This article was published in the September 1979 issue of Car and Driver. It’s pretty sad how little power they were able to make with a turbo small block but it’s still an interesting read, and hey, we wouldn’t be where we are today if the designers of the past hadn’t continued to trudge through the depressing mess that was the automotive industry of the 70s and early 80s. Also, check out that CompuCruise ad at the bottom of the last page. I want one! I’ve also inserted the text from this article beneath the scans in case you’d rather read it that way.
Back in the old days, the Corvette sliced a broad swath of respect across the land as America’s leading edge of engineering. It was a rolling showcase of all the latest automotive advances, a sports car that GM engineers used to introduce fuel injection, plastic body parts, four-speed transmissions, all-disc brakes, and countless other technological advances, most of which took years to trickle down to family sedans. For the last decade, however, the Corvette’s image has stagnated. If it was ten years ahead of its time after the last major re-design in 1968, today it’s at least two years out of date.
Even though nothing exciting has happened to perk up the Corvette’s prestige in the. past twelve years, we’d be the last to predict this car’s glory is gone. At the moment, 50,000 sports cars hardly leave a blip on GM’s annual sales charts. This, along with the fact that dealers still have to fight Corvette buyers off with clubs, is enough to keep the two-seat Chevrolet dead last in priority for re-engineering.
Right now we know the Corvette’s turn for overhaul won’t come before 1984. As we outlined back in December 1978, the new car will approximate a V-8-powered Porsche 924 in concept: front-engine-rear-transaxle in layout, much lighter, somewhat smaller, and as slippery through the air as GM’s wind-tunnel team can make it.
The venerable small-block Chevrolet V-8, now heading into its 26th year of production, will power all Corvettes in the foreseeable future. It will be smaller than today’s 350 cubic inches, for better fuel-economy, but steps will be taken to offset the displacement deficit. Which brings us to the subject of this test, a turbocharged, fuel-injected prototype of the Corvette’s future.
On the street it’s a silver bolt of lightning waiting for your foot to say when to strike. There·’s enough all-American low-end torque to give you a nosebleed, and the dreaded turbocharger lag has been virtually eliminated at any speed. Yet if you tread lightly on the throttle, this turbo time bomb is absolutely docile and drivable, as mannerly as your average Seville. About the only clue that there’s a short fuse under the hood is a distant, eerie whistling from the turbocharger during certain part-throttle conditions.
Call it a turbo-fuelie, if you’d like. Call it Corvette good, times revisited, but don’t rush off to place an order at your dealer just yet. While it was in fact Chevrolet Engineering that cocked this silver bullet and shot it over to tantalize us, you can’t buy anything like it. In truth, there are no plans as yet to produce such a combination. Right now, this Corvette is merely a development tool for Chevrolet’s Product Promotion Engineering Department, and like many turbocharged hot rods of the past, it’s strictly experimental.
Even so, you can tell it’s a serious effort because the design is so production-like. Detroit is old friends with AiResearch by now, so this West Coast firm is the source of the turbocharger. The fuel-injection system is almost exactly like Cadillac’s California Seville equipment, although special modifications have been made by Bendix in the computer controller to suit turbocharging. There’s an Edelbrock intake manifold to feed the engine its pressurized charge-one component that was chosen out of convenience. Since Edelbrock has its own aftermarket fuel-injection system for the Chevrolet small-block (using Bendix-made injectors), its aluminum intake manifold offered a handy bolt-on for this application.
The only specially fabricated parts include a right-hand exhaust manifold- an early Chevrolet “ram’s horn” design with an extra passage welded on, which both supports and feeds exhaust gases to the turbocharger. A simple crossover tube under the engine connects the ram’s horn’s original outlet with a stock, left-side manifold. Ducting from the compressor back into the engine is a short run of tubing, brilliantly chromed to dazzle the eyes of car-show goers, who will undoubtedly ooh and aah over this exercise. There’s an air-filter box near the right front fender, fed by both hot and cold sources for optimum warm up, and an exhaust system that’s largely stock except for the absence of a catalytic converter. (It was left off during fuel-system development to preclude a China syndrome under the floor in the event that an accidental over-rich mixture ever left the engine.)
Two engineering advances are worth noting in this super Chevy. The throttle blade has been located upstream of the turbocharger to forestall compressor surge and loss of boost during lift-throttle operation. (Saab and Renault have used such a design for racing engines.) What this does is let the turbine wheel spin in a near vacuum when you ease off the gas, instead of slamming it with a shock wave ricocheting back from a closed throttle plate. The second breakthrough is a special manifold-pressure sensor developed by Bendix that tells the computer when boost has packed the intake system with air above atmospheric pressure. Added circuits in the brain adjust fuel flow accordingly.
There are a couple of other refinements you’d have trouble duplicating in your back yard. Chevrolet has engineered a detonation sensor into the ignition system exactly the way Buick did in its turbo V-6. A tiny transducer listens for the onset of pre-ignition and then signals the distributor to retard the spark timing long before any damage is done. Since this arrangement keeps spark advance right at the knock limit, the system is always maximized to use every last bit of the octane you’ve pumped into the fuel tank.
The turbocharger is somewhat special as well. The general AiResearch TO3 design is shared with Mercedes-Benz’s SOOSD, although some resizing of com- ponents has been done to suit the dis- placement and flow characteristics of the Chevrolet V-8. This unit features an integral waste gate of the poppet-valve type, set for seven pounds of boost. John Pearce, development engineer on the project, estimates the system is good for 280 to 290 horsepower.
To see how all this works we were allowed a couple of days of blasting around, and a brief test. Interestingly enough, this package is not today’s highest performance plateau, since the turbocharger and fuel-injection systems were added to the slowest Corvette avail- able, an L48-engined car with an automatic transmission. (The L48 was picked for its lower compression ratio and milder cam timing. The Turbo Hydra-matic was felt more appropriate for the upper-management drivers who would review this equipment for possi- ble production in the future.) But it works. It’s every bit as drivable as a stock Corvette and fully compatible with all accessories. No emissions development has been done, but no problems are anticipated since an oxygen-feed back sensor is plumbed into the exhaust pipe, and GM already has plenty of experience with this device matched to a three-way catalyst.
Even though the turbo-fuelie Corvette is only a little quicker than today’s L82 four-speed, it quite effectively demonstrates the potential available from what amounts to off-the-shelf performance upgrades. You could see fuel injection, turbocharging, or both together as early as 1981 (in the current body style). Or Chevrolet may choose to save these titillations for the grand-slam home run scheduled for 1984. So we predict that George Orwell and all those other doomsayers will be proven dead wrong, at least as Corvettes go. Feast your eyes on our spy sketches, tune up your dream machine, and feed your piggy bank.