Yesterday, Ford held a special event for the media, inviting us out to Grattan Raceway just outside of Belding, Michigan, to experience the all-new 2016 Ford Shelby GT350 and GT350R Mustangs. Trackside, we had the occasion to speak with Ford’s Eric Ladner, who served as Engineering Program Lead on the Shelby GT350’s monumental centerpiece: the 5.2-liter flat-plane crank V8.
|Engine Type||normally-aspirated, flat-plane crankshaft V8|
|Peak Output||526 horsepower @ 7,500 RPM|
|Peak Torque||429 lb-ft @ 4,750 RPM|
|Max. Engine Speed||8,250 RPM|
(The following interview has been slightly edited for both clarity and brevity. -Ed.)
Why a flat-plane crank, as opposed to a cross-plane?
Eric: As we go from one engine vehicle to the next, we’re looking for different technologies – different things – to put us to the next level, right? It’s one of those things where you look at the overall package: we’re looking at building a track car, where we want something that has a broad torque curve, revs high, produces a lot of performance. This was kind of a natural fit for what we were doing.
So why wait until now, then? Why weren’t there any flat-plane cranks in any previous Shelbys?
Eric: Good question. I guess I can’t answer for why we hadn’t done it before now… But I don’t know that we’ve ever made a track car – in modern history, anyway – a track car anything like this. So I think it’s part of, again, whatever takes that next step.
It’s something that, you know, it’s a pretty big departure from what we normally do, and it brings a lot of things with it, so it’s one of those things that may be on the list of things we considered [in the past], but didn’t make it into a program. Well, now we’re kind of all-out for a track car, so it made sense to put it in.
We assume it’s not a clean-sheet design? That you started with the 5.0-liter Coyote?
Eric: I don’t want to say “we started with.” It shares some common features and architecture with the 5.0-liter, but it is really an all-new engine. I mean, when you look through the list of parts, from the bottom to the top internals, it’s really all new stuff.
What kind of lightweighting of internal components was necessary to achieve that 8,250 RPM redline?
Eric: So, of course the crankshaft is lighter weight; flat-plane cranks are inherently a bit lighter weight. And to reduce some additional weight, we gun-drilled the center. That’s not really necessary for the speed; it’s kind of unnecessary mass there. That’s just to lightweight the whole thing. But you look at the pistons; we have very small skirts on the pistons… So for the speed, really the piston and rod assemblies.
Some of the valvetrain: you know, we have hollow intake valves, sodium-filled exhaust, things like that for the speed. We went after light weight for other reasons, right, for track performance. But for the speed, it’s a couple of different things.
Is it just the inherently lighter crankshaft that really contributes to the high possible RPM for a flat-plane crank? Or is it, you know, things like the firing order, too?
Eric: I mean, actually, it’s hard to say that we wouldn’t be able to achieve this engine speed without a flat-plane crank, quite frankly. It’s not necessarily one of the key enablers. One of the things you have to think about is its ability to rev quickly as opposed to rev high. A lot of people associate [the flat-plane crank] with revving high, but quite honestly, I wouldn’t say we couldn’t have gotten that with a cross-plane crank.
It certainly helps to have less mass – less rotational inertia. But I wouldn’t say that it’s essential for what we did. It’s more about the performance and the revability than the high engine speed.
So, you probably can’t really tell us, but any indicators what’s next for this engine?
Eric: [laughs] You’re right, I can’t – we don’t talk about future products. Can’t blame you for asking, though.