By John Hunkins
Photography by the author
(Continued from part 1)

Last month we outlined the mechanical composition of our feature engine, a 422-cubic-inch SVO Windsor-based, Yates-headed, fuel-injected shootout motor with nitrous. The owner of the engine, Tommy Gourzis of Coopersburg, Pa., wanted to create the ultimate Ford street bullet that would have uncompromised strength and be able to perform competently in heads-up shootout situations.

With this goal in mind, Tommy decided to employ a stroker engine based on a 351 Windsor (see specs ). To make the engine a reality, Tommy selected Second Street Speed in Perkasie, Pa., to design, build and dyno test the engine. To satisfy the flow demanded by such large displacement, Second Street chose a pair of Weld Tech CNC-ported Yates NASCAR cylinder heads. With a naturally aspirated horsepower target of 700 hp, maximum flow from the cylinder heads was of paramount concern; at 28 inches of Hg, the Weld Tech Yates heads flowed 341 cfm at .600 inch lift on the intake, 229 cfm on the exhaust (see flow chart).

For shootouts, nitrous would be used to be competitive, so the combination would also have to account for this as well. The fuel system, ignition system, camshaft selection, and compression ratio would have to be optimized for both street (naturally aspirated) and competition (nitroused). To help Second Street fine-tune these parameters while satisfying all the operating criteria, a Dynomation engine-modeling program was used. In order to maintain driveability and maximize tuneability, Tommy elected to go fuel injected. While many of today's top shootout Mustangs are carbureted, Tommy felt that a carb would severely limit his street driving. Since cost was a minimal concern, he decided to gear up for fuel-injection components, which included a Hogan's sheetmetal fuel-injection intake manifold, a distributor-less Motec ignition system and Motec engine management.

MOTEC ENGINE MANAGEMENT
At the heart of the 422's fuel-injection setup is a Motec M48 Pro engine control unit The M48 Pro is a sequential unit that has a 32-bit processor operating at 33 MHz, making it the fastest unit currently available for aftermarket use. According to Bill Hunsberger of Second Street Speed, "It's fast. It allows very fast transient response time. Your transient acceleration, fuel, driveability and overall idle quality are improved because of the speed of the processor"

The Motec has several important features that are wont' noting. Besides having tile standard ignition timing and fuel delivery maps, the Motec allows each cylinder to be treated as an individual engine. Trim tables allow adjustment on a per-cylinder basis for both fuel and ignition timing. Hunsberger says, "if you find that there is a variation in injector flow, runner flow or heat distribution between cylinders-all of the common distribution problems of multi-cylinder engines-it can be corrected by the individual cylinder trim capability of the Motec:'

A full complement of onboard diagnostics is employed in the Motec. This provides for online fault checking of sensors and injectors. Onboard data logging is also part of the Motec package and makes use of non-volatile flash memory in the event of a power loss. This has proven invaluable in the tuning and testing of high-powered fuel-injected engines and is usually an add-on (both physical and cost-wise) inmost systems.

Although the Motec unit can be used in virtually any automotive 4-stroke application, it is well suited to Mustangs because it uses the complete Ford wiring harness. "The main thing that attracted me to the Motec was the adaptability," says Hunsberger "It will look at all types of sync reference signals from all types of cars, even OEM signals. We're using the Ford TFI distributor in this application to trigger the sync ref. The Motec can be plugged into the factory Ford harness without cutting or disturbing it. This means you don't have to replace your stock wiring with a new harness."

From a cost standpoint, the Motec is twice as expensive as a DFI unit, but Hunsberger points out that on the basis of processor speed, flexibility and installation, the Motec may be desirable for some applications, such as Gourzis' 422 stroker.

MULTI-COIL IGNITION
The Motec engine management system works hand in hand with the Motec ignition expander, or IEX. The 'EX unit allows the Motec system to fire the engine via a distributor-less, multi-coil ignition system. This offers a couple of advantages over traditional single-coil ignitions.

The Motec has the ability to monitor the voltage condition of the battery and expand the coil dwell time correspondingly. When the battery gets low each cylinder will still get the same spark energy, thus eliminating the common occurrence of misfire or reduced power output.

All OEM and aftermarket distributor-less multi-coil ignition systems (such as the Motec, Electromotive TEC II and Ford EDIS) have an inherent advantage over single-coil systems in that each coil has a far greater potential dwell time at higher rpm. This ensures that an engine's maximum power potential is realized with a robust spark.

Hunsberger explains, "when you’re at 8000 rpm with a single-coil system, your dwell saturation time is basically insignificant. Even if the windings on the secondary side of the coil are ample enough to give you plenty of current in a best-case scenario, this decreases as dwell time decreases. The Motec coils have the capability of 8 amps per coil, and since you're only firing one coil every half crankshaft revolution, the dwell time – and hence the current output –remains constant even at high rpm. This gives you the capability of lighting the air/fuel charge in the most demanding situations. This is why most new-car manufacturers are going to multiple-coil systems, because they can fire a leaner air fuel mixture in a high-turbulence environment?'

In the 422-cubic-inch Yates-headed stroker, the profile ignition pickup (PIP) signal from the stock TFI distributor feeds the Motec unit with a crankshaft sync signal. (Per the Motec's design, it may be programmed to accept any number of OEM signals, including the Ford's.) The Motec calculates the proper ignition timing and outputs the signal to the IEX. The IEX is slaved to the Motec and sequences the timing and dwell to the appropriate coil.

Each coil fires two cylinders simultaneously. This type of system, also called a wasted spark system, fires on both the power and the exhaust stroke. Since the charge density and, thus, the dielectric resistance of the ignition circuit are practically zero at the end of the exhaust stroke, there is only a minuscule token spark produced at this cylinder; but the companion cylinder teamed at the same coil receives a big wallop of a spark right when it's needed.

From a tuning standpoint, the Motec is especially useful when used on high-horsepower applications. This is due in part to its lambda feedback control, which allows fuel delivery to be linked directly to the air/fuel ratio. Most systems are programmed by the trial-and-error process of observing indicated air/fuel ratio and then making a change in the fuel table. However when first-time users of programmable systems attempt to adjust the fuel table (or fail to adjust the fuel table), engine damage can occur fairly easily.

The Motec's fast processor speed combined with its wide-band air/fuel ratio control allows the less experienced tuner to specify a desired air/fuel ratio with one keystroke. The processor can "chase" this ratio with a high degree of precision in normal driving conditions. This is particularly useful in sorting out sour spots in the load table that may escape less experienced tuners.

DYNO TUNING
In the case of Gourzis' 422, Second Street used a wide-band O2 sensor to monitor air/fuel ratio, but not to control fuel delivery. In a dyno environment Second Street believes that the active lambda control function lacks the necessary quickness, so the load table was generated manually instead.

Hunsberger outlines the initial tuning procedure: "Since the camshaft installed in this motor wouldn't produce any vacuum, we chose to use throttle position for our load site selection instead of manifold vacuum. Manifold vacuum is used for load selection in the case of speed density systems where the vacuum signal is good at idle, such as in the '86-88 5-liter Mustang.

"We used rpm control on the dyno to select an rpm site and varied throttle position to pick load sites. Once the load site and rpm site were targeted, the opening time of the injector was calculated in milliseconds to provide the proper air/fuel ratio. We monitored air/fuel via a 5-wire NTK wide-band sensor. This gave us very good resolution with a very fast response time. The only true way to measure air/fuel ratio is to use a wide-band 02 sensor"

The second phase of dyno tuning was dialing in the nitrous. The Motec has the ability to not only control fuel and spark, but to initiate the flow of nitrous in one or more stages. (There are two static stages that give the Motec the capability for three distinct levels of nitrous delivery.) In this application, a single stage was used. As plumbed by Second Street, the nitrous system uses twin NOS Pro Shot nitrous solenoids that feed eight individual NOS fan spray nozzles (one in each runner port). Fuel enrichment for the nitrous system is accomplished by the Motec through the fuel injectors. This, says Hunsberger, provides more precise control over fuel delivery than dedicated fuel delivery.

"When we did the nitrous we used a combination of air/fuel monitoring, exhaust gas temp monitoring and brake-specific fuel consumption numbers," says Hunsberger "With nitrous it is imperative that a minimum BSFC of .55 is maintained. With the nitrous we dyno'd the motor at 600 rpm per second where we had gone steady state for the initial tune. We knew how much fuel we were consuming so we were able to compute for nitrous how much more we would need. It was simply a matter of plugging in the percentage increase-accounting for brake specific-for a given amount of nitrous."

RESULTS
Thanks to careful planning and the use of Dynomation software, the target horsepower levels for Gourzis' 422-cubic-inch Yates-headed mill were all met with minimal difficulty. In naturally aspirated trim, power rose like a rocket, hitting 703.4 hp at a modest 7100 rpm. As we mentioned in part 1, the goal was to make 700 hp in naturally aspirated trim; this way approximately 1,000 horsepower could be achieved with a reasonable quantity of nitrous. Just over 700 hp was obtained naturally aspirated with the dyno set at 300 rpm per second.

(According to Hunsberger, the engine was pulled at a slower 300 rpm per second to acquire better data in the initial tuning stage. In nitrous trim, 600 rpm per second was used to more accurately mimic the running state of the engine downtrack. The difference does, however, create a discrepancy in the power reading. For the purpose of comparison, we've graphed only those pulls made at 600 rpm per second.)

In nitrous tune, the street-destined bullet came close to the 1,000-hp target with 968.2 hp coming in by 7300 rpm. The nitrous graph looks wildly different from the naturally aspirated and bears more than a passing resemblance to El Capitan.

For now, at least, Gourzis should have more than enough power to help him explore the mid-8-second zone. Once he feels comfortable with this level of power, and if all goes well, Tommy plans on changing over to a blower or a turbo to push his Stang into the 7s. In the coming years this should be what it takes to be competitive in most shootout situations. With a bulletproof stroker and state-of-the-art engine management, Gourzis will have a solid performer for those future battles.