# RB26 - Improving the Stock Water to Oil Cooler setup



## jnoor (Feb 24, 2016)

So I was looking to get and oil cooler fitted to my R32, possibly designing my own, and I came across an interesting post on the SAU site that didn't gain much traction.

The guy suggested improving the stock water to oil cooler set up by incorporating a small water cooler/radiator before the actual oil cooler.

It seems quite interesting but I was entirely sure on it's effectiveness. What do you guys think of this idea?


Here's what he posted:

"hey every one this is what i was thinking.

the rb26 runs a water to oil cooler standard.

i was thinking of trying to make this set up more efficient by cooling the water coming out of the block to the oil cooler using a small oil cooler/ radiator before it enters the oil cooler.

you might be asking why bother?

well the reason for this is

1. The stock setup all ready has a thermostat inbuilt.

2. I could use a cheap cooler and worst case scenario is it leaks or splits and i only loose water and oil pressure is not lost there fore no chance of damage to motor due to loss of oil pressure.

3. The overall cooling system is improved be having a second radiator even though it is small.

4. So from what i can gather it is much cheaper. less likely to lose oil pressure and helps with the overall cooling of the car.

please comment on my idea.

has it been done before?

have i missed out something important?

i have up loaded 2 diagrams to help explane one is the stock system and the others shows where i would extend the lines and put extra cooler.

cheers

Ryan"


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## OXzilla (Jul 22, 2016)

I think it is an interesting concept but I think you would struggle to get enough airflow over a radiator tucked in that already congested area of the engine bay. Even then the temperature drop may only be a few degrees.

If you extended the water lines to put the radiator in a new location with more airflow I think that would introduce a lot more complexity than you were after, but I'm no engineer.


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## Bennyboy1984 (Jul 26, 2009)

The main problem is that the standard heat exchanger is known to fail, so I could imagine by lowering the coolant temps you'd only be raising the chances of it cracking and having lots of oil gushing into your coolant, or possibly vice versa...but again I'm no mechanic/engineer.


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## jnoor (Feb 24, 2016)

Bennyboy1984 said:


> The main problem is that the standard heat exchanger is known to fail, so I could imagine by lowering the coolant temps you'd only be raising the chances of it cracking and having lots of oil gushing into your coolant, or possibly vice versa...but again I'm no mechanic/engineer.


So your saying the cooler coolant and hot oil i.e. larger temp difference would increase the likelihood of the heat exchanger failing?

What kind of failures does the standard cooler experience? Is it just risk of it cracking/leaking?


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## jnoor (Feb 24, 2016)

OXzilla said:


> I think it is an interesting concept but I think you would struggle to get enough airflow over a radiator tucked in that already congested area of the engine bay. Even then the temperature drop may only be a few degrees.
> 
> If you extended the water lines to put the radiator in a new location with more airflow I think that would introduce a lot more complexity than you were after, but I'm no engineer.


Your first point is true, you really wouldn't want a radiator tucked away in such a small space.

But extending the water lines wouldn't increase the complexity, it's just increasing the distance the coolant has to travel. 

Also, if you keep the length of the radiator core short, that should also help reduce any pressure drop as well.


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## ahsam421 (Apr 26, 2003)

This is what i m going to use behind the bumper :clap:


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## Bennyboy1984 (Jul 26, 2009)

jnoor said:


> So your saying the cooler coolant and hot oil i.e. larger temp difference would increase the likelihood of the heat exchanger failing?
> 
> What kind of failures does the standard cooler experience? Is it just risk of it cracking/leaking?


According to my tuner it's quite a rare issue but they are prone to cracking internally, you're more likely to see it with engines running big power. I've had it happen to me and I know of a couple others that have had this problem. With me it happened not long after I had a new radiator installed, so I guessed it was down to the lower coolant temps and hot oil flowing through.


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## FRRACER (Jun 23, 2013)

Just fit an after market setup with remote filter with stat and a 16 or 19 row oil cooler using -12 fittings.


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## Mohammad Alajmi (Jul 29, 2017)

It seems interesting idea maybe I should try it instead of summer hibernation


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## tarmac terror (Jul 16, 2003)

FRRACER said:


> Just fit an after market setup with remote filter with stat and a 16 or 19 row oil cooler using -12 fittings.


Yes, just rip it all out, fit a direct filter adapter like this...

Kudos Motorsports: Japanese Performance & Servicing Parts Specialist












and an external cooler and worry no longer. I've done this and added a remote filter assembly too to make filter changes a doddle.



TT


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## Bennyboy1984 (Jul 26, 2009)

I did notice after I fitted mine that my cold start oil pressure dropped by about 1bar, is this normal or are my bearings f*cked? My hot idle oil pressure still sits at 3 bar though...any ideas?


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## jnoor (Feb 24, 2016)

tarmac terror said:


> Yes, just rip it all out, fit a direct filter adapter like this...
> 
> Kudos Motorsports: Japanese Performance & Servicing Parts Specialist
> 
> ...


So TT you stuck a take off plate at that point and put a remote filter assembly in another accessibke area plumbed to a cooler??


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## sebastijanignac (Dec 5, 2015)

isn´t that a bit too complicated ?

why dont bypass that or delete it !!

as TT already postet, just replace it with that stud and run an external oil cooler! looks cleaner and should work

i think tomei is making a good looking adapter but im sure its a bit pricey!!


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## tarmac terror (Jul 16, 2003)

jnoor said:


> So TT you stuck a take off plate at that point and put a remote filter assembly in another accessibke area plumbed to a cooler??


Yup....!!

If you didn't want to go down the route of a remote filter head (I can't think of a reason why you wouldn't!) you could bolt a filter straight onto the block like every other car that doesn't have an external cooler or modine unit..


TT


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## freakazoid3 (Jan 19, 2008)

The modine unit does help shorten oil warm-up time and thus preserves engine-longevity...


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## Bennyboy1984 (Jul 26, 2009)

^^ only by a couple of minutes, but as you say it helps with engine-longevity. Anyone who isn't patient enough to wait for their oil to warm up before giving it the 'beans' needs a :chairshot


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## jnoor (Feb 24, 2016)

Does Modine more or less supply the entire automotive sector for standard cooling units?

EDIT - Just read up on them and turns out they're the manufacturer of the "donut" cooler. Pretty awesome.


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## joshuaho96 (Jul 14, 2016)

Major thread bump here I know, but the Modine "donut" cooler operates functionally on the same principle as the OEM oil/coolant heat exchanger. Putting a radiator on the coolant line going into the oil cooler doesn't do anything, because the point of the system is to bring the coolant and engine oil near each other to allow either the coolant to heat or cool the engine oil. If you want to improve the ability of the factory setup to heat/cool the engine oil you need to physically increase the size of the heat exchanger, preferably to the point where the engine oil cannot get substantially hotter than the coolant. This is doable but is not a simple task to make the part I'm talking about. You would need to make a part that replaces the factory heat exchanger with something that has more thickness to allow for more surface area between the coolant and engine oil. In theory it should just bolt on if you could make said part though.

Something to think about though is that the point of having a separate air to oil cooler is so you can put it somewhere off to the side where the radiator/AC/etc isn't.


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## wardiz (Dec 23, 2008)

I don't think it's been reported but BCNR33 N1 version didn't have a modine unit but an oil cooler and that was from factory.


Oil filter block : standard and N1 version | Wardiz


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## joshuaho96 (Jul 14, 2016)

Right, the N1 uses air cooling for the oil only. I believe the OEM application is more street-oriented because it allows you to warm up the engine oil faster. For street-oriented air to oil cooler I would make sure that the oil thermostat is set to only open at relatively high temperatures like 85C to make sure the coolant is not getting cooled by the oil cooler.


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## lightspeed (Jul 11, 2002)

joshuaho96 said:


> Major thread bump here I know, but the Modine "donut" cooler operates functionally on the same principle as the OEM oil/coolant heat exchanger. Putting a radiator on the coolant line going into the oil cooler doesn't do anything, because the point of the system is to bring the coolant and engine oil near each other to allow either the coolant to heat or cool the engine oil. If you want to improve the ability of the factory setup to heat/cool the engine oil you need to physically increase the size of the heat exchanger, preferably to the point where the engine oil cannot get substantially hotter than the coolant. This is doable but is not a simple task to make the part I'm talking about. You would need to make a part that replaces the factory heat exchanger with something that has more thickness to allow for more surface area between the coolant and engine oil. In theory it should just bolt on if you could make said part though.
> 
> Something to think about though is that the point of having a separate air to oil cooler is so you can put it somewhere off to the side where the radiator/AC/etc isn't.


Laminova do big water/oil coolers. Had one on mine but was rubbish when pressing on. Radiator failed to cope. Switched to a 25 row Setrab with ducting in front left and a new Koyo rad and it’s been perfect ever since.


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## joshuaho96 (Jul 14, 2016)

lightspeed said:


> Laminova do big water/oil coolers. Had one on mine but was rubbish when pressing on. Radiator failed to cope. Switched to a 25 row Setrab with ducting in front left and a new Koyo rad and it’s been perfect ever since.


Good to know. I plan on keeping the stock heat exchanger but purely as a way of heating up the oil to operating temperatures, I plan on putting an oil cooler on the left fender with appropriate thermostat to make sure the cooler only flows once the temperatures are above operating temps for the engine coolant. The one question mark that someone mentioned to me is that the HKS sandwich plate may not have the appropriate relief valve if the oil filter is clogged for example.


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## lightspeed (Jul 11, 2002)

joshuaho96 said:


> Good to know. I plan on keeping the stock heat exchanger but purely as a way of heating up the oil to operating temperatures, I plan on putting an oil cooler on the left fender with appropriate thermostat to make sure the cooler only flows once the temperatures are above operating temps for the engine coolant. The one question mark that someone mentioned to me is that the HKS sandwich plate may not have the appropriate relief valve if the oil filter is clogged for example.


If the oil filter is clogged it’s probably full of your bearings already!!!

Just run a modern ecu with oil pressure protection.


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## joshuaho96 (Jul 14, 2016)

lightspeed said:


> If the oil filter is clogged it’s probably full of your bearings already!!!
> 
> Just run a modern ecu with oil pressure protection.


I plan on that as well, but my concern is conditions like cold start, the filter could have excessive pressure drop or similar conditions like that.


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## AlexJ (Apr 3, 2003)

Don't the filters have relief/bypass valves? I feel like i read somewhere the filters are bypassing on cold start anyway.

Fwiw i have a greddy thermo sandwich plate directly mounted to the block. I got rid of all the gubbins. It's not shit itself yet


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## joshuaho96 (Jul 14, 2016)

AlexJ said:


> Don't the filters have relief/bypass valves? I feel like i read somewhere the filters are bypassing on cold start anyway.
> 
> Fwiw i have a greddy thermo sandwich plate directly mounted to the block. I got rid of all the gubbins. It's not shit itself yet


Some do, some don't. I'm a big fan of retaining OEM functionality where it exists though. For a street car I think the water/oil heat exchanger is valuable, if only to reduce the wait until I can finally get the car into boost.


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