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Jonny Hart

Why is the oil cooler at the front of the car?

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I’ve been poking around under the car today.    It strikes me that an oil cooler would fit in the rear wheel arch above the torsion bar or on the opposite side to the oil tank. 
 

Can’t really think of a good reason why it is at the front.   What am I missing?

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At first there was no external cooling. When the need arose for more cooling, a long length of brass pipe was used, this looped around in the front wheel arch and became known as the "trombone" cooler. I would guess there was not enough room to fit a sufficient length of pipe in the rear arch to get the required cooling. This, together with more efficient air flow up front established the location, which was tested and proven in racing before moving to production models.

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Ok on the evolution.  Not sure about ‘more efficient air flow up front’ though.  I think it is the low pressure in the wheel house that gets rid of the heat.   You’d get the same effect at the back.  

if a modern oil cooler with fan and thermostat was used, then we could delete the troublesome thermostat and oil lines and save a bit of weight too. 
 

 

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I am NOT a wrench, but I thought I recall reading that the long runs of pipe also aided in the cooling process.

Scott

 

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6 hours ago, Jonny Hart said:

Ok on the evolution.  Not sure about ‘more efficient air flow up front’ though.  I think it is the low pressure in the wheel house that gets rid of the heat.   You’d get the same effect at the back.  

if a modern oil cooler with fan and thermostat was used, then we could delete the troublesome thermostat and oil lines and save a bit of weight too. 
 

 

But the 3.2 does have a "modern" radiator cooler at the front doesn't it? I think you are right that it could be mounted elsewhere but how would you be sure that the cooling from the pipes themselves was allowed for, they kick out a lot of heat. Also, doesn't the thermostat assist with maintaining correct engine temperature? If it wasn't there IMHO the engine would run too cool for much of the time. Furthermore, when extra cooling is required, after power upgrades etc, the position of choice is the centre front. If this extra cooling were needed where would it go, opposite rear wheel well?

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Interesting - could use a modern (significantly less spendy than the P one) oil thermostat.

No cill oil pipes for knuckleheads to use as a jacking point as well.

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3 hours ago, Peanut said:

I am NOT a wrench, but I thought I recall reading that the long runs of pipe also aided in the cooling process.

Scott

 

+1 on this

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I can’t think of another engine that needs to have long exposed pipes to aid the cooling as well as an oil cooler itself. 

Surely you just take that into account and size the oil cooler accordingly?  E.g. the lines on the 964 are not exposed - it just has a bigger cooler. 

Must be progression in oil cooling like everything else.  @Phill says the 3.2 has a ‘modern’ cooler, 1984 was 36 years ago!

 

 

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8 minutes ago, Jonny Hart said:

I can’t think of another engine that needs to have long exposed pipes to aid the cooling as well as an oil cooler itself. 

This is true but how many other cars have a performance, oil cooled engine, stuffed in an enclosed space at the back of the car?  Modern water cooled 911s have front mounted radiators do they not?

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The opposite side of the oil tank would quite easily swallow a 964 sized oil cooler.   A quick google suggests modern oil coolers are more efficient and you could fit a 10 inch fan.   My gut tells me this has to be at least as good as 3.2 setup with its tiny fan.

 

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Posted (edited)

Aren’t the rear arches the worst places for an oil cooler? Heat from the motor you’re trying to cool is all around the rear arches and is being forced under the cylinders. If you stand next to a hot running air cooled the air blowing out of the rear arches is hot. Front arches negate all that. Or if you want ultimate efficiency, up in the front bumper. RSR style. 

Edited by Busybee

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^ When stationary yes.  Not so much on the move. 

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None of this matters.  It's all about what oil you fill it up with.

  • Haha 1

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Just now, Nige said:

None of this matters.  It's all about what oil you fill it up with.

Nope, its how you get the oil in there that matters

  • Haha 1

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1 minute ago, Type911 said:

Nope, its how you get the oil in there that matters

 

3 minutes ago, Nige said:

None of this matters.  It's all about what oil you fill it up with.

At the moment, it’s if you can drive the flipping things at all that matters

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Several technical points need correction in this discussion, in my pedantic opinion!

The introduction of the 3.2 did not give a different cooler to an SC.

The matrix type cooler came sometime around third year of production. Even then not all had the addition of a fan.

The main cooling mod between a an SC and a 3.2 was a large notch in the underside rear edge of the front bumper. This allowed more airflow into the front wing.

On the SC and earlier there was/is supposed to be a gap between the front valance and bumper. There to allow for movement of the impact bumper and airflow (?) of sorts.

Pre IB 911 race cars had supplementary cooling up front so the evolution of placement started there.

911 sporting use was always equally focused on rallying. The rear wing area is hardly a clean and safe area when traveling at speed on a muddy forest track.

Just my thoughts.

 

Mark

 

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Agree there needs to be a guard / liner but rear wheel house not that different to front in terms of mud and stones etc. 

I have arch liners and this area is the Probably the cleanest area on the car.

265259BA-3585-4833-9B40-AA05AECEFBA8.jpeg.1f509a815fd21483f1c37705243e192c.jpeg

 

 


 

 

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1 hour ago, Nige said:

None of this matters.  It's all about what oil you fill it up with.

 

1 hour ago, Type911 said:

Nope, its how you get the oil in there that matters

:lol:  you boys................

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4 minutes ago, Jonny Hart said:

imageproxy.php?img=&key=26d24dfdaa8bd0ebAgree there needs to be a guard / liner but rear wheel house not that different to front in terms of mud and stones etc. 

I have arch liners and this area is the Probably the cleanest area on the car.

Don't disagree with you in any way if this is looked at as a modern day reengineering, but IBs and earlier 911 never came with arch liners and the title question was "Why is the oil cooler at the front of the car?". Should the title have been "Does the oil cooler have to be at the front?"?

 

3 hours ago, Jonny Hart said:

E.g. the lines on the 964 are not exposed - it just has a bigger cooler. 

This is not the whole story, the front tub of the 964/993 was engineered with dedicated air ducting channels and corresponding front grills to get air from the front flowing through.

 

Why reinvent the wheel?

 

Mark

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It's not just the long run of pipes that aids cooling I assume the additional mass of oil in them is also a factor

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1 hour ago, SilverWT said:

Don't disagree with you in any way if this is looked at as a modern day reengineering, but IBs and earlier 911 never came with arch liners and the title question was "Why is the oil cooler at the front of the car?". Should the title have been "Does the oil cooler have to be at the front?"?

 

This is not the whole story, the front tub of the 964/993 was engineered with dedicated air ducting channels and corresponding front grills to get air from the front flowing through.

 

Why reinvent the wheel?

 

Mark

No wheels reinvented here but to answer your question of why?

1 - Thermostat is expensive and fragile.

2 - Oil lines expensive and get crushed. 

3 - Cleans up the side of the car if you don’t want cill covers or are doing a backdate.

4 - Removes the need for spendy backdate oil pipes when doing an SSI conversion. 

5 - Allows easier addition of a thermostatic fan as the electrics are right there in the engine bay.  

6 - Engine may well get to temperature sooner with shorter pipe runs.  Better for short journeys.

7 - Reduces the number of joins in the oil system so less prone to leaks.  I think I  can do this in just 8 connections including a modern thermostat.  
 

8 -  Allows installation of twin condensers at the front of the car for better AC performance. 
 

9 - Saves some weight.  Although it moves it to the rear it is counter balanced with oil tank.

10-   because it seems like a fun project and something that is a least worth trying   

 

Btw, on the 964, the duct does not provide ram air.  The fan is fully shrouded which means it is doing all the work.  The front duct does create a little high pressure on the fan inlet side that might aid the fan a little.   
 

 

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Just found out that slantnose cars run a rear oil cooler.   They have the duct in the wing for ram air obviously but think I can scoop some air up and over my arch liner (997 intercooler does similar).    
 

Fan and cooler tech has moved on so worth a shot. 

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4 hours ago, SilverWT said:

Several technical points need correction in this discussion, in my pedantic opinion!

The introduction of the 3.2 did not give a different cooler to an SC.

The matrix type cooler came sometime around third year of production. Even then not all had the addition of a fan.

The main cooling mod between a an SC and a 3.2 was a large notch in the underside rear edge of the front bumper. This allowed more airflow into the front wing.

On the SC and earlier there was/is supposed to be a gap between the front valance and bumper. There to allow for movement of the impact bumper and airflow (?) of sorts.

Pre IB 911 race cars had supplementary cooling up front so the evolution of placement started there.

911 sporting use was always equally focused on rallying. The rear wing area is hardly a clean and safe area when traveling at speed on a muddy forest track.

Thanks you Mark! Saves me doing it.

I like this thread though. People should check the temp of their front coolers sometime - they are usually pretty cold. My car has a nose cooler and it is not what I would call an essential upgrade.

I wouldn't put anything for road car cooling behind the rear wheels. I used to drive my SC in all weathers and that was the muddiest place on it! Arch liners a different story.

Some early Tuthill rally cars had a cooler standing up on the rear wing. That didn't last very long but not really dirt related. Longhood coolers are in the battery box locations now. Those get pretty warm...

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Cool, high pressure air up front, hot, low pressure air at the back would be a good reason the oil cooler is in the front

Only air cooled 911 'factory' rear cooler installation I can think of is on the original RUF CTR with it's NACA duct fed twin cooler arrangement, not exactly the same as an oil cooler as full boost isn't req'd stuck in traffic

 

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what the turbulence and airflow like behind the rear wheel?

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