The B58, S58, and P58 are the same BMW 3.0-liter straight-six living three different lives. The B58 is the everyday engine in your 340i, M340i, and the Toyota GR Supra. The S58 is the version BMW M built for the M3, M4, and M2. And the P58 is the racing engine in the M4 GT3, making up to 590 horsepower. We calibrate the first two every week — and the third is what they are built from. This is the honest map of one engine family across three worlds, and what any of it actually means for the car in your garage.

The short version: these three engines share a bloodline, not just a badge. BMW over-built the foundation once — a closed-deck block, a forged bottom end — and then took it from the street to the M division to the GT3 grid. Understanding what changes at each step, and what doesn't, tells you exactly how much engine you really have.

One bloodline, three jobs

Start with the premise, because it is the whole point. BMW's modern straight-six is a modular design built around a common architecture, and the same core travels the entire ladder. The B58 established the foundation in 2015: a closed-deck block (shared, famously, with BMW's B57 diesel), a forged steel crankshaft and forged connecting rods, and a state of tune good for 320 to 382 horsepower. BMW M took that foundation, changed what a track engine needs, and built the S58 — the M3/M4/M2 engine. Then BMW M Motorsport took it one step further into the P58, the engine homologated for FIA GT3 racing in the M4 GT3.

Three engines, one family. The differences are real and worth knowing — but so is the thing that does not change: the bones underneath all three are the same over-built six. That is why the engine in your 340i is closer to a GT3 race car than almost any other mainstream motor on the road.

The B58 — the everyday six

The B58 is the mainstream member — the 3.0-liter turbo six in the 340i and M340i, the 440i and M440i, the M240i, the Z4 M40i, the X3 through X7 40i models, and the Toyota GR Supra. It runs a single twin-scroll turbocharger and an 11.0:1 compression ratio, and it is widely regarded as one of the most reliable and most tunable production sixes ever built — the stock block and internals run to roughly 600 wheel horsepower before they are the concern. It is the engine you can daily to 200,000 miles and still wake up with a calibration. We cover it in full in the B58 guide.

The S58 — M takes it to the track

The S58 is what BMW M does to the B58 when the brief is a track car. It keeps the closed-deck architecture but changes the things that chase sustained, repeatable performance: twin mono-scroll turbochargers instead of one, a fully forged rotating assembly with forged pistons, a lower 9.3:1 compression ratio, a higher 7,200-rpm redline, 350-bar direct injection, and far more cooling. The result powers the G80 M3, G82/G83 M4, and G87 M2, making from 453 horsepower in the M2 to 543 in the M3 CS and M4 CSL. It is the most capable engine M has put in a road car — the full breakdown is in the S58 guide. It is also the bridge to the racing engine, because the P58 starts here.

The P58 — the M4 GT3 racing engine

This is the part almost nobody explains properly, so here is the real version. The P58 is a race-prepped variant of the S58, developed by BMW M Motorsport for the M4 GT3 — the customer race car that replaced the V8-powered M6 GT3 from the 2022 season. It produces up to 590 horsepower and 516 lb-ft of torque before any racing restriction, which makes it the most powerful straight-six BMW has raced since the M1 in Group 5. And it is roughly 80 pounds lighter than the V8 it replaced, which is most of why BMW switched a flagship GT3 car from eight cylinders to six.

What BMW Motorsport actually changes from the road S58 is instructive, because it is all race-specific:

• Dry-sump lubrication. The street S58 uses a wet sump; the P58 runs a dry sump with an engine-mounted oil tank and an integrated oil/water heat exchanger — so it survives sustained high-g cornering without starving for oil, the exact failure mode that worries tuners on the street engine.
• A changed engine mounting angle, to drop the center of gravity for a race chassis.
• A charge-cycle-split intake with two throttle valves, and a charge-cycle-split exhaust — race induction and exhaust geometry built for response and airflow under competition conditions.
• GT3-spec engine mounts and a rear torsional vibration damper, for the loads and the driveline of a racing car.
• Longer service and rebuild intervals than the old M6 GT3 V8 — a real cost advantage for customer teams.

One more honesty point that matters: that 590-horsepower figure is the engine's maximum. In actual competition the P58 runs restricted by Balance of Performance — the sanctioning bodies cap power with air restrictors and boost limits so a field of different cars can race closely — so a P58 on track often makes meaningfully less than 590. The headline number is the ceiling, not the race-day reality.

The M4 GT3 Evo — going further without chasing power

For the 2025 season the M4 GT3 became the M4 GT3 Evo, and what BMW M Motorsport changed — and pointedly didn't change — is the most useful part of this whole story for anyone tuning a street car.

What didn't change is the engine. The Evo keeps the same P58: same 2,993 cc, same up to 590 horsepower. BMW did not reach for a bigger number. In their own words, the focus "was not necessarily on pure performance but on areas such as drivability, efficiency, and reliability." A car that was already winning did not need more power — it needed to be easier to drive fast, for longer, with less wear.

So the Evo's changes land everywhere except the engine:

• Aero efficiency — smaller aero mirrors, larger air outlets in the front wheel arches, and a wider rear-wing adjustment range, chasing cleaner airflow rather than just more downforce.
• Less wear, more consistency — new front and rear anti-roll bars, larger rear brake discs, and a finer, easier-to-adjust differential, all aimed at saving tyres and brakes deep into a stint.
• Weight pulled from the details — the chassis wears a lighter cathodic dip coating instead of paint, and on the dark areas of the livery BMW deletes the wrap film entirely to expose bare carbon and save the grams.

BMW works driver Jens Klingmann summed up the philosophy better than any spec sheet: "We have not made one big improvement... but have turned many smaller screws, which will especially improve drivability on a long run... several small steps also make a big step." It worked immediately — the Evo took overall victory on its competition debut at the 24H Dubai in January 2025.

Here is why a development story about a €578,000 race car belongs in an engine essay: it is the same lesson we give every customer, validated by a factory GT3 program. The fastest move is rarely more power. Once the engine is strong — and the P58 already was — the gains that actually win races come from drivability, consistency, cooling, and weight, not another twenty horsepower. If that is how BMW evolved a car that was already winning, it is worth remembering before you chase a bigger dyno figure on your own street car.

The triad, side by side

The shape of the ladder is clear: each step keeps the foundation and adds what its job demands — forged pistons and a second turbo for the M car, a dry sump and race induction for the GT3 car. The block family carries all the way up.

What actually carries over to your street car

Here is the question that matters if you own the B58 or the S58: how much of the GT3 engine is relevant to you? The honest answer is the interesting one.

What's shared is the foundation — and it's the part that counts. The closed-deck block, the forged bottom end, the fundamental architecture that lets the S58 become a 590-horsepower race engine is the same architecture sitting in your M3, and a close relative of the one in your 340i. When people say these engines "have room," the P58 is the proof: BMW would not build a GT3 program on a foundation that couldn't take it. Your street engine was designed by the same people, on the same bones.

What's pure race is most of the rest — and you should not try to replicate it. The dry sump, the charge-cycle-split intake, the Balance-of-Performance race calibration, the full competition cooling package: these solve problems a street car does not have, at a cost and complexity a street car should not carry. Chasing "GT3 spec" on a road car is how people spend a fortune making a car worse to live with.

What you can actually do is exploit the same strong foundation the right way — a proper calibration built from your car's own data, the supporting hardware that matches your goals, and the discipline to build in the right order. That is the entire reason the B58 and S58 are such rewarding engines to tune: you are working with a foundation engineered for far more than the street ever asks. When you're ready, build your tune for your exact car, and our Stage 1 vs Stage 2 vs Stage 3 guide lays out the ladder. [LP: an EW first-hand line here — a customer S58 or B58 result, or the shop's take on what "track-ready" actually means on the street engine.]

There is a four-cylinder version of this same story, by the way: the B48 has its own motorsport sibling, the P48, which BMW Motorsport built for racing and which shares its cylinder block with the road-car four. We cover it in our closer look at the BMW P48.

Bottom line

The B58, S58, and P58 are one BMW straight-six in three states: the everyday engine in your 340i, the track engine in your M3 or M4, and the 590-horsepower racing engine in the M4 GT3. They share the foundation that matters — a closed-deck block and a forged bottom end built with margin most engines never get — and they diverge in the race-specific hardware each job demands. The takeaway for an owner is genuinely encouraging: the engine in your car was built on the same bones BMW races, which is exactly why it responds the way it does when you tune it properly.

Frequently asked questions

What engine is in the BMW M4 GT3? The P58 — a 3.0-liter inline-six M TwinPower Turbo race engine producing up to 590 horsepower and 516 lb-ft of torque before Balance-of-Performance restriction. It is a race-prepped variant of the S58 from the road-going M3 and M4, and the most powerful straight-six BMW has raced since the M1.

Is the P58 the same as the S58? They share the same foundation — the S58 is the road M3/M4/M2 engine, and the P58 is BMW M Motorsport's race-prepped version of it for the M4 GT3. The P58 adds race-only systems: a dry sump, a changed mounting angle, a charge-cycle-split intake and exhaust, GT3 engine mounts, and a competition calibration.

What's the difference between the B58 and the S58? Both are BMW's closed-deck 3.0-liter straight-six, but the S58 is the M-built version: twin turbos instead of the B58's single, a fully forged rotating assembly with forged pistons, lower compression, a higher redline, and far more cooling. The B58 (320–382 hp) is the mainstream six in cars like the 340i and Supra; the S58 (453–543 hp) is the M3/M4/M2 engine.

How much power does the P58 make? Up to 590 horsepower and 516 lb-ft at its maximum. In competition it runs restricted by Balance of Performance — air restrictors and boost limits that cap output so different cars can race closely — so on track it often makes less than the headline figure.

Can you put a P58 or "GT3-spec" engine in a street car? You generally shouldn't. The P58's gains come from race-only systems — dry sump, race induction, competition cooling and calibration — that solve track problems a street car doesn't have, at a cost and complexity that make a road car worse to live with. The smarter path is exploiting the same shared foundation with a proper street or track calibration on your B58 or S58.

Why did BMW switch the GT3 car from a V8 to the six? The P58 straight-six makes up to 590 horsepower and is roughly 80 pounds lighter than the V8 in the previous M6 GT3, which improves weight distribution — and it carries longer service intervals, which lowers running costs for customer teams.

What is the BMW M4 GT3 Evo, and does it use a different engine? No — the Evo, which races from the 2025 season, keeps the same P58 with the same up to 590 horsepower. BMW deliberately aimed the Evo at drivability, efficiency, and reliability rather than peak power, with revised aero, new front and rear anti-roll bars, larger rear brake discs, a finer differential, and weight saved through a lighter cathodic dip coating in place of paint. It won overall on its competition debut at the 24H Dubai in January 2025.