<font size="2" face="Verdana, Arial">Next up is the exhaust. With a few notable exceptions, most modern cars will only get very few horsepower from an exhaust system. The state of the muffler art is pretty well advanced, and OEMs have largely figured out how to make the exhaust silent without severely limiting power output. With relatively little power to gain, sound quality, looks and fitment are our highest priority with an exhaust system. Without trying every exhaust (we're not promising to do that just yet) that means listening to every modified Focus we see and trying to pick a good one.
On a recent visit to Thirteen Twenty Morotsports to plan the Focus rally car (see sidebar), our man Josh Jacquot noticed that it was making an exhaust system that wasn't too loud and had a nice, deep exhaust note. Sign us up!
The Thirteen Twenty exhaust is powdercoated mild steel, which means it looks like it's painted black, but when you start it, the paint doesn't burn off. The stock exhaust is one piece from the front crossmember all the way to the rear bumper. This is great for installation at the factory, but replacing the exhaust either means removing the entire rear suspension, or cutting the exhaust in half. Cut, we did.
After hacking through the exhaust just after the first muffler, the front section drops straight out and the rear can be worked free around the suspension. The Thirteen Twenty exhaust is made in three pieces, with two slip joints held together with U-bolts. This means you have to hang the whole exhaust, making sure everything is aligned properly, and then tighten the U-bolts. Once tightened, the slip joints are resistant to any further adjustment, so try not to tweak the alignment while you are tightening. Regardless, this is not an exhaust you would want to install in your driveway, on your back or by yourself. This is one you should have installed by somebody with a lift.
With all the appropriate tweaking, the exhaust fit well. Our only criticism is one of the exhaust hangers just in front of the rear suspension, which is welded to the exhaust with far too small a weld. Since the exhaust is supported by no less than five hangers, it probably won't be a problem, but on most exhausts, we would expect a hanger like this to break off after a few years of heat and vibration. We're hoping that won't be an issue.
The sound quality of the exhaust is good. It seems loudest at a high idle (about 1100 rpm) and around 3200 rpm. Neither loud spot is an annoying, booming resonance; it just seems that every time we notice the exhaust, it is at one of those two points. Strangely, the exhaust seems quieter when you drive hard--and that's really the time when you should be attracting the least attention. Like every Focus with an exhaust, ours now makes lots of little gargling and popping noises on deceleration.
On the dyno, the exhaust was good for a few horsepower above 5000 rpm (where the Zetec needs it most) and a boost of low-rpm torque. As we mentioned earlier, we're not entirely confident in the dyno numbers below 3000 rpm.
<font size="2" face="Verdana, Arial">Problem No. 3: It's loud
OK, this one was our fault. In part one, we installed a Thirteen Twenty Motorsports exhaust that had only one muffler. At the time, the exhaust was surprisingly quiet, had a pleasant, mellow tone and made a few horsepower. Perfect. But then we installed a FocusSport race header and high-flow catalytic converter and all hell broke loose. The stock cat, it turned out, was doing a lot of the muffling. Suddenly the car was obnoxiously loud and had an annoying, sputtering, buzzing exhaust note.
We heard FocusSport's exhaust is the quietest available, so we gave it a try--replacing the Thirteen Twenty exhaust's single, straight-through muffler, with the FocusSport's two; it added a small resonator upstream of the main muffler. Though the exhaust note was still buzzy, it was finally at a volume that'd allow us to drive the car without going to jail. The surprise, however, came when we took the car back to the dyno. To our horror, the car had lost 6 hp relative to the Thirteen Twenty exhaust.
Back at FocusSport, we analyzed the situation and identified the resonator as our key suspect. FocusSport used a louvered-core resonator, a no-no for horsepower, since the louvers hang into the exhaust stream and restrict flow. FocusSport insisted the louvered core was critical to achieving the peace and quiet we so desperately wanted. Their solution is to switch to a larger louvered-core resonator, one in which the effective diameter after all the restrictive louvers is as large as the rest of the pipe. As a test case, they also made up an exhaust with no resonator at all.
The FocusSport exhaust with no resonator made exactly the same power as the Thirteen Twenty exhaust and exactly as much noise. Switching to the new, oversized resonator, the exhaust was quieter than ever--the new resonator is slightly longer, which makes it more effective--and, to our relief, made the same power as the straight pipe. All new FocusSport exhausts will now use the larger resonator, but if you already have the older exhaust and want to upgrade, FocusSport is also making the front section, with the larger resonator, available by itself.