Nerd’s Eye View: McLaren 720S

The McLaren 720S currently sits at the top of the supercar heap when it comes to straight-line top-end as bought off the showroom floor. A 4L, twin-turbo, V8 pushing out 720PS (710HP) in a relatively slippery shape has a way of motivating things quickly. Bigger turbos and recalibration push it even higher, with a 720S having trapped 179mph in a ½ mile, but we’re getting ahead of ourselves. I happened to be at World Motorsport (MotoIQ AWD dyno of choice for testing) and they had an atomic orange colored 720S on the lift with panels removed. So, of course, I had to go in for a closer look!

I forgot to snag a picture of the whole orange car, so I came across this pearl white looking one at a Porsche Club of America meet in Santa Monica. The 720S borrows the side intake design concept from the hypercar stable mate P1. I believe the intakes at the top of the rear fenders are for the turbo compressor inlets. The big side intakes provide the cooling air necessary for 720PS. A row of small vents above the scoops allows heat to escape.

 

Massive cooling is required and the McLaren engineers got creative in a getting the required cooling airflow area while balancing aerodynamics and looks. Here they carved some openings within the headlight assembly. It’s always a battle between the engineers and the designers; engineers want function, designers want looks.

 

Below the headlight is a large scoop to feed more air to the heat exchanger mounted in the front corner of the car.

 

Business in the front, party in the back. This might be the most extensive venting I’ve seen on a street car for a front corner mounted heat exchanger.

16 comments

  1. The turning vanes underneath the car are used to create a barrier layer, so in a way, you where correct. It’s used to separate high pressure turbulent airflow from the tyres from the high flowing, non turbulent air from under the car. It does create a slight bit of lift, but helps the rear diffusor. But probbably the most important factor about it: It cancels road noise.

    1. KS, appreciate the insight! So basically the turning vanes create an air curtain to prevent the dirty tire wake from spilling over to the rear diffuser.

  2. Interesting rear swaybar mount gets a feature cast into the subframe. Though I thought a 720S with the Kinetic suspension setup doesn’t have actual swaybar?

    1. Typically McLaren’s have a “Z” bar. The “Z” bar is a 3rd spring for the rear. They look like a sway bar but the arms are opposing(in the shape of a Z). Since the suspension is hydraulic and connected via a pump/module a sway bar is not needed. There is no antiroll bar or z bar in the front.

  3. The black pump things in the last picture will be the secondary air pumps for getting the cats up to temp quicker under cold start conditions, one for each exhaust bank.

    1. Thanks Alex! I am curious how many cars have air pumps. My s2000 has one and I think my dads FC rx7 has one. I don’t recall my evo having one or most other cars I’ve wrenched on. Though maybe I just wasn’t paying attention.

  4. Behhh… those plastic retention clips on the control arms. I wonder 2 things: 1) If the addition of the almost assuredly threaded holes required for the ribbing on those clips to grab onto introduces potential stress risers, thus requiring the control arms to be made thicker/heavier and 2) if McLaren knows that they make zip ties with wiring loom retention loops attached to them

    1. The middle of the section of a beam sees little stress. The top and bottom of the beam see the highest strain. At least, they put holes in the best place to minimize fatigue, but yeah if you hit a curb hard, I’m sure that’s a point of failure.

      Also, zip ties look janky. If I shelled out big money for a car, I would be disappointed to see zip ties, wouldn’t you?

  5. Oh, as for air pumps, these days most cars use cam timing instead of secondary air pumps to initiate faster cat light-off, but as far as I can tell anything that doesn’t have wide enough control of camshaft position and/or super long duration/low overlap cams from the factory (such as, say, high rpm turbo cams) generally seem to be the culprits for secondary air. Still way, wayyyyyyy better than the belt driven smog pumps from back in the day, but… yeah…

    The air pump on my friend’s pristine FB RX-7 is hilariously large 😛

  6. I don’t see which picture you’re referring to that has subframe swaybar mounts in it, but certainly they use the same subframe across all their cars and the 570 series cars have conventional dampers and swaybars.

    1. Top picture of page 4. Basically McLaren made a ‘hole’ in the rear subframe for the sway bar to go through. Looks like a blue polyurethane bushing for the sway bar. I think it’s creative. It keeps the bottom of the car flat instead of having the sway bar poke down into the airflow and the bar is shorter as it doesn’t have to reach around the rear of the transaxle.

  7. Hmmm. Didn’t think they used swaybars with the hydraulic system on the super series. The mp4-12c , the first of their cars to use the hydraulic system, had a z-bar in the rear instead of a swaybar. Maybe this is the same?

    1. Ah, you’re correct. It is a Z-bar. In the last photo in the bottom left corner, you can JUST see the other end of the Z-bar which is behind the rear tie-rod of the left rear spindle indicating it attaches to the back side of the control arm. On the right side, the end of the bar connects to the front side of the control arm.

  8. Macca must be a great place for an engineer, the whole shop is ‘function over form’. They are on another level over there. Makes me wish I was British. Good thing the weather sucks inthe UK.

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