1991 Acura NSX Long Term Road Test

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1991 Acura NSX: I Don't Want a V8

January 23, 2012

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As the Acura NSX entered its second decade of life and its sales continued to mysteriously plummet, plenty of bright sparks thought the car really needed a big V8.

Of course, this is the kind of witless advice you get from some guy driving down Woodward Avenue to the grocery store in his Camaro.

Even when you look hard today at the details of the Acura NSX V6, you have to say it’s a really, really impressive piece. Who needs a V8?

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In 3.0-liter form in 1991 (it later got punched out to 3.2 liters), this V6 gives you 270 hp at 7,100 rpm and 210 lb-ft of torque at 5,100 rpm. The 90-degree V6 measures out to 2,977cc with very oversquare dimensions of 90mm bore and 78mm stroke, an indicator of a rev-happy nature. The engine will spin clear to 8,300 rpm before the fuel cuts off.

The forged-steel crank has 30-degree offsets in an effort to minimize vibration from this odd V6 configuration. The aluminum pistons work in steel liners cast into the aluminum block. The formulation of the aluminum for the cylinder heads is actually different from that of the block, a measure to resist stress cracks from vibration. Finally, the combustion chambers are Honda’s typical pent-roof design with belt-driven double overhead cams operating four valves per cylinder.

There are plenty of tricks as well, though we take them for granted these days. Some came from Honda’s 1980s F1 technology and others came from Honda’s amazing if unsuccessful GP racing motorcycle of the early 1980s, the NR500 (a connecting rod from which sits on my bookshelf, complete with an autograph from the brilliant Soichiro Irimajiri).

F1-style titanium connecting rods reduce weight (190 grams less than steel rods, the Honda engineers said) for better throttle response and higher operating speed (700 rpm more, the Honda engineers said). The rods could also withstand 65 kilograms of stress along the longitudinal axis compared to the 50 kilogram limit of a steel rod. The moly-coated pistons have low-friction rings. Meanwhile, the use of high-strength steel for the valves permit the stems to be reduced to just 5.5mm, reducing weight for improved response and a higher redline.

Even more interesting is the use of a variable volume induction system that works in combination with Honda’s first variable valve-timing and –lift system. Together they enhance power and torque at low speed, while the VTEC variable valve timing adds 20 hp at the top end. The crossover comes at 4,800 rpm. The programmed fuel injection (a big deal back before everything electronic had become programmed) can deliver 120 liters of fuel per hour at peak operating rpm. Each spark plug has its own coil for stable, effective ignition.

The combination of a high-volume oil pump (a Honda specialty from motorcycle engineering) and a baffled wet sump can maintain oil circulation under a steady cornering load of 0.8 g and also withstand spikes in cornering loads above 1.2 g. The cooling system can give you the ability to cope with 47,100 K Cal/hour. The exhaust headers are made from a lightweight cast iron (required for durability) while the rest of the exhaust system is made from stainless steel.

All this was especially impressive at a time when the only high-tech V6s had been found in F1 during the 1980s (Ford, Honda, Porsche, Renault and even Ferrari), and the cast-iron Nissan VG V6 (then the only decent V6 street engine) had yet to be superseded by the all-aluminum VQ V6 (an engine with goodness that came as a happy accident, its designer Motohiro Matsumara later told me).

Today the virtues of the NSX engine seem just as compelling as they were in 1991. Despite its odd, flat exhaust note (the 90-degree V6 thing?), the engine is both lively and strong. The bright sparks with their Camaros always looked skeptically at this engine’s wimpy torque rating, but those lucky enough to drive an NSX soon came to appreciate the engine’s ability to rev extremely quickly. And when you have a pretty flat torque curve from about 2,700 rpm to 6,200 rpm plus a total of 8,000 rpm to play with, there’s an extraordinarily wide range of drivability, even though the actual horsepower curve from the dyno is as steep as the back of god’s head.

Of course, as things evolved back then, the call for more power from the NSX grew ever louder as the 1990s went on and 300 hp became the norm in street cars and 400 hp became possible from exotic (and heavy) 4.0-liter V8s. That’s why the story has come down to us that this V6 was a kind of failure. But as for me (out of step with reality as always), if there were just one thing I could save from the NSX for a new car, it would be this remarkable V6.

Michael Jordan, Executive Editor, Edmunds.com

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