Project Ford Focus ZX3: Part 3

Adding a ported throttle body.

Most of our project installments center around taking a perfectly good car and screwing it up. At least that's what the masses would think. In personalizing, customizing and focusing our cars on performance above all else, we inevitably upset the delicate balance of ride and handling, horsepower and fuel economy, and perhaps even styling and anonymity that the OEM spent so many billions of dollars to achieve. Whatever, we think they're better.

For once, our efforts with our 2001 Ford Focus ZX3 are a little less destructive. This month, we'll identify a few problems with our Focus and set out to correct them. Admittedly, we caused at least one of these problems in our last installment, but our improvements are solutions we think you'll like.

Despite its European heritage, complex suspension geometry and precise steering, remember the Focus' suspension calibration was developed by the people who brought you the Crown Victoria. The car's springs, shocks and bushings are all designed to perform on the highways of the Motor City, perhaps the worst roads this side of Bosnia. If bump absorption and land mine isolation are high on your list, the U.S. Focus calibration is brilliant, but on civilized roads, the soft settings impair precision and responsiveness and can occasionally even lead to motion sickness.

We heard from sources deep within Ford, that the Europeans get three different suspension calibrations to choose from, each with a catchy name. Luxury is their softest setting, reserved for the four door. Ambiente is the mid-level calibration, offering a well-rounded ride and handling compromise. This calibration is available here in limited numbers on the Street Edition sedan and wagon and the S2 ZX3 model Focus. The Trend suspension calibration, finally, is designed for the youthful, sporty tire squealer. You know, freaks like us.

Problem is, you can't get the Trend suspension in the United States. Or can you? We decided to scrounge one up, put it on and see if it's really as good as we've heard. If enough people want it, we figured, Ford Racing should be able to make the parts available rather easily.

The springs, shocks and rear anti-roll bar are unique to the Trend calibration, though the shocks make the most difference. Front spring rates increase only slightly, from 110 lb/in to 125 lb/in, and the rears bump up from 129 lb/in to 148 lb/in. The ride height remains identical. The rear anti roll bar is also 1mm larger.

From the first trip around the block, it was clear the rumors were true. The Trend suspension is incredibly well controlled. With the U.S. calibration, the front of the car floats over bumps, often taking two or three oscillations to recover. The Trend suspension simply follows the road, soaking up irregularities. And the ride isn't overly compromised. It might be sub par for shuttling your grandmother from one side of Motown to the other, but on the worst roads Southern California has to offer, it's remarkably supple.

Plus, no matter how hard you charge, the Focus is always controllable, always responsive. Photo Editor and master poet, Les Bidrawn, summed up the Trend suspension like this: "It's fucking brilliant."

Eager to learn just how fucking brilliant it was, we headed to the track to test skidpad and slalom performance. Wearing the stock, U.S.-spec Goodyear Eagle RS-A tires--nicknamed "screaming eagles" for their very vocal protests against aggressive driving--the slalom speed improved from 63.9 to 66.0 mph and skidpad grip climbed from an embarrassing 0.81g to 0.83g.

The next natural step was to upgrade the wheels and tires to take better advantage of the new suspension. This proved far more difficult than expected. The Focus uses a very unusual 4 x 108mm bolt pattern rather than the more common 4 x 100mm or 4 x 4.5 in (4 x 114.5mm). This is true European heritage; Renault and Peugeot use the same bolt pattern. Unfortunately, the Focus is just about the only U.S.-market car with this pattern, so wheel choices are limited.

Of course, the size dilemma haunted us as well. Despite our best efforts, the Focus is still underpowered, so we can't afford the weight, rotational inertia and possibly even taller gearing 17- or 18-inch wheels would entail, regardless of how fantastic they would look. We also didn't want to put $1,200 of forged wheels on a $13,000 car.

Searching for the right compromise, we finally settled on ASA EM9 wheels from the Tire Rack. Weighing 19 lbs in the 16 x 7-inch 40mm offset we chose, they're not race wheels, but not inappropriately heavy either. At $149 each, they also fit the price range of the car. The satin silver finish is exactly the same finish used on the BMW M5's wheels. The color is a little too bright for our yellow car, but they look more dramatic as they collect brake dust. What a perfect excuse not to wash them.

For tires, we also wanted something priced appropriately for the car and Kumho's ECSTA Supra 712 fit the bill perfectly. Don't laugh, the best skidpad performance we've ever seen was recorded on a set of Kuhmos. The Supra 712 shares the carcass design with Kuhmo's Victoracer V700 DOT-approved road racing tire, but uses a more rain friendly tread design and a longer wearing compound. We chose a 205/50ZR-16 size to match the rolling diameter of the stock 195/60R-15s.

Grip with the Kuhmos is a solid improvement over the stock tires, and somewhat better than the $78 price might imply, but still isn't as high as we had hoped. Turn in is quite good and breakaway characteristics are linear and predictable, but like the "screaming eagles," they attract more attention than we'd like when pushed hard. Skidpad grip with the Kuhmos increased slightly from 0.83 to 0.84g, but slalom speed jumped dramatically from 66.0 to 68.8 mph.

As conservative as we were on the size, the weight of each wheel and tire still climbed from 34 pounds to 41.4. Imagine how heavy it would be with 18s.

Problem No. 2: It drives funny
We griped about it last time, but with a solution at hand, it's worth bemoaning again. The Focus has terrible throttle response. This is quite intentional, as slow tip-in makes the car easier to drive in traffic, but for enthusiasts, this is annoying. The engine is also reluctant to slow down during shifts and when the clutch is engaged at high rpm. This is intentional as an emissions control strategy that only American manufacturers seem to find necessary.

Don't fret. Both problems can be solved with the installation of a BBK throttle body.

The stock throttle body and intake manifold are both plastic, which makes boring out the stock throttle body impossible. Instead, BBK makes its own aluminum part to replace the whole thing, TPS sensor and all. The stock throttle body is also tiny, only 57mm wide measured parallel to the shaft and 51mm wide measured perpendicular to the shaft. The smaller dimension is a result of the shrouding used to create the slow tip-in. The throttle plate itself is quite thick on one side, causing more restriction than usual.

The BBK throttle body is round, as it should be, measures 65mm in diameter and has a normal, thin throttle plate. The new throttle body corrects the annoying high-rpm hang, which is caused by an idle control valve allowing excessive amounts of air past the throttle body during coastdown. Because the port supplying air to the idle control valve is in the throttle body itself, BBK restricted this air supply by making the port no bigger than necessary to sustain a normal idle.

Installation is quite simple, but as with so many jobs on the Focus, be sure you have a set of Torx sockets. Because the throttle body is mounted vertically, it's very easy to drop screws, sockets and other engine bombs into the manifold. Be careful. Once the stock throttle body is removed, lay the BBK gasket over the top of the manifold and notice how much bigger the new throttle body is than the hole in the intake manifold.

Time to start porting. We used an air powered die grinder with a sanding roll to enlarge the manifold opening. OK, technically the crew at FocusSport did it. We were the ones with the camera barking out orders, but you get the idea. Since the manifold is plastic, we weren't terribly worried about little chunks of it falling into the manifold as we sanded. Anything that did work its way into the cylinders would be burned and spit out without causing harm. The grit from the sandpaper, however, is hard enough to damage cylinder walls and since it does fall off, we stuffed the manifold with greasy rags to catch whatever gritty badness decided to make a run for our engine's innards.

Where the stock throttle body slowly metered out airflow over the first few degrees of throttle opening, the first crack of the BBK throttle body unleashes a cascade of air. The result is instant, almost jumpy, throttle response. If anything, the BBK throttle body is a little too big for the engine's current state of tune. By about half throttle, the engine is ingesting all the air it can. With luck, however, our future cam and head modifications--not to mention that turbo we have planned--will justify the large throttle body. If we were planning to stop engine development here, we'd prefer a smaller diameter throttle body, just to spread power delivery over the entire range of pedal travel.

Despite the small size of the stock throttle body, it wasn't a significant restriction. The dyno showed only about 1 hp gained with the BBK throttle body. Still, while huge gobs of power would've been nice, it's drivability we're after. If you spend a lot of time creeping through traffic, the stock throttle body is the best choice, but if you like a responsive engine, and you want to have engine braking available, we've found the solution.

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.

There you have it. An entire project installment in which we didn't screw anything up. No compromises, nothing that'd make normal people hate the car any more than they already do. Don't get used to it.

The future of Project Focus includes a suspension you can actually buy, some way to advance ignition timing, and some camshaft and cylinder head upgrades to unleash substantial horsepower, while simultaneously messing up the idle and sacrificing low-end performance. Normal people will hate it.

Source
BBK Performance
(909) 735-2400
www.bbkperformance.com
Throttle Body

AEM
(310) 484-2322
www.aempower.com
Intake

Thirteen Twenty Motorsports
(760) 736-4467
www.1320motorsport.com
Exhaust

JBA Headers
(619) 229-7797
www.jbaheaders.com
Short Header

Focussport
(714) 630-6353
www.focussport.com
Long Header, Flywheel, Exhaust

The Tire Rack
(888) 981-3957
www.tirerack.com
Wheels and Tires

Unorthodox Racing
(516) 253-4909
www.unorthodoxracing.com
Underdrive Pulley
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