RacingBeat

i'm late to the party......how bout this example:

yesterday i'm driving my 84 3.2 in what had to be 98 degrees or so outside temps.....we're sweating in the carolinas this week

so my gauge is a solid 8:30 at speed........as i got close to home i had to stop in a drive thru (no wait i can explain.......kids!!). in the space of FIVE minutes i was above nine o clock and well on the way to second white mark, which i believe was approaching 250 degrees....

i'm left with the feeling that if i were stuck for more than just a few minutes i'd be in a situation where i have to shut the car down. is that normal???

this again is why i hestitate to take the car to big events where traffic is a threat.......guess i have to wait until cooler months for that huh?

Mike Murphy

Is this normal? In a word, yes. But if you want to make a change and drop the temp, try installing the BMW thermostat switch at 99C that turns the ext. oil cooler fan on. If you let these air-cooled 911s idle while parked, they will get hotter and hotter and hotter. I usually turn the car off if I'm stuck in a line or something. If I'm in stop and go traffic, I use the gas and hold the RPM at 2000 to keep air flowing. It won't cool the engine once it gets hot, but it keeps the engine from getting hotter.

kplackmeyer

It's hotter than the hinges of hell in Baltimore this week. I have been keeping some notes regarding oil temp vs. ambient temp over the past couple of months. If the outside temps are less than 80 deg or so, I can run the car at high rmps at will...the oil temp will dance around 220, then come right down to 190-200 as soon as I drive easy. When it's 95 degrees, just driving down the interstate it will creep to 225-230. Running it hard is only possible for a short period...it will crank up to 240-250 in a hurry. Sitting in traffic at these temps is out of the question.

I have the carrera front cooler factory option, but no fan or shroud around it. That will probably be the next upgrade.

RacingBeat

thanks for the advice.......is this forum great or what?

tone40

i.e. through the bumper?

The BMW switch modification sounds like a great idea. I am going to have the bumper off next week and would like to tackle the modification.

GothingNC

Roasting here in Raleigh too, heat index is supposed to be around 108 today.

On a 95 degree day my temps will be at the 8:45 position if moving and goes up to 9:00 on the highway.

In the 80's , it does not go above 8:00 on the gauge in traffic and just a hair above the 1st white line when moving. I may run a bit hotrter then normal since I have 9.8 compression JE Pistons and Elgin cams.

The Porsche is now on jack-stands for brake work but it's been too darn hot & humid to even do the work late at night

I mainly plan to drive the car from September through June, why bother subjecting the air-cooled motor (and me) to the extreme heat

John

RacingBeat

yeah.......i guess so.......i've got a targa and here i am wishing for colder days.......sheesh

GothingNC

Outside temp now at 1:45

Temperature 101°F
Dew Point 73°F
Relative Humidity 41%
Heat Index 113°F

John

kplackmeyer

I feel your pain John...the conditions at 2:30 in B-more

100 Temp
109 Heat Index

Just ran out for lunch...less than a 15 minute drive, and the temps shot up to just under 230. And I think I lost about 2 pounds sweating in the car. Ug.

GothingNC

Still much better then dealing with snow, slush & Ice.

Temperature 102°F
Dew Point 74°F
Relative Humidity 41%
Heat Index 115°F


Keep cool

kplackmeyer

Amen, brother!

dshepp806

GothingNC: That's where I'm presently at,..letting her rest during this onslaught,..especially the last week...past 2 days: 99-100 temp with a 111 heat index....although she does quite well insofar as temp levels on a 30 - 40 mile run, even in this heat. Have a manual switch for the aux fan but don't need it so far.......have used it in stop and go just to see what it would do to 220 degrees!!

AC needs a recharge so being in it (EVEN MOVING) is quite a sweaty experience,..the AC system is stock and low on R12 (what else would I expect?).......She's a 89, 3.2L rebuilt (top and bottom) at 99Kmiles. Burns 1 quart every 6K miles (dependent upon which oil I use) !!!! No leaks, other than one VC thread that (eversoslightly) weeps...!!!

Gonna get her recharged in 2 weeks and will apply some exercise...I would expect the temps to remain reproduceable but will gain in the comfort (inside temp) zone...

Back to thread point: I have noticed severe wear in the foam gasket surrounding the aux cooler...Having read the great threads within this backyard, I have a brand new gasket to install this weekend,..to ensure air is focussed THROUGH the aux cooler....minimizing the loss "around" it.....

Right now I could use some snow and ice!!!!

Best to all,

Mike Murphy

Yes, whoever doesn't believe in Global Warming need only read the above posts! LOL.
Yes, this forum rocks.
Yes, these air-cooled engines are awesome and get hot with us. It's funny that the human body relies on air cooling, but technically it is water cooled as well.

Doug Hillary

Hi,
perhaps some additional information on engine lubricants and their operating temperatures may be of interest

Engine lubricants generally perform best in a range from 90C to 110C
Anti Wear (AW) additives progressively become "functional" beyond about 50C

Temperatures taken directly from the sump can be misleading. It is important to note where the temp sensor is located in the previous diagram in this thread

Some typical engine component temperatures are;
Top ring = >380C
Upper cylinder = >360C
Main bearing = >160C
Con rod bearing = >200C
Many turbo-chargers in normal road use have an exit oil temperature >150C (300F)
It is also interesting that many quite viscous lubricants (say a 20w-50 mineral) may take up to 5 minutes to circulate through the ring pack

In all cases the lubricant's viscosity must be suitable for the engine "family"
This is especially so regarding the lubricant's High Temperature High Shear (HTHS) viscosity which is measured at 150C. The minimum HTHS vis. requirement for a Porsche engine is >3.5cSt. At 100C the minimum is >11.1cSt. These are measured in extended test protocols (beyond ACEA's requirement) as part of the Porsche Approval process
Combined, these factors preclude the use of SAE30 lubricants (except in the Cayenne V6)

Note that just because a lubricant is quite viscous (say 20w-50) does NOT mean it will have a HTHS viscosity above Porsche's minimum. This is especially so with mineral lubricants as they age in use
Both SAE50 (20w-50 & etc) and SAE60 (25w-60 & etc) lubricants are only required to have the same minimum HTHS viscosity as a 15w-40 HDEO lubricant - 3.7cSt!

Mineral oils (car type) (continuous >110C)
These lubricants will operate quite well at up to around 115C
Beyond this figure they tend to oxidise quite rapidly. This leads to engine deposits and (usually) a permanent loss of viscosity and quite rapid oil degradation

Mineral oils (Heavy Duty Engine Oils ("mixed fleet" HDEOs 15w-40) (continuous >115C)
These lubricants will operate quite well up to around 125C
Beyond about 120C these oils tend to oxidise quite rapidly along with those associated "factors" noted above
Mixed fleet HDEOs must have a minimum HTHS viscosity of 3.7cSt - above Porsche's minimum.
Typical popular "mixed fleet" 15w-40 HDEOs are Shell Rotella T, some Delvac products, Castrol RX Super, some Delo products and etc.

Semi synthetic oils (car type and HDEOs) (continuous >120C)
Depending on the base oil and additive formulation these lubricants are quite reliable at up to 130C. They tend to resist permanently losing viscosity for extended periods and tend to degrade at a slower rate. Many now perform better than some "old" fully synthetic lubricants

Synthetic oils (car type and HDEOs of 5w-40 viscosity) (continuous >130C)
Depending on the oil's base stock and additive formulation these lubricants are quite reliable at up to 140C. They tend to be capable of retaining viscosity for very long periods and will last for extremely long periods with slow degradation rates in normal road use

It can be seen that all lubricating oils reach very high temperatures when in contact with certain engine components - how they are able to handle this is one reason why Porsche only Approve synthetic oils for all >1984 motors

I hope this is of some interest

Edward

Another option for Carrera oilcooler-equipped cars is to either install a fan, or wire a manual switch for the existing fan that overrides the thermostat's operation of the fan.

FWIW, quite a few of us 993 guys have added a simple switch so I can manually turn the oil-cooler fan on any time I feel it is necessesary. Even in the summer heat of SoCal (which can be in the 90s-100s), the oil temp drops like the proverbial rock from 9:00 down to 8:00 within a minute of hitting the switch. IMHO, this is the solution if you really must drive your SCs/Carreras in heat + potential traffic.

My SC is a track car, so I prefer NOT having a fan obstructing airflow, and so far even in 100-degree heat the temps "may" just kiss the 9:00-9:30 mark, but then drops as soon as the cooldown lap comes. Hope this helps

Edward