BMW S58 tuning: stages and things to watch.

The S58 is the engine BMW M used to make the move to the G series: 3.0 litres, six cylinders in line, two turbos and a closed deck block. It sits in the X3 M and X4 M, in the M3 and M4, and in the M2. This guide covers what you can do with that engine, what it takes and what to watch out for. Every power figure below comes from BMW's own press releases or from bootmod3's published data, not from an estimate.

What kind of engine is the S58

The S58 debuted in 2019 in the X3 M and X4 M, replacing the S55 from the F series. The block is closed deck, the exhaust manifolds are integrated and water-cooled, and it runs two mono-scroll turbos. Depending on model and year, factory output ranges from 460 to 530 hp.

Peak power arrives at 6250 rpm and the limiter sits at 7200. That is a high rev range for a turbo engine, and it is exactly where the S58 sets itself apart from most of its competition.

Stage 1: software only

With Stage 1 nothing changes on the car except the software in the engine computer. You flash through the OBD port with the bootmod3 licence for the S58. No parts to remove, no ECU to ship, and going back to stock is always possible.

Bootmod3 quotes these gains for the S58. Pay attention to the difference between fuel grades, because on this engine it is large:

• Stage 1 on RON95: up to 13 percent more power and 26 percent more torque
• Stage 1 on RON98: up to 20 percent more power and 30 percent more torque
• Stage 1 on E30: up to 28 percent more power and 36 percent more torque

That gap between RON95 and RON98 is the most important lesson in this entire guide. Seven percent of power from your choice at the pump alone is more than most people expect from a tune. Anyone sticking to RON95 leaves a substantial part of the tune unused.

The biggest gain, incidentally, is not in the headline power figure but in the torque. An S58 with Stage 1 pulls noticeably harder from low revs, and in everyday driving you notice that more than the extra power up top.

Stage 2: software plus hardware

Stage 2 means opening up the intake and exhaust and adapting the software to match. For the S58 bootmod3 quotes:

• Stage 2 on RON95: up to 22 percent more power and 34 percent more torque
• Stage 2 on RON98: up to 23 percent more power and 34 percent more torque
• Stage 2 on E30: up to 33 percent more power and 44 percent more torque
• Stage 2 on E50: up to 37 percent more power and 46 percent more torque

On the intake side we use Eventuri systems. For the M2, M3 and M4 that is the carbon intake system for the G8X, and for the X3 M and X4 M we stock the Eventuri panel filter. We also supply the complete intake system for the F9X, but it is not listed online at the moment. Give us a call if that is what you are after.

What we do not sell is downpipes. You do need those for a full Stage 2, so call us if you want to go that way and we will think along about what suits your car.

Ethanol: where the big numbers come from

You can already see it above: the jump from RON98 to E30 and E50 is bigger than the jump from Stage 1 to Stage 2. Ethanol is far more knock resistant than petrol, which allows more ignition timing. That is where the real power sits.

It does take hardware. You need a flex fuel sensor that measures the ethanol content, so the software adapts to it instead of you having to reflash at every fill-up. That is what the FlexFuel Kit Basic is for, in the G series S58 version. It is plug and play and fully reversible.

A realistic note: finding E85 in the Netherlands takes planning. Before you start, check whether there is a pump on a route you use regularly.

What to watch out for

The engine computer is locked

On the S58 this is the rule rather than the exception. The G80 M3, G82 M4 and G87 M2 always need a DME unlock first before anything can be flashed. For the X3 M and X4 M that applies from a software level of November 2019 onwards. So budget for that step from the start, it is not an optional extra.

Which unlock you need depends on the build year: the DME bench unlock for cars built before June 2020, and the DME unlock where the ECU is shipped in for June 2020 and later. We do both in our workshop.

The gearbox has its own torque limiter

The eight-speed automatic limits the torque it will pass through, separately from what the engine can deliver. On a tuned S58 you run into it. Bootmod3 can raise that limiter in software, and from Stage 2 upwards that is not a luxury but a necessity: without it you simply cannot put your new torque on the road.

Heat on track

The fact that bootmod3 offers a dedicated Max Cooling mode for this particular engine tells you enough: on track, heat is the limiting factor, not power. If you do track days, watch the oil and coolant temperatures before you think about more boost. With bootmod3 you can read that live in the app.

When buying an early car

If you are buying an X3 M or X4 M from the first model years, ask for the service history and look at what was done under warranty. That is sensible with any M engine, but on a car you intend to tune afterwards you want to know what you are starting with.

Maintenance

BMW uses a condition-based service schedule, so the car tells you when it is due. If you drive it hard, there are a few things we are stricter about than the schedule:

• Oil. With track days or a lot of full-throttle driving we prefer to change it earlier than the counter says. Oil that has been hot no longer does what fresh oil does.
• Spark plugs. More boost asks more of the plug. If you go to Stage 2 or run ethanol, expect a shorter interval than standard.
• Let it warm up. Wait for oil temperature before full throttle, not coolant temperature. Those two are far apart and oil temperature is the one that counts.
• Let it cool down. After a hard drive, take it easy for a bit before you shut it off. The turbos are up to temperature and want to keep being fed oil.
• Read along. Datalogging in the bootmod3 app is not a toy. If something is shifting you will see it in the data before you feel it in the car.

What you need to get started

Besides the licence you need a bootmod3 wifi adapter or an ENET OBD cable. And as described above, on virtually every S58 a DME unlock first.

What we do with it

We work with bootmod3 daily in our workshop in Elburg. You can order the licence from us and flash it yourself, or have us do the whole job: unlock, licence, tune and the intake alongside it if you want. After your order we will contact you to make an appointment.

Wondering whether Stage 1 is enough for what you want, or what it does to your warranty? Read what Stage 1 tuning actually is and how tuning relates to your warranty, insurance and roadworthiness test. If you are still not sure, just give us a call.