Question about reman engines and IMS

[kcpaz]

Originally Posted by Jake Raby

The cams are driven at 1/2 crankshaft speed.. That is accomplished via the IMS.

The surface speeds of lots of timing chains are being elevated..

Flaws take a while to note, the new engine was also subject to Porsche Accounting, just like the M96.

This doesn't justify the need for an intermediate shaft at all. Obviously there are a LOT of other successful engines out there that don't use intermediate shafts to accomplish proper operation.


Also, can anyone tell me why there was a need to drive the cams from opposite ends of the engine? Again, it seems unnecessarily overcomplicated.

[Jake Raby]

Originally Posted by kcpaz

This doesn't justify the need for an intermediate shaft at all. Obviously there are a LOT of other successful engines out there that don't use intermediate shafts to accomplish proper operation.


Also, can anyone tell me why there was a need to drive the cams from opposite ends of the engine? Again, it seems unnecessarily overcomplicated.

Its impossible to make my point here on the forums.. And its nothing but hypothetical anyway.
Practical application and time will illustrate the weaknesses of the "IMS-less" engines, as with every engine throughout time.

What people generally don't understand is the "lay shaft" as an intermediate drive for the valve train has been in place since the mid 1950s with Porsche engines. This is depicted here in this image of a 1955 Porsche Spyder engine I was working with a few years ago.. That shaft below the crank is the lay shaft, it transmitted mechanical energy through bevel gears and shafts up to the exhaust camshafts, that then drove another shaft and bevel gears to drive the intake cam, just like an M96, the only difference is chains Vs. bevel gears.


Notice the plain bearings, not a roller bearing like the M96.


Shaft that is driven by bevel gears, driving exhaust camshafts


Exhaust cam and bevel gear to drive intake cam




The moral of the story is the fact that Porsche used an IMS style design since 1955 when this engine was produced, the IMS was NOT a new design for the M96, but the roller bearing support Vs. plain bearing support was. The IMS isn't the reason for engine failures.

We'll see just how wise removing the IMS was in time.. We are already beginning internal development on the "new" engines.

[kcpaz]

Originally Posted by Jake Raby

The IMS isn't the reason for engine failures.

I understand that, and I know the bearing itself is the only reason most people even know that the M96 has an IMS. It just seems to me like if there was a way to eliminate the IMS all together, you would be better off, and in-fact, other manufacturers have been able to. Now if you are saying that there is a possibility that the current design of the 9A1 would have benefited from having an IMS, I can't argue because I can honestly say I have absolutely zero experience with that engine, but based on what Subaru (just an example) has done with their engines, I don't see why Porsche wouldn't have the ability to make it work too.

[Jake Raby]

Originally Posted by kcpaz

I understand that, and I know the bearing itself is the only reason most people even know that the M96 has an IMS. It just seems to me like if there was a way to eliminate the IMS all together, you would be better off, and in-fact, other manufacturers have been able to. Now if you are saying that there is a possibility that the current design of the 9A1 would have benefited from having an IMS, I can't argue because I can honestly say I have absolutely zero experience with that engine, but based on what Subaru (just an example) has done with their engines, I don't see why Porsche wouldn't have the ability to make it work too.

Some component must reduce camshaft speeds by 50%, no matter what the engine may be.. In my experience you want that 50% reduction to occur as early in the mechanical "chain" as possible to reduce surface speeds of chains and etc.

When I first saw the proposed "new engine" I knew it was going to be hell on timing chains.. From the reports that I hear within some dealer networks I am part of failed timing chains are occurring.

[Steve Tinker]

Originally Posted by kcpaz

This doesn't justify the need for an intermediate shaft at all. Obviously there are a LOT of other successful engines out there that don't use intermediate shafts to accomplish proper operation.

Also, can anyone tell me why there was a need to drive the cams from opposite ends of the engine? Again, it seems unnecessarily overcomplicated.

The reason why the cams are driven from the opposite end of the engine via the intermediate shaft is because Porsche can use the same cylinder head on opposite banks of the engine. If they used the same end to drive the cams, then a "mirror image" second cylinder head design would have to be employed.
Another cost cutting excercise.....
Jakes pictures of the twin cam bevel drive engine is very illuminating - it would have taken a Porsche master tech quite a few hours to select, assemble and shim the componants to spec - something that Porsche wanted to get away from when adding up the assembly hours to produce a financially viable car.
Beautiful engine design though - I hate to think what it would cost to manufacture today though

[kcpaz]

Here is the front of the EZ30R engine with the chain cover removed, and from what I've read, timing chain failure has not been a problem up to and beyond 100K miles. Jake, I've never seen the 9A1, is it similar in design?

[mikefocke]

Why did Porsche develop a mass market engine in addition to the older high end design they still use on some cars?

Because they had to achieve a profit or go out of business. Volume and low manufacturing cost lead to profit. Long production runs with the same basic design allow development costs to be amortized over many more units. Same reason the '97 Boxster used the 996's front endparts.

You can hand build a limited number of engines in cars that sell for $100k but not for one that you sell in volume for as low as $40k or even one that sells for $70k.

[kcpaz]

Originally Posted by mikefocke

Why did Porsche develop a mass market engine in addition to the older high end design they still use on some cars?

Because they had to achieve a profit or go out of business. Volume and low manufacturing cost lead to profit. Long production runs with the same basic design allow development costs to be amortized over many more units. Same reason the '97 Boxster used the 996's front endparts.

You can hand build a limited number of engines in cars that sell for $100k but not for one that you sell in volume for as low as $40k or even one that sells for $70k.

Nobody said they had to be hand built. I hate to use LS engines as an example again, but look at the entry level versions of that engine. All mass produced using machines and relatively cheap parts. Then there's the higher-end version like the LS7's and LS9's that are hand built with more expensive parts and more performance.

I can't imagine it was a cheap process to design, test, redesign, tool, and manufacture a completely new engine... especially when you consider the cost of revisions (although I'm sure they didn't anticipate the enormous failures of the early motors). I understand parts bin construction, and actually, I think that theory would prove what I'm saying. How would it be more cost effective to have two different engines to manufacture and two different engine assembly systems?

Not only that, but good luck selling a "high-end" German sports car with the mentality of "Well we pinched as many pennies as we could to give you the least expensive thing that we thought we could get away with and still turn a profit". Obviously that's not their marketing strategy, but this seems to be the reasoning a lot of people use to explain things like the M96.

[Jake Raby]

Jakes pictures of the twin cam bevel drive engine is very illuminating - it would have taken a Porsche master tech quite a few hours to select, assemble and shim the componants to spec - something that Porsche wanted to get away from when adding up the assembly hours to produce a financially viable car.
Beautiful engine design though - I hate to think what it would cost to manufacture today though

This engine pictured cost 125,000.00 to rebuild and thats fairly cheap.

It takes no less than 16 hours to complete the cam timing procedure as the components must be surface ground for precise adjustment. These engines were produced when a single builder assembled the entire engine, the same way we do the process here under our roof.. No automation, no robotics, nothing less than human hands.

The IMS/Layshaft provides a means of inherent balance for the engine as well

The higher the surface speed of timing chains, the more they will wear and the faster the chain rails that support and tension them will wear. I'll bet that the designers also didn't "master link" these chains, so changing them can prove to be just as near impossible as the M96.

I';ll know all about it when I get the 2010 Cayman engine apart in 2-3 months.