Tearing Down The New 2020 Supra B58 Inline-Six Cylinder Engine

Tearing Down The New 2020 Supra B58 Inline-Six Cylinder Engine

There has been a lot of hype surrounding the new 2020 Toyota Supra. The resurrection of the iconic Japanese nameplate comes some 22 model-years after the final Mark IV was sold in the United States. However, it has not been met with unanimous praise, as the new Mark V Supra shares a significant amount of genetic development with the new BMW Z4.

However, this is EngineLabs, and we don’t focus on cars, as much as their powerplants. However, much like so many other inter-brand crossover vehicles, this new Toyota is powered by a BMW engine: The B58. First introduced in 2015, the BMW B58 was named to the 2017 Ward’s Ten Best Engines (powering the M240i), which is no small achievement.

The factory-turbocharged dual overhead cam 3.0L straight-six-cylinder engine sounds reminiscent of the infamous 2JZ-GTE engine that powered the legendary Mark IV Supra, albeit with a single turbocharger. However, that’s where any similarities end, as we see in this video by Papadakis Racing and the company’s namesake, Steph Papadakis.

To get a look inside of the exact B58 variant powering the new A90 Toyota Supra, Papadakis had to source a brand-new Supra, which have only been reaching customers in Southern California (where he’s based) for two weeks at the time of filming. So, for his knowledge and our viewing pleasure, Papadakis pulled the engine out of a 500-mile, two-week-old car and recorded himself ripping it apart.

Not Purely Altruistic

Papadakis isn’t tearing down this engine just for the sake of seeing what’s inside. He already has a whole four-part project planned for the engine build. “We have a big goal for this,” Papadakis says. “We want to make 1,000 horsepower with this engine.”

While an inline-six is the usual fare for a Supra, this B58 is a completely different animal than the 2JZ. “This one is so much more modern. It’s cool to see all the new technology incorporated into it,” expresses Papadakis. “Everything is really lightweight; there’s oval tubing in the exhaust and surprisingly [pulling the engine] feels simpler.”

The intake manifold is an all-plastic unit with the intercooler core molded into the assembly. While that is a cool engineering feat, it’s going to make intercooler upgrades difficult in the aftermarket.

It wasn’t long after the time the engine came out of the car, that just how different the B58 is, made itself known. “The first thing we realized when we got the engine out was that we couldn’t mount it to a normal engine stand. The timing chain is actually on the back of the engine, and that’s where the engine stand usually bolts,” says Papadakis. “We had to fabricate a bracket that goes from the engine stand to a motor mount on the side of the engine block, and then reinforce the stand itself.”

The Intake Side

Starting the teardown on the intake side, the first item noticed is that the B58 is a drive-by-wire system, as most new cars are. While that used to be a performance enthusiasts nightmare, electronic throttles have come a long way in the past decade or two.

“The electronic throttle bodies can react quicker than your foot can,” explains Papadakis. “So if you feel like the throttle response is laggy, that is a problem in the tuneup, not an inherent flaw in the electronic throttle body or drive by wire system itself.”

Moving to the intake manifold, like many modern vehicles, it is a composite material. However, this one does have an unusual twist. “The intake manifold is all plastic, and somehow they manufacture it with the intercooler core already inside of it. You can’t separate the two, they are bonded together,” Papadakis says. While that might be a neat OEM feature, that will hinder the ability of the aftermarket to make upgrades.

Below the intake manifold is the thermostat housing, which is pretty wild compared to the single-temperature thermostat we are all used to. “It doesn’t use a traditional thermostat that opens and closes at a certain temperature,” Papadakis explains. “The ECU controls a rotary valve which it can open to varying percentages to change the water flow at different temperatures based on its programming.”

The built-in block-mounted oil cooler uses engine coolant to both bring the oil up to temperature faster, and keep it cool, without having to run lines to the front of the car, as is typical with remote oil coolers.

Also beneath the intake is the canister-style oil filter that is becoming far more common on modern engines, but also a block-mounted oil-to-water engine oil cooler. “Not only does that bring the oil up to temperature quicker, but it also eliminates lines running up to the front of the car,” says Papadakis.

The Exhaust Side

One of the more noticeable features on the cylinder head is that there are only two exhaust ports, where there should be six. “What they’ve done, is there is actually an internal exhaust manifold cast into the cylinder head,” Papadakis explains. With only two exhaust ports, there is no need for a separate turbo manifold and the twin-scroll turbocharger assembly bolts directly to the cylinder head.

“Only six bolts and one bracket on the bottom, and the whole turbocharger system comes off,” says Papadakis of removing the assembly. “It is all noticeably lightweight, which is nice.”

Sliding up to the top of the cylinder head, there are six direct coil-on-plug coils, which is decidedly less complex than the 2JZ’s ignition system. “No more ignitors, or any other components. There is just direct wiring from the ECU straight to the coil packs,” Papadakis says.

On the exhaust side, the twin-scroll turbocharger assembly bolts to the engine with only six bolts. That is due in large part to the internal exhaust manifold cast into the cylinder head and only two external exhaust ports on the head itself (right).

Sharing the valve cover valley with the coil packs are the high-pressure fuel rail and direct fuel injectors spraying directly into the top of the cylinders, unlike Toyota’s in-house direct injection system, D-4S, which enters the cylinder at an angle closer to horizontal than vertical.

To supply the high fuel pressures needed, a cam-driven mechanical fuel pump is mounted above the exhaust camshaft on the valve cover. That takes advantage of the tri-lobe fuel pump lobe on the exhaust cam to actuate the pump, three times for every full rotation of the camshaft.

Tearing Down the Top End

Once the valve cover is removed, we are greeted with a pair of ECU-adjustable cam gears, allowing both the intake and exhaust cams to take advantage of variable timing.

The exhaust-side valvetrain uses a relatively typical arrangement. The cam lobes act directly on the rocker arm, and that pivots on a hydraulic lifter (much like a Coyote engine).

“One thing I really like about this valvetrain is that the rockers have a little spring clip which keeps the lifter attached to the rocker,” Papadakis says. “So in the case of, say, valve-float at really high RPM, the rocker shouldn’t fall off the lifter, which we’ve seen in other designs.”

Both the intake (left) and exhaust (right) cams feature variable timing control through the ECU. The variable lift on the intake cam is controlled via a separate system.

However, the intake cam’s valvetrain is more complex, incorporating variable valve lift, as well. There are two separate rocker arms, and an eccentric to change the rocker ratio through geometry,” Papadakis explains. The second rocker arm’s geometry is altered by mechanical rotation of the eccentric, which itself is controlled by the ECU based on parameters such as RPM and load.

Additionally, the variable valve lift system incorporates a set of beefy torsion springs which makes the removal of the exhaust cam rather interesting, as you can see in the video as Papadakis battles the assembly without the proper tool.

In this photo (left) you can see the intake cam on the right and the exhaust on the left. The exhaust valvetrain (center) is a relatively traditional overhead cam arrangement with a hydraulic lifter and roller rocker setup. (Right) The intake cam features variable lift, achieved through the use of the second rocker arm and a mechanically actuated eccentric lobe, which changes the effective rocker ratio.

Exploring the Short-Block

With the timing chain removed (from the back of the engine) and the cylinder head off the block, several things become immediately apparent. The first of which is that the block is a closed-deck design. “The closed deck design is much stronger design,” says Papadakis. “I believe this block has tons of potential.”

Flipping the block over, we find a solid cast-aluminum oil pan with an oil level sensor built-in. “There are no gaskets used on the oil pan, just sealer,” explains Papadakis. “In fact, there are very few gaskets used anywhere in this engine.”

Once the oil pan is removed we can see the windage tray, that appears to be beefier than your average windage tray. That is an ingenious design feature from German engineers. “The windage tray actually doubles as a block girdle. It ties all of the main caps together along with the skirt of the block, making the block a lot more rigid,” says Papadakis.

Also helping with windage and oil control in general are the oil drain-back passages built into the perimeter of the block, putting the oil from the cylinder head directly into the oil pan, without hitting any of the rotating assembly. Additionally, high-pressure piston oiling jets are employed to keep the pistons cool under hard use.

The windage tray for the B58 is sturdy cast aluminum and doubles as an engine girdle, tying into both the main caps and block skirt.

Moving to the rotating assembly, the forged steel connecting rods feature a cracked-cap design and coated rod bearings straight from the factory. The pistons are a unique shape, ostensibly to help save weight while maintaining strength and stability in the bore, and feature both a full floating wrist pin, and an anti-friction skirt coating on them.

Moving on to the factory crankshaft, it is also a forged steel piece. Like the rods, it also features coated main bearings. “The forged steel crankshaft looks relatively stout, so I think we’re actually going to start with that crank in our quest for 1,000 horsepower,” reveals Papadakis.

(Left) Gone is the traditional crank snout, and center bolt, replaced with a flanged crank pulley and four-bolt arrangement. (Right) The factory forged 3.720-inch crankshaft will serve as the base for Papadakis Racing's attempt at making 1,000 horsepower with the new Supra engine.

At first glance, the B58 engine looks like it’s going to be a solid performer in the 2020 Supra, and its performance in the last four model years of BMW products suggests that’s the case. However, Papadakis goal is farther than anyone has pushed the engine design before.

“This looks like a solid race block. So far, I’m pretty impressed,” says Papadakis. “But the big question is, will this be a worthy successor to the 2JZ engine?”

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About the author

Greg Acosta

Greg has spent nineteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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