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?