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Bolt-On Coil-On-Plug Tech for Fox-Body & SN95 Mustangs
Pro-M Racing brings the latest ignition technology to the venerable small-block Ford
The forefathers of speed could only dream of street cars that were both reliable and capable of 800 hp or more—funny thing is, these days it is commonplace. We can thank technology’s rapid advance along with a strong performance aftermarket and solid stock platforms for the great times that are upon us. In fact, with the advent of wide-band oxygen sensors, ultrapowerful ECUs, and remote tuning, the modern Mustang enthusiast almost forgets that not long ago the now classic Fox-body rewrote the rules of late-model Hot Rodding with its EEC-IV fuel injection system. Just as the first Mustang flanked with the 5.0 badges was a game changer, the current crop of Mustangs adorned with the very same fender badges are changing the game for the very same reasons.
Early pioneers used timing lights and adjustable fuel pressure regulators as their tuning weapons of choice, but those were eventually replaced with chip tuning, a revolutionary step forward at the time but not without its flaws. Add a new intake? Time for another chip. Swap the cam? Another chip. Upgrade your throttle-body? Another chip. You get the point. Paying a tuner to re-dyno your car and burn a new chip with every modification can be costly.
Despite the advances in technology in recent years, Fox-body and SN95 owners were relegated to tried-and-true chip tuning unless owners wanted to tackle wiring a standalone ECU from scratch; that was, until companies like Pro-M Racing released a plug-and-play standalone ECU system for small-block–powered Fox and SN95 chassis.
We have had great luck with the Pro-M standalone ECU system in our 1992 SSP coupe project car, Smog Legal Killer. For the details you will have to check out the Mustang360 website, but just know that we made an emissions-legal 610 hp and 595 lb-ft at the tires, ran 10.70s at 130 mph, and pulled over 1.0 g’s with only a wheel and tire change. An integral part of our emissions friendly combo was the Pro-M Racing plug-and-play standalone ECU. We thought it best to hit the high points of the system before we break into one of the company’s latest options, coil-on-plug technology.
The brains behind it all
When Chris Richards, owner of Pro-M, set out to design a plug-and-play ECU for the Fox-body and SN95, he pulled out all the stops. Richards wanted OEM quality and reliability, so he sourced an OEM-based Spanish Oak computer and then modified it with even more computing power. Tech heads will note that it is, in fact, a souped-up version of the Visteon units found in the V-10–powered trucks of a few years ago, which means it takes a Fox-body to a whole new level.
The ECU is also self-diagnosing and is wired into the factory CEL light, which means should the ECU itself or anything in the system malfunction, simply use the supplied OBD-II plug (yeah, the Pro-M computer comes with an OBD-II plug) and scan the codes just like a new car.
Cracking the code
A high-powered ECU is only part of the equation. The right software is also needed to make the perfect standalone computer. Pro-M takes a unique approach few competitors do. Pro-M give the user full control over the air/fuel ratio and timing using an elite formula the company calls “load and lambda.” Without getting bogged down here in an engineering lecture, we’ll say that Pro-M uses the mass airflow sensor (MAF), the supplied wideband oxygen sensors, and other settings in the ECU to determine the load of the engine by way of the amount of air ingested divided by the maximum potential of the given engine. Pro-M takes it one step further by also incorporating lambda rather than the typical air/fuel ratio because lambda is more accurate and doesn’t change depending on the given fuel—users select their given fuel, and the ECU adjusts accordingly.
While all that might sound complicated, in actuality Pro-M has taken the trouble out of tuning because using the aforementioned load and lambda figures allows them to create a preloaded tune that is nearly perfect for all combos. No, that’s not a typo. We’re not kidding. On Smog Legal Killer we swapped pulleys, cams, and intake manifolds, and no matter the change the tune was always spot-on because the airflow changes seen at the MAF were then accounted for in the tune—it really is a wonder.
Other noteworthy features include a two-stage rev limiter; decel features that cut fuel when decelerating for better fuel mileage; built-in fan control wiring; an interface that uses the stock coolant temp sensor to activate electric fans; nitrous and methanol control capabilities; dual MAF capabilities; and individual cylinder tuning, which means if your back cylinders are lean you can simply fatten them up for added safety. If that’s not enough, it also has programmable outputs should you want to run a shift light or a failsafe. For those who'd prefer to run Speed Density or Speed Throttle (Alpha N) instead of MAF-based tuning, the Pro-M will easily accommodate those as well.
While the incredible Pro-M plug-and-play standalone isn’t newly released, the new coil-on-plug ignition setup is. Before we dive into the details though, know that users can order their standalones with the traditional single coil and distributor setup or with the new coil-on-plug harness that features eight individual coils, one for each cylinder. Those who already have a Pro-M standalone system and want to upgrade can buy the coil-on-plug harness separately.
It’s no secret that most modern performance cars have gone away from single coil setups, like what was originally found in our Fox-body, in favor of coil-on-plug or coil-near-plug ignition systems for a hotter, more consistent spark. In this case, eight coils is better than one. But why? It’s all about timing.
According to Richards, all ignition coils have an optimum charge and discharge time. In a single coil system, the coil must fire its charge to a given cylinder and then quickly recover (recharge) before it can discharge into the next cylinder. So long as the coil has the needed time to deliver a full discharge for each cylinder event, all is well.
With a single coil, the charge and discharge cycle becomes a problem as engine rpm increases, since there is less time between cylinder events and therefore less time to achieve an optimum charge and discharge—at some point the coil doesn’t have the time to completely charge before discharging, which means the spark is so weak that it has a hard time jumping the spark plug gap. The old and inefficient methods of combatting the inherent problem included a pair of commonly utilized but equally flawed fixes. The first was to close the spark plug gap, but according to Richards, that can only make so much difference. The second method was to add a CDI box that cranked up the current to the primary side of the coil, therefore increasing the output of the coil as well. Richards explained that while the output is increased, the discharge time is also shortened, which means it isn’t a complete fix.
What’s the better fix for increased charge and discharge times with a coil? Add multiple coils, that’s what. “Where a single coil system has to fire four times per engine revolution, each coil in a coil-on-plug system only has to charge and discharge one time for every two engine revolutions, which means the spark will be hotter, more consistent and incredibly reliable compared to a system with a single coil,” Richards explains.
That’s exactly what Pro-M did: added an octet of Delphi coils, the hotter ones with the heatsink, to the already stellar standalone system, so even the venerable small-block Ford engines can be brought into the 21st century.
As you’d expect, the coil-on-plug upgrade is much more than a powerful set of coils. It starts with the ECU and its unique programming. The Pro-M ECU uses an integrated ignition module inside the ECU with eight individual drivers (but it has the capabilities for 10 in case you want a V-10 swap) that run the ignition coils for the utmost accuracy. This was made all the easier when Pro-M decided to be clever and use the OEM distributor as a cam and crank sensor so older engines not so equipped could communicate with the powerful Pro-M processor.
“Since distributor-type ignition systems are typically victims to distributor gear lash that can cause inconsistent signals, when we designed our original standalone system we made sure the ECU averaged the signals produced by the distributor," Richards says.
This incredible software strategy means that no matter whether you’re using the standard single coil Pro-M system or the coil-on-plug Pro-M standalone, the coil discharge and charge events will be powerful, consistent, and accurate. In fact, according to Richards, if you were to examine the spark advance on a typical ignition system with a CD box, ignition timing for all eight cylinders would be off—but thanks to the high-tech software from Pro-M, ignition events happen at precisely the right moments. As you already know, the more accurately timed the spark the more efficient the combustion.
Mounting the coils
When it came time to install the Pro-M coil-on-plug harness, we paid a visit to Stanton Performance, the Northern California Mustang specialist, who helped us with a tidy install. While some choose to run longer ignition wires and either mount the coils on custom racks affixed to the firewall or hide them elsewhere in the engine bay, we chose to mount them in plain view for all to see.
Initially Stanton Performance was going to modify coil racks, but space was at a premium thanks to our tall Coast High Performance valve covers and the Trick Flow intake manifold, which necessitated that we mount the coils directly to the valve covers in a staggered format. Stanton Performance carefully drilled and tapped the valve covers and then used plastic isolators to securely mount the coils for an OEM-like fit. We can’t even count how many people missed the coils on first glance when the hood was popped, only to do a double-take in bewilderment about a coil-on-plug setup controlling a small-block Ford. Ah, the marvels of technology.
The first thing you’ll notice is the motor cranks longer before starting—not because there’s a problem, but because according to Richards, the motor must make one entire revolution to orient the crank trigger before firing. From there, throttle response was much stronger and the car not only revved crisper but pulled cleaner toward redline when the boost from the Vortech V3si blower comes in hard. Considering that we liked the former Pro-M setup with the stock FoMoCo coil, we were blown away that we felt an improvement in throttle response with the new coil-on-plug setup.
1. Pro-M Racing is bringing the latest technology to the venerable small-block–equipped Fox-bodies and SN95s with its plug-and-play standalone ECU system, which is available in two versions: the coil-on-plug setup we’re installing here, and the single coil setup that uses a distributor like we thoroughly tested on Smog Legal Killer.
2. We’ve said it before and we’ll say it again: The quality of the harness on the Pro-M ECU systems is topnotch. You’d swear it was OEM thanks to quality construction, factory connectors, and perfectly tailored lengths for the tidiest of installs.
3. There are many methods of mounting the coil packs, but due to the tight space constraints from our tall Coast High Performance valve covers (as a result of the ultralong Trick Flow 1.73 roller rockers) and the Trick Flow Street Burner intake manifold, we decided to mount them directly to the valve covers. We used masking tape to help us measure and mark the mounting surface before drilling and tapping.
4. After measuring to ensure that all of the coils would clear engine-bay obstructions and marking the spots, we drilled each of the holes.
5. Next it was time to tap the holes for the incoming coil mounts. Again, while space constraints forced us to mount them directly to the valve covers, you could use coil racks mounted atop the valve covers or relocate the coils out of sight for a super-sano install.
6. Here is a closer look at the tapped hole and the shiny chrome on our Coast High Performance Venom valve covers.
7. The passenger-side valve cover was especially tight due to the throttle-body and intake tube cutting off precious space between the valve cover and the intake manifold. Our solution was to mount three of the coils forward of the throttle-body and one behind it.
8. Here is a closer look at the tidy install from Stanton Performance with the coils all securely mounted in place.
9. Stanton Performance chose to use low-profile, hex-head bolts and plastic isolators to combat vibration. It also doesn’t hurt that they look great too.
10. Pro-M Racing uses the hottest coils for its kits that offer a reliable and strong spark no matter how much cylinder pressure you throw at it. Here is another perspective on the installed coils.
11. Stanton Performance bought low-profile, cut-your-own spark plug wires from the local speed shop, Monument Car Parts, and cut them to the desired lengths.
12. Pro-M has always been ingenious, so when the company realized that the stock distributor was tremendously accurate (when coupled with Pro-M’s trick software) as a crank trigger, it integrated the unit into the standalone system with great results. This trick billet aluminum cap comes with the kit to dress the hole where the cap and wires once sat.
13. Have a look at that! A row of high-tech, high-output coils controlling the sparking duties on our 347ci stroker small-block. Thanks to companies like Pro-M, the venerable small block continues to get better with age.
Finally, a Proper High-Flow Fuel Pump Hanger
The Mustang aftermarket has been selling high-flow fuel pumps for decades, but until now nobody sold a properly modified high-flow, stock-style fuel pump hanger for 1986-1997 Mustangs. Why do you care? Because the big pump is only half the problem.
“The quarter-inch return tube in the original hanger cannot flow any real volume of fuel,” says Pro-M’s Chris Richards. “At idle and cruise, the engine’s fuel demand is very low and the vast majority of the fuel being sent to the engine must return to the fuel tank. The fuel pump will attempt to deliver its rated volume of fuel regardless of engine demand. So if we are using a 255-lph pump, nearly all of that fuel needs to return to the tank via the return line. If we need a 3/8-inch line to get 255 lph of fuel to the engine, don’t we need that same size line to get it back to the tank? We absolutely do.”
If fuel can’t pass through the return line at a volume at least equal to the feed line, then the fuel pressure regulator can’t regulate the fuel, the fuel pump can’t move the proper volume of fuel it’s designed for, and then it cavities, sending air through the lines, which can cause lean conditions and prematurely burn up a fuel pump.
Richards says, “Fuel supply problems also show up in the form of drivability problems, fuel starvation, and eventually engine failure. The Pro-M Fuel pump hanger solves the three major issues with the stock hanger.”
How does it solve the problems? First, both the feed and return lines are 3/8 inch in diameter for proper fuel flow. Secondly, both AN-6 fittings are used for the fuel line connections, allowing the direct connection of AN-6 fittings to the Pro-M hanger. While adapter fittings were previously available that connected AN-6 fittings to the stock hanger, they were as restrictive as the stock hanger itself because the larger fittings were simply connected to the stock tubes. Lastly, the return tube goes to the bottom of the tank, eliminating a serious design flaw in the stock hanger—the return tube in the stock hanger sprays the return fuel onto the surface of the fuel in the tank. This isn’t a huge concern with the original 88-lph pump, but with larger pumps this causes aeration of the fuel in the tank, resulting in aerated fuel being sent to the engine.
According to Richards, other companies might sell stock replacement hangers with AN fittings attached to the stock quarter-inch return line, but nobody else offers a hanger that resolves all of the real issues with the hanger.