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!
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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.
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.
Yep!
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?
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.
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.
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.
Man that’s such an old school technique too. Right up there with the old school turbos this thing utilizes.
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
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?
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 😛
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.
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.
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?
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.
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.
Obviously, I can’t be sure, but what you label an AC compressor, looks like an electrically driven water pump, to me.
Yeah, certainly could be! My thought was the water pump was being driven internally in the engine block somehow and that was a clutch between the water pump and that thing on the right. I thought it might be an A/C line going into the thing on the right. But yeah, certainly could be an electric motor on the right driving the water pump on the left.