1995 Acura Integra GS R Coupe

Generating huge horsepower numbers from small displacement engines is not a new phenomenon. For example, the small, turbocharged 1.5-liter Formula 1 engines used in the '80s regularly churned out in excess of 1,000 hp, and kept it up for a solid two-hour race.

Reliability is key. One would expect a purpose-built engine like an F1 mill to make reliable horsepower. But it's a whole different matter for a modified stock engine. For example, it would be relatively easy to make a Civic DX engine crank out stratospheric horsepower numbers: Just feed it plenty of nitromethane and rev the sucker to 10,000 rpm. You'd get great power and torque . . . for a few moments. Then, the laws of thermodynamics would run amok, turning a perfectly innocent commuter engine into smoldering industrial slag.

As fun as blowing up engines may be, if your goal is to actually finish a race, you'd better have a more reliable way of making power. The recipe almost always involves forced induction and high revs, but things get a little tricky when the engine in question started life naturally aspirated, with no plans whatsoever from the factory for turbocharging. But where there's a will, there's a way.

Anaheim, Calif.-based Holeshot has plenty of will, and the way is embodied in the black '95 Acura Integra GS-R owned by proprietor Aaron Bonk. With almost 500 hp at the wheels, the car runs with astonishing reliability, enough so that a real die-hard could conceivably drive it every day with only a few modifications for the sake of comfort.

Don't let this car's mostly stock looks deceive you. While the badges have been shaved, the wing removed, and the embossed "INTEGRA" lettering on the bumpers filled in, this car is about go, not show. Look closely at the exterior and you'll find clues to its true mission. Note the long studs on the front wheels. Do they look funny? Maybe, but tell that to the 25-inch wrinkle-wall drag slicks that Bonk uses at the track.

Under the midnight-black hood is a fully modified powertrain, with virtually no stock or unmodified components. Bonk is serious about his power, and the attention to detail of his engine shows it. The red Integra Type-R valve cover is the only nod to visual pizzazz; everything else under the hood is dedicated to the task of squeezing as much power out of the 1.8-liter engine as possible.

The most notable modification is the huge turbocharger hanging in front of the engine. Connected to a Drag turbo exhaust manifold, the Garrett pinwheel is a T3/T4 hybrid of the type that is commonly used on powerful Honda race engines. With a .50 A/R ratio, the turbo sacrifices low-end response for high-end power. An HKS external wastegate dumps directly to the atmosphere, and remaining exhaust gases are routed through what can only be a lightly modified sewer pipe.

Air is dramatically sucked through a Tenzo air filter for its short journey to the compressor. By the time it leaves the working side of the turbo, it has been squeezed considerably, up to 28 psi. This generates a lot of heat, so it travels from the compressor through custom intercooler piping to a front-mounted Spearco intercooler.

Properly chilled, it continues its journey to the engine. An HKS blow-off valve dumps excess pressurized air into the atmosphere when the 62mm JG throttle body snaps closed between shifts. Past the throttle body, the air enters a Type R intake manifold. Despite the similarities between the GS-R and Type R engines, the intake manifolds do not share the same bolt patterns. Bonk modified this one to fit, a tricky job, but one accomplished cleanly in this case. Once through the manifold, the air passes into the head, smoothly polished and ported by Jair Valle of Westminster, Calif. Stock GS-R cams actuate the 1mm-oversized Ferrea valves, although the camshafts themselves are connected to Holeshot's adjustable cam gears.

Past the valves, the air is shoved brutally into the polished combustion chamber along with plenty of high-octane fuel squirted in by GReddy 550cc injectors. Bonk has modified his fuel system extensively. Rather than the puny, low-pressure stock fuel pump, a Paxton Granatelli pump pulls fuel from the tank. The entire fuel system uses big -8 fuel lines with A/N fittings. Even the fuel tank has been modified to accept the bigger lines, a setup which delivers gas to the engine as well as a racing fuel cell. An SX fuel regulator keeps pressure constant, and the injectors themselves are mounted in an STR billet fuel rail.

The stock Integra engine management computer can't handle this modified engine any better than your home computer can render "Jurassic Park"'s CGI velociraptors. Instead, Bonk uses an Accel DFI, tuned by Harv's Dyno in Whittier, Calif. The DFI maintains strict control of the engine's fuel delivery and spark throughout the rev range, and even controls the VTEC change from low- to high-lift cams. A Crane HI-6 and PS92 coil ensure that plenty of spark races through the Magnacore wires to the NGK BKR7 spark plugs.

Shoving so much extra air and fuel into an engine, not to mention the resultant bigger bang, puts incredible stresses on the internal components. Thus, Bonk modified his engine's bottom end to cope with the added pressure. JE pistons are not only lighter, but lower the compression from the stock GS-R's 10.0:1 to a more turbo-friendly 9.0:1. The pistons are connected to high-strength Crower rods, which in turn are connected to a stock GS-R crankshaft. While it sounds like a strange choice, Honda has done an admirable job of overbuilding this forged piece, and it holds up just fine. The entire engine assembly has been carefully balanced and blueprinted, in this case by Valley Engine and Machine.

The biggest weakness in the Integra's engine is the block. It's an open-deck design, which means that the head forms the top of the water jacket for each cylinder. While a relatively inexpensive way to build an engine, the result is cylinder walls that will actually wobble very slightly at high levels of boost. The aftermath includes a blown engine, a lost race, and a suddenly poorer car owner.

The solution is to "deck" the block, which basically consists of welding in a metal plate that looks like a pair of figure eights. Once in place and properly machined, the engine is ready to accept the high levels of boost planned for it. Bonk also sleeved the block with ductile iron and uses copper O-rings around each cylinder for even better sealing.

From the crankshaft, raw power runs through a Clutch Specialties Hyperclutch. This dual-diaphragm unit features a prototype iron disk. While plenty capable of holding the massive power of the engine, it is way too stiff and grabby to drive on the street. Connected to the clutch is an Integra LS transmission. The taller (numerically smaller) gears of the LS tranny help this drag car achieve higher top speeds at the track. Past the transmission, power is evenly divided to each drive wheel by a Cusco limited-slip differential. A clutch-type diff, this one is wound so tight that you can hear it popping as the car goes around turns.

Amazingly, the interior of this high-performance Integra is stock. And by stock, we mean all the carpeting, leather seating, headliner, switches and sound deadening are still in place. In fact, the only really obvious changes are enough AutoMeter gauges to make a B-52 blush. Situated immediately in front of the driver on the steering column is the all-important boost gauge. Mounted to the left of the stock instrument pod is a huge tachometer, scaled to 10,000 rpm. Where you would normally find the dimmer dial for the dash lights is a graphical air/fuel ratio meter. Finally, arrayed above the glovebox on the dash are gauges for oil pressure and temperature, exhaust gas temperature and coolant temperature. An HKS turbo timer is located under the stereo, and an APEXi AVC-D boost controller is hidden away in the glovebox. Bonk also has a small thumb switch that he uses to keep boost to a streetable level: button-in is 15-pounds of boost, button-out is the full 28. About the only other modification is a Tenzo short-throw shifter.

Chassis modifications are minimal. The suspension is lowered, thanks to Neuspeed springs on Tokico shocks. The brakes are also modified, although not as you'd expect. Tiny Civic DX brakes are up front to give the big slicks more room. The ABS system has been removed completely, replaced with a non-ABS set of pipes and valves from an Integra RS. This allowed Aaron to build a straight path from the intercooler to the throttle body. When the slicks are in storage, the Integra runs on super lightweight Mugen RnR wheels. At only 7.5-lbs each, these 15-inch wheels are made with a special magnesium/aluminum alloy that frankly isn't up to the daily pounding of city streets. They are wrapped in stock-sized 195/55R-15 Dunlop SP Sport W-10 tires.

Parts, parts, parts. How does it drive? Very well, thank you. A quick blast near the Holeshot headquarters at a mere 15 pounds of boost was enough to demonstrate the engine's characteristics. As one would expect from a small, low-compression engine with a big, fat turbo, there is not a lot of activity until boost builds. This occurs at about 4000 rpm, with full boost by 4500. At that point, the Integra rips forward, the front tires scrabbling for traction as they are overwhelmed by the power of the engine. At full boost, traction is virtually nonexistent, with smoking burnouts possible at freeway speeds. On the track, Bonk has posted a best time of 12.007 seconds at a blistering 128 mph.

Despite the DFI's best efforts, it is a cranky engine until fully warmed. Even then, the idle is lumpy, and there is plenty of vibration at all engine speeds, thanks to the solid engine mount installed to reduce engine rock when shifting. Driving placidly down the street, the whirring turbo sounds more like a taxiing F/A-18 fighter than any kind of automobile. And that massive power is always just a few degrees of ankle movement away.

This humble Integra is a racecar, despite its stock interior and unadulterated exterior. It is built and designed for fast track driving. Bonk uses it for exactly that purpose, training himself to drive his real racecar, currently hidden under a tarp at Holeshot's headquarters. Bonk admits that this Integra was once his daily driver, and was gradually modified to its current state over several years. Applying the lessons learned along the way to a straight-up drag car should yield very satisfying results.