Stock System

The stock oil cooler is a liquid-to-liquid heat exchanger and therefore relies on the radiator to cool the oil, as well as the coolant. This style of oil cooler also acts as an oil warmer, bringing the oil to operating temperature, which is beneficial for colder climates. I know with the heat wave that is currently engulfing a large portion of the country, not many of us are concerned with the oil reaching temperature; but in the dead of winter, it can certainly be helpful.

As you can see below, coolant is supplied via the two lines connected to the right side of the cooler. Of course with every liquid-to-liquid cooler pro, there is a con. The most critical issue is that the radiator has to work twice as hard to keep the RS’s oil cool, as well as the coolant. This often results in higher oil temps, especially with any sort of track use.

Designing the Prototype

Our game plan is to retain the stock oil cooler, if possible; we will then add our own liquid-to-air heat exchanger in order to combat high oil temps. The first step was deciding where to mount our oil cooler. It’s no surprise that the RS is low on space, but after becoming acquainted with our RS during our intercooler R&D, we knew just where to locate this cooler.

The upper-grille area should provide the maximum amount of air flow while minimizing the space that the cooler takes up. Speaking of minimizing space, we will be using the heat exchanger that was born during our Mustang GT oil cooler project. For that project, we designed small, medium, and large bar-and-plate heat exchangers to test. After choosing the best for the GT, we produced the rest for universal applications. The medium cooler should do the trick here. It has a large surface area while still saving space, something that is a hot commodity for the Focus.

Once we had a location, we set out to design a bracket. Based on the location we chose, this proved to be on the difficult side. The air diverter directly above the opening in the grille is plastic and is not likely able to support the size cooler that we want to use. Not to worry. Our engineer, Dan, often shoots for the stars with his designs and came up with an excellent plan. He designed an aluminum bracket to replace the entire plastic air diverter. This will be strong enough to both hold our cooler and continue to function as an air diverter similar to stock. Check out some renderings of the bracket with our cooler!

We began with constructing our prototype bracket for fitment testing. After cutting the bracket on our waterjet, we tack-welded it together and bolted up our cooler to take a better look at fitment. We will be using one of our larger bar-and-plate coolers designed for our Mustang GT oil cooler project for the RS oil cooler kit.

You may have noticed the scoop on our prototype above, or in our render from our previous post. When designing the bracket, we saw an opportunity to go the extra mile by adding this feature. It works to direct some of the air that does not pass through the cooler, up and into the intake duct. We plan to test this feature to ensure that it functions as designed before including it on our final product.

Testing

Now that we are sure the bracket and the oil cooler fit our RS, we are one step closer to testing! The rest of the kit was constructed, including a custom center bolt for our sandwich plate, which our engineer, Dan, fabricated for this project. We will leave the stock cooler intact and install our cooler in tandem with the stock setup. This should provide the benefits of a larger aftermarket oil cooler without compromising oil warm-up times. That said, it is on to testing!

Our on-road testing is important because it replicates how our kit will perform in every-day driving situations. We know that there are more than a few track-dedicated Focus RS’s out there, but for everyone that bought this car to enjoy on a daily basis, our products must function properly on both the street and track. Repeatable baseline testing will ensure that our cooler demonstrates excellent performance in daily driving situations before we move on to more stressful testing.

As you can see in the chart above, on-road testing showed the stock cooler holding at 200°F, which is perfectly normal for a stock setup. With the addition of the Mishimoto cooler, we were able to reduce temperatures to 170°F at the inlet and 155°F at the outlet, making for a 45° temperature drop from the stock cooler. By choosing the cross-flow cooler setup rather than a dual-pass cooler, we were able to keep the pressure drop to about 7 psi. Excellent results for on-road testing!

Not only did our oil cooler perform favorably during our preliminary testing, but we also found that the design of the bracket produced a 6°F reduction in intake air temperatures. Talk about a freebie!

Second Prototype

For additional track testing, we constructed a second prototype bracket from aluminum, which gives it a much better appearance than our first prototype. In addition, it will be lighter and more comparable to the final product, which will also be constructed from aluminum. This prototype will go to a third party for track testing, and we are eager to hear their impressions of our kit in action. We will report back with an update as soon as their testing is complete. For now, check out our final prototype and let us know what you think!

What more could a company filled with automotive enthusiasts want than a track day as a workday?! If it were up to me, I would start building our offices adjacent to my favorite tracks and have every meeting in the infield, because I can’t think of a more excellent way to spend the day.

I have to begin by thanking you all for collectively pushing for track data. While the type of testing we normally conduct is sufficient for learning how well our products perform under most conditions, nothing instills confidence at the track like pushing your creation to the ragged edge. Because, after all is said and done, that is where it counts. I am no stranger to racing of all sorts, and I can’t think of anything more frustrating than working all week, or month even, just to break down at the track.

For proof, here is a picture of my pride and joy that only made it to the pit entrance before exploding a power steering pump and leaving a nice coating of power steering fluid over my entire engine bay. The shortest track day in the history of motorsports.

That being said, after much convincing, we were given permission to release our Nitro-blue beauty to track-test our oil cooler; and we couldn’t wait to tell her the good news.

We Get Our Track Day

We arrived at the track the second the gates opened and hopped out of our cars with the excitement of Ferris Bueller skipping school. We were, in-fact, cutting out on our responsibilities for the day: no meetings, no mundane emails, just a track to ourselves and a car that wanted to kill us.

Alright, maybe the RS isn’t a murderer. Maybe it’s just an enabler, whispering its horsepower numbers to the driver as he rounds a bend, heading towards the back stretch, with his foot plastered to the floor. The less-than-ideal conditions didn’t stop our resident Stig from propelling our German-made monster around the track at speeds that made spectators grab for something sturdy and hang on tight. Thanks to our driver, engineer, and all of you, we have our track data, and here it is.

Results

Before getting into any numbers, let me clarify how the Focus RS does (and doesn’t) collect temperature data. The Focus RS does not read oil temperatures directly from the oil, as there is no stock oil temperature sensor. Instead, it calculates the oil temperature based on other information, like coolant and intake air temperatures. Given this, it is important to use testing equipment that measures the temperature of the oil directly, rather than rely on the RS’s oil temperature readout, which is only an estimation.

The ambient temperature at the track was about 70°F during testing. We first let the RS warm up until the coolant temperature hit 200°F to be sure that the RS was nice and heat soaked, like it would be on a warmer day. We then took to the track and completed at least 10 laps (about 25 minutes of hard driving) without stopping. We completed one cool-down lap, then headed into the pits to change setups. Our initial round of testing monitored temperatures with the stock liquid-to-liquid oil cooler alone. Then, after a pit stop to install the Mishimoto cooler, we measured temperatures with both the stock and Mishimoto coolers at work.

All test results are below, beginning with the stock setup.

The testing results show that the Mishimoto oil cooler works well to reduce temperatures under both highway driving as well as track driving conditions.  With the Mishimoto cooler, the oil temperature decreased approximately 35°F compared to stock temperatures, and 22°F under aggressive track driving conditions. This oil cooler will keep the engine oil at a lower temperature under both street and track conditions while maintaining safe coolant temperatures, making this Mishimoto direct-fit oil cooler an excellent addition to the 2016 Ford Focus RS.

Pressure Data

We’ve received some feedback from the community that called into question the 7 PSI pressure drop that we saw on previous rounds of testing. While on the high side of what we like to see, it doesn’t interfere with safe operation of the RS. Furthermore, it is difficult to compare pressure testing from this kit to testing done on only the core from another kit. Bench testing pressure drop across the core alone will not give you an accurate representation of how the kit as a whole (the cooler, lines, and fittings) will affect the pressure of the entire system. In order to accurately compare pressure testing results, you must be sure that the flow rate of the test system matched the flow rate of the stock Focus RS system, the same oil was used, and the testing was performed at same temperature. Anything less would yield inaccurate results.

We intend to look into the pressure more, with further testing to determine if the results could be attributed to factors such as the oil temperature testing rig we had on the RS. We intend to test our theory more thoroughly with the final product. Of course, we will share with you any findings that result from our testing, as we did here, in order to be thorough and straightforward about our process. We appreciate the conversation as it allows us to bring our best products to you all.

Additional Testing 

We know that some were curious how the RS would perform without the stock liquid-to-liquid oil cooler, and only the Mishimoto cooler installed. We had a bit more time, so we decided to complete this test and share it with you all. We conducted this test using the same methods as the tests shown above.

As you can see, coolant temperatures dropped without the stock oil cooler installed, which makes sense given that the oil is not exchanging heat with the coolant. For those with a track-dedicated Focus RS, who don’t want to sacrifice coolant temperatures for oil cooling, this setup may make more sense. Either way, we wanted to share our findings so everyone can make an informed decision.

Coming Up!

The pre-sale for this kit will be coming to a close very soon, so get your orders in to take advantage of pre-sale pricing. As always, let us know what you think in the comments below!