Driveline Tunnel Plate

by: Hib Halverson

Description: To break-in my 2012 Z06, I took a 3500 mile trip from where I took delivery, Tom Henry Chevrolet in Pennsylvania, down to Virginia, over to Bowling Green and the National Corvette Museum, to Santa Fe, New Mexico for two days, then home to Southern California. My Wife, the Fairest Sandra the Red, and I spent long hours in the C6's interior. Sandy was first to notice a lot of heat radiates from the console and driveline tunnel. After the trip, I used my Fluke/Raytek "Autopro" infrared (IR) thermometer to take some measurements. I drove about 10 highway miles, then another five miles on city streets ending my test in a downtown parking lot where I took the measurements. I read the temperature of locations on the console and the sides of the tunnel. The hottest area was the front wall of the console compartment where, in three spots , I measured 151°-154 F. The floor of the console compartment was pretty hot, too, measuring 143°-132°F, front-to-rear. A third hot area was the side of the tunnel, just below the top of the seat bottom cushion. I measured two spots, the front corner and adjacent to the seat belt buckle, both at 133°F. The basic structure of a C5/C6 Corvette is very stiff and one of many design factors which result in that stiffness is a plate attached to the bottom of the driveline tunnel. Once the plate is bolted in place, the tunnel becomes a very stiff, boxed structure. The correct name for this part, according to the Corvette Service Manual is: "floor panel tunnel panel reinforcement". Sheesh–who comes up with these names? Corvette Parts vendor, Zip Products, sells an extra-thick, thermally-insulated tunnel plate (PN-EX-869), made by Elite Engineering, which fits both C5s and C6es. Not only is the plate Zip sells treated with a metallic-ceramic, thermal barrier coating, but the bottom side, which faces the exhaust, has an additional two-ply (aluminum outer layer to reflect heat and a glass fiber inner layer to insulate) thermal barrier bonded to it. Because of its thermal properties, I ordered one of these tunnel plates from Zip hoping to reduce the temperature inside my car. The Elite Engineering tunnel plate is relatively easy to install on C5s and C6 base Corvettes and Grand Sports, but, because it comes with no instructions, first, you have to find out how. Instructions are only available on-line, but there is no notice in the box nor contact information printed on the outside of the box as to the web address. The URL for the instructions is: https://store-581ad.mybigcommerce.com/template/pdf/Installation_Instructions_Thermal-Abs.pdf. We think Elite Engineering needs to at least give customers a clue as to where to get instructions. Installing this the plate on C6 Z06es or ZR-1s was not quite as easy. The instructions erroneously tell the installer to reuse all 36 stock tunnel plate bolts, but on Z06es and ZR1s, the last eight thread inserts are set higher in the tunnel structure than the same holes on cars with steel frames, so the stock bolts are too short for those holes. If you can get any of them started, they'll strip before you reach the required 89-in/lb. of torque. Zip Products, is packing eight longer bolts with the tunnel plates they sell but, if you don't get your Elite plate from Zip, you have to buy bolts which are about ¼-in longer than stock from a hardware source which sells metric fasteners. Making this worse is the thread specification is wrong in the instructions. The bolts are listed as 6x1.25-mm but the thread is actually 6x1.0-mm. If you inadvertently strip one of the stock bolts, clean the threads in the insert with a 6x1.0-mm tap before you install a longer bolt. The stock plate is 0.130-in thick, slightly over ⅛-in. Elite's tunnel plate is ¼-in, about twice as thick. All makers of aftermarket tunnel plates claim extra thickness increases the car's rigidity in torsion and bending. Elite Engineering says its plate makes the car stiffer giving the driver "…a greater sense of control behind the wheel when cornering." and reduces the amount of squeaks and rattles. There's no doubt a thicker plate stiffens the tunnel. The question is: how much? I had no way to measure changes in the car's rigidity. In subjective road testing, I detected no change in the car's handing, but during a second temperature measuring road test, I sure noticed a decrease in temperature. I took measurements in the same places on the tunnel. I noted temperature reductions everywhere. In the three hottest areas, there was quite an improvement. The front of the console compartment now ranged 126°-134°F, about a 20° decrease. The floor of the console box was now 116°-124°, about a 20° drop and the tunnel next to the seat was 93° and 100°, a 33-43° reduction depending on where I measured. Bottom line: in-spite of problems with instructions and hardware, once I got the Elite Engineering tunnel plate installed, it did exactly what I wanted–reduced the temperature of the driveline tunnel. Want more info? www.zip-corvette.com www.eliteengineeringusa.com