1985 Ferrari 308GTSi Quattrovalvole Twin-Turbo Is Built, not Bought

From the February 1985 issue of Car and Driver.

Ever since the rebirth of the GTO, Ferrari fanatics have been pushing and shoving to queue up for the new supercar. None that we know of have actually succeeded in lay­ing hands on one as yet. The process seems to be a lot like waiting for campaign prom­ises to come true: the factory in Maranello is known for talking big and delivering lat­er, if at all.

An alternative worth considering is the injection of some of the GTO’s twin-turbo magic into a current Ferrari Quattrovalvole (308GTSi). This requires doing without the GTO’s other exotic performance ac­couterments, but the prospect of old-fash­ioned twelve-cylinder muscle in a car wear­ing the rampant-stallion insignia is usually enough to make the faithful salivate in anticipation.

We recently tested such a double-blown car, a 308 Quattrovalvole supplied by Prancing Horse, Inc., a Ferrari service and high-performance emporium in Campbell, California. Although Prancing Horse supplies and installs its own kits, this particular development was undertaken jointly with now defunct Pfaff Turbo, in nearby San Jose.

As turbo kits go, this is one of the most straightforward installations we’ve ever seen. Each bank of the V-8 feeds an IHI RHB52 turbocharger via a special exhaust manifold. Each compressor mouth is pro­tected by a K&N air filter, and the twin streams of compressed air produced by the turbos are gathered and then routed through the K-Jetronic fuel-injection sys­tem’s metering unit on the way to the origi­nal intake manifold. Peak boost pressure is 7.0 psi, regulated by the turbo’s integral wastegates. Minor modifications to the fuel-pressure regulator provide a slightly richer mixture whenever manifold pres­sure rises above atmospheric. On the ex­haust side, Prancing Horse has fitted a Eu­ropean, catalyst-free system to minimize back pressure. There are no internal changes to the 32-valve engine, no major intake-system revisions, and no complicat­ed engine-control systems.

According to Rick Brady, the proprietor of Prancing Horse, this simplicity is made possible by the inherent stoutness of the Ferrari V-8. The good combustion and detonation resistance inherent in a four­-valve combination chamber are also help­ful, and the modest, 8.6:1 compression ra­tio doesn’t hurt.

There’s no denying that this turbo instal­lation really brings the 308 engine to life. As a matter of fact, it transforms the mid-­engined machine into one of the fastest road rockets going. The twin-turbo 308 sprints from a standing start to 60 mph in just 5.6 seconds, to 100 mph in 12.3 sec­onds, and then claws to 130 mph in 23.0 seconds. In the process, it devours a quar­ter-mile in 13.5 seconds, achieving 107 mph through the traps. Top speed is limit­ed to 147 mph by gearing and the engine’s redline, but with an estimated 350 horsepower, it doesn’t take long to get there.

Any 308 driver should be able to appre­ciate the benefits of a major boost in horse­power. The turbos trim nearly two seconds from zero-to-sixty and quarter-mile times, so the homemade GTO should never have to sneak around, fearing encounters with Porsche 911s or 928s, Chevrolet Cor­vettes, or the current domestic pony cars. In fact, the double-blown 308 reminded us of the much revered Ferrari Daytona. Ex­cept in top speed, its performance almost perfectly matches the older twelve-cylin­der’s, putting the 308 at the overachieving end of the speed spectrum, exactly where Ferraris belong.

In exchange for this vast improvement, the modified engine extracts little penalty in everyday, nonfrenetic driving. One rea­son is the essentially stock intake system, which keeps low-speed response respect­able. In top gear, the modified 308 goes from 30 to 50 mph in 9.5 seconds and from 50 to 70 mph in 8.1 seconds—versus 8.7 and 8.8 seconds, respectively, for the stan­dard car. Obviously, in the 1500-to-3500-rpm range used in this test, there’s not much boost available; but once the engine is turning 3000 rpm, the boost gauge is on the rise and there’s a full 4000 rpm worth of engine operation left.

The engine’s sound is also thoroughly refined. At the upper end of its rev range, the well-known Ferrari shriek is very much in evidence. At the low end, however, the twin-turbo V-8 is surprisingly silent and docile. Indeed, at a steady 70 mph, we mea­sured a sound level of 78 dBA, 3 dBA lower than a standard car. Our impressive C/D fuel economy of 17 mpg is another indica­tion that this car is a capable cruiser.

The 308’s chassis accepts the extra pow­er with eagerness. Our test car, equipped with Goodyear NCT tires, retained the ba­sic combination of initial understeer and terminal oversteer, but the transition could be prompted a bit sooner with the stronger engine. The 308’s handling characteristics are still quite manageable, as long as the driver doesn’t get carried away with the extra horsepower.

Obviously, this twin-turbo installation eliminates all the emissions controls, and it’s unlikely to enhance the engine’s lon­gevity. Still, the system did withstand the rigors of our performance tests, and Brady says he’s seen excellent reliability in several similar installations. The complete pack­age costs $6000, but you can save a grand if you bolt the hardware on yourself. Consid­ering that some dealers are demanding $10,000 for a highly dubious GTO “reser­vation,” $6000 for a pair of turbos to tide you over sounds entirely reasonable.

Csaba Csere joined Car and Driver in 1980 and never really left. After serving as Technical Editor and Director, he was Editor-in-Chief from 1993 until his retirement from active duty in 2008. He continues to dabble in automotive journalism and LeMons racing, as well as ministering to his 1965 Jaguar E-type, 2017 Porsche 911, and trio of motorcycles—when not skiing or hiking near his home in Colorado.