Macster

Oil pressure rises but oil pressure alone is not sufficent to complete hydrodynamic oil bearing film. The bearings' rotation acommplishes this. For this protective oil film to develop and remain in place requires oil pressure and flow but the bearings must be rotating.

I know the claim is most engine wear occurs on cold engine startup but the definition of a cold engine start is not given.

Furthermore, I have to dispute this claim to some extent based on my experience with my 02 Boxster with over 237K miles and more cold starts than most cars have starts and the engine doesn't seem to have suffered any noticable wear. It is quiet upon startup and and remains quiet once hot and oil consumption while up from nearly nothing to about 1 quart per 5K miles is still darn good.

Might add that even if one ignores my experience there are many cars out and about that experience if not infrequent cold starts cold starts nonetheless and there doesn't appear to be a very significant number of cars running about worn out from this experience.

What I think harms an engine more is very infrequent starts, infrequent enough not enough residual oil remains in the various bearing interfaces to protect these surfaces at startup. A car that has sat during the winter unused or one that has just sat for weeks at a time unused. In this case a dry cranking may benefit the engine.

(For most cars I believe the biggest contributor to wear is oil that is contaminated and develops acidic compounds. This acid action loosens the metal matrix of all the metals it comes in contact with and upon start up and during running the violence and friction of the oil tears aways metal that has been weakened by this acid. This is wear even though no metal to metal contact occurs.)

But back to the dry cranking: If I believed I had to do this upon every cold start to protect the engine I'd sell the car.

If the engine's oil pressure takes time to build after a cold start I'd suspect the oil check valve at the oil tank may be hanging up, sticking. Probably from a lack of use of the car coupled no doubt by the owner going too long between having his car engine's oil changed.

Sincerely,

Macster.

Kevin

Macster your Boxster shares nothing with the turbo engine. From bearings to oil pump..

We are talking about oil changes.. When you change your OIL the recommendation is to PULL the fuel pump fuse. IT is NOT the recommendation everytime you start the engine.. That's insane..

Kevin

The bearings do not rotate in this engine. The crankshaft does. And the crankshaft MUST fill up with oil to lubricate the rod journal bearings..

How does the oil get from the main engine oil tank to the rod bearings? How long does it take when you change your oil?

PAULUNM

Perfect, thank you

Macster

Actually the two engines have much in common. In fact most modern gasoline (and diesel) engines share many common features and crank main and rod bearings and how the work. The principles and physics involved are relied upon by all engine makers.

I am not able to find anywhere in the Turbo info I have that it is advised that upon an oil change the fuse be removed and the engine cranked for oil pressure's sake.

In fact, in the section covering the replacement of the oil tank check valve and the oil cooler neither section has this.

In the oil change section caution is to "fill in engine oil slowly to allow the oil sufficient time to flow from the oil container into the crankcase". The next step is to check the oil level which means the engine has to be started and run long enough to get the oil hot enough for the oil level check to occur.

It seems like a lot of extra work to avoid waiting for the oil to make its way where it will to instead try to eliminate this wait by pulling the fuse and cranking the engine, then installing the fuse and then starting the engine and then letting the engine run long enough to get an oil level reading. I have never tested this, confirmed this but I would not be surprised that if one left the crankcase oil drain plug out that before one was finished pouring the first quart of oil into the oil filler tube some of that fresh oil would be running out of the crankcase drain plug hole onto the ground under the engine.

I mean I can certainly understand the desire to keep one's Turbo engine in good working order but some of this business, like fuse pulling and cranking the engine after an oil change, well, let me just say I think it way overkill. But of course each owner is free to do as he wishes.

Can't help but wonder though how many who do or contemplate doing this bother to drain the turbo oil collectors during an oil change? This is one of the steps in a Turbo oil change.

The bearings consist of the bearing shell *and* the crankshaft main (or rod) bearing journal diameters.

As you well know the crank main bearing journals rotate in the bearing shells as the crank turns. The crankshaft's main bearing diameters and the main bearing shells *and* the oil film makes up the hydrodynamic bearing that supports the crankshaft and allows it to run suspended by an oil film so no metal to metal contact occurs.

Sincerely,

Macster.

Kevin

That's where your logic is in error. The oil that is being poured into the oil filler DOES NOT go into the engine case. It fills the oil tank. AND we have a check valve that keeps the oil IN the tank. Porsche designed this system with a check valve. Unlike the 993TT where the check valve is inside the oil filter which fails frequently. There will be NO oil draining into the engine case where the oil pump and crankshaft assy is. You have ZERO oil capacity in the engine case until you start to crank the engine over. With removing the fuse we are trying to limit the crankshaft rotation in time. It is far LESS of a impact to build oil pressure in 30 seconds with less revolutions vs turning the ignition switch and having the engine turn over 250 times with zero to no oil pressure.

The oil pump has to fill both the sump and pressure circuit in order to begin to make oil pressure. It does require time when you fire the engine off after a oil change.

If there is NO oil coming from the scavenge side we get cavitation and a interuption of oil flow to the bearings. The engine is idling at 700 to 800 RPM's with a period of starvation. You will get metal to metal contact. The lack of oil results in a reduction of "film support"

While your Boxster engine was engineered with the latest technology the main bearings in the 996TT engine came right out of a 930 with matching part numbers. Rod bearing come from the 993..

In the end "one" can take the minute endeavor to remove the fuse and crank the engine over. If you don't want to>that your right not to do so.

bena

Is there a video or DIY on how to change the oil on this site? Are there any special tools one needs? Any gotcha's?

Thanks
ben

bena

Where do you have your oil analyzed and what does it cost?

No HTwo O

I use Blackstone Labs. I buy in bulk (6 test). Average cost is about $23. Add another $2 for shipping (regular mail...$5 for Priority US Mail) sample. I test both my used engine oil and trans/gear lube.

Mikelly

Same here... Blackstone has been very user friendly, and any questions are always answered as technical or as layman as the end user requires...

Mike

Macster

I'm trying to locate an oil diagram for this engine. Techs tell me there was a good one in the initial product release paperwork but this info tends to get set aside even discarded after a while to make room for newer literature.

I do not understand how with an oil tank the engine must first fill the oil sump (crankcase I guess you mean?) in order to generate oil pressure. The dry sump oiling systems I have had some experience with the oil from the tank is routed directly to the oil pump high pressure side's oil intake and this oil is then of course pressurized and pumped to the main bearings/et al.

At no time should a properly functioning dry sump oil system's high pressure pump intake side see any air in the oil suffer any cavitation.

The scavage pumps are located to collect the oil after it has left the bearing (crank, rod and in the heads the camshaft) interfaces or from other oiled hardware (like valve lifter hardware and chain lubrication etc). The scavage pumps are overdriven to help provide a lower pressure in the area they service to help pull in not only liquid oil but oil vapor. In doing this they can and do aerate oil. But this oil is then fed to defoaming/de-aerating chambers/pots which remove the air and pass on de-aerated oil to the oil tank. The oil tank's construction is designed to avoid feeding oil that arrives directly to it right to the supply outlet to the oil pump's high pressure intake side.

I would not be surprised that these pots have as an exit the crankcase in which flows the air (and some oil vapor) that is removed from the aerated oil. This air/oil vapor then of course returns to the crankcase sump where the crankcase scavage pump then picks up whatever oil comes from these pots and of course any new oil that is shed by the whirling mass of crank/rods and such.

BTW, at engine start (once the engine is running on its own power) idle speed is around 750 revs per minute. To believe the engine spins 1/3rd of a minute, 20 seconds which works out to 250 rpms (1/3rd of 750 idle speed rpms) with little or no oil pressure if true suggests these engines have a horrible oiling system. Which of course they do not or the sides of the road would be littered with worn out Turbos owned by people who do not pull the fuel pump fuse and dry crank the engine before every start or even the first start after every oil change.

By my observation after I've changed my Turbo's oil -- many times due to time pressure changed immediately after backing the car up ramps which means the engine was run sometimes just minutes before I start the oil draining from the crankcase and oil tank drains -- I see the oil pressure gage's needle begin to climb as the engine turns over and once the engine fires -- after just barely a second of cranking -- the oil pressure climbs to way above the 2bar level it normally resides at once the engine/oil is up to operating temperature. Further I hear no noises from the engine that suggest even the remotest (or nearest) internal engine components are suffering any lack of oil or oil pressure.

If one has been inside the engine and thus the oiling system is without its normal residual oil or if the car/engine has sat for a long time unused (like over winter) pulling the fuse and cranking the engine may be a worthwhile action but for any other time it borders on the excessive/complusive.

Sincerely,

Macster.

Dock

What nonsense in the discussion about oil change intervals? Please be specific.

jpflip

Macster was it this one....

ltc

FWIW, the Porsche mechanic who told me to pull the fuel pump relay fuse after storage is someone who is held in very high regard by Porsche Germany. He has been invited to Germany many times by Porsche. He has decades of Porsche experience. I would never second guess any advice he gives me regarding my cars...ever.

As for the madness, differing opinions are within the RL guidelines.
It is unto the individual member to use the information and opinions posted in an adult manner and come to their own conclusion,

Besides, there is nothing like discussions regarding oil viscosity, tow vehicles or H&N restraints on Rennlist.

Carry on.

raineycd

So I noticed the other day that my local walmart has M1 0w-40. Just in time for me to start wanting to use 5w-50!!!!