June 11, 2007

This report marks the final stage of our '86 T-top coupe project. The road to completing the Fox-Rod resto of our special notchback was 11 months long. There were many peaks and valleys along the way, but the experience leaves us with a satisfying sense of accomplishment. Each time we hear our 'Stang's Keith Craft big-bore 347 and Paxton Novi 2000 supercharger scream to life, even the tasks we suffered through during the build process don't seem to be as trying as we thought.

We've covered a lot of ground in the past year, showing you many of the parts, technologies, and engineering that can and should be included in a bad-to-the-bone, street/strip 'Stang. FAST's XFI engine-management setup is among the components we've mentioned, and it's one of the really key parts on the car.

XFI is the operations center for the coupe's powerplant. It includes all the features we need for tuning the supercharged bullet, such as the ability to control every aspect of the engine's functions, with respect to air, fuel, spark, and boost. It's also capable of real-time datalogging and much more.

The management system is a breeze to install, and despite our initial apprehension, XFI is intuitive, easy to use, and isn't "too much" for the caliber of street-driven, race-ready beast we've created. Our unease was unfairly based on the opinions of 'Stangbangers who have used other laptop-controlled systems and had problems understanding them. The anxiety also came from parrots who have no hands-on experience, but authoritatively repeat incorrect information they've heard from others.

Despite its ease of use, we're novices with laptop tuning. We sought assistance from XFI experts TJ Tracey of Advanced Performance and Tom "Tom H." Habrzyk-believe it or not, that's pronounced "habb-chak"-of Advanced Product Engineering, as we made our initial venture into perfecting the 347's performance with XFI. Asking someone knowledgeable for help is something you should never be too proud to do, especially when dealing with an engine package that has the potential to make a lot of power when properly tuned.

TJ helped us dial in the motor's naturally aspirated program while we were at Keith Craft Performance Engines' facility last year and tuned our big-bore stroker to 478.9 flywheel horsepower at 6,400 rpm and 471.2 lb-ft of torque at 4,500 rpm ("Big-Bore Score," Dec. '06, p. 58). Once the blower was installed and the coupe was ready to run, TJ sent us a program to use as a baseline starting point for tuning.

Working with the Dynapack Evolution 4000 chassis dyno at Extreme Automotive and using XFI's various fuel and timing tables to make adjustments to TJ's program, your tech editor and Saul "The Surgeon" Gutierrez got the supercharged stroker up and running. Through trial and error, we established a tune that gave us good air/fuel mixtures at idle and wide-open throttle.

XFI isn't a rocket-science type of management system. We credit our quick understanding of how it works to watching the instructional DVD that's included with the unit and having a general knowledge of how an internal-combustion engine functions. XFI is a laptop-controlled method of doing the same thing carb guys do with screwdrivers, jet-change tools, and a 11/42-inch wrench to loosen the distributor hold-down bolt. We manipulate an engine's air, fuel, and spark to achieve optimum performance.

As we've stated on many occasions during this project, our goal was to produce a drag-oriented 'Stang capable of going through the same motions as a good high-horsepower street car.

It was frustrating getting the engine to start right up when we began tuning, as the motor would intermittently have a hard time cranking over. Tom H. showed us how to correct the issue by phasing the MSD distributor, and he guided us through the finer points of XFI's graphs and data-capturing ability. That helped us dial in the coupe's street-ability and dragstrip performance. Now the engine starts immediately, the motor runs and idles without having to throw it in Neutral or pedal it with simultaneous doses of throttle and brakes at stop signs, and it runs well.

We have to say, we've nailed it with this Mustang. The T-top coupe is impressive on the dyno, as it has great power and monster torque-we haven't really touched the Novi 2000's full boost-potential yet. It's a blast to drive around the streets of LA's San Fernando Valley-and, yes, for those who know the area, we have made a few full-tilt passes on "The Road." Based on results from the car's maiden voyages down the 1,320, it's clear that we've covered all the bases with our project buildup.

On The DynoOur first tuning effort was made on the chassis dyno at Extreme Auto-motive. Through trial and error, we were able to dial our blown big-bore engine combination to an impressive 473.57 hp at the rear wheels at only 5,800 rpm and 8 psi of boost. Note that the figure was derived with our Precision Industries Stallion torque converter locked up during the dyno hit.

We experimented with the lockup function a lot during our tests. With the lockup on, horsepower seems to come on/increase a bit later in the rpm range than it does with the converter unlocked. For example, with the lockup off, our engine made just more than 100 hp at 2,200 rpm. With lockup activated, we didn't see 100 hp until the engine reached 3,300 rpm. Peak horsepower-the aforementioned 473.338-really does shine with a locked converter.

Peak torque was our overall performance champion on the dyno. With the converter unlocked, our 347 put out a brutal 641.652 lb-ft of rear-wheel torque at 2,566 rpm. When we reported the results to Jeff Henry of Keith Craft Performance Engines, the man who built the big-bore bullet for our project 'Stang, his reply was, "That car is gonna blaze the tires like nobody's business-or stand straight up on the rear bumper if it hooks."