5.0 Mustang & Super FordsHow To Engine
E-Force Coyote Blower - Force Unleashed
Edelbrock packages its supercharger for the latest 5.0
Horse Sense: If you’re interested in a detailed understanding of the new Coyote blower’s background, inspect our Aug. ’09 story on the Three-Valve E-Force supercharger at www.mustang50magazine.com/techarticles/m5lp_0908_edelbrock_e_force_s197_supercharger/index.html. That story has much that pertains to the ’11 Mustang GT kit we’re introducing here.
As we’ve said before, from the instant we saw our first Coyote engine we’ve been excited by the thought of supercharging it. And sure enough, to date the blowers we’ve sampled on the ’11 Mustang GT have been successful, to say the least. Even better, we’re happy to be back reporting on another winning Coyote blower aimed at real-world Mustangs.
This time it’s aftermarket giant Edelbrock that has fitted its E-Force positive-displacement supercharger to the Coyote. In a few words it’s an excellent real-world combination. The performance is strong and the support what you’d expect from a large company such as Edelbrock. Certainly the Big E will take a front-row position in the ’11 Mustang GT owner’s list of supercharger options with its new offering.
To save you from thumbing to the back of the article, we saw 466 rwhp on Edelbrock’s chassis dyno in stock kit form—that’s at just 4.5 pounds of boost and breathing through the stock airbox and throttle body. On Edelbrock’s engine dyno the numbers were 575 hp with a 1/4-inch-smaller pulley, and 636 hp with the same smaller pulley and a less restrictive inlet. To put that in perspective, with about 3 pounds less boost, the Edelbrock Coyote makes the same power at its tires as an Edelbrock-assisted Three-Valve does at its flywheel. Another way of looking at it is the Coyote gains 120 hp at its tires with the stock Edelbrock kit. It’s enough to make you want to howl.
Rob Simons is Mr. Supercharger at the sprawling Edelbrock HQ, and after our coverage of the Edelbrock blowers for the Three-Valve S-197 Mustang, he figures the Coyote version is pretty easy to understand. That’s because the ’11 Mustang GT E-Force blower and the Three-Valve version differ only in the blower’s runner length, throttle body, front drive section, drivebelt and pulleys, and, naturally, the tuning.
On the other hand, the new blower’s basics are easy enough to understand even if you’ve never seen the Three-Valve variety. It all starts with the well-regarded TVS rotors supplied by original-equipment supplier Eaton. These twisted Roots-style rotors are designed for Eaton’s original equipment business and whittled out by sophisticated CNC machines, so they are durable, quiet-running units. In fact, they are the same rotors as used on Roush Mustangs and ZR-1 Corvettes.
Edelbrock makes everything else, casting its own supercharger housing, manifolds, runners and so on. The Edelbrock design places the supercharger low in the engine’s valley, blowing upward through an air-to-water charge cooler. The charge air then turns 180 degrees, dropping nearly straight down 15-inch-long runners and into the cylinder heads. This hides the blower under the intake manifold, so the supercharger is not immediately apparent visually with the view being dominated by the intake runners.
Those long intake runners are a focal point of the E-Force blower and aren’t there by accident. In short, the runner length aids breathing in the 2,500 to 5,500 rpm range by taking advantage of a pressure wave keyed by the intake valve opening (Edelbrock knows about such things). This is in the prime street rpm range, promoting respectable off-boost torque and fuel economy, a muscular midrange, and streetable top-end power.
Yes, these runners are also an airflow restriction at high rpm and boost levels, but we doubt the effect is of any practical concern at non-racing boost levels. In any case, the torquey long-runner design is well matched to Edelbrock’s target of street-friendly performance and slightly lowers the heavy supercharger to preserve handling.
Another long-runner characteristic is lower-than-expected boost, the E-Force/Coyote making a nominal 4.5 pounds compared to the E-Force/Three-Valve combination, which is more of a 6- to 8-pound operation. As Rob puts it, “With the longer runners, the manifold is ‘tuned’ for an rpm range of 2,500 to 5,500 rpm, so while in this operating range, the boost pressure will be much lower, for a given air flow rate … The traveling wave is helping to evacuate the plenum more effectively, thereby lowering the restriction, thereby lowering the boost pressure. At high rpm, that advantage goes away, and you see the boost begin to rise. It is a trade-off. We believe that the majority of driving is done in the 2,500- to 5,500-rpm range, so we chose to tune the runners for that range.” And that is why the E-Force makes happy power at just 4.5 pounds of boost.
As with all E-Force superchargers, this blower breathes from the front. This gives a short, direct air path and packages easily under the Mustang hood. Because the Coyote throttle body is already a generous 80mm, it is retained with this E-Force blower.
Making room for the incoming air, the blower’s drive mechanism connects to the front of one rotor, which is in turn geared to the other rotor at the rear of the rotor pack. Careful blending of the intake air passage and the driveshaft ensure good airflow into the supercharger. Thanks to minor packaging differences between the Three-Valve 4.6 and Coyote 5.0 engines, the drive snout on the Coyote E-Force is similar, but not identical to the ’05-’10 Edelbrock Three-Valve E-Force kits.
The standard Coyote kit also retains the stock airbox and mass air meter, although a replacement air-inlet hose is used to accommodate the slightly displaced throttle body. Reusing the airbox and its built-in hydrocarbon trap avoids legal complications with the California Air Resources Board; a freer-breathing cold air intake is optional for off-road applications.
We’ve seen the E-Force/Coyote combination doesn’t need much boost, and consequently its need for charge cooling is minimal as well, but this kit essentially has the same good water-to-air charge cooler found on the company’s Three-Valve E-Force kits. It consists of a flat-element intercooler inside the supercharger assembly, plus the heat exchanger mounted just behind the front bumper and an electric water pump to circulate the coolant. A plastic header tank provides fill and venting points.
For daily runabout duty the intercooler is a nicety, but it comes into its own when having a long horsepower session on back roads and plays an important role in steadying the air-charge temperature during hot transients such as big decelerations followed by wide- open throttle. It’s also needed with the elevated boost pressures generated by a small blower pulley, which many of these Coyote kits will no doubt see.
It was only a few years ago that chronic belt problems—thrown, shredded, and slipping—were the constant background squeal in the Mustang supercharging world. Attention to engineering details has retired those issues says Rob, and in Edelbrock’s case collaborating with an original equipment belt-drive specialist engineering firm was key in developing a trouble-free drive. Extensive computer simulations of belt drive loads and dynamics were the main engineering thrust, with approximately 20 possible belt and pulley layouts thoroughly analyzed to arrive at a quiet, stable system.
Naturally Edelbrock took advantage of the notoriously unused-by-Ford bosses cast into the timing cover to mount a flat aluminum plate. The plate, in turn, provides mounting for a busy bunch of idler pulleys plus a seriously upgraded belt tensioner. (Rob characterized the stocker as “wimpy.”) The blower pulley thus gets a full wrap of the six-rib drive belt shared with the Coyote’s alternator and water pump. As with the Three-Valve E-Force, the shared blower belt has proven issue-free even at elevated boost levels.
We were able to drive Edelbrock’s automatic ’11 Mustang GT test mule. It drives just like the dyno sheets says it would, with a good hard hit right off the bottom, then tearing up the tach to the fuel shut off without a hitch. The automatic and blower make a great combination; just laying into the loud pedal is enough to haze the tires from a standing start, and with an abundance of torque on tap acceleration is your ready companion. Top end, we can assure you, is hardly in short supply, either. It was far more power than we were expecting from such low boost.
What is uncanny is how silent the E-Force Coyote combination is. In over 20 years of testing supercharged Mustangs we’ve endured the coffee grinding of the early centrifugals, heard belts and gears so loud they’d wake you up if you’d been dead but a week, noted how the move to helical gears was a huge step forward and we’ll admit just barely being able to hear some newer blowers. However, this is the first time we truly couldn’t hear anything. Oh, there’s the faintest boost whistle at full chat, but the rest of the time there’s nothing. No softly grrrring gears, no screams of ecstasy—just an otherworldly Coyote thrust.
Thankfully Edelbrock has been letting us sample their projects earlier in their development cycles, which means our test car was fully calibrated for power, but final driveability tweaks were still forthcoming. Still, the only anomaly was occasional light surging at low speed, part throttle that will be gone in production E-Force tuning. In other words, the E-forced Coyote has the manners of a showroom stock GT, but simply runs much harder. Given the refined nature of the newest Mustangs it’s a great upgrade.
Edelbrock is in a good spot with its Coyote blower. The performance is certainly there with surprisingly low boost. While there is an argument pitting the Eaton TVS against the Lysholm screw in heat efficiency, at the single-digit boost levels the Edelbrock-Coyote responds to so well on the street the argument is likely academic, but at 15 psi or more another technology might have the advantage.
What is a clear advantage for the Eaton TVS is less expensive manufacturing, which reflects in the Edelbrock Coyote kit’s “approximately $6,500 retail” price as quoted by Edelbrock. Now, pricing is always a minefield, and Edelbrock has many dealers, including the aggressive major mail-order houses, so actual sales prices could well be lower. Edelbrock noted the Coyote blower would likely be slightly less expensive than its Three-Valve because the Coyote deletes the Three-Valve’s cosmetic coil covers and unnecessary-with-the-Coyote-throttle body upgrade. Given the Coyote kit’s completeness, handsome finish, and Q9000-quality internals, that’s good speed for the money. 5.0
On The Dyno
We were lucky enough to have Edelbrock demonstrate supercharged 5.0 engines on both chassis and engine dynos.
On the chassis dyno we saw a simple readout of what the standard E-Force assisted ’11 Mustang GT puts to the tire—466 rwhp—and Edelbrock provided us with its 344 rwhp baseline chassis test for comparison. In graph format, the results are unambiguous. The supercharger amps up the 5.0’s commendably smooth and well-rounded powerband almost comically. There is so much area gained under both the supercharged power and torque curves that the stock runs look like they are hiding under an umbrella. These chassis dyno tests are with stone-stock configurations. The baseline was set by the car in as-delivered condition, and the E-Force numbers were obtained by bolting on a standard kit. That means a 3.750-inch pulley for a nominal 4.5 pounds of boost and breathing through the stock airbox.
The engine dyno provided equally smooth and repeatable curves as well. We sampled two demonstrations, both with the more aggressive 3.500-inch pulley for about 6 pounds of boost. The first was through the stock airbox, the second test was with the optional Edelbrock cold air inlet and associated tuning.
Thanks to apparently more aggressive ignition timing along with reduced air restriction, the CAI—or low-restriction inlet, as it is more appropriately called—shows gains all the way around the tach, especially after 5,000 rpm and swelling near redline as the airflow keeps building. This is the expected behavior from a tune and cold air, so if you can legally run this option, it’s worth 58 hp at the top end.
Like everyone else who’s tried, Edelbrock has found tuning the latest Mustang engine management software complex and involved, but working with SCT tuning hardware and software, Edelbrock calibration-guru Chris Johnson discovered new capabilities in the Coyote’s brain. The Coyote oxygen sensors are wideband, so “the fueling is easy to get where you need it to be. The first couple of pulls and it was good to go,” reports Chris.
Whatever time was saved setting the air/fuel ratio was more than spent fiddling with cam timing. Chris says his TI-VCT is strategy totally different from what other positive displacement blowers are using. Echoing others who have twiddled with the Coyote’s twin-independent cam timing, Chris says there are significant power gains throughout the powerband in the cam timing, but the added complexity of varying four camshafts means extra time spent calibrating.
Chris also noted the automatic transmission adds another layer complexity, so he starts with an automatic car. Once it’s tuned he can simply subtract the transmission-specific code to quickly arrive at a manual transmission tune. Furthermore, peak power tuning at full throttle is, as always, the easiest part of calibration. Nearly all calibration time is spent on cold-starts, transient responses and other details generally lumped under the Driveability heading.
Chris did say the impressive revving capacity of the Coyote engine did have him considering durability tradeoffs. Somewhat uncharacteristically of a supercharged engine, Chris was “amazed at how high that engine will rev.” That makes peak horsepower easy to come by, but at what cost in long-term durability? Instead of revving it to the moon, Chris and Rob point out Edelbrock sells the next smaller blower pulley for all of $18, and you can make more boost rather than revving the poor canine to death. At our visit, Chris had the stock 3.750-inch pulley tune (4.5 psi) nearly complete and was working on the optional 3.500-inch pulley tune (about 6 psi).
Racers will want more, of course, and Edelbrock will offer a 3.250-inch pulley for track use, but you’ll be on your own tuning-wise. Edelbrock is putting its resources behind the CARB-approved 3.750- and 3.500-inch pullied street kits. Not to worry, as the 3.500-inch pulley goes deeply into 600-flywheel-horsepower territory and that’s about the limit for pump gasoline. Custom tuning from a local tuner makes more sense past that point.
It’s also worth noting that Chris’ calibration and the low 4.5 pounds of boost in the standard kit are related. Initially more boost was tried, but Chris had to retard the ignition timing so much to meet the power target that it made more sense to simply lower the boost level. The deep-breathing Coyote is almost too eager to make power, apparently.
Most interestingly, Chris said he found working with the Ford software, “straightforward—a pleasure to work with.” Maybe the aftermarket is coming to grips with Ford’s Copperhead engine management, as this has not been the typical response of other, more frustrated tuners we’ve interviewed.
Who ever thought a bolt-on supercharger would have a 302 Ford making 636 mild-mannered street horsepower?
|3.5 Pulley||CAI & Tune||Difference|