M xDrive Intro

One of the biggest changes in the F90 M5 was the introduction of a 4-wheel-drive system. This change was greeted with a lot of trepidation from the community because 4WD had a history of poor handling. However, because of the difficulty of getting the M5's torque to the road, and because of competitors who were smashing BMW's 0-60 times with 4WD, BMW was forced to follow suit.

As I explained in Horsepower:

In practice, 1g of acceleration (+22 mph per second) would never happen with the M5 because its road tires just aren’t that sticky. Generally a good rule of thumb for a decent road tire is that it can push forward with about the same force as the weight pushing down on it.

Since the M5 is a rear wheel drive car, and about half the weight of the car is on the rear wheels, it can only accelerate at about 0.5g to start. It gets a bit better than this in practice because as the rear wheels start accelerating, the weight goes more onto the back wheels resulting in an effective acceleration of about 0.7 g’s (about +15 mph per second) with good tires on good pavement.

The above implies that regardless of how powerful the engine, no 2-wheel drive car with 50-50 weight distribution can accelerate to 60 faster than in about 4s on road tires. However, with 4WD with road tires on a good surface, a car could achieve 1g of acceleration if the engine is powerful enough (2.7s to 60). Because the F90 M5 engine can't quite generate 1g of acceleration in 2nd gear (more like 0.9g), and you have to shift to 2nd at around 30mph, in practice it's about 3s to 60.

While 0-60 is the most visible metric dramatically impacted by 4WD, acceleration out of corners is also improved with BMW's M 4WD. This is because the traction of the tires is divided between turning and accelerating. If you put too much torque into a RWD car while turning, it will spin out ("oversteer"). If too much torque on a FWD car, it will not turn in ("understeer"). If you divide the acceleration amongst all 4 tires, the total acceleration available from all tires out of a turn can be more given the same traction available for turning on both front and rear tires.

This last point is crucial to the development of the 4WD system on the M cars (called "M xDrive"). The M xDrive can actively direct torque between front wheels and the rear right and rear left wheels. So during turning the system can exactly provide torque to where it's needed at any given moment in time in order to optimize the handling (which was the big bugaboo with 4WD systems in the past).

Quoting from the BMW site 5 Facts about M xDrive:

[The system] monitors real-time parameters from the accelerator pedal position, steering angle, road speed, slip at the front and rear axle, longitudinal and transverse acceleration, friction coefficient, yaw rate, etc. This information is analysed to establish the vehicle’s current situation. M xDrive can then support the driver in every set of circumstances.

When accelerating out of a bend, M xDrive successively puts more and more torque on the front axle when it detects decreasing lateral acceleration. At that moment, it becomes possible to transmit the longitudinal forces without understeering. This occurs so gradually that it’s possible to exit the bend with a slight drift, as one would expect from an M automobile. It feels as if you are coming out of the curve in a controlled catapult.

From my test drive of the car, I can tell you that this absolutely is a real thing and puts a huge smile on your face even in regular road driving. I was instantly sold! The faster 0-60 is a bonus.

We'll get into the development and the technical details in follow-up blog posts.

Introduction to the F90

 In this post I'll give an introduction to the car I ordered: the 2022 BMW F90 LCI M5 Competition.

The designator "F90" is an internal BMW chassis designator. Originally the chassis designators all started with the letter "E" which stands for the German word "Entwicklung" which means "Development". BMW ran out of two-digit designators and moved into "F" and now "G". The designators are handed out once development begins. So we can conclude that work on the F90 (M5) began before work on the G30 (the regular 5-series) or even the G12 (the latest 7-series on which aspects of the latest 5-series is based).

For a history of BMW, see History of BMW.

For a history of the 5-series, see 5-Series History.

For a history of the M cars, see History of "M" and M5.

The G30 was unveiled in October 2016 and the F90 in September 2017.

Usually the M5's have the same chassis designator as the regular 5-series, but not this time. This is apparently because work on the next generation M5 began before the work on the new 5-Series, whereas usually it is the opposite, although in the end many of the elements are merged.

This car is the LCI, meaning "Lifecycle Impulse", a collection of minor changes and improvements midway through a car's lifecycle. The LCI was released for the 2021 model year.

The F90 is an incremental improvement off the previous generation F10 M5, using essentially the same engine (although further developed). Big differences are

• the introduction of 4-wheel drive (M xDrive)
• a significant increase in torque and horsepower
• a lighter and stiffer chassis
• the adoption of an automatic transmission
• the adoption of an electric power steering system (M EPS)
• a complete update of the vehicle electronics

This generation of 5-series comes in multiple engine styles and performance levels as follows.

• 530i - B46 turbo 4-cylinder / 248 HP / 295 lb-ft
• 530e - B46 turbo (detuned for fuel economy) + hybrid electric / 248 HP / 310 lb-ft
• 530d - 6-cylinder diesel / 261 HP / 461 lb-ft
• 540i - B58 turbo 6 cylinder / 335 HP / 332 lb-ft
• M550i - N63TU2 turbo 8 cylinder/ 455 HP / 480 lb-ft
• M5 - S63TU4 turbo 8 cylinder / 600HP / 553 lb-ft
• M5 Competition - S63TU4 turbo 8 cylinder / 617HP / 553 lb-ft
• M5 CS - S63TU4 turbo 8 cylinder / 635HP / 553 lb-ft

The M cars have a different engine, beefed up components to deal with the power and torque, different steering, and a more rigid chassis.

In the next few posts we'll cover off the big changes from the F10 M5 (the car you can read all about in the earlier part of this blog).

BMW Technical Information

The very best source for technical information about BMW cars is the BMW TIS (Technical Information System).

https://www.bmwtis.com

You only really need a single day's access for $30, and that allows you to go into the training section and download literally any of the pdf documents that are in there (about 180 or so). It's wise to cast a broader net, as a document about your car may refer to other documents.

This is what I downloaded that day for my $30:

But don't worry, if you're interested in the BMW F90 LSI M5 Competition, I'm doing all the reading for you and will present my synthesis on this blog. The previous generation F10 M5 was similar in many ways to the current generation F90, so if you're interested in the F90, best to go back to the start of this blog and read through it to catch up to me. Also, all the history and basic car engineering principles are the same, so good to read that as well.

As I go through the new car, I will explicitly refer back to earlier blog entries and then carry on with the differences, so nothing lost if you want to prepare yourself.

New Car Ordered

 I just ordered a new M5 and so... I'm back!

This will be my third BMW. I started with the 2005 E60 BMW 545i:

2005 E60 545i. RWD V8, 3748lbs, 330lb-ft@3600rpm, 0-100 in 5.8s; 325 HP

I was considering an M5 at the time, but it was a big naturally aspirated  V10 engine with an SMG transmission that I did not like, so I went with the much more practical and drivable 545i. It was a great car and did not give me a lick of trouble the whole time.

In the 2011 model year BMW launched the F10 M5. It corrected all the flaws with the previous M5 and so I stepped up to a 2013 model year M5.

2013 F10 M5. RWD turbo V8, 4387lbs, 501ft-lbs@1500rpm, 0-100 in 3.9s, 560 HP

I stuck with the blue because I really liked the blue. It was the first turbo-charged V8 from BMW and had a paddle-shifted Dual-Clutch Transmission which was absolutely brilliant. The torque was magnificent and available at from low RPM right up to screeching RPM. It has also been very trouble-free over the years (except it used a lot of engine oil, by design). Only recently they noticed the engine leaking oil in a way it ought not to be, which necessitated a gasket job, which was pricey and off warranty. I thought maybe this was the beginning of the end for me for this car, going onto 9 years, and there had been a new generation of M5 introduced in 2017 that I was wanting to get into, so I recently pulled the trigger and put in my order.

2022 F90 LCI M5 Competition. 4WD turbo V8, 4370lbs, 553ft-lbs@1800rpm, 0-100 in 3.2s, 617 HP

The M5 now comes in three variants, the base M5 (not available in Canada), the M5 Competition, and the M5 CS. The CS raises horsepower (though not torque) and lightens the car with more carbon fiber, especially the seats. It also has a considerably rougher ride and is much more expensive as a "limited edition". So the M5 Competition was my variant of choice.

The "LCI" stands for "Lifecycle Impulse" and is BMW's new word for a midcycle refresh. That was done for the 2021 model year, and there are some important upgrades which I will get into later, which made it more attractive.

I went with the "Ultimate Package" which has most of the bells and whistles. The colour is "Aventurine Red Metallic" and the interior is "Tartufo Brown Full Merion Leather".

It should arrive before March, so I'm looking forward to that!