Cool Integration – Performance Heat Exchanger R&D, Part 1 – Stock Review

Nothing shows progression in technology quite like integration. The means of creating one item that performs the function of four is the way of the future. Just take your mobile phone that you’re likely reading this on. Fifteen years ago, it was just a phone designed for talking and texting, with some limited internet access, and now it’s a computer in your pocket. Similarly, the intercooler inside of the B58’s intake manifold is a pure form of integration in the name of performance. The marriage of these two components, though, means that the intercooler’s heat exchanger is now the key to performance gains for the A90 Supra, and we here at Mishimoto are on the case.

To the Air to the Water

The improved efficiency between an air-to-air and an air-to-water system is clear to see in just the amount of piping alone.

Air-to-water isn’t exactly brand new when it comes to intercooling. This method of exchanging charged air temperatures is a favorite among high-horsepower racers, and most modern supercharger kits. This method of intercooling made an appearance on some performance production model vehicles in the past, with the 1991 GMC Syclone coming to mind.

Straight from BMW’s technical documents, the intercooler’s coolant circuit in diagram form.

What’s new about air-to-water intercooling is that it’s becoming the norm in production turbocharged vehicles, and positioning the intercooler is now inside of the intake manifold. This method is an advantage over air-to-air intercooling since the intercooler can be placed anywhere within the system, which reduces any PSI drop, and turbo lag. Also, liquid, water specifically, provides improved thermal conductivity over air, meaning that a much more effective heat transfer is taking place inside of the air-to-water intercooler. The drawbacks? It’s a more complicated system, and it means that another heat exchanger needs to be on the front of the vehicle, but these are much easier to upgrade than an intercooler manifold combo.

The Supra has long since been the poster child for tuning culture, it’s in the spotlight for tuning and modification. With more power comes more heat, which means the intercooler’s heat exchanger is going to require an upgrade to keep up. Let’s start by looking into how BMW intended to keep temperatures down.

Nestled under the transmission cooler and plastic rock guard, the heat exchanger practically has first dibs on fresh air pushing through the Supra’s front air duct.

The stock unit is a central component in the Supra’s front cooling stack, packed in tightly amongst the primary radiator and cooler for that stellar ZF 8HP transmission. Given the proximity to these other coolers, it’s essential that BMW designed this heat exchanger for maximum heat dissipation, while also allowing enough of a flow through to the radiator. Since it’s close quarters in there, we extracted our Supra’s heat exchanger for a closer look at the stock design.

Our first impression is that this cooler uses just about every design feature we see in OEM radiator construction. A light tube-and-fin-core with a pair of plastic end tanks crimped to either end. This means of radiator construction is perfect for large scale manufacturing since it’s inexpensive to produce by the thousands and is still adequate for most uses. However, as we see in plenty of OEM radiators and heat exchangers, once the boost turns up, these units will fill with heat and rob your B58 of performance. The plastic end tanks aren’t ideal for the vehicle’s long term since they’re prone to degradation after so many heat cycles.

That all said, BMW still has some tricks up their sleeve when it comes to the factory heat exchanger. For starters, you might have noticed the lack of AC condenser in the cooling stack list. BMW’s method of integration means that there is now a liquid-to-liquid cooler tied into the air-to-water system that takes the place of the traditional condenser. The absence of this additional cooler means there’s just one less barrier for the ambient air to pass through before reaching the heat exchanger. The BMW engineers also designed this heat exchanger with a dual-pass flow design, which keeps the coolant in the heat exchanger longer and allows more time for heat transfer.

At 27mm thick, the stock heat exchanger doesn’t seem like much. However, under closer examination, we found a similar fin construction to what we found on the Supra’s radiator. By utilizing offset fins on the heat exchanger, the BMW engineers were able to add some theoretical millimeters to this heat exchanger by forcing the air through the core at an angle. This way, the ambient air technically has more contact with the fins to dissipate heat from the coolant. Even with this method, a thicker core would still be ideal for improving the cooling performance of the B58’s intercooling system.

Toyota may be on the way to returning to the top of its sports car game with the Supra, but there are still a few obstacles to clear. The BMW engineers who designed plenty of the Supra’s inner workings are thorough but constrained under tight budgets and razor-thin margins resulting in cut costs on specific components, which can affect furthering the performance from your A90. The integration between Toyota and Mishimoto is an innovation sure to keep your Supra cool. Stay tuned for a look at what we have planned!

Thanks for Reading!

-Nick

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