Ford Family Fun – 2020+ Ford Explorer ST Performance Intercooler R&D, Part 4 – Dyno Testing

While piling into your Explorer ST for a long haul, it’s tough not to have that cliché mantra running through your head – It’s more about the journey than the destination. However, we here at Mishimoto think that saying depends on the context. We, enthusiasts, are quickly intoxicated by the ST’s 3.0 EcoBoost powerplant and easily hypnotized by the surprisingly nimble chassis’ ability to tackle the curvey backroads, making us prefer to savor the trip. When it comes to the journey of building that speed machine, however, things become much more destination-focused. While that journey is necessary, we’re much more eager for the result. In the quest for more power, though, a pit stop at the intercooler is required to reach your final destination.

Improving intercooler designs is a delicate balancing act between flow and core density. Both of these aspects are vital to improving the system’s performance, but they have reciprocating results on each other. An ultra-dense core may shrug off the heat before it can break a sweat, but it becomes a choke point in the system. Loosening up the core allows the intercooling system to breathe deeper, but it will quickly heat soak. So, to ensure that we struck the perfect balance with our design, we lined up a list of intricate tests, starting on the flow bench.

Our flow bench is equipped with an array of pumps allowing our engineering team to measure the component’s restriction across a range of flow rates, or CFM. In our design, we were able to reduce flow restrictions by 19% even after doubling the size of the intercooler, making this design much better suited for the 3.0L Ecoboost, especially those sporting performance tunes.

With the flow side determined, we still needed to ensure that this intercooler could keep up with the warding off rising temperatures, so we relocated to our DynoJet for more testing.

After strapping our donor Explorer to the rollers, our testing starts with determining this intercooler’s heat dissipation properties. This test consists of singular power pulls while monitoring the temperatures on both sides of the core. This gives us insight into how effective the core is at shrugging off the heat generated from charging intake air.

Shrugging off the heat is putting this core’s performance lightly. When keeping the charged air temperatures at bay, our new design completely bars the heat from entering, dropping intake air temperatures by almost 100°F when compared to the stock unit.

Cooler and more consistent intake temperatures aren’t the only thing to be gained from this new design. Even though intercoolers are intended to be a stepping stone to handling more power, the combination of improved flow and lower intake air temperatures results in the beneficial side effect of bolt-on power. In our case, we noted a bump of 34HP and 7TQ after installing our intercooler in conjunction with the stock tune.

While the results of our testing with Ford’s factory ECU mapping are already impressive, the primary reason behind improving your intercooler is to better manage increased charged air volume and temperatures generated from performance tunes and big turbos. So, to find out how our design would cope under these conditions, we loaded a stage 1 performance map on our donor Explorer ST and ran even more tests, starting again with observing heat dissipation properties. In this variation, we repeated the single power pull test along with a heat soak test to simulate even harsher conditions.

During this test variation, we saw the stock outlet temperatures climb above the 200°F mark, where our intercooler held steady.
Once we turned up the heat on our intercooler, it was still able to keep its cool, maintaining an almost 200°F difference between the inlet and outlet of the core. Typically, we would compare the heat soak against the stock intercooler but elected not to after reviewing the outlet temperatures on the OEM unit. On a single pull, the outlet temperatures from the stock intercooler reached over 200°F and would only increase during the heat soak test. These extreme intake air temperatures could cause excessive detonation resulting in permanent engine damage.

Ok, so it can keep the charged air cool, but what about the primary cooling system? Keen observers might have noticed that this hefty new intercooler finds itself almost completely obscuring the Explorer’s primary radiator, which needs access to the same fresh air source to keep coolant temperatures in check. This could be a problem thanks to our intercooler’s thicker core and effective heat dissipation characteristics. The heat pulled from the charged air needs to go somewhere, which, in this case, is passed to the radiator. We wanted to ensure we weren’t bartering high engine temperatures for lower IATs. So, during our dyno testing, we monitored and logged our donor vehicle to ease any concerns about coolant temperatures.

Even during the grueling heat soak test, the Explorer’s cooling system maintained safe coolant temperatures even with the much thicker intercooler installed.

So everything stays cool, but can it maintain boost pressure? The short answer is yes. One of the other balancing points when developing an intercooler is pressure drop across the core. Due to the operation of these heat exchangers, some pressure will inevitably be lost during the cooling process. Still, we aim for the lowest possible differential between the inlet and outlet of the unit for the best performance and reduced stress on the turbos. In our case, we actually saw an improvement in the Explorer’s intercooler pressure drop, even with a much larger core. Reducing this pressure drop also means that the turbos are making more power with less boost, giving this platform even more room to grow.

With all of these qualities combined, we were not only able to give the Explorer room to grow but also an unmitigated growth spurt in terms of power. Of course, this platform is no slouch from the factory, but the addition of cooler charged air temperatures and an appropriately sized intercooler resulted in an additional 65HP and 12TQ on top of the stage 1 performance tune.

Right off the assembly line, the Explorer ST puts the ‘sport’ in Sport Utility Vehicle. Ford ensured every ounce of any journey would be savored by pairing the potent 3.0 twin-turbo Ecoboost with an agile chassis, but this platform is poised for plenty more potential. Our updates to the Explorer’s intercooler system ensure that this practical speed machine can adequately fit into the shoes we expect it to fill and get back to the build journey before anyone can utter, “are we there yet?”

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Thanks for Reading!

-Nick

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