Tom Wilson
April 6, 2011

Horse Sense: In case you just tuned in and are wondering what all this animal talk is about, Ford often tags its in-development programs with a code name. You’d have to be living under a 4.6 block not to know the latest 5.0-liter was code-named Coyote. However, you might easily have forgotten that the GT500 program was code-named Condor, hence our little bit of canine-versus-bird alliteration.

We’re fond of saying there is no replacement for displacement, because, in the end, there isn’t. However, supercharging and refinement do much to overcome the advantage of large engine displacement, a fact brought to our attention by Jim Bell at Kenne Bell.

Clearly Jim is happy to tout the advantages of his popular twin-screw blowers, but we had to admit a comparison of his two most recent projects--adding a supercharger to the 5.0 Coyote engine in the Mustang GT and upgrading the Shelby GT500 to a Kenne Bell Twin Screw--illustrate how the smaller, lighter 5.0 ultimately makes more snort than the rip-roaring Shelby.

There is no new hardware involved in this story, as we recently introduced the 2.8 Kenne Bell Twin Screw blower on the new GT, and the 2.8 blower on the Shelby is well known at this point. What we haven’t mentioned, and why Kenne Bell just had an ’11 GT500 in its shop, is the current Shelby uses the same engine management system as the Coyote-powered GT. Thus, Kenne Bell was burning midnight oil getting its electronic tune on the ’11 Shelby, which is how the company got started comparing the Shelby and GT outputs.

With few hardware differences between the ’11 GT500 and earlier models, both the KB-tuned ’11 and earlier GT500s make the same power. On KB’s dyno, that means the ’11 GT500 measured 481 rwhp stone-stock, and ran up to 689 rwhp at 18 pounds of boost with the KB blower. For the Coyote-powered Mustang GT, Kenne Bell had a variety (hundreds) of dyno runs gathered by both manual- and automatic-transmission ’11 GTs. Picking through the data allowed some reasonable apples-to-apples comparisons with the GT500. We’ll admit this did require a sharp eye on things such as throttle body size and so on, but with so much data to work from, we’re comfortable making the comparisons.

To get right to the point, at just under the 9 pounds of boost, the stock GT500 was at 481 rwhp and the 5.0 Mustang GT with the KB blower hit 547 rwhp. This is an Eaton-to-Kenne Bell comparison, which accounts for some of the huge power differential, but it shows how eagerly the Coyote responds to boost. At 12 pounds of boost, the manual-transmission GT500 laid down 615 rwhp, while an automatic trans Mustang GT came in with 657 rwhp. At 15 pounds of boost, the same pair of cars were 654 rwhp for the Shelby and 720 rwhp for the GT. There was no higher GT boost pressure available at our deadline, but the Shelby was cranked up to 18 pounds of boost and 689 rwhp, where even with a manual transmission, 2 extra pounds of boost, and 400cc more displacement, it still came up about 30 rwhp shy of the GT. Hmmm...

Granted, the above summation is far over-simplified, if for no other reason because it compares just peak power figures, but the direction is clearthe smaller 5.0 makes more horsepower than a 5.4. Why is this? Shouldn’t Ford’s top-dog Mustang engine eclipse its smaller brother?

Well, at first glance, the two engines are quite similar. Each is an all-aluminum V-8 with four valves per cylinder, double overhead camshafts, and performance tuning from the factory. Their basic internal dimensions are also similar, but differ in at least one key standpointstroke. Where the 5.0 stroke is 3.563-inch, the 5.4 gains the majority of its displacement by swinging a longer 4.165-inch-stroke crankshaft. And that longer stroke means a faster piston speed, and consequently a lower redline.

Now, with enough expensive parts, it’s possible to rev a 5.4 with Formula 1-like piston speed--witness the ’00 Mustang Cobra R. It redlines at 6,500 rpm with a fuel shut-off at 6,800 rpm, and if that doesn’t do it, the ignition cuts off at 7,000 rpm. Of course, this most exciting of Mustang engines was expensive and rare--only 300 produced. The Shelby GT500 on the other hand, is less exotic and redlines at 6,250 rpm.

The mass-market Coyote, however, has a stock redline of 7,000 rpm. This is something the Coyote engineers worked some to get, not only with the shorter stroke, but also with a lighter valvetrain. When used as surrogate parts during Coyote development, the GT500 valve-train wasn’t able to make it to 7,000 rpm, so there’s one big advantage to the Coyote. It simply runs faster, and since horsepower is torque times rpm divided by 5,252, more rpm is a direct path to more horsepower.

Indeed, when looking at the horsepower and torque graphs, the 5.0 and 5.4 typically run near each other until 6,000 rpm, and then the 5.0 keeps on climbing another 1,000 rpm or more. Right there that will put the Coyote well ahead of the 5.4 Shelby.

Another Coyote advantage is compression ratio. The GT500 puffs up 8.4:1 compression, while the Coyote puts the squeeze on things with 11.0:1 compression. This is significant because compression is a fundamental aspect of power production. The whole idea in a piston engine is to build cylinder pressure, and higher compression puts more oomph into the power stroke.

The rule of thumb is four percent more power per point of compression, and the Coyote has 2.6 more points of compression than the 5.4. Multiply 2.6 by 4 percent and the Coyote should make 10.4 percent more power than a 5.4, or so it says here in the brochure. Looking at our data, at 15 pounds of boost the 5.4 makes 654 rwhp, so 654 hp times 10.4 percent gives us 722 hp, and we see the 5.0 Coyote put up 720 hp at that boost. Of course, the Shelby used a manual transmission and the 5.0 was an automatic, which is worth 20 rwhp on Kenne Bell’s dyno, so the power differential is even greater than the raw dyno data indicates. But we can safely say the compression accounts for a measureable portion of the 5.0’s power gain.

Another Coyote advantage is breathing. We don’t have hard data comparing GT500 and Coyote heads, but the Coyote engineers have assured us that the 5.0 heads are some of the best-flowing V-8 castings ever to roll off a Ford assembly line. Thus they are clearly ahead of the GT500 units. We do have data on camming, where the GT500 valves lift about 12 mm and the Coyote’s 13 mm, so there’s a breathing advantage in favor of the Coyote as well. We’re not sure how much it really matters at streetable or pump-gas power levels, but the Coyote sports more sophisticated exhaust manifolding than the GT500 as well.

There is one thing you might consider a 5.0 advantage that isn’t directly in play during these dyno tests. That’s the 5.0’s sophisticated Twin Independent Variable Cam Timing. It is not important here because at wide-open throttle, the cams are adjusted to their maximum power setting and don’t vary during the run. Therefore the 5.0 has no particular cam-timing advantage over the less adjustable 5.4 engine.

Yet, there still could be a small, but measureable advantage to TiVCT. Because the cam timing is variable, that allows the engineers to build in a more radical cam lobe profile, which makes more power. The reason TiVCT allows a more radical cam is because the variable timing feature allows toning down the valve event timing at low rpm or part throttle for a smoother idle, lower emissions, more low-end torque, better mileage, and crisper throttle response during less than all-out driving. All that and you still get all the glory at full throttle and high rpm.

Inevitably the 5.4 in the GT500 will go away, as it has in every other Ford application. Luckily the 5.0 is more than a worthy replacement, even if it is almost half a liter smaller in displacement. It certainly makes the prospect of an Ecoboosted version quite titillating, but that will remain speculative for the moment. What we do know now, is that there might just be a replacement for displacement after all-technology.

On The Dyno

  5.4, 8 psi 5.0, 8 psi 8 psi vs. 8 psi 5.4, 12 psi 5.0, 12 psi 12 psi vs. 12 psi
RPM HP TQ HP TQ HP TQ HP TQ HP TQ HP TQ
2,500 199 418 180 379 -19 -39 223 468 n/a n/a n/a n/a
2,750 222 423 212 405 -10 -18 255 486 n/a n/a n/a n/a
3,000 250 437 242 423 -8 -14 287 503 n/a n/a n/a n/a
3,250 277 447 269 435 -8 -12 319 515 237 382 -82 -133
3,500 301 452 294 441 -7 -11 349 523 323 485 -26 -38
3,750 325 455 323 452 -2 -3 374 524 358 501 -16 -23
4,000 348 457 344 452 -4 -5 404 530 392 515 -12 -15
4,250 371 459 373 461 2 2 434 536 420 519 -14 -17
4,500 390 455 392 457 2 2 459 536 450 525 -9 -11
4,750 412 456 417 461 5 5 485 537 481 532 -4 -5
5,000 430 452 434 456 4 4 513 539 499 524 -14 -15
5,250 445 445 448 448 3 3 533 534 531 531 -2 -3
5,500 459 438 468 447 9 9 559 534 553 528 -6 -6
5,750 470 429 487 444 17 15 578 528 576 526 -2 -2
6,000 478 419 503 440 25 21 596 522 591 517 -5 -5
6,250 475 400 514 432 39 32 616 518 611 513 -5 -5
6,500 n/a n/a 528 427 n/a n/a n/a n/a 627 507 n/a n/a
6,750 n/a n/a 545 424 n/a n/a n/a n/a 640 498 n/a n/a
7,000 n/a n/a n/a n/a n/a n/a n/a n/a 650 488 n/a n/a

5.4 , 15 psi 5.0, 15 psi 15 psi vs. 15 psi 5.4, 18 psi 15 psi vs. 18 psi
RPM HP TQ HP TQ HP TQ HP TQ HP TQ
2,500 236 495 n/a n/a n/a n/a 248 521 n/a n/a
2,750 270 516 n/a n/a n/a n/a 283 541 n/a n/a
3,000 306 536 n/a n/a n/a n/a 324 567 n/a n/a
3,250 342 552 n/a n/a n/a n/a 356 576 n/a n/a
3,500 370 556 n/a n/a n/a n/a 385 578 n/a n/a
3,750 397 556 n/a n/a n/a n/a 417 584 n/a n/a
4,000 427 561 371 487 -56 -74 448 588 -77 -101
4,250 462 571 419 518 -43 -53 482 596 -63 -78
4,500 492 574 466 544 -26 -30 515 601 -49 -57
4,750 521 576 489 541 -32 -35 548 606 -59 -65
5,000 548 576 522 549 -26 -27 574 603 -52 -54
5,250 573 573 551 551 -22 -22 603 603 -52 -52
5,500 596 570 579 553 -17 -17 627 599 -48 -46
5,750 618 565 601 549 -17 -16 649 593 -48 -44
6,000 637 558 621 543 -16 -15 672 588 -51 -45
6,250 635 534 640 538 5 4 n/a n/a n/a n/a
6,500 n/a n/a 660 534 n/a n/a n/a n/a n/a n/a
6,750 n/a n/a 679 529 n/a n/a n/a n/a n/a n/a
7,000 n/a n/a 692 519 n/a n/a n/a n/a n/a n/a
7,100 n/a n/a 710 514 n/a n/a n/a n/a n/a n/a

Selected dyno runs from Kenne Bell’s voluminous testing regime are shown here. Careful attention to reducing variables makes this data accurate, but just the same, don’t bother picking one or two horsepower nits here. The trend to better power from the 5.0 at higher rpm is clear, and that’s the important point. Of course, the blown 5.4 looks pretty good in the midrange. Keep in mind that the first GT500 test was with the stock Eaton supercharger, while all the rest were with Kenne Bell’s 2.8H blower.

There is no 18 psi of boost run for the 5.0 because the two times the test car was tuned up that far, it blew up its oil pump. Yes, the oil pump. This happened because to get past 15 pounds of boost, a larger crankshaft pulley is needed, which means changing the integral harmonic dampener. Something in the aftermarket dampener and the oil pump didn’t get along, resulting in a shattered inner oil pump gear each time the larger aftermarket damper was tried. A stronger pump gear will soon be available to cure that problem.

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