numbers to point you to. Sorry. Also, yes,
we should have had the McLaren 600LT
Spider instead of the 720S Spider, as the
former’s base price of $259,000 is much
more in line with the other two than the
latter’s starting price of (yikes) $317,500.
Don’t even think about the as-tested price
of (gulp) $372,750. However, there wasn’t
a 600LT Spider available. So we took
one for the team and grabbed the only
convertible Macca had on offer, the 720S
Spider. The sacrifices we all make, right?
I’d also like to toss out a caveat for the
AMG GT R Roadster. It’s old. Say huh?
True, the GT R Roadster is only about a
year old. I’m talking about the platform
itself, which goes back to 2014. However,
that’s only the current generation. The
C190/R190 (C190 is Mercedes geek-speak
for the GT Coupe, R190 means GT Road-
ster) is actually a modified version of the
C197/R197 Gullwing, aka the SLS AMG.
That chassis goes back to 2009, and the
GT body-in-white is essentially the same
structure but with 50mm lopped off the
wheelbase.
I mention these caveats because
the Porsche 992 Turbo S is brand-
spanking-new. We know AMG will
be introducing an all-new GT in the
not so distant future. Please don’t
read this as me making excuses for
the AMG, but more like when the
SLS AMG was developed, 19-inch
R-compound tires were cutting
edge. The Porsche showed up on
staggered 20/21s. The persistence
of time and all that.
Intriguingly, these three road-
sters do not follow a set template.
The AMG is front-engine, the McLaren
has a mid-mounted engine, and the 911’s
mill lives behind the rear wheels.
The GT R Roadster uses a racy, modi-
fied version of AMG’s 4.0-liter twin-turbo
V-8, called M178. You can think of it as a
dry-sump version of the more ubiquitous
M177, which is used in every other AMG
with a V-8, including, confusingly, the
GT 63. Its 577 hp and 516 lb-ft of torque
flow down a carbon-fiber driveshaft to a
seven-speed dual-clutch transaxle.
The 720S also uses a dry-sumped
4.0-liter twin-turbo V-8 that makes 710
hp and 568 lb-ft of torque, though there’s
one major difference—the McLaren
uses a flat-plane crankshaft. Flat-plane
V-8s rev quicker, are typically lighter,
and make turbocharging (a bit) easier.
However, they vibrate much more
(there’s no inherent secondary balance
like a cross-plane V-8) and tend to
be more brittle. Great for race cars,
problematic elsewhere. Like the AMG,
the McLaren employs a seven-speed
dual-clutch transaxle.
The Turbo S is different still, with
its rear-mounted 3.8-liter twin-
turbo flat-six producing 640 hp and
590 lb-ft of torque. Like the other
two, the Porsche has a dual-clutch
transaxle for a transmission
(a transaxle is just a combi-
nation of a transmission and
a differential where driven axles
exit the case, as opposed to forces
being sent down a driveshaft
to a differential), with eight
forward gears instead of seven
like the other two entrants. ThePorsche drives all four wheels, whereas the
others are both RWD. The AMG and the
Porsche have all-wheel steering, and all
the cars have carbon-ceramic brake rotors,
but only the Porsche has four seats, even if
two of them don’t actually work.
As for performance, all are lunatic-
quick. Let’s look at comparables, as you
real estate types love to say. The McLaren
720S coupe hits 60 mph in 2.5 seconds
and runs out the back of the quarter mile
in a startling 10.1 seconds at a blazing 141.5
mph. That last one is 0.1 second off the
AWD 887-hp Porsche 918 Spyder. Again,
the 720S is rear-wheel drive.
The 991.2 Porsche 911 Turbo S coupe—
the previous-generation 911 that this one
replaces—also hit 60 mph in 2.5 seconds
before flying through the quarter mile
in 10.5 seconds with a trap speed of 131.8
mph. (We never tested a 991.1 or 991.2
Turbo S Cabriolet.) The nearly 10-mph
difference in trap speeds proves the
McLaren makes a lot more juice than that
old 580-horsepower Porsche. As Top Gear
America co-host Jethro Bovingdon says,
“All McLarens make 800 horsepower.”42 MOTORTREND.COM SEPTEMBER 2020