Preface: This review would not be possible without the help of Wesley Chan of Rally Innovations, and Ravi Dolwani of CSF Radiators - Racing and Performance Division. Wesley was able to introduce me to Mr. Dolwani of CSF, and help negotiate a partial sponsorship between JSR and CSF Radiators. Mr. Dolwani was generous enough to sell me one of CSF’s BMW Aluminum Racing Radiators at cost, in exchange for track testing, and reviewing their product.

As a result of their collective generosity, this will be the first ever sponsored article by JSR. That said, I will be describing, to the best of my ability, my honest thoughts, opinions, and results from installation, multiple track tests and about 3,000 street miles.

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While perfectly suitable for the day to day commute, and occasional somewhat spirited run through your favorite back road, most BMW’s, especially the more plebeian “Non-M” models, are woefully under-prepared when tasked with aggressive driving, or track day use. Popular BMW enthusiast models, ranging from the E36 3-series to the more modern E90 3-series, and everything in between, all suffer from insufficient cooling ability when tasked with aggressive driving.

Few BMW models make this more apparent than N54-powered “35i” models. Regardless of potential potency from it’s torque-rich, twin-turbo powerplant, these engines are easily neutered when faced with high engine oil and water temperatures. When oil temperatures exceed 270*F, the DME (BMW parlance for ECU) will begin to cut power. If oil temperatures exceed 300*F, it’s game over for you, as the car heavily reduces power and enters “limp mode.” Equally upsettable are water temperatures. Tasked with cooling an engine that is boiling oil at 300*F when pushed, the factory cooling system will also see high water temperatures in a very matter of fact way. It’s not a matter of if, it’s a matter of when. The factory allotted water temperature of 205*F will easily climb in excess of 220+*F, also sending the car into limp mode.

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Cooling concerns became an ever-present concern for the N54 that for the 2008 model year of the 335i, BMW began offering an auxiliary oil cooler along with the often selected “sport package.” A noble gesture, but it’s paltry size put nary a dent in the epidemic. If this seems like an overblown issue to you, may I suggest some casual reading. By casual reading, I of course mean a detailed 45-page thread (with a spreadsheet!) covering people’s accounts of overheating and hitting the dread limp mode.

With the stock cooling system, flushed with mostly distilled water and water wetter, I routinely experienced oil temps exceeding 280*F, and on occasional 300+*F. Even one minute autocross runs would result in oil temperatures exceeding 270*, and water temps creeping up, with the fans kicking on in full blast in an attempt to diffuse the situation. When a simple autocross run is overwhelming the car, that is simply unacceptable.

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At first, my water temperatures largely remained steady at 205* on track, but then as I began to find quicker ways of making up time, water temps began to rise as well. This all culminated in a brutal beating at the Streets of Willow Springs during the Summer, wherein oil temps hit 310*F, and water temps hit nearly 230*F, causing me to enter an immediate cool down lap and eventually leave the track. That occurred 3 laps into the session (7 minutes, including the out lap), which for any vehicle, should not be an unreasonable amount of time to sustain hard driving. Keep in mind, this is with the heater on at full blast to scavenge any marginal help I could give to the cooling system.

It was time to go to work on cooling the 3 Liter Heater.

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With CSF’s help, it was time to check out the goods.

The CSF unit was very well packaged, and despite being made of aluminum, no bent cooling fins from transit.

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Upon un-boxing, it is clear that CSF makes a quality unit. Polished end tanks, and clean welds throughout, the price of admittance can be called money well spent.

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The clean, functional aesthetic quality is matched with some equally nice touches, and marks of pride in the product. No proprietary drain plug tool required (looking at you, BMW), a flat head screwdriver or basic socket set and ratchet will do the job.

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Installation

Installation guides can be found online without too much issue, so please do not consider this a technical guide. I instead wanted to make some notes and comments about installation that other sources may have omitted, or not noticed.

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First off, any reference materials you may find for this on the internet are 3-series specific. It’s the same engine, and same components on the 1-series, but pieced together on a different, more cramped chassis, which makes this installation more tedious. Judging on the pictures and videos I’ve come across, it looks like the 1-series gives up an inch or two between the radiator core support (which the radiator and A/C condenser sit) and the engine, relative to a 335i. That makes removal and installation of things a bit more tricky.

“Optional” idea: take the front bumper cover off. It’s a tight fit in the 135i, and visibility of your working area is poor. Also remove the airbox or aftermarket intake. Consider removing the turbo chargepipe that runs from the intercooler to the throttle body as well.

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The factory intercooler sits directly underneath the radiator and condenser, it’s easily removed, and 100% necessary.

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So tiny, so cute.

The nice thing is that from here “a radiator is a radiator,” remove the upper hose, remove the lower hose, pull the fan out of the way, and out it comes.

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Of course, that’s how it would go, if there was enough working room to do such a thing. The aforementioned 1-2” shortage of working room makes this VERY tedious. By this, I mean removing the fan and shroud, and removing the radiator itself. Getting the fan out without breaking the shroud was quite the process, with the plastic shroud continually catching or snagging the engine’s front end and pullies, or snagging the radiator core support. At first, it looks like there’s more room pulling it out from the bottom. Don’t be fooled, the only way this works is by pulling the fan out from the top. Same for the radiator.

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The face of pain:

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Many thanks to my Saint of a girlfriend for handling my copious swearing. Also many thanks to my roommate for helping manhandle the fan out from the car.

If you have a 335i or other larger BMW, pat yourself on the back for buying the easier to work on body, this will take all of 5 minutes for you.

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Let us take a quick reprieve from wrenching, and check this out. With both radiators sitting in front of me, take to crack out the ever faithful digital scale. It’s always consistent in telling me I need to lose 15 pounds, so let’s see what the CSF is packing.

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OEM radiator: 9.4lbs

CSF Aluminum Racing Radiator: 7.4lbs

Despite the OEM radiator being quite light, with it’s plastic end tanks and small dimensions (it’s VERY narrow), the CSF’s aluminum construction makes it exactly 2.0 pounds lighter, despite having 25% more capacity.

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Coming back to the garage, and headfirst into installation, here are a few observations:

The majority of the CSF’s increase in capacity comes from thickness, as heightwise and lengthwise, the two radiators are very similar in size. This is dictated by available working area on the radiator core support: go taller and the radiator will contact the radiator support up top, or the intercooler down below. Going greater in length and again, you bottom out against the radiator support and other accessories. This means that the increase in thickness makes reinstallation of the new radiator marginally trickier, but nothing unexpected, as the most common edges to snag when fussing with the radiator are the edges due to the length and height.

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With the radiator in place, it just clears the intercooler piping. Original or aftermarket, you should be okay here.

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Getting the fan in place proved to be a point of contention. The driver’s side fastener meets up perfectly.

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However, the passenger side fastener doesn’t seem to match up with the fan shroud at all, regardless of positioning or fitment. Granted, it is perfectly secure without this attachment point, but it is something to point out. I’m guessing that there may have been a revision in the fan/fan shroud design over the years, and CSF’s prototyping was based on that different fan.

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Looks like the fan shroud is about 2” short of reaching this attachment point.

With the radiator and fan installed, I ran into an issue reinstalling the intercooler. The drain plug of the CSF radiator sticks out about 1/2” more than the OEM radiator’s drain plug, which sits flush.

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The factory intercooler has a small bit of shrouding on the outside edge that contacts the CSF radiator’s drain plug. I’m guessing that aftermarket intercoolers will not run into this issue. A quick bit of filing down of the shroud, and the issue was remedied: In terms of intercooler clearance, it should not affect even larger aftermarket intercoolers.

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With that, everything was reinstalled. Fill the car with water, and start it up, make sure it comes up to temp (thermostat opens) without leaks, then drop the car down and take it for a test drive.

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Pre-fan installation. Hello, Beautiful!

Track Testing

Since installing the CSF radiator, I’ve put the car through six track days at four different tracks, in conditions between 60-90*F ambient, and varying levels of humidity. It should be noted that only large shifts in ambient temperature affect engine operating temperatures at all. It seems like by and large this can be catagorized as “sub-80*F, and above-80*F,” at least for my car. In addition to this, crucially, is that not all tracks are created equal. Shorter tracks with less straight aways tend to punish cars much harder, as they have less air being rammed through the radiator and engine bay. Also, open tracks tend to trap less heat than heavily banked tracks like Streets of Willow Springs, which is shaped like a giant bowl, or Auto Club Speedway Roval, which utilizes a NASCAR half oval. In addition to this, with a turbo car, there is another factor involved here, namely that there is a direct correlation between boost pressure and engine operating temperatures. The more boost you run, the hotter the car will run.

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With stock radiator:

- Oil temperatures would sit around 275-280*, excluding the more technical Streets of Willow, where oil temps would routinely skirt 300*F.

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- Water temps between 205-210 at all tracks, excluding Streets, where average water temps hovered around 215-220, peaking at 230*F.

This meant that the car was constantly skirting between the 13psi of JB4 tune set at Map 1, and stock boost (~7-8psi). Once oil exceeds 270*, the tune bypasses itself and goes back to stock. In the case of Streets of Willow, the car could barely even be operated under stock boost without hitting limp mode. Indeed, that was the reality of the beast. This made performance very inconsistent, with the car occasionally giving 13 psi of performance for half a lap and then cutting to 7psi (or less!) during the same lap. That’s incredibly frustrating to not know how much power you’re going to get, or when you’re going to get it.

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With the CSF Racing Radiator:

- Oil temperatures now sit around 260-270, excluding Streets of Willow where oil temps touched 280*F.

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- Water temps are rock solid at 205*F all day, excluding Streets, where water temps peaked at 210*F.

- Temperature drops from the cool down lap are incredible compared to the stock unit. Oil temperatures would drop to 240* or so during the cool down lap, and by the time I reached the paddock, the engine would be running at it’s normal 230-240* oil temperatures. Additionally, it’s now possible to cool the car down substantially mid-session with just rolling one cool down lap. Previously, this was not possible and would require about 5 or so minutes to cool down noticeably.

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That’s a tangible difference for no other cooling aides to the car. However, it’s even more impressive than the numbers show at face value. Remember the more boost = more heat principle established a few minutes ago? With the CSF radiator, I set those engine temperatures running a blend of 91 octane and E85, with a 17.5psi boost target. For the most part, that would have been impossible before, but now, it’s a reality for the car. Lap times have dropped massively with the power bump, and arguably it’s provided the biggest change in lap times, short of the tire compound upgrade from stock. The difference is that dramatic.

Let me repeat that: Despite cranking up the boost, the car now runs even cooler than it did before.

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That’s incredible. Retail price for the CSF racing radiator for the N54/N55 is around $500. It’s plug and play, requiring no accessories or noticeable modifications to fit and perform. I’ve put over 3,000 street miles on the car since installing it, there are no downsides. Put a few hours into installation, and go. It works excellently, and seriously helps combat high engine operating temperatures, for both water and oil. With the CSF radiator, the car now runs cool enough to set blazing fast hot laps. Lap times dropped substantially due to being able to turn up the boost, and lap to lap consistency is noticeably better as the car can now provided repeatable, consistent performance.

Thank you, CSF, for making a great product that is affordable and works. No hype, only results. Consider me a believer.

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Spend a couple hundred bucks on a well-engineered product that will keep your engine cool, or spend a lot more than that when you blow your head gasket from overheating. The choice is obvious. Check out CSF Racing Radiators here. If you are tracking your car, and want to keep it running safe and cool, you know what you need to do.

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Jake Stumph is a rabid car nut, autocross junkie and track day enthusiast. If you want to learn more about setting up your car for track days, or autocross, then you can follow him on Facebook, where he posts live updates from the track, and talks about trying make a slow driver into a fast one. Currently, he wants to set N54-powered street tire records at all of Southern California’s race tracks, and win that cherished SCCA Championship jacket with an H-Street Civic Si.

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