Why The New BMW M5’s Lower Grille Is Actually Weirder Than Its Main Grille

While on the Concept Lawn at Pebble Beach yesterday I stumbled upon the new BMW M5 Touring — the green wagon that’s been making waves all over the internet. And while normally you might expect me to talk about its gorgeous wagon shape or its humongous girth or its powerful 717 horsepower engine or its interior, what actually caught my attention was the car’s cooling system — specifically, the way the cooling module is packaged in the lower front fascia. Let’s have a look.

Back when I was developing the the Jeep Wrangler cooling system, we were having some issues meeting our trailer tow targets (basically, we wanted to tow 3500 pounds up Davis Dam, an ~11 mile,  ~5.7-percent grade at 100F with AC on). We tried enabler after enabler to fix our capacity problem that was fundamentally caused by our limited  packaging space above the front bumper and behind the seven-slotted grille — better heat exchanger-to-front end module sealing, a higher-power fan, larger grille openings, a different transmission shift schedule, and on and on. A given in all the calculations was that the front grille would be similar to the JK Wrangler’s in that it would have no texture.

Like this:

Notice how the transmission oil cooler and AC condenser are clearly visible, since there’s no grille texture in those seven slots. That’s fairly unusual for most cars, as designers typically love grille texture, which is why the the production JL Wrangler launched like this:

I have to say, I was surprised. We’d only been marginal on the J2807 towing requirement; how could we afford to reduce airflow to the cooling module by adding texture? The truth is that our simulation models probably had a bunch of safety factors baked into every level of the design (the fan airflow, the heat exchanger performance, the CFD for the front end, etc etc), and all those safety factors (or “margins”) stacked up to yield a cooling system that was overdesigned (this model fidelity issue is, in my view, part of why Chrysler products have been historically so heavy — if you can’t trust your models, you have to overbuild the car). This likely became apparent when physical mules began hitting the dyno, and then whoever replaced me realized that airflow was totally fine and that the designers who were champing at the bit to add grille textures were good to go.

 

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Anyway, the point here is that grille texture reduces airflow to heat exchangers markedly, but is typically a darling to designers and it also offers the practical benefit of protecting the heat exchangers from road debris. Most vehicles have grille texture, and the few that don’t — including the JK Wrangler — only have small individual grille openings (slots in this case). That’s why I was surprised to see the new M5:

Holy cow; look at that humongous lower grille opening! I’ve never seen an unobstructed grille opening that big in my entire life (well, on a modern car)! This M5 sucks in air like a blue whale sucks in krill — with mouth agape!

It’s worth briefly digging into the M5’s front cooling design, because it’s extremely interesting. In those huge rectangular openings you can see an AC condenser, and while there is no texture whatsoever, you’ll see a nylon cage right up against the heat exchanger, protecting it from debris. Just to the left of that opening you can see a smaller rectangular opening; that feeds the front brakes cool air. To the left of that in the diagonal slot is another opening for remote-mounted heat exchangers, and to the left of that on the very outboard side of the front fascia is an air skirt to route air past the front wheels for improved aerodynamics.

Here’s a look at the nylon cage in the main opening, protecting the AC condenser:

Notice that the floor of this opening is another heat exchanger! (an oil cooler, of sorts). This is the same design that I showed off in the Cadillac ATS-V, and it’s actually kind of brilliant. As air enters that huge grille opening, it “rams” up against the condenser, whose restriction creates a high pressure. The difference between this high pressure in front of the condenser and the low pressure from the high-velocity air moving below the front fascia as the car drives “pulls” air through this horizontally-oriented oil cooler. It’s clever.

Here’s a look inside one of the brake cooling ducts; you can make out (barely) part of a control arm in the wheel well, where the duct ends:

The diagonal slots outboard of the brake cooling ducts house heat exchangers — possibly remote-mounted radiators, of sorts:

Here in the wheel well you can see where the heat exchanger diagnose slot exhausts, and you can see the brake cooling duct outlet:

And here you can see the outlet of one of the side skirts meant to “smooth” out flow just outboard of the wheels to improve aerodynamics:

Other things I noticed when looking at the new M5 Touring — the engine is a ridiculously tightly-packaged “Basket of Snakes”:

And the rear cargo area is gigantic, making this a seriously useful performance wagon:

I did happen to spot a BMW M2 in the Pebble Beach parking lot on my way out, and it has a very similar setup. Still, while the openings are big, they’re not M5 huge:

I say in the Instagram reel above that the M5 has the biggest unobstructed grille opening of any car I’ve ever seen. I’m mostly referring to modern production cars when I say that, because look at the Model T and other cars from the early 1900s:

The whole grille is the radiator!

Anyway, that was just a quick peek at the M5’s cooling system. Most cars’ lower grilles are bigger than their upper ones (upper ones are often completely blocked off, though the M5’s isn’t), but few cars have completely wide-open apertures, especially not ones that big. I didn’t see any engineers around, so I couldn’t really get into which radiators are where, how everything is plumbed, what went into that gaping grille opening decision, etc. But I figured it was worth sharing anyway.

P.S. Jason is convinced that cats will walk into that opening and sit on the oil cooler for warmth in the winter.