It’s a strange time in the automotive world when it’s an insult to call a Toyota a BMW. Yet, it seems that is one of the only small clouds hanging over the otherwise flawless return of the legendary Supra. I would say that’s a win. Sure, it’s Z4 in a cooler outfit, but I can’t remember the last time BMW wasn’t considered to be one of the benchmarks for automotive engineering. Why not shine a light on the real matter at hand, something that actually makes a difference? The only real speck on the otherwise gleaming Supra moniker is the issue of blow-by.

BMW was on the forefront of direct injection technology on its production vehicles like the N54 back in the early 2000s. In turn, that means they were also on the front lines of the carbon buildup frontal assault that plagued these otherwise top performers. It’s been almost 15 years between then and the B58, but this issue of blow-by even shows up to this very day in the Toyota/BMW tag team effort.

BMW’s innovation has a funny way of complicating these catch can projects. Once we lifted the engine cover, and paged through some technical documents of course, our engineer Dan discovered that there are three possible routes sending the oil and blow-by back into the system. We’ll start on top of the engine.

Like the B58’s younger brother, the N55, the crankcase pressure is corralled via a series of one-way check valves depending on the amount of load the engine is experiencing. The above port is the B58’s PCV breather and is utilized under full load, with the partial load routing from the back side of the head.

Under closer inspection, we found this air line is sporting a venturi sensor port, which further complicates our quest for warding off carbon buildup. Strict emissions standards mean sensors with tight perimeters, ensuring the byproduct of the millions of tiny explosions is less harmful to the polar ice caps. Thankfully we’ve had previous experience with these sensors.

Hiding under the valve cover, both ports have their own means of sorting the contaminants from the air. Before the crankcase pressure can route to the intake system, it has to pass through a series of expansion chambers and baffles which condense the fuel vapors and oil and send them back to the oil pan.

With the lines of defense in place on the top end, the intake tract is still flanked by the blow-by that can potentially sneak through the crankcase ventilation (CCV) line from the bottom of the block straight to the air intake pipe. Pitching oil directly in this route could mean an eventual clogged up intercooler since it now sits in the intake manifold. Not to mention that any tenacious droplets of blow-by would take up real estate on the intake valves.

The Supra’s return could be considered close to perfect. The tag-team effort between the two automotive giants revived an icon whose main flaws are that it’s confused with a BMW (if that could even be considered a flaw), and it still suffers from the potential of carbon buildup. Stay tuned as we dig further into the B58 and narrow down the main source of the Supra’s blow-by.

Just about every major launch these days is complemented by some unforeseen bug in the system. It’s just the way of the world, and manufacturers are quick to solve these small hiccups with a recall or a software update. Some bugs aren’t easily remedied with a code revision or swapping for updated parts. For many vehicles, including your A90 Supra, blow-by will be an issue no matter the measures taken by Toyota and BMW to prevent it. When it comes to protecting your intake components, the solution requires a hardware upgrade, and we have that hardware.

It’s taken a few months of poking, fabricating, and testing, but our engineering team has struck oil. If you remember back to our first post, our engineer, Dan, was in the process of equipping the Supra with a trio of catch cans to cover all possible routes that blow-by could take to the engine. To find which of these routes was the primary contributor of blow-by, Dan took a two-pronged approach, starting on the dyno.

It should come as no surprise that a modern vehicle like the Supra comes equipped with highly calibrated emissions sensors throughout the car. Changing the airflow through emissions sensors by, say, adding a catch can could lead to a very stubborn check engine light. This is something that we’ve dealt with before and wanted to avoid on the Supra. To prevent a check engine light on the Supra, Dan monitored the pressure through each line at various engine loads. If any line showed a significant variance from stock, that would give us an early indication that one of our cans could cause an issue. From this initial test, we only started running into a problem after the installation of all three cans. Luckily, we didn’t need the full set.

The next step was to determine what, if anything, each can would collect under real-world conditions. For this test, Dan installed all three of our catch cans and drove the Supra for 750 miles. This test accounts for factors that dyno testing cannot, including road-going load and weather conditions, both of which affect blow-by collection. Our initial collection will also indicate the service interval for our kit. Let’s take a look at what we captured in our road testing.

From our testing results, we concluded that the Supra requires a catch can on only the CCV system. The next challenge was mounting the catch can in the vehicle. Even with the Supra’s long snout, space under the hood is limited. The line that we’re tapping into is also much more accessible from under the car. For those two reasons, Dan decided to explore possible mounting locations under the vehicle. In the end, Dan decided to mount the catch can on the front cross member of the sub-frame.

The cutout in this cross member provided Dan with the opportunity to get a little extra creative when it came to his bracket design. Typically, we would search for a location where another component is mounted and piggyback off of that or utilize unused mounts. However, the Supra did not present us with many of those opportunities. So, the bracket includes a mounting plate, that keys into the cutout, and squeezes the main bracket firmly into place.

Admittedly, mounting the can underneath the vehicle isn’t an ideal location when it comes to draining the system. Dan thought so too, which is why we also opted to include a draining system. In cases like these, we would ship our catch can with one of our petcock drain kits, but we decided the Supra deserved a special touch. Dan created a hard line drainpipe, complete with a threaded drain plug routed to a more accessible location.