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Jonny Hart

Rear Mounted Oil Cooler project

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So do you need to get to a point when the fan only really kicks in at idle or extreme pressing on situations.  I.e. you don't it on all the time?

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@Nige.    Well there’s a couple of things that I’m mulling over...

Oil thermostat opens at 82C.   Looking closer at the fan stat it runs at 88C but has to get down to 79C before it will switch off.  

I’ve mounted the fan temp stat almost  directly on the thermostat housing.   This probably explains why the fan always runs.  The body of the thermostat and hence the fan stat is always going to be at least 82C. 
 

The next move could be to put the fan stat nearer to the oil cooler.  
 

I’ll also see what happens with the fan off so I can gauge its performance.  

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Out of interest do you do your tests with a protective guard in place? Also, how much less oil do you think is in the system without the long oil pipes?

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15 minutes ago, Phill said:

Out of interest do you do your tests with a protective guard in place? Also, how much less oil do you think is in the system without the long oil pipes?

The guard is going back on for round two of testing.   I doubt it will make any difference as fully sealed fan arrangements like this do not use ram air.  All they need is ample pathway to grab enough air from the input side.  My full arch liners are worst case scenario but still allow air in from above and below.  

A full sealed fan is part of the reason why the fan will run most of the time.    Interestingly, having played with a 964 last few days it totally needs the fan also when stationary.   

I’m ordering an even larger cooler as I can now see a way of fitting it, plus a higher CFM fan.   I want to get to the stage where I can push the temp down on demand under prolonged load.   

I’m treating this like any product development. If you know anything about our products, you should know how thorough we are at testing but it takes time.  Lots of time.

 

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Interesting project Jonny.

When I made the custom cooler in the nose of mine, one thing that I learnt was there are significant differences in the performance of the core itself. Changing to a higher quality more efficient core could be an easy win.

If you ended up going down the custom cooler route you could also incorporate an alternative method for heating the car instead of blowing air around the exhaust......

Something along these lines (but better):

https://www.demon-tweeks.com/uk/demon-tweeks-lightweight-heater-tsdlwh/

 

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22 minutes ago, ALEX P said:

Interesting project Jonny.

When I made the custom cooler in the nose of mine, one thing that I learnt was there are significant differences in the performance of the core itself. Changing to a higher quality more efficient core could be an easy win.

If you ended up going down the custom cooler route you could also incorporate an alternative method for heating the car instead of blowing air around the exhaust......

Something along these lines (but better):

https://www.demon-tweeks.com/uk/demon-tweeks-lightweight-heater-tsdlwh/

 

Two steps ahead of you there mate.  🤓

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Our for a blat again.  25C ambient.  This time with arch liner fitted.  As predicted, no change in oil temperature.

Next, with the engine already hot,  I disconnected the fan and let it sit there.  It warmed up and then plateaued just below the half way mark and stayed there.  A bit cooler than a 964 with a failed oil cooler fan.

E7408F96-0CC8-4D3A-9392-6568E9C12952.thumb.jpeg.5fb3e14676503c5fd9f09538c36a67be.jpeg

Driving with no fan resulted in reaching the half way mark but I didn’t go any higher in normal driving but probably would under more load.

Fan connected again and normal state of affairs is resumed as below:  

2CA0026E-287B-46A6-93DC-F4C2C9C5DD63.thumb.jpeg.9cf603ba66c783bcfe3c9a52f2598f68.jpeg

 

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Jonny, you are very tenacious and I’m sure the end product will be masterful.

Unfortunately my pipes and Cooling now I’ve add the additional  front fan are fine so in the near future I don’t see a need for me to change, but hopefully There will  be many that do.

Good luck 

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If you were paying attention you’d have seen that I added 10 litres of oil.    There was a bit in the bottom of the engine as I did not have to remove the sump plate.  I knew I’d be having less oil but was a bit surprised to find it is quite over filled!

So I measure the capacity of the original system.

brass oil cooler.  1 litre  

All external pipes including those around engine.   I did not fancy getting messing with these so I took a estimate based on 20mm bore and 5.5m total length.  That gives about 1.8 litres.

So a total of 2.8 litres for the cooler and pipes. 

My modern oil cooler is 0.4 litres and I have 2 metres of hose (0.6 litres)  so 1 litre in total.   So 1.8 litres less than stock.  

Plus the bit left in the engine explains that then!

Out and about again today.  Just sits right on the 90 deg mark +/-  a needle width.  

 

 

 

 

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Posted (edited)

I’m still in the same configuration for the oil cooler.   There are zero overheating issues when standing still.  Prolonged full load appears ok for our climate.   Still going to try a larger fan and look at this for cabin heat at some point. 
 

At the front, now I’ve fitted a second AC condenser, I fitted these small horns on the original oil cooler bracket.   I had to remove the lower oil cooler bracket to accommodate the condenser. 
 

421C0F66-1CF3-46E6-B025-08B649EEB7D0.jpeg.0d67cf44e78dd09b3db56d1202457c69.jpeg

Edited by Jonny Hart

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Ok, this project is starting to get interesting now.   It’s 13 deg C here so a slightly chilly day.   After draining a couple of litres of oil, I took the car out for a spin. I travelled perhaps 5 miles and the car was barely warm, showing half way between lowest and 90C mark.  No fan on obviously at this point.  
 

Pulled over and was surprised to find that the thermostat was open and the oil cooler was hot.   Conventional wisdom says that on a normal 911, the thermostat would not be open yet.   I switched on the fan manually and found that the air coming out was around 60 deg C.  
 

Many people over the years have poo pooed the idea of using the front mounted oil cooler for heating but this now makes that a viable option.   Next thing is to see if I can duct the cooler output to the flappers. 

Oil temp:

F03291DD-2451-4614-B7B3-1DD864DAAD0A.jpeg.a9809adf5fef986e1fd44893698b9358.jpeg

Temp of air exiting cooler:

1887DD8A-A568-427C-AD81-2C0B8C8E7B31.jpeg.a4e967efdee074bd214ac046f272a091.jpeg

 

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17 hours ago, Jonny Hart said:

Many people over the years have poo pooed the idea of using the front mounted oil cooler for heating but this now makes that a viable option.

Have they? It makes perfect sense to me. It will be interesting to see how you duct the air out without impacting on the actual cooling performance.  At least with the cooler in the rear arch, it is nice and close to the flapper boxes.

I've always kicked myself for not incorporating some heat functionality into my front cooler. I had ideas about either adding a jacket to the oil entry end of the cooler for water/coolant to flow through and then a small inline pump and something similar to the off the shelf fan I showed above.  Alternatively, incorporate it into the oil line plumbing.

Good project Jonny, a decent alternative heat solution opens up a whole new world of exhaust/header options so well worth cracking. I bet one of the questions that you get asked most about the Classic Retrofit electric A/C is when a heat option is becoming available!!

 

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6 hours ago, ALEX P said:

Have they? It makes perfect sense to me. It will be interesting to see how you duct the air out without impacting on the actual cooling performance.  At least with the cooler in the rear arch, it is nice and close to the flapper boxes.

Yes, seen it on forums on many times.  It's probably true with the original oil cooler as they hardly get warm in the winter.  Also you have the complication of ducting it from the front of the wing or valence to the cabin.    The idea here is to open the stat a bit earlier and get some heat going.  

My current thinking is:

1) Move the axial span fan to the inlet side.  It can become larger and will be a pusher.

2) Construct a manifold covering oil cooler which has a letter box opening at the bottom but also allows for a centrifugal fan to be mounted on the outlet side.  Axial fans are crap at pushing down a long duct so I cant rely on the axial fan.

 

In hot weather when the flappers are closed and the heating fan is off, the air will come out of the letterbox and go to the ground and away.  Path of least resistance.

In cold weather, the flappers are open and the Centrifugal fan will take over.  Counterweight the letter box so it is sucked closed.  Heat goes to cabin.

 

 

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