21. REVIEW: Replacement for stock oil cooler / VK Motorwerks + Setrab core
This is part of my extended review thread that you can find in its entirety here: 335i E90 LCI - Experiences and review of various modifications (long!) but that I reposted here separately in order to make this part easier to find.
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Why?
As I've already mentioned in my extended review on the various modifications done to my car (see here:
335i E90 LCI - Experiences and review of various modifications (long!)), I've had the
AR Design oil cooler installed in my car. It's the second version that is installed in front of the radiator and has a big Setrab core. Here are two photos of it installed but with the bumper removed for better visibility:
AR Design oil cooler - installed (1)
AR Design oil cooler - installed (2)
The AR Design oil cooler already improved things quite a bit, and compared to the stock setup (note: all cars in Europe - so mine as well - already have the stock oil cooler installed!), the oil temperatures rose much slower and peaked considerably lower. After driving thousands of kilometers with it, I would say that the delta (i.e. the difference in temperature between the stock setup and the addition of the AR Design oil cooler) is roughly around 10 degrees Celsius.
However, after switching from my initial Evotech flash (yielding around 400hp crank) to the GIAC stage 2 with even higher boost, I noticed that the oil temperatures were again too high: When going faster than 200 km/h, they rose to around 125 degrees Celsius (257 Fahrenheit), and if I went faster than 230 km/h, the temperatures even exceeded 130 degrees Celsius (266 Fahrenheit). Also, when driving with my car on the Nürburgring (Nordschleife), I also saw temperatures of slightly over 130 degrees Celsius.
I'm driving quite often in Germany, and it's frequently possible to drive faster than 230-250 km/h (155 mph) for some time; furthermore, I'm going to the 'Ring on a regular basis. As a consequence, the reliability of my car and the absence of any oil temperature-induced limp mode (which I didn't see until now) is of considerable importance to me - and oil temperatures of 130 degrees Celsius or beyond are not improving the long-term reliability and stress the engine as well as the turbos. I do believe that if I were to run my car under these high oil temperatures, the resulting thermal stress on the components would - not immediately, but after a while - lead to failure of one or the other component, if not the engine or the turbos as such. That was, obviously, not acceptable to me and I was looking for ways to further improve the oil cooling of my car.
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How?
. I did some research and came upon three alternatives:
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Evolution Racewerks Sports Series Oil Cooler Upgrade Kit: This kit replaces the stock oil cooler with a bigger core (795 USD)
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STETT Performance oil cooler: Also replaces the stock core with a Setrab core, with the option of a thermostate delete or a modified thermostat.
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VK Motorwerks oil cooler upgrade kit: Similar to the two previous options, but doesn't use a Setrab core.
Now, the problem for me was that I needed something that was compatible with my existing additional AR Design oil cooler which I didn't want to throw out as it did improve the oil temperatures. I was reasonably sure that the ER option would be compatible, as well as the VK Motorwerks one. As far as the STETT was concerned (a company that I had already bought several items from - Cold Air Intake, charge pipe - and that I was very satisfied with), I was doubtful about the thermostat modification: a great idea as such, certainly, but as I'm living in rather cold climates I feared that in winter the oil might not reach its operating temperature of slightly about 100 degrees Celsius. I excluded the VK Motorwerks option, too, as I knew several people that had experience leaks with it, due to the cutting of the oil cooler core that weakened its structure; I had even personally witnessed such an event.
Luckily for me, a friend of mine was getting rid of his 335i and contacted me on whether I wanted to acquire his upgraded oil cooler - which was a VK Motorwerks set, but with a modified and much better Setrab core instead of the leak-prone one that VK Motorwerks installed. I was immediately interested, also knowing that another friend of mine was running this setup with upgraded turbos (E92Fan), and therefor bought it from him for a fair price, along with the necessary oil lines and adapter to hook it up to the stock cooling system.
The installation was, according to my garage
Daum Motorsport that installed it, fairly straightforward, in particular as it had already been installed on a similar car and therefor all necessary parts were there. Here are two photos that illustrate how this solution looks (I know that the second photo is not so illustrative but you can at least see that it's a very stealth solution and looks like OEM - but is far, far better):
Comparison between stock oil cooler (left) and new Setrab core (right):
Installation passenger wheel well (behind grille):
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Improvements?
1) German Autobahn
A few days after having picked up my car from the garage, I was driving on an unlimited portion of a German Autobahn, one that sees little traffic and is rather straight. I therefor "gave it the beans" (although I don't like beans that much…) and pushed the car to almost 300 km/h before letting off as I ran out of straight road. The oil temperature gauge went just slightly beyond 120 degrees Celsius, and it stayed there. Later on I drove for a few minutes between 230 and 260 km/h, and again the same picture presented itself. In the end, there seemed to be a delta in oil temperatures of around 10 degrees Celsius to the setup I had before. Excellent!
2) Nürburgring
I have done three full track days so far with this setup on the Nordschleife of the famous Nürburgring. Although the temperatures were not very high (we had a rather crappy summer here this year), even if pushing the car really hard I never saw temperatures beyond slightly above 120 degrees Celsius. I found this very reassuring, as it was therefor excluded to go into a limp mode or even stress the engine much due to high oil temperatures. There also seemed to be some margin - so if going for bigger turbos (which is an option I'm considering), at least the oil cooling should be sufficient.
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Problems?
None at all. Of course, the oil cooler itself is not cheap, and the installation takes a few hours - but the result is very well worth it.
In summary, if you're running your N54 with high boost applications (like GIAC in my case, but cars with JB4 or PROcede or COBB will have similar issues) and drive it very fast for extended periods of time (i.e. tracking it or, when living in Europe, drive on unlimited German motorways), upgrading the oil cooler is definitely a must. In my opinion, a single upgrade will be enough for most; a double one like here - AR Design in parallel with an upgraded stock core - could be a good solution for demanding drivers.