Elite Engineering's "Abs-of-Steel" product replaces the stock stamped-steel tunnel reinforcement plate for the express purpose of stiffening the already remarkably stiff C5 chassis and reflecteing some of the heat radiated by the exhaust system away from the central tunnel to help keep the passenger cabin cooler. Elite offers 304 stainless steel and 6061-T6 aluminum versions and either can be ordered with or without heat-dissipating ceramic coating. I opted for the uncoated SS version since I already have some effective central tunnel insulation that I installed last year.
When I received the Abs-of-Steel (AoS) plate, I was pleased immediately by the sturdy packaging. Upon opening and carefully inspecting the plate, I was quite impressed with the obvious quality of the product. The laser-cut work was beyond reproach. The edges were completely deburred while the surface finish felt extremely smooth - almost polished.
Totally unexpected was the C5 logo machined into the back end of the plate. Remember, when installed, this plate does not show at all. Finish details like this are strictly a matter of pride in workmanship and product. This reminds me of the kind of effort I put into my own fixtures and tooling at work. It doesn't matter that no one will see it - it's a matter of pride in one's work.
I set about to install it in my 2002 coupe and document the procedure while I was at it. The first order of business is to jack up the car and place it securely and safely on jackstands, ramps or a combination of the two (as I did) to allow access to the central exhaust section and tunnel plate.
Below you see the section of the exhaust system which needs to be removed to gain access to the stock tunnel plate. The one pictured is the aftermarket FLP x-pipe assembly. On a stock C5, this section is a single large, heavy piece consisting of the flanges that connect to the exhaust manifolds, the catalytic converters (including the 2 pup cats on some later models), the main h-pipe section and the flanges which connect it to the rear muffler over-axle pipes.
First, use a 22 mm wrench to unscrew the rear O2 sensors from behind the cats. Be careful removing them to avoid damage. Allow them to hang free and be aware of them when you get to the steps where you lower and raise this section of exhaust past them.
Next, use a 13 mm socket and wrench to loosen the spring hanger bracket bolts pictured below. Don't remove them yet. You'll want to leave these until last so that the exhaust stays in place unti you're ready to lower it. Remove the bolts on the front and rear flanges that connect the h-pipe (or x-pipe) to the exhaust manifolds and to the catback over-axle pipes.
Place a jack as best as you can under the center of gravity of the exhaust. It's nice to have a helper at this point since it's a bit clumsy, but I managed it pretty easily on my own. Holding the exhaust steady, unscrew the spring hanger bolts and the front exhaust mounting bracket screws completely and slowly lower the exhast down and maneuver out from under the car. Once again, make sure you're careful to clear the O2 sensors and other structures.
Below is a shot of my cat/x-pipe/cutout assembly and, below that, a stock h-pipe for illustration. I took the opportunity to inspect it and add a bit of heat insulation to my cutout motors and to clean the assmebly up a bit.
Here you see the stock tunnel plate exposed and ready for removal. There are 36 6-mm screws holding it in place. This view is looking from the rear of the car.
This shot is from the front, looking back.
The stock plate has two locating features - one is the fifth hole back from the front of the plate on the driver's side. The diameter of this hole is noticeably smaller than the rest.
The second feature, also on the driver's side, is this elongated slot which is the fourth hole from the end on the rear of the plate. Remember this position, as it comes into play during the install of the new plate.
To remove the stock plate, use an 8 mm socket on a 6-inch extension to first loosen, but not remove, two of the center-most screws, one on each side opposite each other. Then completely remove the other 34 screws. See the picture below. Finally, remove the two you firtst loosened while supporting the plate to prevent it from falling. Then carefully move the plate away from the car.
This is essentially what your tunnel should now look like. A great opportunity to inspect the torque tube and central tunnel area and to clean up a bit while it's exposed.
I put both plates side-by-side to compare the two. The Elite Engineering SS AoS plate mimics the stock plate in shape and size but is extremely stiff in comparison.
The material thickness difference is notable as is the much niceer finish of the Elite Engineering AoS plate.
To install the AoS plate, locate the elongated slot and make sure you position it so that it is in the same location as the slot on the stock plate - namely on the rear driver's side. You should be able to read the C5 logo from underneth and it should be at the rear of the tunnel. Carefully lift it into place (a helper is nice here since it weighs a bit more than the stock plate) and start two of the screws on opposite sides near the center of the plate to hold it in position and to bear it's weight.
Next, start a screw in the hole that's in line with the slot because it's narrower than the rest of the holes and the screw would most likely bind and possibly break if you leave it for later. Start the rest of the screws and then carefully hand-tighten them using the 6-inch extension with the 8-mm socket. Snug them all down sequentially until they are completely seated.
Dont't force a screw in if it feels as if there is an unusual amount of resistence. A drop of Tap Magic or machine oil might help to thread it in more easily. Push the plate up against the frame rails to relieve tension on the screws as you turn them in by hand. Turn them in evenly as you go to avoid binding one side relative to the other. Once they have all seated by hand, you're cleared to torque them.
Starting at the center of the tunnel and working side to side and then front to back, torque the screws to 89 lb. in. (yes, that's 89 pound-INCHES). Don't over-torque as the screw heads are likely to break off.
Below is what the AoS plate looks like torqued into place.
Note the beautiful fit near the collectors . . .
. . . and the awesome C5 logo. Too bad this won't be showing.
A stock h-pipe. The exhaust manifolds (or headers) do not need to be removed for the installation of the AoS plate.
Another shot of the AoS plate.
Finally, reverse the process of removing the h-pipe (or x-pipe) to reinstall it. Loosely connect all your bolts on the flanges and hangers and then sequentially tighten everything until you have it all lined up to your satisfaction. Don't forget to reconnect the O2 sensors. Next, lower the car back to the ground and make sure all tools and other objects are clear of the car. Fire it up and check for exhaust leaks and retighten if you find any. Then take it for a spin and enjoy the new tight feeling of the chassis and the heat reduction in the tunnel.
If your exhaust has the stock h-pipe, you'll need to also loosen the two front exhaust mounting bracket bolts using a 3 mm socket. Do not remove them at this time. Leave them attached to help support the exhaust. The h-pipe should now be hanging loosely by these two front bracket bolts and the spring hangers.