logray

Hey cool feature, you have a window in your cam cover.

How neat would that be to have a completely transparent engine case.

Macster

While engines shed metal over their service lives the pieces are small and in the overall scheme of things inconsequential. If the metal pieces get big enough to not be inconsquential, no amount of screening is going to really help. All it does will be to catch the even bigger pieces that the engine sheds as it comes apart.

I would advise you against putting any more screens/filters in the oiling system. If a screen is deemed necessary the lack of a screen is not the problem, the source of the debris the screen is catching is the problem.

My info is the IMS was used to reduce the length of the chains that drive the cams. Additionally having an intermediate shaft between the crankshaft's chain sprocket and that of the cam chain drive sprockets provides a way to ensure that wear of the chain rollers and sprockets is spread around.

The crankshaft sprocket and IMS sprocket have a number of teeth the requires IIRC 9 trips of a specific chain roller around the circuit before the same roller encounters the same sprocket tooth.

The concern is if the same roller and sprocket tooth always come into contact uneven wear will occur which can lead to problems.

For the choice of a ball/roller bearing, this type of bearing has a smaller impact on the engine's available oil budget.

A plain bearing requires a considerable amount of oil to generate and maintain the hydrodynamic oil film that a plain bearing depends upon.

Additionally a plain bearing because of its oiling needs means high pressure oil needs to be routed to it and a considerable volume of low pressure/aerated oil routed away from it. Dealing with getting oil to and from the plain bearing increases the risk of an internal or external oil leak and makes the oiling system more complex.

Sincerely,

Macster.

JM993

Agree. The 993 (and other 911s before it) and the GT/Turbo cars all have an IMS. However, that IMS runs in plain bearings which require a more elaborate (read expensive) oiling system. However, the plain bearing IMS bearings are virtually troublefree. In trying to save $$, Porsche shot themselves in the foot. Fortunately, the LN bearing is available for those of us with M96 engine cars.

logray

+1,000,000

Also, I would be worried the/a screen itself could become a troublesome or worrisome point of contention.

jdcorbitt3

The screen would be pulled out and inspected at every oil change. This could give warning signs of impending failure. Also, in the event of a chain or bearing failure, it could save the $463 scavenge pumps.

logray

Spammer!

logray

Last I checked scavenge pumps were $190 each discounted.

But again, I still vote for keeping the contaminants out of the engine in the first place, and keep a fresh filter and oil.

Macster

You of course can and should do what's right for you, but my opinion is about all you should have to do is schedule/follow a reasonable oil/filter service interval and resist adding any screens to the scavage pumps.

Being able to do what you want and for it to have any chance of paying off like you are counting on still relies upon the engine manifesting a serious problem or early warning signs of a pending serious problem on a schedule that had better not come too early after the previous inspection or too soon before the next inspection.

You can accomplish much the same thing -- without having to modify the engine any -- by every so often removing the oil filter housing and its filter element and pouring the contents into a *clean* drain pan and looking for scary metal bits, or IMS bearing seal bits, or tensioner o-ring bits or camchain guide/rail padding bits.

Do what you think is right for you, but if I felt I owned a car with an engine that required sifting through screens/filters/old oil for any signs of pending engine doom I'd sell the engine along with the car it came in and take the money and apply it towards another brand of car's purchase.

Sincerely,

Macster.

jdcorbitt3

If this engin had my screen idea, it would have not failed. I refer to Mazda again, but it has a screen on the oil pickup to protect the pump. The filter is after the pump and protects the rest of the engine. This is a simple mod that I am supprized Porsche didn't include when they built the engine. Instead of a plug, when they were honing the journal out, they easily could have threaded it and put a bolt in there instead.

John

txhokie4life

What ever got caught in that pump was going to find a home someplace -- screen would have diverted
it else where.

The chains coming up from the crank act like conveyer belts into the cam housing/heads.

have you determined what the source of the piece of debris that fowled the pump?

Mike

jdcorbitt3

I haven't found the source of the metal. The screen would have trapped the metal until the next oil change. There would be no other place for the debris to go.

John

logray

The scavenge pumps are the #10 stop out of #16 for the full round trip.

Sure there are plenty of places debris could get "stuck" before it reaches any filter inside the scavenge pumps.

Not to mention oil galleries, passageways, etc.... before the oil gets to the scavenge pumps it must first travel through important places like the IMS shaft, oil cooler, camshafts, and crankshaft.

jdcorbitt3

I just bought a Boxter S 3.2 engine. I am going to replace the IMS bearing and inspect the oil pumps. i am getting the engine harness and the ECU for the 3.2 from the car as well. that should be all I need to convert the 2.7 to a 3.2 I hope.

John

mikefocke

As I've said before, the whole idea of inspecting the oil filter or a screen depends on the interval between the beginning of failure and total failure being the interval you choose for inspection.

So if the failure interval is 200 miles and your inspection is 3000 miles ... you have a less than 10% chance of catching the problem before boom occurs. After all, how often are you going to go to all the trouble of pulling a filter even if you have the equipment.

You need to either be lucky and have no failure on the original part, replace the original part before it fails or detect within the failure interval.

Fortunately the failure rate is relatively small though the cost in cash and angst is large if you are among the unlucky.

jdcorbitt3

I goth the engine and transmision out .Bank 1 exhaust valves are bent. I fount 2 metal fragments from the Scavange pump tab stuck in between the teeth of the timing chain. I still havn't seperated the Automatic transmision. I am looking for videos on line to figure that out. I am hoping there is a way to seperate the torque converter from the flywheel prior to splitting them apart. this way, i don't open the transmision fluid system.

here is a photo of my 1999 non interference Miata towing the boxster. The numbers on the Boxster are from my RX-8.