Confusion about oil path/flow diameter

[rnln]

I don't have the carrera cooler to measure but I remember reading somewhere that the oil path/flow ID need to be somewhere close to 1".

Reading this page, ELEPHANT RACING 911 Widemouth Oil Cooler, about wide mouth fitting, look like the stock fitting ID is 17.5mm? Am I correct? Anyone measured this? What is correct?

I have a spare thrombone loop cooler. Measured the ID, I found that it is around 20mm.

I bought a used rx-7 cooler recently and found that the bung's ID is around 16mm or 17mm.

Can come one veryfy if these numbers above correct? If so, I don't need to replace the bung. I can just weld on a 16an on top of the existing bung is enough. Am I correct?

Another question I have is about the stock oil filter. Is it on the way oil comming back from the oil cooler into the engine? If it is, then I am safe if I modify the cooler and accidentaly leave some metal shave in the cooler. Correct?

Thanks.

[kodioneill]

[Tyson Schmidt]

The filter is on the scavenge side, and is the first in line, then to the thermostat, then either right back to the tank, or through the auxiliary cooler, then back to the tank.

So no, if you have shavings left behind in the cooler, they will not be filtered before going back to the tank, and then to the engine.

[kodioneill]

Originally Posted by Tyson Schmidt

The filter is on the scavenge side, and is the first in line, then to the thermostat, then either right back to the tank, or through the auxiliary cooler, then back to the tank.

So no, if you have shavings left behind in the cooler, they will not be filtered before going back to the tank, and then to the engine.

looking at the diagram I have to disagree. It appears the oil from the auxiliary cooler goes directly to the oil filter first.

[boyt911sc]

Originally Posted by rnln

I don't have the carrera cooler to measure but I remember reading somewhere that the oil path/flow ID need to be somewhere close to 1".

Reading this page, ELEPHANT RACING 911 Widemouth Oil Cooler, about wide mouth fitting, look like the stock fitting ID is 17.5mm? Am I correct? Anyone measured this? What is correct?

I have a spare thrombone loop cooler. Measured the ID, I found that it is around 20mm.

I bought a used rx-7 cooler recently and found that the bung's ID is around 16mm or 17mm.

Can come one veryfy if these numbers above correct? If so, I don't need to replace the bung. I can just weld on a 16an on top of the existing bung is enough. Am I correct?

Another question I have is about the stock oil filter. Is it on the way oil comming back from the oil cooler into the engine? If it is, then I am safe if I modify the cooler and accidentaly leave some metal shave in the cooler. Correct?

Thanks.

rnln,

The oil flows out from the engine and goes to the auxiliary thermostat. When the oil temperature is below 180°F (approx.), it flows back directly to the oil tank via the aux. thermostat by-pass valve. Oil enters the oil tank passing thru the oil filter and down to the oil reservoir. The oil line to the auxiliary cooler (trombone or Carrera) is filled with oil after start of the engine and stops at the thermostat return valve. Return valve does not open until about 180°F. For every opening of the by pass valve, an equal amount of opening is also occuring in the return valve. So at any given time, the combined orifice area/opening thru the aux. thermosat is maintained at the same level.

So what ever debris or metal shavings inadvertently left in the cooler would go thru the oil filter before mixing with the oil in the botton of the tank. Hopefully, the metal shavings won't cause any problem in the aux. thermostat's operation. The wider mouth fitting is unnecessary and I'm sure Chuck won't be happy reading this line.

Tony

[rnln]

thanks everyone, thanks Tony. I feel safe to play with this now.
Anyone know what is the ID of the carrera stock cooler fitting?

[JFairman]

Tony's correct on the oil flow but if the oil is cold and the viscosity is thicker because of it, it will have more resistance trying to flow through the filter element and the oil filters internal bypass valve will be pushed open and some unfiltered oil will bypass the filter element and drop into the oil tank along with the dirt and metal filings.

...then the pressure side of the oil pump will suck some of them up with the oil through the large S hose and pump them into the oil galley so they can become embedded in the main and rod bearings lead babbit layer scratching the crank journals, some will clog the piston squirters and the rest goes down the oil galley to clog the cam spray bars, eventually destroying the cams, rockers, valve guides and valve stems from lack of oil spray.

[rnln]

so bascially, the oil filter is by passed when it's cold? Meaning we are all always driving without filter for the first couple miles?

[JFairman]

not all of it, some goes through the pleated element while some bypasses the element due to resistance to cold flow.

[Tyson Schmidt]

Just realized I was envisioning the '72 system, and the 964/993 system instead of the others like the diagram shown.

That's interesting that the '72 and 993/964 systems don't filter after the cooler but the others do. Hmmmmm.........

[rnln]

So I should do this in hot summer to avoid, or less chance of, damage.

[DW SD]

Originally Posted by rnln

So I should do this in hot summer to avoid, or less chance of, damage.

After modifying, send your cooler to pacific oil coolers for pressure testing and cleaning. This service is $120, far cheaper than the cost of a replacement engine.
Pacific Oil Cooler Service, Inc. - Home

A friend told me he adapted fittings to an old Mercedes Benz oil cooler from the 300D model for a front mounted application. He changed to AN fittings. The cooler was $50 at a junk yard.

Doug

[boyt911sc]

Originally Posted by rnln

so bascially, the oil filter is by passed when it's cold? Meaning we are all always driving without filter for the first couple miles?

rnln,

NO!!!!The oil filter is never by-passed as far as the SC/Carrera configuration is concerned. When the engine is cold, the oil is circulated within the engine until the engine thermostat opens up and send the 'warm' oil to the auxiliary thermostat. Auxiliary thermostat does not come into play until around 180°F (+/- 5°). Some portion of the oil is diverted to the auxiliary cooler, the tube (cooler) is filled and stop its travel at the return-valve (aux. thermostat) and the rest of the oil is by-passed at the aux. thermostat going straight to the oil filter and down inside the oil tank. This cycle will continue until.........the oil temp. of about 180°F is reached.

At this point (oil temp. @ 180°F), the by-pass valve starts to close and the return-valve opens too. Remember that the by-pass valve and return-valve are configured on a single cylindrical slide valve. It is designed in such a way that the amount of closing/opening is always equal to 100% at anytime during its operation. The slide valve operation (aux. thermostat) is temperature dependent.

For example as the engine oil is heated:
By-pass valve fully open........Return-valve fully closed.
By-pass valve 90% open.......Return-valve is 10% open (90% closed).
By-pass valve 50% open.......Return-valve is 50% open (50% closed).
By-pass valve 40% open.......Return-valve is 60% open (40% closed).

In summary, all the engine oil circulated to the auxiliary thermostat passes thru the oil filter cold or warm. HTH.

Tony

[rnln]

Thanks Tony,
Thanks for the explanation. I am happy to read your detail which makes me feel much safer to play with the cooler, but I think JFairman was talking about a valve somewhere in the fitler/tank area, not the aux. thermostat, if I read JFairman correct. Honestly, I never heard about this before. Are you familiar with this area?
Anyone familiar with this?

[boyt911sc]

Originally Posted by rnln

Thanks Tony,
Thanks for the explanation. I am happy to read your detail which makes me feel much safer to play with the cooler, but I think JFairman was talking about a valve somewhere in the fitler/tank area, not the aux. thermostat, if I read JFairman correct. Honestly, I never heard about this before. Are you familiar with this area?
Anyone familiar with this?

rnln,

I haven't heard it before but JF could be completely correct. So this is something to investigate and learn from his information. Anyone would like to share their knowledge and experience about this topic? I got a spare oil tank that I could inspect and dissect. Thanks.

Tony

[Bill Verburg]

Originally Posted by boyt911sc

rnln,

NO!!!!The oil filter is never by-passed as far as the SC/Carrera configuration is concerned. When the engine is cold, the oil is circulated within the engine until the engine thermostat opens up and send the 'warm' oil to the auxiliary thermostat. Auxiliary thermostat does not come into play until around 180°F (+/- 5°). Some portion of the oil is diverted to the auxiliary cooler, the tube (cooler) is filled and stop its travel at the return-valve (aux. thermostat) and the rest of the oil is by-passed at the aux. thermostat going straight to the oil filter and down inside the oil tank. This cycle will continue until.........the oil temp. of about 180°F is reached.

At this point (oil temp. @ 180°F), the by-pass valve starts to close and the return-valve opens too. Remember that the by-pass valve and return-valve are configured on a single cylindrical slide valve. It is designed in such a way that the amount of closing/opening is always equal to 100% at anytime during its operation. The slide valve operation (aux. thermostat) is temperature dependent.

For example as the engine oil is heated:
By-pass valve fully open........Return-valve fully closed.
By-pass valve 90% open.......Return-valve is 10% open (90% closed).
By-pass valve 50% open.......Return-valve is 50% open (50% closed).
By-pass valve 40% open.......Return-valve is 60% open (40% closed).

In summary, all the engine oil circulated to the auxiliary thermostat passes thru the oil filter cold or warm. HTH.

Tony

It's always possible for some oil to bypass the oil filter due to it's internal spring structure, if there is enough pressure on the unfiltered side the spring compresses allowing oil to by pass the filter element. Under what conditions this applies I do not know, if you measure the strength of the spring you would know, it is a fairly stiff spring.

993s filter on both the scavenge and pressure sides, others only on the scavenge side

[rnln]

My finger is still hurt. I took a filter out, looked into the hole and saw a big spring. Let see how much force needed to compress this spring, just curious. I use a flat screw driver to push on it. It is very hard, enough for me to jam my finger when the screw driver slipped, arggg. So look like there will be a chance, some situations, the oil will by pass the filter. Learn something new everyday.
Thank you everyone.

Can I come back to the second question?
What is the ID of the carrera stock cooler's fitting, anyone know?