Why does a 3.0 have two oil coolers?

[TeeJayHoward]

I'm trying to find a way to fit some oversized oil temp/pressure sensors into my 3.0SC motor and stumbled across a post showing the 964 oil pressure/temperature console.

"Man, that'd be perfect!"

...Except it takes the place of the OEM thermostat. Which makes me think the 3.6s don't HAVE a thermostat there. Checking it out and... Sure enough, looks like they removed the engine oil cooler entirely, relying instead on the front fender cooler. So why does my 3.0SC, which has a fender cooler, still have the engine oil cooler from the earlier models? Can I remove the in-engine thermostat and swap over to a 964-style setup so I can have that valley for my sensors? It looks to me that if I just plugged the engine oil cooler lines (something like this and I wouldn't even need to tap...) and yanked the thermostat, I could rely on the fender cooler for all oil cooling, no?



(...Also replacing the "auxiliary cooler loop" with a proper rad/fan a la 993)

Or am I massively overthinking/overspending this, and there's an easy and obvious solution I'm missing?

[Bill Verburg]

Originally Posted by TeeJayHoward

I'm trying to find a way to fit some oversized oil temp/pressure sensors into my 3.0SC motor and stumbled across a post showing the 964 oil pressure/temperature console.

"Man, that'd be perfect!"

...Except it takes the place of the OEM thermostat. Which makes me think the 3.6s don't HAVE a thermostat there. Checking it out and... Sure enough, looks like they removed the engine oil cooler entirely, relying instead on the front fender cooler. So why does my 3.0SC, which has a fender cooler, still have the engine oil cooler from the earlier models? Can I remove the in-engine thermostat and swap over to a 964-style setup so I can have that valley for my sensors? It looks to me that if I just plugged the engine oil cooler lines (something like this and I wouldn't even need to tap...) and yanked the thermostat, I could rely on the fender cooler for all oil cooling, no?



(...Also replacing the "auxiliary cooler loop" with a proper rad/fan a la 993)

Or am I massively overthinking/overspending this, and there's an easy and obvious solution I'm missing?

964 and 993 have only front mounted oil coolers
964 has a blocked off oil gallery that would need to be drilled to run an engine mounted cooler

993 has this drilled and installs a second oil filter in that spot

there are also different console caps used depending on how it's all supposed to work

to eliminate the engine mounted cooler on an SC or 930, you would use 964.107.073.20

to use a second oil filter ala 993 you would use
the difference in the covers is the depth of the inner wall
930.107.073.02


here's the .02 cover top and bottom

[TeeJayHoward]

Originally Posted by Bill Verburg

to eliminate the engine mounted cooler on an SC or 930, you would use 964.107.073.20

to use a second oil filter ala 993 you would use
the difference in the covers is the depth of the inner wall
930.107.073.02

Bill, those parts numbers (073) seem to correspond to the breather cap, not the thermostat cover in your pics.

Thanks to your pic, I now know that 930.107.767.02 is the part I'm interested in purchasing and using in lieu of my thermostat.

Thanks!

edit: Making notes.

930.107.767.02 would block off the top (cold) port, making it so that the oil always flows through the on-engine oil cooler/radiator. Useful if I wanna replace the engine oil cooler with the 993.107.057.01 secondary oil filter housing.
964.101.768.00 would NOT block off the top (cold) port, making it so that the oil cooler isn't a flow-through system. Marginally cooler than eliminating the radiator, warmer than blocking off the top port.
993.101.768.01 would NOT block off the top (cold) port, making it so that the oil cooler isn't a flow-through system.

I'm guessing the difference between the 964 and 993 parts have something to do with the threads on the sensors or angle of same.

edit2: Ordered the 930 part. My car will take longer to warm up since the on-engine oil cooler is now permanently engaged, but this way I have some leeway before spending thousands upgrading the rest of the oil cooling system.

[TeeJayHoward]

Next question: With the 964/993-style sensor locations, how does the oiling system prevent that whole ex-thermostat hole from becoming a giant air bubble?

On a cold start, that entire hole is empty, right? Just air in there? How does that air get displaced with oil given that the high point where the sensors are mounted is above the "drain"? Basic physics tells me that the hole would fill with oil only up to the uppermost hole, at which point the air would just compress - it's got nowhere to go. At this point, the pressure sensor would be getting an incorrect reading (air pressure vs oil pressure), the temp sensor would be reading air temp, not oil temp since it's not submerged... Just doesn't seem right. Made a little diagram to try and explain what I'm talking about, not sure if I am asking the question right. Blue = air, red = oil.

[PeteKz]

Why are you trying to fit "oversized" oil pressure and temp sensors? This seems like an extremely difficult and expensive solution to a non-problem. Is your oil getting too hot right now?

[Bill Verburg]

here's a 964 side
the 911/930/964/993 block are all similar w/ some differences

the 2 passages used by the 911 cooler or 2nd oil filter on a 993 can be seen undrilled here on a 964

the t-stat in the chamber is only present on a 911 or 930 and is not used on a 964 3.6 or 964 3.3t or 993

a 911 or 993 will have these holes drilled

there are 3 top covers, the 2 I mentioned above and a 993 cover, there are small difference in the sensor holes in the covers

to remove the 911 oil cooler and t-stat you need to plug the 2 holes or install a 964t or 993 oil filter console and use the 964 .02 or .20 top cover, then that area functions as on a 964

since you have the holes already drilled the easist thing to do is install an oil filter console and use the .20 top cover, the .20 cover has a deep inner wall that directs flow to the cooler

[TeeJayHoward]

Originally Posted by PeteKz

Why are you trying to fit "oversized" oil pressure and temp sensors? This seems like an extremely difficult and expensive solution to a non-problem.

I have aftermarket gauges. These gauges require a specific sensor - I can't re-use the Porsche ones. The temperature sensor in particular is extremely long - think 964 temp sensor. It cannot go in the factory temp sensor hole, as that's super short depth with a right-angle spade connector. Even if I were to somehow fit it in, the connector would be going right through the belt and the engine support.

New sensor:


Old sensor:

[ErrorMargin]

Originally Posted by TeeJayHoward

...Or am I massively overthinking/overspending this, and there's an easy and obvious solution I'm missing?

Option 1 - Plumbing
I'd think about adding some plumbing where the factory oil temp and pressure sensors are located.

For example, remove the factory oil temperature sensor, and run some plumbing from where the factory temperature sensor plugs in over to a small vessel where you can have your sensors mounted and the factory oil temp sensor mounted.

You could do the same thing at the back of the engine with the oil pressure light switch. You would then have an outlet with a very small orifice to maintain pressure at the top of the vessel to ensure that it fills completely so the vessel fills up completely allowing for accurate temperature and pressure readings.

The outlet can run back to the breather cover or the oil tank.

The orfice would have to be very small in order to ensure that this setup does not cause a loss of system pressure.

Option 2 - electronics
Do some testing to characterize the outputs of the factory temperature and pressure sensors vs given temperatures and pressures in ohms. For example, 180F might be 90 ohms, 20psi might be 45 ohms, etc. I think you can probably find tables with this data on this forum.

Next, do some testing with your new sensors or new gauges to find out what resistance or voltages they expect so that you can build a mapping table.

Then, find an aurduino or Pi developer to write a program and fabricate the hardware to connect to the factory oil pressure and temperature sensors so that it can read the data and then output the correct voltages to the various gauges.

This setup could log the data and automatically upload it to your computer over your house wifi when the car is in your garage, etc.

You could also add additional sensors like exhaust/cat temp, oil tank temp, rpm, maybe even a knock sensor.

I think you can find someone to do this for you fairly easily on the aurdino or Pi forums.

Aside from logging and getting data from other sensors, the benefit of this is that you don't need to do any plumbing or make any changes at all to the oil flow or cooling.

[snbush67]

Caution; I think that for typical street driving or short trips, that the oil may not come up to operating temp quickly or at all. If the oil doesn’t get hot enough then it doesn’t boil off any condensation, moisture or contamination.

Edit: reading through your comments I think you’ve already discussed this.

[dannobee]

Oh, you have aftermarket gauges!

Look up the specs on the sensors that were provided and compare to the Bosch PST-F1, which is a sensor that measures both pressure and temperature in one compact unit. You'll need a 5V reference to drive it, either from one of the factory ECU's or any of the aftermarket ECU's. If you're still on some version of mechanical injection you can buy a 12 volt to 5 volt converter for under $10.

http://www.bosch-motorsport.de/content/downloads/raceparts/en-gb/54249355.html#/Tabs=9007199309001995/

[spuggy]

Originally Posted by TeeJayHoward

I have aftermarket gauges. These gauges require a specific sensor

If the people who make the gauges won't tell you what the senders are, then they suck and you should call them out so the rest of us can avoid them...

Temperature sensors are just a thermistor in a package. There's 2 slightly different chemical compositions for NTC (negative temperature coefficient) sensors that I've encountered/know of - the original Bosch, and the one that Magneti Marelli uses. While these do result in slightly different temperature curves if you graph the calibration table, they're not wildly different - using the wrong table might make them read as much as 10C off at various points during warmup - and the difference tends to disappear at higher readings anyway, IIRC.

Ducati uses a Magneti Marreli short-reach temp sensor - also used in Fiats and certain years of Land Rover etc. Bosch short reach sensors include Porsche and VW ones.

VDO also make temperature sensors (the sender you show has what might be a VDO part number on it). I'd SWAG that they likely use the Bosch composition. If not, their tech support should be able to provide a calibration table. Or just test yours, compare to a Bosch/MM calibration table - and/or pick one from the VDO catalog in a more convenient package.

Gotta be easier than screwing with the thermostat/oil console...

As far as I know, pressure sensors are linear, variable resistance, typically against a 5V reference. So pick a sender with a convenient thread size.

[Showdown]

TeeJay-

You might look into a different sensor. If you can get the specs on the sensor you were going to use you can replace it with something else.

I replaced my oil temp sensor with this temp/pressure sensor for use with my ECU:

https://www.platinumracingproducts.com/en-us/products/mscs-10-bar-gauge-pressure-temperature-sensor

[TeeJayHoward]

There's the temp gauge chart. I don't have one for the pressure sensor. If there's a combination temp/pressure sensor (100psi) out there that has the same specs, I'm not against using it and keeping my thermostat. I could just replace the pressure switch next to the thermostat with it and be fine. After all, my engine doesn't overheat or anything. My current cooling system is adequate. I just really like these gauges and would like to use them.

Also, I've got the wrong sensor for the pic above. 901 641 632 00 is my factory sensor, which is indeed long depth - it's just that the connector on top is short depth, vs the new "sealed" style connector. If anyone knows a way to get a table for that... I'd appreciate it! (edit: Is this it?).

Now that I think about it, it's not a bad thing to have the extra sensors anyway. I can feed the factory senders' data to the ECU for monitoring, and the new sensors data to the gauges.

[Jonny H]

NTC thermistors are non-linear and use a 'correction constant' so that software/electronics can linearise the reading. Porsche state the resistance and sometimes the beta value their sensors in the wiring diagrams. Typically the 'base' resistance is 10k, 15k or 25K usually stated at a particular temperature e.g. 10k at 25 deg C.

Even without this info, the resistance can simply be measured and the beta can be calculated. See here:

https://www.ametherm.com/thermistor/ntc-thermistor-beta#:~:text=The%20beta%20value%20of%20an,temperat ures%20over%20a%20given%20range.

Option 1.

Since the only temp you really care about for oil temp is above 90 deg C, you should compare the Porsche and new sensors resistance in hot water at 90 deg C to say 100 deg C. Plot the 2 graphs. If they are the same base resistance and not wildly different then just use the old sensor.

Option 2.

Characterise/calculate the resistance and beta of the new sensor or ask the supplier - they might tell you. Then find another NTC with the same spec and buy it as a PCB component from Mouser - it will look like a small bead capacitor with legs. Drill out the old sensor housing and bond the new sensor into the old housing.

[unclebilly]

You need a 2nd cooler with a 3.0L.

The 76 3.0 Turbo I had was horribly undercooked with just an engine mounted cooler and the trombone cooler. It was fine while driving at speed but when I took it to Luft in 2019, I had to keep shutting it off in LA traffic to keep it from overheating.

My 77 track car was fine with the trombone when the engine was stock. When I rebuilt it to high comp 2.7 RS spec, the cooling system was no longer able to keep the engine cool at the track.

I installed a RX7 cooler spliced into the trombone cooler and everything was fine.

https://forums.pelicanparts.com/porsche-911-technical-forum/492336-budget-oil-cooling-myth-dispelled.html

All these years later and lots of street and track use, car still running fine and the factory scavenge pump had held up fine.

[PeteKz]

Follow on to what Jonny said: I'd first try hooking up the Speedhut gauges to the existing Porsche sensor and see if it reads he same. If so, drive on. If it's off by a certain amount, just figure that into your reading. Brain-ware is cheaper than software or hardware.