BMW M8 Competition versus BMW M5 G90 — related engineering, incompatible jobs

Two cars from the same division, both with a 4.4-litre eight-cylinder engine, both with all-wheel drive and a front axle that can be taken out of the equation. On paper the choice between them looks like a choice between two doors and four. In practice the same technical ancestry hides two different generations of engineering logic and entirely different journeys.

In short. Take the M5 G90 if there are more than two of you, if you want electric running through the centre of Warsaw, and if the trip runs longer than three hours. Take the M8 Competition if there are two of you, the trip is short or purely open-road, and a two-door silhouette matters in its own right. Technically the saloon is two generations of logic newer: it has a plug-in hybrid, more torque and a higher quoted top speed — but also almost half a tonne more mass.

What the numbers say

One caveat to the table matters more than the rest. For the saloon the figures come from the catalogue card and describe that particular car. For the coupé no specification card exists, so output and acceleration are given as characteristics of the M8 Competition version in general and are not attributed to the fleet vehicle.

A second observation: the saloon is faster on top speed yet slower to a hundred. There is no contradiction here — the coupé’s acceleration figure belongs to the factory version rather than to a measurement of a specific car, and three tenths of a second is within what the difference in mass would produce anyway.

Two eras of one division

The coupé belongs to a generation in which the idea of a high-performance car meant maximum boost and minimum electronics in the powertrain. The S63-family engine is a twin-turbo eight with the turbochargers inside the vee of the block; its earliest ancestor arrived in 2009 and became the first forced-induction engine in the division’s history. By the time the 8 Series appeared, the family already counted several revisions spread across different platforms.

The saloon belongs to the era that followed. Electrification here is neither an option nor a marketing addition: no version without an electric motor exists in the generation. The electric machine is built into the gearbox casing, the battery lies under the floor, and combined torque has grown to a thousand newton-metres — a value that until recently described heavy lorries rather than executive saloons.

The difference in approach has a simple explanation: another tightening of emissions rules sits between these two cars. Keeping output on its upward path while staying within the limits turned out to be impossible without an electric component. The price of that solution is mass.

What they have in common

The list of overlaps runs longer than the exteriors suggest.

Both cars use an eight-cylinder engine of 4,395 cc whose pair of turbochargers sits within the vee — the hot-vee layout, which shortens the path to the intake. Both work with an eight-speed automatic. Both get all-wheel drive assembled to the same philosophy: a transfer case driven by chain rather than by gears, an electronically controlled multi-plate clutch and a locking rear differential.

Their torque distribution logic is shared as well, and it differs from the way all-wheel drive works on the brand’s ordinary models. There is no fixed proportion between the axles: drive goes rearwards by default, the front axle joins in only once the rear wheels can no longer cope, and in relaxed driving its share falls to zero. Both cars offer three modes — fully backed up, with a wider allowance for rear-axle slip, and completely rear-driven with the stability system taken out.

The kinship here is structural rather than decorative. The coupé was designed from the outset on the same mechanical base as the previous-generation saloon, and that became the sceptics’ main argument: reviewers wrote that the model brings nothing the saloon could not already do while taking away its practicality.

Finally, both cars stand in the same relation to Polish road infrastructure. Neither needs a vignette — no such instrument exists in the country for passenger transport. Both travel freely on the S-designated expressway network, which is entirely free of charge for vehicles lighter than 3.5 tonnes. Neither has anything to do with the state electronic tolling system, which is designed for freight transport and buses. And both enter the Warsaw clean transport zone without obstacles — the requirements of its current stage are framed so that a modern petrol engine clears them with an enormous margin.

The body decides more than the engine

This is where the real dividing line of the choice runs.

The 8 Series existed in three bodies: coupé, convertible and four-door Gran Coupé — the last of these roughly twenty-three centimetres longer, three and a half wider, and with a wheelbase twenty centimetres greater. The fleet holds the coupé, that is, the shortest variant of the range and the tightest in the back. Its four seats are formal: an adult passenger will travel in the second row, but more willingly for forty minutes than for four hours.

The saloon offers five seats, proper access to the second row and a boot appropriate to its class. With four people and their belongings aboard that is not an advantage but a precondition.

There is a flip side. The coupé is lighter: kerb weight to the American specification is quoted at 1,948 kilograms, while a European test by one publication returned 1,885 kilograms for the same car — the discrepancy comes from different measurement standards. The saloon pulls the scales to roughly 2,445 kilograms, about four hundred of which belong to the hybrid system. Half a tonne of difference is felt not in acceleration, where torque compensates for it, but under braking and on turn-in.

The specialist critics were meanwhile harder on the coupé than on the saloon. One publication doubted the model’s standalone value outright: its mechanicals are shared with the previous-generation saloon, the base is shorter, the damping firmer, and no tangible gain in handling follows — while comfort on a long road is taken away. The conclusion was put like this: the philosophy of the 8 Series works better in saloon form.

Where they part company on Polish routes

Warsaw lies in the middle of the country, and the radius of trips from here is larger than in compact European capitals. Only two directions can honestly be covered in a day — Lublin and Kazimierz Dolny, both within a hundred and seventy kilometres. The rest works out like this: Gdansk 340 kilometres, Wroclaw almost 360, Krakow 294 on the through S7, Zakopane 413, Mikolajki in Mazury 223, Gizycko about 260.

On the short leg to Kazimierz Dolny the coupé wins: the road is scenic, speeds are moderate, two people travel comfortably in a two-door body, and a two-hour run is not yet long enough for the firm suspension to wear anyone down.

On the leg to Gdansk or Krakow the saloon wins. Four hours along a straight expressway is a trial for the passengers and the driver’s back, not for the engine. Five seats, a softer setting in comfort mode and a boot settle the argument without any reference to performance figures.

Towards Mazury the saloon’s advantage narrows: the final third of that route runs on ordinary provincial roads between lakes and forests, and both cars feel equally out of place on them. For that direction it makes more sense to take something with more suspension travel.

Inside the city the score changes again. The saloon can cross Śródmieście without ever starting the petrol engine, provided it was charged in the morning. The coupé offers nothing of the kind, but it parks more easily in the narrow courtyards of the centre — though the gain there is more modest than it seems, since the difference in length between a two-door and a four-door car of this class is small.

As for the quoted maxima — 250 kilometres per hour for one car and 305 for the other remain lines in a specification sheet on Polish roads. Nowhere in the country may you exceed a hundred and forty, and even that bar is open on motorways alone; on S-designated roads and on ordinary roads the limits are lower.

Which one for whom

Take the saloon if you are travelling as a group, if the itinerary contains a four-hour leg, if you want electric running through the centre, or if a boot is not an abstraction for you. It is the more versatile car, and the specialist press agrees that all this engineering works more convincingly in saloon form.

Take the coupé if there are two of you, the trip is short or open-road, and the two-door silhouette is part of the plan. It is the lighter and the rawer-feeling car: the rear-drive character comes through more distinctly, the steering is more precise, body roll is smaller. The price is firm suspension, noticeable road noise and a rear row meant for short distances.

Take neither if the bulk of the route runs over broken surfaces or if you need a high seating position. For that scenario the fleet has SUVs and crossovers, and among four-doors with the emphasis on long-distance comfort there is the Mercedes-AMG GT 53.

Current specifications for the saloon are on the model page. The rest of the fleet is gathered in the catalogue section. Terms for taking a car abroad, insurance and surcharges: confirm when booking.

FAQ

Do these two cars have the same engine? No, but a related one. Both units are eight-cylinder, 4.4 litres, turbocharged, and the second develops the line of the first in engineering terms. The fundamental difference is that in the saloon an electric machine built into the gearbox casing works alongside the combustion engine, with a battery under the floor, whereas the coupé has no electric component in its powertrain at all.

Which of the two is faster? It depends what you count as speed. On quoted top speed the saloon leads: 305 kilometres per hour on the card against 250 from fleet data for the coupé. On acceleration to a hundred the coupé’s factory figure is slightly shorter — 3.2 seconds against 3.5. On Polish roads neither is realised: you may not travel faster than a hundred and forty, and even that is allowed on motorways only.

How different is the capacity? Substantially. The coupé is designed for four, yet the second row under the sloping roof of a two-door body suits short stretches. The saloon gives five seats, proper access to the second row through its own doors, and a business-class boot. With four people and luggage aboard for a weekend, the difference between these bodies decides whether the journey is comfortable or not.

Is it true the saloon is half a tonne heavier? Very nearly. Official data gives around 2,445 kilograms for the saloon and something in the region of 1,885 to 1,948 for the coupé depending on the measurement standard. The difference is created by the hybrid system, which adds roughly four hundred kilograms. It tells above all under braking and in long sweeping corners.

What is the 2WD mode, and do both cars have it? Both do. It is the mode in which the electronics fully open the multi-plate clutch of the transfer case and switch off the stability system, leaving the car rear-driven in character. No mechanical disconnection of the front axle takes place: propshaft and front differential remain linked and turn freely.

Which one should I choose for a trip from Warsaw to the coast? The saloon. Gdansk is 340 kilometres along the toll-free S7 expressway or 415 via the A1 motorway with one tolled section, so about four hours each way. Over that distance the decisive factors are seating, capacity and the boot, not the difference in acceleration between two very fast cars.