A flat-plane crank is one of the great mysteries of the world, or so it would seem. It gets its name from its physical appearance, but you’re not going to see the Voodoo engine’s crank any more than you’ll see the regular Mustang GT’s Coyote crankshaft.
What you need to know is that the flat-plane crank changes a V-8’s firing order so that the two banks of cylinders fire at even intervals relative to each other. In other words, as the engine runs, one of the cylinders on the left bank fires, then the right, then the left, and so on.
Conventional V-8s don’t alternate evenly between the banks, so the benefit of a flat-plane crank is all in the way the intake and exhaust manifolds are tuned. Because of the even firing, engineers can construct the manifolds to take advantage of resonances. More air in and more air out means more power.
The 5.2-liter Voodoo revs to 8,200 rpm and makes 526 hp, but its power delivery and sound aren’t like anything you’ve experienced from a Mustang.
So we strapped it to the dyno, thanks to our friends at K&N engineering.
Have a listen.
And now take a look at the results.
The GT350 is rated at 526 hp and 429 lb-ft of torque. Because we’re using a chassis dyno, the output we measure will be less than that, as it takes into account losses in the drivetrain. Additionally, the ambient temperature at the time of the test was more than 100 degrees with only 20 percent relative humidity. Although these are SAE-corrected numbers, we’d expect higher output at lower temperatures.
GT350 DYNOJET RESULTS:
467 hp (wheel) @ 7,200 rpm
374 lb-ft (wheel) @ 4,900 rpm
The GT350 put down 467 hp and 374 lb-ft to the wheels. Given the ambient temperature especially, that’s a very healthy result.
As always, peak numbers are just one set of data points. It’s the shape of the curve that matters. Notice that at very low revs, the V-8 struggles to make torque. At 1,500 rpm, it’s producing just 238 lb-ft—not a lot for a big-displacement, long-stroke V-8. In real-world driving, that output is accompanied by occasional stumbles; it’s clear the engine isn’t happy at low revs. Torque builds slowly, however, until 3,250, when something big happens.
Very big. From 3,250 to 3,750 rpm, torque output jumps by a huge 27 percent. And from there to about 6,250 rpm, it’s essentially a huge plateau of peak torque with a few bulges likely caused by resonances in the intake system. Even then, torque starts to fall only slowly all the way to the fuel cut. Ford quotes that as happening at 8,250, but our GT350 cut fuel earlier—8,200 rpm was the highest we saw, and even that only occasionally. Our best run made it only to 8,050 rpm before the limiter kicked in.
The GT350’s horsepower peak occurs at 7,200 rpm on the dyno, almost 1,000 revs short of the limiter, but output stays at or near that peak number almost that entire way, dropping by less than 10 hp at the 8,050-rpm limiter.
If Ford had limited the Voodoo to 7,200 rpm, it would have put down the same peak number on the dyno, but you’d miss out on that last, glorious 1,000 rpm of pull, where the 5.2-liter V-8 is all but maintaining that peak. See the dangers of just looking at the peak number?
In sum, this is a beautiful example of an engine that loves to rev. The kick in the pants you get around 3,500 rpm is exhilarating, and the fact that this engine pulls so hard all the way past 8,000 rpm makes it an absolute riot to run to redline.