Impressive in stock trim,...
Impressive in stock trim, there's plenty of extra power just waiting to be unleashed under the hood of a Thunderbird Super Coupe. Rather than go with the 5.0L V-8, Ford chose to equip the Super Coupe with a 210hp supercharged 3.8L V-6.
Compared to the 300hp Mustang GTs and 500hp Shelby GT500s, the specs of a '90 Thunderbird Super Coupe seem pretty tame. Back in the day, however, the supercharged 3.8L was a pretty heavy hitter. Though down on displacement, the 3.8 thumped out nearly as much power as the 5.0L Mustang (210 hp versus 225 hp), and torque production was equally impressive, with the supercharger helping to up the twist to a V-8-like 315 lb-ft of torque. The impressive torque curve is why the Super Coupes offered such impressive acceleration. With a peak power output that occurred at just 4,000 rpm and torque peak some 1,000 rpm earlier, these motors offered diesel-like torque curves.
Unfortunately, placing the emphasis on the impressive low-speed power production meant the supercharged 3.8L was not rev-happy. There was little sense in revving the motor to 5,500 rpm or beyond since the peak power occurred at just 4,000 rpm. On the plus side, the Super Coupe offered an impressive combination of ride quality, handling, and braking (given the hefty curb weight).
Super Coupe owners are intensely loyal to their chosen mount, and they should be. It's a great-looking package and without a doubt much more aerodynamic than many other cars of the time. If you're looking to go fast (as in Bonneville fast), the T-bird is a much better package than a Mustang. Aesthetics aside, the real reason to own a Super Coupe is because it sports forced induction.
 The highlight of the Super...  The highlight of the Super Coupe engine was the Eaton M90 supercharger pumping out roughly 12 psi. |  Running 12 psi with a Roots-style...  Running 12 psi with a Roots-style blower means an elevated inlet air temperature. To lower the inlet air temperature, Ford saw fit to equip the Super Coupe with an air-to-air intercooler. |  On the Super Flow chassis...  On the Super Flow chassis dyno, the bone-stock Super Coupe produced 192 hp and 265 lb-ft of torque. |
Any motor that comes from the factory with a turbo or blower will always provide plenty of additional performance with some tweaks. The easy route is to simply turn up the boost, but as we found during many sessions on the chassis dyno, there's more to the performance equation than what's indicated on the boost gauge.
Given the flow limitations of the small M90 supercharger employed by Ford on the 3.8L, it would take more than just a smaller blower pulley for us to drastically enhance the power of the '90 Super Coupe. We've heard of modified Super Coupe motors exceeding 300 rwhp, though we've yet to verify the claims.
Naturally, the first order of business was to establish a baseline. The five-speed Super Coupe was taken to the Super Flow chassis dyno and run in bone-stock trim. The virgin motor (meaning high mileage but no performance modifications) ran well despite being nearly 16 years old and having logged over 180,000 miles. Rated at 210 flywheel horsepower, the stone-stock T-bird belted out power numbers of 192 hp and 265 lb-ft of torque with a peak boost reading of 11.9 psi. Literature from Ford indicates the motors were supposed to run 12 psi, so it looked like our little 3.8L was still running strong.