Race To The Clouds – Honda R&D’S ’91 NSX (Part 1)
Conquering Colorado’s Pikes Peak in a
500hp Le Mans-derived NSX
Colorado’s Pikes Peak is among the most
treacherous courses known to motorsports, spanning 12.42 miles, 156 turns, and
culminating at a 14,115-foot summit that's no stranger to rain, fog, even snow.
There, the air is thin, reflexes are slow, muscles are weak, and engine power
is diminished. To make it to the top, error by driver or machine cannot be
tolerated.
It came as a surprise to nearly everyone
when, in 2013, American Honda signed on as partnering sponsor for the
world-famous International Hill Climb for the first time ever, fielding 11
entries that spanned a 25-year gamut of 250cc motocross bikes to an electric
B-segment hatchback. It isn't the Fit EV that you care about, though, but
instead the company's R&D division's '91 NSX—a partially completed ALMS
(American Le Mans Series) endurance car initially built at the hands of HART
(Honda of America Racing Team) only to later be repurposed for the world-famous
hill climb—driver, project leader, and Honda powertrain engineer James Robinson
explains.
It
isn't the Fit EV that you care about, though, but instead the company's R&D
division's '91 NSX—a partially completed ALMS (American Le Mans Series)
endurance car initially built at the hands of HART (Honda of America Racing
Team) only to later be repurposed for the world-famous hill climb—driver,
project leader, and Honda powertrain engineer James Robinson explains.
James and associates secured the chassis
from the company's internal racing affiliate in early 2012 and began its
transformation in April, which would only take seven weeks. Outside, much of
the work had already been completed. The wide body carbon-fiber panels
previously fitted by HART that help reduce overall weight to less than 2,200
pounds were retained as was the car's one-off suspension that's made up of
CNC-machined, billet-alu-minum control arms and spherical rod ends. Also
recycled from the would-be endurance program are an oversized AP Racing braking
system, SSR multi-piece wheels, and a singlenut hub conversion at each corner.
Virtually all that's been left of the early '90s supercar chassis' factory
components is its all-aluminum structure that's been seam-welded for even more
rigidity.
Underneath the vented hood, HART had
already pushed aside the NSX's 3.0L C-Series engine, which meant James, who
specializes in V-6 engine development for Honda, had a decision to make: source
another 25-year-old, 90-degree powerplant or look to something newer and
presumably better. For this, Honda's racing development arm, HPD (Honda
Performance Development) was called upon for its HR28TT engine that's used
throughout the ALMS LMP2 prototype class and helped win the manufacturers championship
in 2012.
Underneath
the vented hood, HART had already pushed aside the NSX's 3.0L C-Series engine.
HPD's twin-turbocharged HR28TT is based off
of the automaker's current 3.5L J-Series engine that can be found in select
Accord, Odyssey, and Pilot models but has been destroked to 2.8L. James went on
to make his own changes to the engine, though, which included bumping
displacement back up to 3.5L, resulting in 500 hp and 380 lb-ft of torque. The
endurance engine was carefully disassembled and put back together using a
combination of forged pistons and rods that lower the compression ratio to a
manageable 9.5:1. HPD's dry-sump oiling system was also removed in favor of the
3.7L TL's oil pump and the cable-driven throttle body that ALMS rules call for was
swapped for a more modern drive-by-wire version from a later-model TL. James
explains that the one-off dry-sump oiling system's pump and drive system was
integrated onto the transmission-side of the engine and, as such, there simply
wasn't room for it. “The cost to make that change was not worth the benefits
that we could have realized from the dry sump system,” he explains.
HPD's
twin-turbocharged HR28TT is based off of the automaker's current 3.5L J-Series
engine that can be found in select Accord, Odyssey, and Pilot models but has
been destroked to 2.8L.
