To fan or not to fan, that is the oil cooler question

[tdskip]

Hi guys - getting serious about dropping engine so now seems like a good time to install the front oil cooler on my '74 with a 3.2 conversion.

Any thoughts about going with a set up with vs without the fan? Is the fan overkill for a street car in SoCal?

Are the hard lines different for the front cooler w/ the fan?

Thanks

[Danny_Ocean]

Lots of debate on this matter in previous threads. If you're going to go through all that work to add a front oil cooler, why not put a fan in? Although you're in temperate SoCal today, you might be living in AZ next year.

Hard lines are the same. Fan piggybacks on the cooler.

[Targa Me]

Put the fan on and you can use; either a thermostat or manual on/off switch to control it.
So CA can get quite warm, especially if you find yourself in typical So CA traffic.

[IROC]

I don't see how you can get along without a cooler with a 3.2. Also, if you're going to install a radiator style cooler, a fan is a must unless you're going to mount the cooler in a front bumper opening. Even with a fan, if the cooler is a fender mount, you really need to ensure the fan is ducted in such a way to ensure that the airflow goes through the cooler and not around it. BTDT.

[tdskip]

Thanks guys.

(I didn't do the 3.2 conversion, DPO did, so I get to rework lots of, um, stuff)

[sc_rufctr]

Originally Posted by tdskip

Thanks guys.

(I didn't do the 3.2 conversion, DPO did, so I get to rework lots of, um, stuff)

Nothing to ad about the fan but I can relate to having to redo what a PO has done...
I took me nearly 18 months of weekends to get my car right.

[tdskip]

Originally Posted by sc_rufctr

Nothing to ad about the fan but I can relate to having to redo what a PO has done...
I took me nearly 18 months of weekends to get my car right.

Yes, a lot of "value add" to remove I bet.

[dipso]

I didn't put the fan in. Cools just fine.
I went from no oil cooler to the Elephant big mouth. My temps dropped about 40 degrees. I don't see the need for the fan.
With all the oil in the engine, in the tank, the additional oil in the lines and then in the cooler itself. I don't see the benefit of just blowing air on the oil in the cooler. It's not that much by itself.
By the time it leaves the cooler and mixes with the oil in the lines on it's way back to the motor, I don't think it would be any cooler, maybe one or two degrees.

[cashman]

I just replaced my non working OEM fan with a 7.5" Spal. There are many comments that you actually restrict air flow with the fan while at highway speeds. That may be somewhat true but with all the hardware (bumper, horns, foglights, wiring) I found the entire area to be rather air restricting to begin with. So I replaced the fan and changed the thermo switch to the BMW version. That way, regardless of where I am I have the additional air flow if needed. I don't expect it to kick on often but at least it can if needed.

[86 911 Targa]

Originally Posted by dipso

I didn't put the fan in. Cools just fine.
I went from no oil cooler to the Elephant big mouth. My temps dropped about 40 degrees. I don't see the need for the fan.
With all the oil in the engine, in the tank, the additional oil in the lines and then in the cooler itself. I don't see the benefit of just blowing air on the oil in the cooler. It's not that much by itself.
By the time it leaves the cooler and mixes with the oil in the lines on it's way back to the motor, I don't think it would be any cooler, maybe one or two degrees.

The late '86 911 cars were factory equiped with the oil cooler fan, similar to the 930.

However, the early '86 911's were not equiped with a fan for the radiator type cooler.

Having to re-seal a lot of the '86 M/Y 911's, under the 50k miles/5yr warranty,
Porsche added the fan on the late 911 '86 models.

We added the fan to our '86, along with a 210F on/195F off temp switch
which dropped the temps by about 25F during 90F+ in town, and highway.

Try to keep your oil temps between 185F-210F.

Good luck,

Gerry

[SCrescue]

FWIW, I run a finned cooler on my car without a fan, and my temps hover a tick above the low hash mark during the hottest days of Florida's Summer heat...in traffic no less. Have not seen a need to add a fan.

[dipso]

Just a little update.
For the first time since the cooler install, and i was paying attention, I had a chance to drive in some warm weather. It was about 90 the other day and after about 3 hours of driving my temps never broke 200.
This was all highway.

The fan dropping temps 25 might be worth looking into. I am going to keep an eye on the temp from now on and might think about adding one in the future if I touch 210.

[tdskip]

Thanks for the update

[mepstein]

I'm adding an aux cooler & fan on my 914 3.2 conversion to plan for worst case, long, slow traffic jam in middle of summer. It happens so I'd rather be prepared.

[Head416]

If you find yourself stopped in traffic on a 100-degree day without a fan you'll be kicking yourself. Just my prediction.

[Grady Clay]

Our cars have a thermostat (aah yes, they have two).
Being ‘too cold’ never seems to be a problem as the thermostats only open to maintain a ‘minimum’ oil temperature.

The problem arises when the cooling capacity (combination of cooler size, driving air flow, fans, etc.) is exceeded by the heat output into the oil.
When this happens, the temperature of the oil goes up while the thermostats are ‘full-open’ (this happens about 200ºF).
With the higher temperature the heat is dissipated. More heat, higher temperature.

The only way to keep the system operating ‘on-the-thermostat’ (where the thermostats are not full-open) is to increase the oil cooling capacity.
This can be with larger (or multiple) oil coolers.
Better air ducting (only effective at driving speeds).
More powerful or larger fans (most useful in traffic) and appropriate air ducting.


There is ‘another way’ to add additional cooling.
This is at the source of the heat: heads and cylinders.
There is the combination of standard Porsche parts that lets the engine fan turn 1.82:1 of the crankshaft speed.
Original fan ratios are from 1.3:1 through about 1.6:1.
The additional air cooling of our (air cooled) heads and cylinders reduces the heat that the oil system must dissipate.

There is an additional advantage: more air is drawn through the engine lid A/C condenser, improving the A/C function.

In my humble opinion every 911 should have a cooling system that keeps the temperatures under control, on the thermostat in the range 180ºF to 210ºF, never above.

Too high temperature is the killer of our machinery.

Best,
Grady

[Tidybuoy]

My '74 has the front cooler but without the fan.

Recently, I broke a headlight and when the fixture was removed, there was a large hole behind the light that the prior owner used when at auto-x. He would remove the passenger headlight which allowed more air to the fan.

Anyway, when my headlight broke, I had to drive home (about 100 miles) without the fixture and the car ran noticably cooler; presumably because the cooler was getting more fresh air.

So, I would assume that the fan helps.

[DaddyGlenn]

Originally Posted by Grady Clay

{snip}....There is the combination of standard Porsche parts that lets the engine fan turn 1.82:1 of the crankshaft speed.....{snip}

Pray tell, what is that combination? And how much, if any, HP is consumed turning the fan that much faster?

[Grady Clay]

Glenn,

There are LOTS of threads about this.
Do some searching and post a summary.
There are part numbers and proceedures.


There is a ‘Tutbo’ fan (used on many other 911s) that is 245 mm diameter and has a 80-84 mm split pulley.
The latest version is used on the 3.2 Carrera.

There is a 134 mm OD crankshaft pulley (with and without A/C shiv) used with the 226 mm fans on the ’78-’79 911SC and others.

This combination turns the fan about 1.81:1 (Porsche says) of the crankshaft.
You can measure your exact ratio as it varys slightly with the pulley half shims.

Additional power loss is minimal.
Even turning the engine 8000 rpm, the fan blades are well sub-sonic.
If you are driving at 6500 rpm, the higher speed fan has reduced some efficency (power/flow) but not to the extent of less flow.
With the engine cylinders and heads cooler, the engine produces more power.
It is a net gain.

The big gain is keeping the heat–producing parts cooler.
This extends to high-wear parts like the camshafts and rocker arms.
With all the parts cooler, the oil is required to carry away less heat.

Best,
Grady

[rusnak]

The fan is a must-have. I'd say from experience that 25F reduction is about right.