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A Guide to Modular Motor Coil Packs

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Ignition systems have come a long way in the last two decades. It used to be if you were going to upgrade your ignition system you’d most likely buy a control box, high output coil, better spark plug wires, and a distributor. While this is still the case on a lot of older engines, it has not been the case on Mustangs or Camaros since the mid 90’s.

Today’s ignition systems are 100% computer controlled, there is no breaking out the timing light and wrench to adjust the distributor. A late model Mustang’s distributor and plug wires are now merged into one piece, called a Coil on Plug (COP) and if you want a hotter spark, it’s about the only way to go. We are going to take a look at the leaders in COP technology for mod motors and then follow up with a Granatelli coil packs install on our supercharged 2011 Mustang project [2].

Why Upgrade?

Even a mildly modified or completely stock vehicle can benefit from an upgrade to higher output ignition coils. By running these coils instead of the stock units you can expect a “hotter” spark. What this means is the voltage output of the coils is higher than stock, allowing the spark plug to ionize the gap between the ground and electrode more easily or to jump a larger gap with greater ease.  This also means that the coils firing time can be longer allowing for more complete combustion of gasses in the chamber.

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Upgrading your existing coils on stock or modified cars can have more than just horsepower benefits. GMS Pro-Series Xtreme Coils shown here.

Larger plug gaps or jumping the existing one more easily allows for better drivability and more complete combustion – it also allows combustion to occur more quickly. This not only allows the current combination to make more power but can also improve idle quality, throttle response, starting and even fuel economy.

Increases in cylinder pressure are usually the main reason why most people find it necessary to upgrade their ignition system. This increased pressure may be caused by higher compression in naturally aspirated engines or the power adder of your choice, turbo, nitrous or supercharger – however as we said earlier even a stock engine can see some benefits from a coil upgrade.

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The Players

For this article we are focusing on coil on plug (COP) ignition systems which first made their appearance on a Ford in 1997 (F150 5.4L) and on the Mustang since the New Edge body style made its debut in 1999. The coils themselves have also changed several times over the years to require different part numbers for 2-valve, 3-valve, 4-valve and 4-valve Coyote engines.

Our research indicates that stock coils in most Mustangs equipped with COP ignition have an output voltage of 20,000 volts. While this sounds like a lot, we’ve found that one of the companies offering replacement coils offers as much as 65,000 volts of output per coil. That level of output is well over three times the output of the stock part they replace.

MSD [4]

If you’re a performance enthusiast you know the name MSD. The company is synonymous with race winning efforts in nearly all forms of motorsports. Even today if you’re at the track and look under the hood of nearly any car with a distributor chance are pretty good that you’ll find an MSD ignition system or MSD components there.

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MSD Offers coils for 99-2010 Mustang V8's 2, 3 and 4 valve.

Like their competitors, MSD offers a direct replacement ignition coil for Ford Coil On Plug equipped vehicles. Specifically for 4.6 liter Mustangs from 1999-2010. MSD’s parts offer significant design benefits and performance increases over stock including an output of 38,000 volts. This output voltage offers customers significant improvements in idle, throttle response, starting and a gain in horsepower. MSD recommend their coils for stock, naturally aspirated or forced induction applications.

While MSD does not currently have any coils available for the 5.0L Coyote engine they assure as they’re working diligently on the development of such a product.

MSD’s Coil on Plugs

Performance Distributors [6]

[7]Specializing in ignition parts, Performance Distributors has developed coils, distributors and many other parts for a wide range of vehicles over the years. For the Mustang they offer their Sultans of Spark (SOS) coils. These coils provide a definite increase in voltage over the stock units with 40,000 volts of output. SOS coils utilize a heavy duty spring for a better connection between the spark plug and ignition coil. These coils come with a one year warranty.

Performance Distributors tells us you can open up the gap on the plugs all the way to .065” (stock spec is .040-.050” on most Mustangs). This increase in gap again gives you all those benefits. The additional output of these coils also makes them candidates for more heavily modified cars such as those running boost or nitrous. However, cars running power adders should probably run a tighter gap due to the increased cylinder pressures. Performance distributors does not currently have a Coyote application available.

Performance Distributor’s SOS Coil on Plugs

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ACCEL [8]

Accel ignition offers their Super Coils coils for stock or modified applications. These coils offer performance in the range of 10-15% improvement over stock. [9]

Installing these coils should improve idle quality and drivability and offer an increase in horsepower at the tires as well as improved throttle response from idle and tip in. Another added benefit should be better, faster starting. These coils use an optimized design over stock with better windings and magnetic steel cores.

ACCEL recently released the Super coils for the Coyote engine and we’ve seen claims online so far of about a 5-10 horsepower gain at the tires. ACCEL also offers coils for older 4.6 two, three and four valve engines.

American Muscle has tested [10] a set of Accel coils on their 2011 Mustang project and they recorded a gain if 10 rwhp and 9 rwtq with only an intake and throttle body as supporting modifications.

Granatelli Motor Sports [11]

Granatelli Motor Sports a broad range of products when it comes to COP ignition for Mustangs. Products range from a stock type replacement to coils with 65,000 volts of output which is over triple what the stock coils are capable of. GMS claims their coils will improve fuel economy, drivability, horsepower and won’t affect the factory warranty.

GMS uses better materials in both quality and in size for the winding as well as better processes for coil construction, as the windings of GMS coils use a finer wire diameter over the stock design. While a stock ignition coil has a turn ratio of 42 to 1, the GMS coils have a turn ratio of 72 to 1. This helps them get the increase in output voltage. This difference in windings also allows for a more accurate and precise primary resistance of .0394 ohms and a better secondary resistance of 5.01K ohms.

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Granatelli Motorsports offers the widest range of coils for Mustang applications, their line of coils for the 5.0 Coyote offers something for everyone from stone stock daily drivers to all out track warriors.

Another feature of most of the GMS line of coils is the solid stainless connector. If you look at a stock coil the connection is made utilizing a very thin spring, it almost looks like something you’d pull out of your favorite ball point ink pen. GMS has designed a solid stainless steel connector that is similar in appearance to a rope.

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Better Connections

 

 

 

This stainless steel rope connector kit available for any GMS C-O-P coil is designed to transfer voltage more effectively while eliminating RFI and EMI interference. These connectors come standard on many GMS coils, including the Pro-Series Xtreme coils we’re installing on our Vortech blown ’11 5.0.

This connector is obviously sturdier in design and better suited for carrying the higher voltage loads. You’ll also find on these connectors an RFI/EMI ring to prevent radio frequency interference so nothing interferes with your car’s stereo or electronics GMS’s JR Granetelli says, “We call it a magic donut, this ring suppresses all the EMI and RFI as it goes through the coil.”

While spring type connectors are still used on their Street Fighter and OE replacement series coils, the stainless connectors are included with many of the coils standard and compatible with all GMS coils. They can also be purchased separately to upgrade your existing stock coils.  Grantelli sums up the advantages offered by their coils like this, “They are a direct fit, exceed OEM standards and offer a lifetime warranty.”

All GMS coils are 100% OBD-II compliant and safe so you have no worries about damaging an expensive PCM either.  Another great feature that we really liked is that the coil body, bracket and tower are all molded into one piece and utilize brass inserts. This helps to relieve compression pressure that occurs when coils are installed and tightened down, which in turn ensures you get a better installation and reduces the risk of damaging a coil during installation.

This molded in design allows the customer to use a stock type spring or the GMS connector for their coils. This design is also an improvement over the “potted” stock design which is epoxy or gel filled. GMS offers a 90 day no questions asked money back guarantee on their coils. After 90 days they offer a lifetime guarantee against parts failure and will exchange a defective coil for a new replacement if one fails.

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Granatelli offers their coil on plugs in a variety of ranges. The MPG coils produce 35,000 volts, while the Hot Street version produce 45,000 volts. For forced induction Granatelli recommends their Pro-Series and Pro-Series extreme, which produce 60,000 and 65,000 volts respectively.

Granatelli Coil On Plugs:

Doing the math on fuel economy in a stock type application Granatelli says, “The reality of it is if you were to buy a set of our coils they’re going to save you realistically about $8-$10 per tank of fuel.” With that in mind if your Mustang is your daily driver and you burn at least a  tank of gas per week in your car, you’re looking at an annual savings potential of over $500, just about paying for the upgrade in a year’s time. “This is not marketed as a payback but the reality of it is, it does give you better mileage, but what’s really important to our company is that’s just an added benefit it really gives you more performance too.”

Installation

GMS released coils for the Coyote engine in March of 2011, fairly close to the same time these cars were hitting the streets for the first time. Granatelli explains,”The average customer reports a 5 to 8 rwhp increase on natural aspirated motors and as high as a 25 rwhp gain on forced induction applications.” For our testing purposes we will be installing a set of GMS Pro-Series Xtreme coils on our Vortech Supercharged 2011 Mustang GT.  These coils are specifically designed for boosted applications where weaker coils might fail, these are rated at 65,000 volts each to ensure we don’t blow out the spark at high RPM or high boost conditions. The installation of the coils really is a cinch, the Coyote might in fact be the easiest platform to swap coils on in recent memory. Installation should take you about 30 minutes and you’ll only need some basic hand tools, namely a ratchet, sockets and extension.

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Left to Right. Swapping the coils is a matter of removing the coil cover, sliding out the red lock, removing the retaining bolt and gently pulling out the stock coil. To install simply reverse these steps. The whole job with basic hand tools usually takes around 30 minutes and no additional tuning is required.

To install simply remove the coil covers, disconnect each coil and remove the bolt that secures it to the valve/cam cover. Firmly, but gently pull up on the coil, using a slight twisting motion will help the connection loosen and make it easier to break the seal, the coil will disconnect from the spark plug and slide out. Make sure your spark plug tubes are clear of any debris then reverse the procedure to install the coils.

Be certain you tighten all the coil retaining bolts back down, but don’t over tighten them or you could strip the threads or crack the coil housing, factory torque spec on the retaining bolts is 53 lb-in. You should also check to make sure that you have reconnected all the coil electrical connectors securely before finishing up. There’s nothing else special to do at this point but fire up the car and make sure you don’t have a misfire. Install time averages about 30 minutes, it took us 2-3 minutes total per coil on average to perform this swap.

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On the Dyno

The dyno is the real test of any manufacturer’s claims of power improvements. Track conditions can change, seat of the pants feeling while good for impressions is still all only subjective. So we of course strapped our Coyote equipped GT to the rollers for a few spins.

We’re still amazed to this day at the consistency of the Coyote engines. Even though our Vortech supercharger was installed 20,000 miles ago and the plugs have yet to be changed (it’s important to note they’re one step colder than stock), the car baselined within a few horsepower of our original best pulls done at the time of the supercharger installation. It’s also important to note that we have done absolutely no additional tuning on this car since the charger was installed. Meaning this car still runs the ultra conservative Vortech factory tune, which has a air fuel ratios at 10.8-11.1:1 at wide open throttle.

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Baseline pulls before swapping the coils showed a max of 564.4 rwhp and 456.2 rwtq. After swapping in the GMS Pro-Series Xtreme coils we made a gain of nearly 20.4 horsepower and 17.7 ft-lbs under the curve. That’s pretty significant for thirty minutes worth of work.

Where it gets even more interesting however is when you breakdown the information in the dyno graphs. On average we picked up 15.3 rwhp and 14.3 rwtq across the entire RPM range. What that means is that unlike some modifications where power increases are not seen until high RPM’s, we’re seeing power across the engine’s entire operating range which translates to a noticeable improvement in the car’s performance. With respect to power at peak output, at 6,000 RPM these coils really had everything coming on strong with increases of 20 HP and 18 lb-ft.

Driving

The modern era of performance we’re currently experiencing is in many cases can be a double edged sword. As manufacturer’s continue to engineer better performing and more efficient engines it takes better performing parts to make significant gains, sometimes those parts come at great cost. We’ve seen people spend well over what a set of these coils cost to gain half the horsepower, which in these economics times doesn’t necessarily make good fiscal sense. Further as JR Granatelli pointed out if you’re using these coils on a daily driver you can expect an increase in MPG that will pay for itself in just a few months.

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While the dyno gives us the numbers, the real story is in how much throttle response crispness and part throttle driving are improved just cruising around town, not to mention when we stab the gas.

Heading down the road you can definitely tell a difference in the car’s throttle response, this is especially noticeable in sixth gear at low RPMs, the engine is much more responsive. When your engine was already making 570 rwhp it’s hard to notice a peak gain of 14 rwhp. The mid level gains are what you really notice a difference, this is where the engine spends the majority of it’s time rowing through gears and cruising around town. This is why all the dyno data is so important why even though we all marvel at peak horsepower numbers it’s always important with any modification to view all the data and get a complete picture.

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