Horse Sense: Though it seemed fairly obvious to us, we thought we'd better check with Zex sources who confirmed that, although this kit (PN 82034) was originally advertised specifically as being for the S197 GT, it installs and works equally well on the 4.0.
We've already reported how well the S197's 4.0 V-6 seems to like boost. Now it appears the SOHC six is just as enthusiastic about nitrous, as Paul Svinicki found out when he plumbed Zex's S197 Mustang GT kit into his Paul's High Performance '05 V-6, with dramatic results. How about a 12.80-second pass at 109 mph on an 84-degree day with a 26-mph headwind? This was more than a full second quicker and 12 mph faster than the car's best naturally aspirated run-not bad for a 75hp shot on a V-6.
Jamie Meyer, our resident mad doctor, reported on the installation of an identical Zex kit on an '05 GT in our Feb. '06 issue ("Spray Pattern," p. 102), so the hardware should look familiar. In case you missed that one, some of the interesting highlights of Zex's S197-specific kit include a Nitrous Management Unit that monitors the new Mustang's electronic throttle-control circuitry to precisely determine a wide-open throttle condition, a fuel-rail adapter to easily access fuel for the nozzle, along with a selection of jets for 75 to 175 hp. Zex's nozzle design also has active fuel control that is said to ensure proper air/fuel mixture by monitoring nitrous bottle pressure and adjusting fuel enrichment accordingly. Another neat feature for those of us who are, well, electrically challenged is the option of using a nitrous-arming switch that simply plugs into your 12V power point (also known as a cigarette lighter in less politically correct times).
The kit was already installed on PHP's racer at the time of our visit, so this isn't a follow-along how-to, though you'll see from our photos and captions how Zex can suggest the kit might be installed in as little as a couple of hours. A glance at our dyno sidebar should be convincing that it will be time well spent.
Arrayed from left to right in front of the distinctive purple bottle are the fuel-rail adapter, nitrous/fuel nozzle, bottle-pressure gauge, and the oh-so-wise nitrous management system. These items form the guts of Zex's S197 Mustang kit and are just some of the big stuff. The kit is utterly comprehensive in content, and we applaud the company's thorough and easy-to-follow instructions. Expect to pay around $620, plus about another C-note if you'd like a bottle warmer.
Two choices of arming switches are included: the traditional shielded toggle on the left-that requires connection into an underdash circuit capable of handling the system's 10-amp solenoid draw-or the slick little setup on the right that simply plugs in and draws power from the cigarette lighter.
The kit brings along five different nitrous and fuel jets for a 75-175hp hit spread. The 75 shot's a no-brainer; Zex says it doesn't even dictate any timing retard assuming use of premium fuel on a stock calibration. Going to any of the larger jets certainly requires recalibration at the least, and possibly fuel-system upgrades. In other words, proceed carefully.