Jim Smart
June 9, 2016

When Ford introduced the SEFI 5.0L High Output Mustang in 1986 many predicted the end of the tunable engine. Ironically it was the beginning of a new era of super-tunable small-block Fords that would ultimately get Mustang racers into single digits. Speed density, which was used extensively the first two years, was a dog because you couldn’t do anything with it. It was a factory sealed, nontamper system. If you did a cam swap, for example, engine performance fell off the cliff.

When mass air sensing arrived in 1988-1989 it represented hope for Mustang racers and tuners because it did allow for some performance tuning. If you were savvy enough you could tune your way into better performance in the wake of a cam or induction swap. Technology has only evolved from there with great aftermarket electronic engine control systems you can tune and play with.

It is remarkable what technology has brought us in a world of white-hot Mustang performance. Mustang racers are going faster than they ever have in the marque’s history. Much of it begins with good bones—the right combination of cam, heads, induction, and just the right amount of bore, stroke, and compression. Getting these things right has always been a horrendous challenge for street and strip racers alike. Once you have proper elements in place the trick is spark timing and fuel curve. If you’ve installed power adders, such as a supercharger, turbo, and/or nitrous, it gets dicey. You better have a plan for spot-on tuning or you could lose the farm.

AEM Performance Electronics presents us with tuning perfection with a plethora of products designed not only to get tuning on the beam but make tuning easier. The new Infinity standalone ECU features a VE-based tuning model that uses air/fuel ratio feedback control to easily dial in a VE table. We’re working with a 1990 Mustang GT drag car fitted with a 347ci stroker on boost with an 8.5-second quarter-mile game plan. To get the kind of fine tuning desired for this Fox-body rocket ship, owner Kelly Henry decided to look to AEM Performance Electronics for pinpoint tuning accuracy and power. He managed to get both along with 901 hp and 942 lb-ft of torque at just over 20 psi boost. This thing jams!

AEM Infinity Series 5

The AEM Infinity 508 electronic engine control system takes performance tuning and knowledge to new levels on a par with professional racing, only you won’t have to sell the farm to get there. Check it out: The Infinity 508 is built around a state-of-the-art, 32-bit, 200-MHz automotive processor and Real Time Operating System (RTOS) capable of processing 400 MIPS (millions of instructions per second), which makes this guy fast. By comparison, most systems use 20- to 50-MHz processors. AEM claims that the Infinity ECU has the fastest processing speed of any aftermarket Motorsports ECU currently available. This allows the Infinity to do more faster, in a more stable programming environment, meaning the processor doesn’t get bogged down running computations for the engine while simultaneously executing strategies for boost control, nitrous control, launch control, traction control, and so on, all while logging up to 100 channels at 1,000 samples per second.

The Infinity 508 is designed for racing engines with up to eight bores. AEM tells us the Infinity ECU modules are designed for flexibility across many applications, including fuel-injected 5.0L H.O. Mustangs. Knowing that a major barrier to standalone engine control is the harness, AEM developed a unique approach to creating a quality harness for a wide selection of V-8 engines (see below). Working in his garage, Kelly Henry was able to convert the car from its carburetor and distributor setup to Infinity EFI-ready with AEM High Output coil-near-plug Smart Coils without needing to call tech support. After using the Infinity’s Set-Up Wizard to configure the car, Henry got it started on the first try using a flat VE value in the table.

What this means for you is full tuning capability in ways you’ve never experienced before. All AEM needs to know is airflow, injector size, and your target air/fuel ratio. Then, Infinity, which is a VE-based (volumetric efficiency) system, automatically determines fuel requirements at any rpm under any conditions. This means once you establish the Infinity’s VE table you will never have to make fuel mapping corrections again because it is automatically done for you. The VE table enables you to see what your engine needs in order to make more power. You can see in real time how much air your engine is moving.

Volumetric efficiency changes with every modification we make to the engine. Swap cams and the VE changes. Change out the exhaust system and the VE changes. Do a cylinder head swap and the VE changes. Different induction system and the VE changes again. The result of these changes can be positive or negative. You learn quickly which modifications work and which do not because the Infinity system responds to these VE changes.

Cam profiles and induction packages directly affect at what rpm range the engine will make power. There are profiles and intake manifolds that make power down low and in the midrange, while others do their best work at high rpm. You can have an aggressive cam profile yet not have enough intake manifold or cylinder head to meet the demands of that cam. Or perhaps you have a lot of manifold and not enough cam. Exhaust scavenging also plays a major role in how an engine performs. In fact, not enough attention is paid to exhaust selection and tuning, which hinders performance. Component compatibility is the key to better VE. Infinity enables you to see what you have for VE and where changes and adjustments need to be made.

When it is time to go to the dyno to prove out your modifications made from a baseline test, Infinity enables you to see where the engine’s powerband is and how it relates to VE. AEM tells us that volumetric efficiency generally runs parallel to the engine’s torque curve, with peak VE occurring at peak torque. This is not only something you can feel in the seat of your pants, but it’s something you can see via the Infinity system on a laptop.

AEM explains there are two approaches to electronic engine control and tuning: pulse width and volumetric efficiency. According to AEM, VE tuning allows you to get the fueling dialed in quicker than having to adjust injector pulse width using correction factors, enabling you to move onto other aspects of tuning right away. VE tuning is something you set up going in and basically never have to sweat it out again unless you make a change to the engine’s airflow characteristics.

Universal Wiring Harness

The Infinity 508 needs a reliable network of wiring, sensor inputs, and directive outputs to get the job done effectively. AEM’s Universal Core Harnesses allow you to easily assemble an engine control harness for the Infinity 508 on your Ford small-block or big-block V-8 engine, according to AEM. The harness has the ability to mate to multiple subharnesses for injectors (EV1 or EV6 connectors), coil-on-plug or distributed ignition (including popular dual-sync distributors from MSD and FAST), cam/crank in any Hall or MAG configuration, idle, and more, and the harness has flying leads for common sensors like MAP, oil pressure, fuel pressure, coolant temp, and air temp.

Let’s talk about exceptional attention to detail. A fuse and relay panel is integrated (five relays and seven fuses) to remove load from the ECU circuitry, with flying leads for switched ignition, an optional fused 12-volt relay for auxiliary outputs, and optional +12-volt relay outputs for the fuel pump and fan.

A wideband connector is included for the onboard Lambda controller, too (Henry also added and external X-Series Inline Wideband Controller for feedback control on both banks). A DTM connection for AEMnet CANbus also resides on the core harness, and eight-pin auxiliary ports are included for adding additional sensors and functions. It’s all in there, and you can use what you need. You get a true plug-and-play system that enables you to get back into the action in short order. Wiring is covered in automotive-grade conduit for durability and longevity. Power/ground leads are heavy-duty serrated to ensure a solid connection. What’s more, a thick firewall grommet is included for a clean pass-through to the Infinity ECU. All wires and connectors are clearly labeled for ease of installation.


We’re taking Henry’s 347ci stroker and fitting it with AEM coil-near-plug ignition to give this boosted beast spot-on ignition control. AEM explains to us that the tradeoff between adequate spark energy and adequate spark duration comes to an end with AEM’s High-Output Inductive Coils. These are the first inductive coils that deliver CDI-like spark energy and voltage along with the long spark duration necessary for vehicles running high compression, high rpm, forced induction, and/or nitrous engines. Henry’s turbocharged small-block definitely comes under the description “forced induction.”

Enthusiasts like Henry who have forced-induction, high-rpm engines or who run nitrous oxide are aware of the compromises that come with using inductive coils instead of converting to a capacitive discharge ignition (CDI) system. Boosted and nitrous-fed engines will not tolerate spark interruption. Though inductive ignition coils deliver lengthy spark duration along with simplicity, they don’t have the electrical energy to adequately ignite the mixture under extreme pressures.

Likewise, CDIs deliver an intense burst of spark energy, according to AEM, but with practically no spark duration, which makes having just the right air/fuel mixture in the combustion chamber paramount for durability and performance. You don’t have to live with this compromise anymore with AEM’s High-Output IGBT Smart Inductive Coils. These eight individual capacitive discharge ignition coils do the grunt work of fuel light-off without consequence. They get the fire lit under extreme conditions.

When you equip a powerful turbocharged small-block with a fiercely intelligent form of electronic engine control like Infinity and tie it in with the Smart Inductive Coils that Henry has installed atop the valve covers, you get needlepoint spark timing and fuel curve to where all you have to is aim and shoot.

While the AEM Infinity 508 system and Smart Inductive Coils are an exciting twist of technology, AEM will tell you they are not for the novice. Having a fundamental knowledge of electronic engine tuning and function is necessary to get up and running, although many reading this with wiring ability will be able to install everything themselves. AEM has a factory-trained tuner base nationwide who can get an Infinity dialed in safely and reliability on a dyno, followed by a responsible track test to see how the engine performs out there under real-world conditions. Henry’s result? A personal best 8.48 at 170 mph off the trailer at his first event after the conversion.

1. First order of business is this close look at the AEM High-Output IGBT “Smart” Inductive Coils. You can install these coils close to the spark plugs on brackets. You may also do as Kelly Henry did. He fabricated and welded coil mounts to the valve covers as shown to minimize coil distance from the spark plugs.

2. Here is the 5.0L DIS module, which drops in place of the distributor.

3. This is AEM’s Universal Core Wire Harness for the Infinity 508 electronic engine control system. Everything necessary to a successful Infinity install is here, including all input sensors and output directives, fuses, relays, and more.

4. The Infinity 508 electronic engine control systems deliver state-of-the-art electronic fuel injection (EFI) control capabilities normally found only in high-end motorsports competition. The Infinity 508 makes this technology affordable for both professional race teams and amateur racers. What’s more, AEM makes this system easy to install and get up to speed with simple plug-and-play technology and all the associated wiring harnesses.

5. We’re installing the AEM Infinity 508 system in a 1990 Mustang GT drag car. A 2-inch hole is being bored in the firewall to accommodate the AEM Universal Wiring Harness. Henry has chosen to bore this pass-through at the cowl and route the harness through the cowl and down through the vent into the right-hand cabin area. Another approach would be to bore this hole below the cowl vent balloon assembly for a straight shot into the right-hand dashboard area.

6. Henry routes the AEM Universal Wiring Harness through the cowl area to the vent to the right-hand interior area behind the dashboard.

7. The AEM Universal Wiring Harness lays all connections where they belong. All connectors are labeled and easily identified. These labels, coupled with detailed instructions, will get you through the installation.

8. These two grounds must be solidly connected to the body and/or the engine block/heads.

9. Five connectors provide power to and from the Infinity 508 system. Red is obviously positive power and black negative ground.

10. Multiplex plugs make it easy to connect and disconnect the engine electrics any time you have to pull the engine, heads, or induction.

11. Fuel pump, fan, and power leads are marked for easy identification. You will be stunned at how easy the Infinity 508 system from AEM is to install.

12. Henry routes and connects the fuel injector leads for the Five-0 Motorsports Black Ops injectors on the left-hand side of his 347ci stroker. Because all of these leads are labeled, installation falls right into place. A footnote to this installation is the need for high-impedance fuel injectors when using the 508. High- or low-impedance injectors can be used with the larger Infinity 708.

13. AEM provides everything you need to get the Infinity 508 up and running. You are going to need the tools, however, such as wire crimpers, cutters, and the like. Many of the sensor plugs have to be crimped onto color-coded and labeled wires, then connected as shown here.

The Motherland

We’re going to go inside the cockpit to get Infinity 5 installed along with fuses and relays. You can locate the Infinity ECU just about anywhere you’d like as long as it is dry and away from excessive engine heat. Wiring should be wrapped, secured, and protected.

14. Kelly Henry has chosen to fabricate an electronics mounting board for the Infinity and fuse/relay box.

15. The Infinity 508 is a genuine plug-and-play package once all wiring is properly routed and secured. Think of the Infinity as a director or traffic cop for electrical signals. Power goes into the Infinity, then it evaluates all sensor input faster than you can think and makes a determination on fuel delivery and spark timing and intensity. It does this while also including the ability to control boost, nitrous, traction, launch, and more—all while data logging 100 channels at 1,000 samples per channel.

16. Fuses and relays for the Infinity 508 are located in this protected yet easily accessible panel tied to the AEM Universal Core Wiring Harness. The Infinity 508 is easier to install and service than OEM.

17. The fuse/relay box can be located anywhere near the ECU so long as it is cool and dry. Easy access to this electrical box must also be considered, especially when you’re going racing.

18. Back at Henry’s 347, we have connected each of the ignition coils, which can be considered independent ignition systems within the AEM Infinity 508. Did you know you can dial in spark timing and intensity on a cylinder-by-cylinder basis with the Infinity? It treats each cylinder as a one-cylinder engine in terms of injection pulse width and spark timing and intensity, which takes engine tuning to new levels.

MMFF Performance Snapshot
1990 Mustang GT Hatchback
Ford Performance Boss Block
AFR 205 cylinder heads
Edelbrock Super Victor induction
Custom-grind billet cam
Five-O Motorsports Black Ops 2,000cc injectors
AEM Infinity 508 ECU
Garrett GT47-88 Turbo
901 hp
942 lb-ft of torque
Mike’s Transmissions Powerglide with PTC Converter
Best e.t. 8.48 at 170 mph