Cylinder Head & Valvetrain
"The Coyote head at a given lift actually outflows a Yates D3 head." Now that Adam Christian, internal combustion engineering analyst, has your attention, "It's a Four-Valve, right, we're cheating [The radical Yates NASCAR race head is a two-valve.-Ed.], but up to our peak lift, 13mm, we're actually out-flowing the Yates head. And that pretty much means we're outflowing Brand X, Y, and Z."
That's a great recommendation for your next Mustang GT's breathing capability. To put it in a Ford production car context, Mike Harrison noted, "These are the best heads we could find that are as-cast production cylinder heads. Adam and Todd made sure that at every valve lift that we were superior in the performance numbers, not just at the top end. It's not a compromised port, it's wonderful."
We'd love to show a flow chart of the new head, but Ford was reluctant to post exact numbers. It causes them headaches from snivelers who don't precisely replicate the published results. But don't doubt the Coyote heads howl all over the V-8 competition. Our guesstimate is these intakes flow a bit over 300 cfm.
More importantly from the Coyote team, "And that's only half the story, because the team didn't just focus on the intake ports ... it was designed as a system; to work with the intake manifold ... It was designed from the valve to the plenum, and not as separate pieces as is often the case because of the way things turn out."
This systems engineering, where powerful computers, innovative software, flexible cross-team communication and parallel development allow keeping many variables updated in real time was repeatedly cited as central to the Coyote's engineering success.
To make such an impressive head, the team knew it would need all the tricks. Four camshafts were a given, both for the four-valve-per-cylinder architecture, but also to enable the hugely important TiVCT function. The best previous modular production casting, the GT500 head was looked at first, and given the short wick on the entire project the initial thought was to use that head. But the GT500 casting had two strikes against it: it was too large and couldn't make the performance numbers! So even though there wasn't time to design a new cylinder head the head specialists went through six months of 12-hour days and working weekends to design and deliver a new casting.
To speed the design the Coyote head had two starting points: architecturally the GT500 head and conceptually the recently designed 3.5/3.7 V-6 combustion chamber-both twin-cam, Four-Valve designs. The Coyote head's architect, Todd Brewer, cylinder-head-design technical expert explained the approach: "We took things we knew how to do and started there."
Don't think Todd copied anything directly from either of these heads. These starting points just gave the general layout and relationships; not a single part was carried over from either head into the Coyote.
Beginning, as always, from inside the head and working outward, from the 3.5-liter concept Todd changed the distance between the valves, the valve angles, the back-cut angles on the valves, and the valve seats. This was all done virtually, with CFD modeling showing what worked and what didn't. The intake valves were stood up so the intake ports would be farther from the engine's centerline. This got the valves away from the pistons, allowing more valve lift and TiVCT range of authority. It also facilitated gentler curves in the intake manifold, increasing breathing.
Port design was driven by Adam Christian's analyticals and Jeff Kolodziejczk's surrogate engine work. Working back-and-forth, Adam would do the quick and dirty one-dimensional computer modeling at his desktop, followed by Todd's three-dimensional work and then a combination of the two-the so-called 1D3D CFD-at Ford's forebodingly named Numerically Intensive Computing Lab. This is where the serious number-crunching is ground out, with the 1D3D software combining both pressure and flow functions into one mind-numbing exercise.
It's difficult to overstate the power of these levels and volume of computing. It is more accurate and vastly quicker than building test parts for something such as a flow bench, even with rapid prototyping. Without it the Coyote would not have made it on time. Even at the design level Todd enjoyed being able to change one variable such as valve angle and have the software automatically update everything else, all the way out to valley volume or exhaust manifold placement.