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1991 Acura NSX - Race To The Clouds

Conquering Colorado's Pikes Peak in a 500hp Le Mans-derived NSX

Aaron Bonk
Sep 22, 2014
Photographer: Henry Z. DeKuyper

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.

1991 acura NSX chargepiping 02 Photo 2/11   |   1991 Acura NSX - Race To The Clouds

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 widebody 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-aluminum 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 single-nut 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. 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.

1991 acura NSX kirkey seats 10 Photo 3/11   |  
This NSX’s interior is all business.

The paddle-operated, Hewland sequential transmission that's normally paired with the HR28TT wasn't used either and, instead, James saw to it to fit the six-speed gearbox from the TL Type-S into place. Custom shifter cables were made up to complete the conversion while, underneath the dash, a Tilton pedal assembly communicates with the Spec clutch and flywheel combination. Although displacement and a number of internal components have been altered, the HR28TT's twin-turbo configuration remains and is based off of the same pair of BorgWarner EFR B1 turbochargers used within the ALMS program. James' team also fabricated one-off exhaust manifolds and downpipes along with an intercooler and plumbing to fit within the confines of the NSX's engine bay. All 500 hp is brought together at the hands of a special vehicle development ECU exclusive to Honda's engineers that's based upon what James says is a typical, mass-production computer, but with the ability to allow changes to be made to accommodate just about anything, like a twin-turbocharged ALMS powertrain.

1991 acura NSX former ALMS carbon fiber aero kit 03 Photo 4/11   |   1991 Acura NSX - Race To The Clouds

There's arguably no other race course in the world that'll compare to Pikes Peak, which hosts the annual International Hill Climb, the second-oldest motorsports event in the country. Here, teams travel from across the globe to compete, doling out hundreds of thousands of dollars for a single race. All of this makes James and company at Honda's R&D headquarters in Ohio all the more proud for finishing fourth in the Pikes Peak Open Category in a chassis that was completed entirely in-house. Engine modifications, turbo system intercooling and plumbing, the exhaust system, even paint and bodywork, were completed by Honda's own R&D technicians. Even the electrical system was done on-site, which is based off of an MDX engine wiring harness that was used, James says, because that's what they had lying around.

James, who plans to return to the mountain later this year along with his team, explains how the program began: "I've always had an interest in Pikes Peak, and in 2011 made a proposal [to bring] something new and different to represent Honda at this event," he says. "I think this project is important to Honda. It represents the spirit of our company." Indeed it does.

Bolts & Washers
HR28TT J35A engine
Custom Honda R&D billet aluminum engine mounts
CP 9.5:1 pistons
Carrillo connecting rods
RLX crankshaft
TL SH-AWD oil pump
ARP head studs
TL cylinder heads
TL throttle body
HPD HR28TT camshafts
HPD HR28TT valvesprings
HPD HR28TT valve retainers
HPD HR28TT valve keepers
Accord VCM aluminum rocker arms
BorgWarner EFR B1-frame turbochargers
Custom Honda R&D intake system
HR28TT intake manifold
Custom Honda R&D intercooler and piping
Custom blow-off valve
Custom Honda R&D exhaust manifolds
Custom Honda R&D downpipes
Aeromotive R1000 fuel pump
Aeromotive fuel filter
Aeromotive fuel pressure regulator
Modified RDX fuel injectors
HR28TT fuel rails
Custom AN fittings and steel-braided lines
JEGS universal aluminum radiator
Silicone radiator hoses
NGK iridium spark plugs
Accord ignition coils
Custom modified ECU
TL Type-S transmission
Custom shifter cables
Spec Stage 5 clutch
Spec aluminum flywheel
Driveshaft Shop axles

1991 acura NSX former HR28TT J35A engine 05 Photo 8/11   |  
The twin-turbo, J35 V6 makes a reliable 500 hp.

Penske remote reservoir coilovers
Penske linear rate springs
Custom adjustable front antiroll bar
Custom spherical joint suspension
Custom billet-aluminum control arms

AP Racing vented/cross-drilled rotors (front: 300 mm; rear: 240 mm)
AP Racing pads
AP Racing aluminum calipers (front: six-piston; rear: four-piston)
Steel-braided lines

Wheels & Tires
SSR three-piece wheels (front: 18x9; rear: 18x12)
Michelin P2G tires (front: 24/64-18; rear: 30/68-18)

1991 acura NSX former ALMS carbon fiber aero front bumper 04 Photo 9/11   |   1991 Acura NSX - Race To The Clouds

Seam-welded and reinforced chassis
Custom Honda R&D paint
Former ALMS carbon-fiber aero kit

Custom Honda R&D rollcage
Kirkey seat
OMP Rally steering wheel
MoTeC SDL3 display
G-Force safety equipment
Tilton pedal assembly

Huge thanks to Honda for their continued support of racing and of the Power of Dreams—specifically, all of the fantastic associates who work in the fabrication department, purchasing department, and all of the supportive engineers who helped us get this car knocked out. And, most importantly, my very supportive and loving wife, Shana, who has always encouraged me to try to create new things and challenge myself in racing.

1991 acura NSX james robinson 08 Photo 10/11   |   1991 Acura NSX - Race To The Clouds

Owner Specs
Daily Grind
Honda R&D Powertrain Development Engineer

Favorite Site

Screen Name

13 Years

Dream Car
Can't say

Inspiration For This Build
The passion and drive of all Honda associates

Future Build
Can't say

NSX Suspension Study
Part of what made the first-generation NSX the special car that it's become is its suspension. Ask most NSX owners to explain what makes it so great, though, and they'll likely tell you that "it just is." As it turns out, there's a whole lot more to it than that, and it starts with same sort of double-wishbone configuration up front that your Civic has, only different. The difference is that the NSX's is made of lightweight, forged aluminum and pivots not entirely off of the chassis but off of a compliance pivot that reduces overall weight, bumpsteer, and road absorption. Here, the shock that you feel from the fore-aft movement of plowing over a pothole in your hatchback is dissipated by the compliance pivot that the front of each arm is bolted to. The remainder of the front suspension, like the knuckles, is made out of equally light yet not nearly as durable cast aluminum. Unlike your Civic, out back, the NSX also features upper and lower control arms and adjustable, turn-buckle toe links right from the factory. It's the sort of suspension you wish your Civic had and is the last thing you'd expect from something designed more than two-and-a-half decades ago.

1991 acura NSX penske coilover reservoir 09 Photo 11/11   |   1991 Acura NSX - Race To The Clouds


CP Pistons
Irvine, CA 92614
SPEC Clutch
Bessemer, AL 35022
Santa Clarita, CA 91355
By Aaron Bonk
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