication causes heat build up, leading to galling and failure. As the dual row has twice the contact area, the heat build up in the bearing should be both faster and to a higher temp, which should be leading to its failure sooner than the single row. But that is not what happens in the real world, were single rows fail at a rate near ten times that of dual rows.

Yes all good thoughts but I am not sure a dual row would produce more heat, or critical heat levels because there are more points of contact. Friction is driven by “normal” loading of one element against another and in the case of a dual row one can argue the loading is split between two bearing assemblies. Normal loads are lower at each yielding lower friction forces perhaps below critical levels.

Having said all of this I am of the opinion that poor brearing design is a main factor and that no amount of lubrication in a rolling element bearing will circumvent an overload condition

[thom4782]

Having sold my 986, this is probably my last comment on the IMS question.

Most people look at this issue in the wrong way. If all IMS alternatives have similar longevities, which is a big assumption in itself, the substantive issue then is what happens when they begin to fail.

Any bearing that fails in a mode that allows the engine to jump timing is inferior to one that doesn't.

My view is simple. Failing plain bearings cause less damage than failing roller bearings than failing ball bearings. On this metric, the IMS Solution wins.

So the question turns on does one spend more money up front (the Solution) to avoid higher replacement costs later (the alternatives)