2003 Mercury Marauder Exhaust Install - Finding Grunt

It sometimes takes a little while to get the new assembly to fit, so armed with a jack, the converters were slotted onto the ends of the downpipes and the assembly test-fitted on each side to ensure a good fit and adequate clearance.

After a bit of fiddling, the downpipe and converter were properly aligned. It was time to weld the converter to the downpipe. Once the left side was completed, we turned our attention to the right.

It also took a little while to get the downpipe assembly to properly line up with the manifold flange, but once it was, the right cat was welded on to the pipe and the assembly test-fitted again.

The downpipe and cats were fabricated, so the rear part of the mid-pipe assembly was next. This consisted of dual angled pipes that were welded up to the cats and then mated with an X-crossover at the other end. The X-crossover configuration and new mufflers were meant to swell the 281 V-8's mid-range torque.

In this view you can clearly see the location of the 02 sensors, which were moved farther downstream for a better fit.

Then it was time to tackle the mufflers. For this project, we went with a pair of Magnaflow 2 1/2-inch oval body units with offset inlet tubes and center outlets linking the tailpipes. More 409 stainless steel tubing was used to fabricate connecting pipes from the rear of the X-crossover flanges to the new mufflers.

Here are the completed mufflers welded and installed on the car.

Conventional wisdom says that you should also include new tailpipes with an exhaust install. In this case, Mitas advised against it, saying that the factory muffler back system was perfectly adequate and the biggest gains in power and torque would be realized from the change in the mid-pipe and muffler sections.

Like with any late-model performance car, a good custom tune is critical to optimize driveability as well as extract maximum power, so the big Merc was taken back to DaSilva's and strapped on the Dynojet.

Our first run with the exhaust installed netted a 12hp and 7-lb-ft improvement at the tires, with 247 hp and 260 lb-ft of torque registering. DaSilva's shop manager and tuning specialist Diego Lopes then uploaded a custom SCT tune before giving the car another run.

So how does Keilhauer feel about the upgrades? "There's a noticeable difference in the driveability, it's got more mid-range pickup, and my gas mileage has actually improved. I'm getting about 17 more miles to a tank of fuel than I did before." Now that's one happy camper.

The initial tune resulted in 275 hp and 301 lb-ft of torque at the tires. A few more tweaks by Lopez and the car made 280 hp and a whopping 310 lb-ft of torque on the final tune.