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1995 Chevrolet Corvette Coupe - Blue Mule

This '95 Grand Sport Prototype Was Likely The Last R&D C4

Scott Ross Sep 21, 2008

In all the history of the Corvette, the cars that have received the least amount of attention for their role in shaping Vette history are the prototypes. That's because many of them were not only thrashed in the name of performance, safety, and durability, but were also unknown to all but the few who worked and/or beat on them daily. The fate of many of them-like all but one of the "1983" Corvettes-was the crusher. Many times, that fate was due to liability concerns by The General about these cars getting loose among the common folk. But many other times, it was because there was not much left of them to save, especially the cars that were crash-test "survivors." This Admiral Blue '95 Corvette coupe escaped that fate and is now at home in the National Corvette Museum in Bowling Green, Kentucky.

The 27th car off the Bowling Green Assembly line at the start of model year 1995 production, this one was shipped to Michigan after it was built as an engineering tool and testbed. Delphi Automotive Group, which was owned by GM at that time and included GM's former chassis-component-parts-maker Delco, took custody of this car and used it as the mule in developing the RPO Z16 Grand Sport package for the following ('96) model year. this car is very likely the last C4 Corvette ever used by a GM entity for research and development of that generation of Vette, after a decade-plus of R&D.


Look beyond the accumulated dirt and you'll see a prototype LT4 engine, which entered Corvette production with the '96s. Long sticker on fan shroud (at left) is GM's prototype engine emission-control information.

During the '95 model run, the decision was made that 1996 would be the C4's last go-round, and the all-new C5 would now get the lion's share of research and development attention and funding. But there was still enough money left to come up with a special edition to end the fourth generation with; one that included mechanical upgrades under its special-edition color scheme.

The biggest upgrade is the one that's most visible when you open the hood: A prototype LT4 engine, which didn't join the Corvette options list until 1996. This one has hand-lettered job numbers on both valve covers that topped its all-new aluminum heads. plus there are more than a few prototype-only stickers in the engine bay, including a big one saying this vehicle was exempt from Federal and California emissions regulations, and that copies of its emission-test data were available from GM's Corporate Affairs office (and that the sticker should be removed before GM sold the car). Because it was an as-tested vehicle, it has a nice "patina," the same color as Midwestern dust/dirt/topsoil, characteristic of a car that's spent more time on the road than being pampered.


The LT4 boosted the second-generation small-block V-8's horsepower by 30, to 330, thanks to good stuff like the new heads, which boosted compression from 10.4:1 to 10.8:1, plus a new camshaft/roller rockers combo. Combined with the early LT4 is a production RPO MN6 six-speed manual transmission that, for 1995, featured a newly redesigned reverse lockout on its shifter. Out back, in this last-of-the-nontransaxle Corvette test cars is the differential housing a set of 3.45:1 rear gears.


Data Display
Delphi's R&D crew counted on this C4's production gauge display whenever they were underway. Note the lack of drilled holes or other indications of temporarily attached lab gear. (It likely was plugged into the diagnostic port under the dash.) Also note lack of mileage on odometer, which was never connected.

But if you know your late-edition C4s, you know that a huge change came in the chassis with the RPO F45 Selective Real-Time Dampening suspension system that debuted in 1996, along with the Grand Sport package. Developed by Delphi-the new name for the GM component-parts group that included the former Delco Moraine-Option F45 was intended to replace the existing RPO FX3 Selective Ride Option. F45 sent data from the wheel travel sensors at each corner and the car's Powertrain Control Module (PCM) to a controller that figured out the special shock absorbers' dampening mode to give them the ideal control, doing so about every 10-15 milliseconds. Before that system was ready for production, it had to undergo plenty of in-the-real-world testing, and this blue '95 was the car on which the prototype F45 hardware was installed and rigorously tested, whether on Delphi's computer-controlled laboratory "bump-and-shake" rigs, outdoors at GM's Milford Proving Grounds, or on tracks like Grattan Raceway Park near Grand Rapids, Michigan, as well as the weather-beaten roads and highways of Michigan and Ohio.


Some Lab Bench
Who wouldn't like to perform research here instead of on a hard-backed chair indoors? "Grand Sport" lettering is the only giveaway to this car's purpose. The rest of the cabin is stock '95 Vette.

One visual cue to this car's Grand Sport test-mule heritage is aft of each door. There, at the top of each rear wheelwell's arch, you can see an add-on flare that extends the bodywork outboard to cover-and thereby made street-legal-the wide wheel/tire combo within. It's very likely that the wider rear quarters that had been used on the '90-'95 ZR-1s were considered, but not used on the Grand Sport out of cost concerns. At that late point in the C4's life cycle, GM wasn't putting any more development dollars into it than absolutely necessary.


Lab Tool
Another piece of Grand Sport R&D hardware: the six-speed shifter, whose reverse lockout was redesigned for 1995.

Eventually, the F45 system got the green light for production, and this C4's days as a test mule ended. It then became an around-the-plant errand-runner, much like many other test cars before it. In early 2006, Delphi earmarked it for elimination. "They said they had to downsize their inventory," says the National Corvette Museum's Betty Hardison. "They were getting ready to put it in the dumpster." Instead of a date with the dumpster or crusher, this car was donated by Delphi Automotive Systems to the National Corvette Museum, where it's now a part of the Museum's collection of historically significant Vettes. Betty adds that it's still in its as-driven/as-tested condition, with a layer of "patina" that you won't find on other Museum-kept cars. "We don't want to touch it," Betty says, "because that's history sitting there."

Even with the documentation from Delphi and GM, one big hole remains in this C4's history: How many miles are on it? "The odometer was never hooked up," says Betty.

That lack of documented mileage hasn't stopped Corvette lovers from taking a good look at it. Especially during the Museum's Gathering, which was taking place as this story was written. Betty says, "We have it out on display, and the Grand Sport people just eat it up! They can really appreciate the history behind it." Especially if that history is written by the "sands of time" that coat this C4's prototype pieces.




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