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Discussion Starter #1
Mishimoto 6" Intercooler - The Journey From R&D to Release (Warning Long Read)

I enjoyed reading Mishimoto's post on their new BMW F Chassis intercooler. I hope you guys enjoy it as well:thumbsup:

Original author: NICHOLAS THOMAS


Mishimoto prides itself on the ability to improve the cooling systems on just about any vehicle that rolls through the garage door. Intercoolers have become our bread and butter at this point. That being said, BMW’s are notoriously over-engineered, so improving on the meticulous German design isn’t going to be an easy task.

It seems that the engineers at BMW wanted to make sure they provided the best equipment on their “Ultimate Driving Machine,” which means tight spacing. Peeling the front bumper cover from our loaner 2014 335i M Sport reveals a space no bigger than a toaster oven. A tricky intercooler project lies ahead, but that’s OK, because we’re up to the challenge.

The front fascia is secured on tight, but our engineer Steve, left, and project manager, Rob, make short work of it.

The F30 335i with the front fascia removed. The M-Sport aero package includes its own full set of shrouding and duct work.

BMW already has an adequate design on their stock intercooler. It’s a stout tube and fin unit with a fair balance of fin density and spacing. On top of that, the diverters residing in the inlets ensure the full use of the core when cooling charged air. The shaping of the M-Sport aero bumper cover and use of shrouds directs maximum airflow not only to the intercooler, but to the four other different cooling units mounted on the F30’s front end. It’s also apparent that there was a collection of careful engineering that went into the stock intercooler’s mounting configuration. The plastic end tanks are cut to precision to ensure the intercooler nests between the primary radiator and the undercarriage cover. In short, the intricacies of the front-end design mean that we have our work cut out.

The Stock intercooler unit. Note the guides on the end tanks for seamless mounting under the primary radiator.

BMW packed a lot of fins into a small space.

The well-designed front end adds a second degree of difficulty to our design process. In a perfect world, we would increase the density, and surface area, and take up whatever available space is left. The problem with this model is there isn’t much space, and blocking the other components could lead to increased coolant temperatures. One of the challenges we’re facing in this process is the shrouds. Our loaner 335i has the aggressive M Sport aero package on it, which is not the most commonly used front fascia for the current 3 series.

The full array of shrouding and ducts that had to be removed just to get to the intercooler.

The standard cover not only uses a different shape, but also different shrouding. Ideally, our new intercooler will be designed to fit on the 4-series, as well as the 2-series, but, you guessed it, each model has its own set of fasciae and shrouding. The size requirements vary from each model and accessory package, so we are working on a solution to have a unit that fits across the board but still retains the factory trim.

The available space we have to work with for our intercooler design.

Because of our limited timeframe with the Bimmer, and the intricacies of the project our engineer is already at work on the improved design of the intercooler, and sifting through the complexity that is BMW’s abundance of fasciae and shrouds.

Steve using our Faro Design ScanArm to create a 3D model of the stock unit so he can determine the envelope for our improved design.


When I last left off our engineer, Steve, was busy scanning and creating a 3D model of the F30 stock unit as a reference for our new design. There is an impressive amount of engineering that has gone into this intercooler project already, with more to come. One of the reasons for this attention to detail is because of the wide range of models that this new cooler is going to fit, as seen by our photo gallery. Another reason is because BMW has a pesky habit of living up to their moniker, “The Ultimate Driving Machine,” they leave little room for error.

Steve working the Faro Design ScanArm to create a 3D model of the stock intercooler unit.

I’ve always been a huge fan of BMW, especially when it comes to the meticulous engineering that goes into each of their vehicles. Every model they put out is designed to last. Whether it be a 28-year old 3-series speeding around the flat back roads of New Jersey, or the much bigger and heavier X3 taking on the winding mountain roads of the Colorado Rockies, leaving a smile on your face also seems to be a design requirement. For most BMW owners, the thorough engineering and attention to detail is more than enough, and typically such thought in the design process shouldn’t lead to adverse characteristics. However, we saw differently upon peeling back the front bumper cover of our loaner 335i.

There were a few recurring themes in the stock review of BMW’s intercooler which were the abundance of different shrouding and duct work behind the bumper cover, the lack of space to work with, and the wide range of fitment our new design has to fit. These three factors left us with two different designs to choose from.

The disassembled front end of our loaner 335i xDrive. The section of the fan that is showing is about as far down as we can go with our new design.

The first design we were thinking of was an intercooler similar to our E9X unit in which we would just expand the width of the core to increase the volume. We already have a baseline of the general performance and fitment of this design, so it seemed almost like a no-brainer. Almost. One of the problems we would run into includes, of course, fitting it with the factory shrouding. Unlike the E9X, we’re designing an intercooler to fit on 3 different models, each with different variations on the equipment and styling packages.

Our E9X 335i intercooler.

Performance with this design also becomes an issue. With a thicker core, yes, there is an increase of volume, but as it heat-soaks, the returns would be at a higher temperature since there are now more layers of fins for the airflow to penetrate. Increased core volume is always an improvement, but as the core thickness increases, the return temperture increases. As the cold air travels from the front of the intercooler to the back, it’s picking up more and more heat. So, the front of the core might receive ample cooling, but the rear section will still see higher temperatures.

Another viable design option was to stretch our new intercooler over the available space in the front of the Bimmer, with a design that is both tall and thin. Filling the space between the primary radiator and the crash bar means having a core that has an increase in volume and surface area over the stock heat exchanger. An additional benefit to this design would be a thinner core, meaning the heat can be transferred from the charged air more efficiently.

There are, of course, some drawbacks to using this design. The biggest obstacle is operating around what keeps the car in one piece, the crash bar. The small price to pay for keeping you safe in the case of a crash is that this bar blocks airflow from the upper section of the intercooler. We plan on keeping the inlet diverter to make sure the full core is being used, but that won’t matter if there isn’t any airflow to a third of the core. On top of that, there’s still the stock shrouding to contend with for fitment.

A comparison of the shrouding and duct work found behind the M-Sport fascia, left, and the standard fascia, right, on the F30’s.

There is one main thing that keeps getting in the way of our design process: the shrouding. If it’s a constant burden, why not get rid of them all together, or make them fit the design? Well, it’s not that simple. For starters, modifying stock parts can get a little dicey. The biggest concern would be voiding the manufacturer’s warranty on your BMW, since most of the F2X and F3X models on the road today are still covered. We wouldn’t want to be the reason why you would have to pay out of pocket for all your maintenance needs. On top of that, any kind of modification to the car or original components will only make the installation more complicated.

The only model on our fitment list that would possibly require any modification would be the M2 because of the more intricate front support, but we’ll leave it up to you on whether you want to modify this piece or just remove it. So, we decided that instead of modifying your shrouding, you just won’t put it back in after installing our intercooler. With the factory shrouding out of the way, Steve had more freedom to work on a design that would not only fit across the long list of models, but also outperform the stock unit and competitors.

The orange arrows indicate the front support braces that would impede installation on the F87 M2. These will need to be trimmed if the full support brace is not removed.

Removing the factory shrouding will change the flow of air into the intercooler and cause issues with directing airflow, of course. Without all that plastic mounted behind the bumper, the airflow is not guided, and while most of it will be passing through the intercooler, we want to make sure that all the air is being crammed through those fins and delivering the best returns into your intake manifold. We saw that as an advantage.

While the shrouding on the standard bumpers will still fit with our design, we took the liberty of designing our own sets of shrouds to direct the airflow to the intercooler. Steve has designed a set specifically for the M-Sport kits, which will mate with the factory brake ducting, and seal against the crash bar at the top back side of the bumper cover. For those of your without the M-Sport aero kit, don’t worry. There will also be a set included for the standard bumpers. They will feature a similar design, but will have a cutout for the lower bumper support bar. In both cases, these new shrouds will create almost a sealed passage directing the incoming airflow straight into the intercooler.

We want our included shrouding kits to have a snug fit to make sure that the intercooler is getting the maximum amount of airflow.

Before we get to the big reveal or what our plans are, let’s go over the other improvements to the intercooler. On the top of that list, aluminum end tanks. Plastic, while light and easier to produce, just won’t be as durable as our aluminum tanks. Over time the stock plastic end tanks will degrade, which can cause cracks and leaks, leading to less power to your N55 or N20, but the metal tanks can stand up to the elements, and improve the airflow into the core. The end tanks will get some help from diverters that will be incorporated into the inlets to ensure the air makes full use of our new core. The core construction will also be changed from tube-and-fin to bar-and-plate with our new design. While the tube-and-fin construction has its advantages for the manufacturer, a bar-and-plate core will have better cooling properties. However, the improvements to the core can only be as good as the overall design of the intercooler itself.

Although we repeatedly talk about the downsides to plastic end tanks, it’s still a great material to use for 3D printing and quick turnaround on fitment prototypes.

Computer rendering of the new intercooler design

We are getting around these drawbacks by taking the stepped core concept and making it our own. We’re adding width to the base of the core, and Steve gave the top section of the step a 115-degree angle. We designed this intercooler to mate up with the bottom edge of the crash bar, meaning all airflow from the bottom will be directed into both sections of the intercooler, without blocking the radiator and AC condenser. When all is said and done, we’re looking at an estimated 963in³ core volume which is a 96% increase over the stock unit. As I mentioned, there will be two sets of shrouding included specifically designed for both the M-Sport and standard models, to make sure the air flows where we want it.

Our initial test fitting with the first take on the shrouding on our 335i loaner. With the weather stripping the top section rests against the crash bar and the shrouds will mate up to the fascia.

A peek as to what the installed intercooler will look like on your F30. Plenty of room for the optional brake cooling ducts.


It’s been a long time coming since we last left off with the development of this intercooler. While it might have been trying on your patience, and a little on ours, it’s not necessarily a bad thing that it took some time. Simply put, how are we going to make sure that what ends up at your door step is perfect if the first doesn’t possess the same qualities? And sometimes doing things a little differently takes some time.

If you look back to our last post outlining the design plans, you’ll see exactly what I’m on about when it comes to doing things differently. We did end up giving a good amount away then, but since it’s been a while, I’ll refresh your memory.

Yes, the stepped core is nothing new nowadays. With the F2X and F3X Bimmers, the design of the stock system almost requires a stepped core in order to squeeze more performance out of the N55 and N20 engines. During our development process, we investigated the idea of a few other core configurations, but neither quite stacked up to the stepped design.

We wanted to make sure that our stepped core design stood out from the other companies with the same idea, so we added a 115° angle to the top section. This angled step-core design not only increased the volume of the intercooler by 96% to 963 cubic inches, but also ensures a direct flow to the top section of the core. To help with shrugging off heat-soak, we’ve swapped out BMW’s original tube-and-fin core construction with the more heavy-duty bar-and-plate construction. The new core design might add a few extra pounds to the front of your Bimmer, but the improved air passages allow for better flow of the charged air through the system, and the improved fins are better suited for wicking the heat out of the channels.

It’s not often we are able to show you what lies beneath our sculpted end tanks, but since we decided to chop off the tank, it’s a perfect opportunity to show you what a bar-and-plate core looks like.

In addition to assembling a curvy core, we put some serious engineering time into the end tanks as well. We completely ditched the plastic surrounding the core and substituted in cast tanks, purpose built to allow the charged air to flow freely in and out of the core and maximize your N55 or N20’s potential after a tune.

While the new core might look out of the ordinary when it comes to intercoolers, we still need to test it to make sure that it performs as good as it looks. We have plenty of testing in store to ensure that standing out with our design paid off. From the flow bench and making a racket on the dyno to figuring out what the best shrouding situation will be when it comes to swapping out your intercooler, there is still plenty of information coming your way.

For an even closer look at our design make sure to check out our latest video:

6,574 Posts
Discussion Starter #2

Everyone loves a dynamic character. Think about it. When have you ever read a book or watched a movie and said to yourself, “Wow, I’m really glad that the main character didn’t develop throughout the story”? We long for that feel-good moment when the protagonist reaches a turning point and changes. The development for our F20/F30 intercooler has a relatable plot line.

R&D is a process with its own ups and downs. That’s what makes it a challenge, and thus fun for us problem solvers. Even with a lot of research and simulations, some things lead to unexpected outcomes. If you look back through the beginning stages of our development, it’s clear that we’re taking a unique approach when it comes to the stepped-core intercooler. If you’re worried that adding the angle to the top of our intercooler core was the part that worked out differently, never fear, it does its job. The topic of shrouding is the aspect that eventually took a different turn once we arrived at the testing phase.

Heavy Shrouding

No matter which specific 2, 3, or 4-Series you might have, there’s still plenty of shrouding that seals the intercooler in place.

We all know that BMW is notorious for putting some serious engineering hours behind just about every component of their vehicles. When our first loaner car arrived here at our Delaware facility, one of the first things we noticed was the multitude of shrouding that sealed in place the intercooler and front-mounted heat exchangers. We figured that those German engineers were on to something and began developing different sets of shrouding of our own. However, when it came to the wide fitment list, we ran some extra wind speed testing to help narrow down which shrouds specifically we would need.

We ran this test in four parts. For each test, we fixed one of our airspeed meters to the front of our loaner M2 and took it for a spin to collect real world data on how the air flow hits the front end of the Bimmer. We ran the car with the stock intercooler and our core, both with and without shrouding, and found that the shrouding actually made little to no difference when added to our intercooler.

Under Pressure
When it comes to upgrading any turbocharged car, pressure drop is a hot topic that always comes up, especially if you’re talking about larger intercoolers. Increasing the volume and packing the internal fins tight is bound to slow the airflow through the system and account for some drop in boost pressure. The hard truth is that pressure drop is inevitable when upgrading the intercooler, unless you like having an intercooler that easily heat-soaks.

Creating an aftermarket intercooler that performs is a balancing act, since we’re looking to accomplish much of the following: a drop in charged air temperatures, maintained boost pressure, and additional power. We have to find an equilibrium with the core size and fin pitch to deliver. The stock unit has a fairly loose fin pitch and a smaller core, meaning it has a decent flow reading. However, that, combined with the tube-and-fin construction, means this core will soak up heat with ease.

Our core utilizes a bar-and-plate construction, which aids in the charged air flowing through the core. We did pack some extra fins inside the core, and crammed them closer together, but we were still able to drop the outlet temperatures and add power to your turbo-Bimmer all while keeping the pressure drop under 2psi.

The Real Test

Our new F20/F30 intercooler design might be a looker, but looks come second in the case of this performance intercooler. For our dyno testing, we chose to use the cream of the crop on our fitment list, the F87 M2. Transplanting the heart of the mighty 335i into the body of the nimble 2-Series has been one of BMW’s best ideas yet, and now we have the opportunity to put it to the test on our Dynojet system.

Our loaner M2 started bellowing through its aggressive aftermarket exhaust with our standard power pull test. When we run this test on our Dynojet, our engineer, Jason, will cycle through the gears. At 5th gear, he’ll put the hammer down. This test gives us a benchmark of how our new core design dissipates heat under a single load, and also answers the question that everyone has: How much power does it add?

With an added max gain of 10hp/8tq, and a 45°F drop in temperature on the outlet over the stock intercooler, we can call it a day, right? Definitely not. Unless 100% of the driving you do with your BMW is drag racing between the stoplights, there’s another chapter to this story.

We talk a lot about heat-soak when developing our intercoolers, which is why we have a test to see how our designs stand up to torture testing. For this test, we run a sequence of power pulls, one after the other, which allows the system to fill with heat and is a true test of how well our new core can shrug off those increased temperatures.

Even after putting our loaner M2 through the ringer with our intercooler equipped, the outlet temperature was kept at the average 45°F difference over the stock core.

When we first started this project, we found ourselves asking the question, “How do you make the Ultimate Driving Machine more Ultimate?” BMW has a long and extensive history of putting serious engineering prowess into all their vehicles so that you get that ultimate driving experience. Even with all those engineering hours spent, there are still some things to improve on. If you also find yourself asking how to add to the BMW driving experience, it looks like we found your answer.
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