Please excuse the noob question but with all the buzz about the IMSB failures, I began to wonder why Porsche uses an IMS. Why not drive the cams directly from the crank?

 

http://theimssolution.com/ims-101/

 

you heathen...you dare to question how the gods build cars. us mortals are not permitted to know the workings of the evil elves from the enchanted black forest

 

IMS is a myth

 

Heathen eh? I can live with that. So the sole purpose of the IMS is to reduce the chain speed and in turn increase chain life? I'm sure sharper minds than mine have long ago figured out that this is the best solution...but I just can't help think that more robust chains and/or more robust oil cooling of the chains would be a simpler, lighter, and possibly even less expensive means of extending chain life.

Thanks for the link...that is a very interesting write-up on the subject.

 

The accountants were calling the shots on the 996 not the engineers.

 

 

The 547/1 4 Cam Carrera engine was the first with an "IMS", known as a layshaft in the mid 1950s. Porsche retained the layshaft (IMS) through all aircooled engines and through the 2013 GT3 and Turbo. In all the aforementioned applications that shaft was supported by a plain, journal bearing that was pressure oil fed. These never failed, in fact I've never, not once ever seen one fail.

The reason for the IMS was to drive the camshafts with a lower drive chain surface speed, and also to drive the oil pump.

The 9a1 DFI engines drive the cams from the crankshaft as the IMS was omitted. Porsche utilized the IMS for almost 60 years for a very, very good reason. Not until they utilized a ball bearing to support the IMS did problems begin to occur.

Yes, my IMS Solution (www.theimssolution.com) backdates the engine and retrofits the M96/M97 with a pressure oil lubricated and supported plain journal bearing. This supports both radial and longitudinal loads.

 

I think the pertinent question isn't why they designed the engine with an IMS, but rather why they chose to have one end of that shaft ride on a sealed ball bearing, not significantly more robust than what you find in a swimming pool pump...

 

All you noobs need to ask or discuss this in the appropriate thread in the sticky above(The IMS DISCUSSION Thread). There was a reason why it was created and stickied in the first place. Thank you and welcome.

 

Would have been Nice to see Friday out with a few 'heres my new 911", "why I love my 911", threads not this crap again.

dont know why we all dont go out and beat the crap out of our 911 bodywork with a ball pean hammer, be quicker that the depreciation by a 1,000 IMS threads

 

Thank you for the admonishment and I understand the frustration that comes from "noobs asking questions that have been beat to death" problem that happens on these forums. I've read the sticky. I've read many many threads related to the IMS bearing issues. I have no desire to rehash the failures, the rubbish bearings, or any of that. What I'd never been able to find is a discussion for the reason a layshaft/IMS is employed in these engines. That is all I wanted to learn about or discuss; NOT IMS bearing failures of the M96/M97 engines. I'd like very much to one day post "here's my new 911" but in the meantime, I enjoy learning as much about them as I possibly can.

 

I understand your question might be slightly different but it still belongs in the IMS discussion sticky above.

 

While we are on the subject...what's the best oil to use to avoid IMS failures? Please be specific about brand and weight and don't be afraid to be subjective.

 

Absolutely. Nothing wrong with an IMS, everything wrong with using a sealed ball bearing to support it.

If having an IMS was a bad thing, Porsche wouldn't have even made it into 1960.