The Difference Between Flat-Plane and Cross-Plane Cranks Explained Using a Drummer

If you’re a fan of the new Mustang, then you must be a fan of the new GT350 and GT350R models. Heck, even if you’re not a fan of the blue oval car, you’ll still be intrigued by them because in today’s world, they are two shining beams of light in a forced (induction) darkness.
Ford Mustang GT vs GT350 1 photo
Photo: Screenshot from YouTube
Yes, forced induction does bring noticeable improvements in the figures engines can put out, but they take away their souls in return, a trade not many of us are willing to make. These last beacons are intriguing to say the least, but even more intriguing is how they are being marketed, the “flat-plane crank” expression being heavily used and sending you back to school once again.

Any car guy knows that V8s are probably the best sounding engines on the market, but few know the differences between them so well that they can tell you exactly what makes them sound so good. Well, luckily for us, the guys from Ignition took their time to explain what makes a flat-plane crank different from a cross-plane one and why everyone is so hyped about the GT350 Mustang.

Cross-Plane versus Flat-Plane: how does the construction differ?

When it comes to comparing the cross-plane V8s with their flat-plane counterparts, we first have to take a look at how they are different in construction. The norm today is the cross-plane version because of some reasons we’ll get into later on.

As Jason points out here, you can tell two engines are different by the way they sound. The cross-plane V8 has a distinctive burble compared to the flat-plane one, but to us they both sound great.

The difference comes from the ignition timing. The cross-plane crankshaft has a shape that, overall, creates a cross when looked at from the side. This way, you have 90-degree angles between crank throws, helping to even out the vibrations of the engine.

That means you’ll also have a different firing order, to maintain NVH levels in check. As Jason points out, instead of firing the left and right pistons in order, the engine is set up so that it fires in an alternation (left-left-right-left and so on). As a consequence, the cross-plane V8s have a particular soundtrack.

On the flat-plane crankshafts, when looked at from the side, all you see is a flat surface. No crosses, just a straight shape. That allows the engineers to program the ignition in a perfect alternation: left-right-left-right. That also dictates a different soundtrack that was perfectly emphasized by their “enhanced” drummer.

Regarding volume, the flat-plane crank V8s are louder because they rev to higher limits (after all, you do get more strokes in the same amount of time), but also because the materials used are lighter. All in all, more sound gets through.

What’s the big deal, why are flat-plane V8s so sought after?

So the two engines sound different, but there’s more to it. After all, it can’t be that people are so mad about them just because they have a different soundtrack, right? Right.

As we said, cross-plane engines are easier to balance. They keep the vibrations in check more easily and are less expensive to make. However, their crankshafts are also heavier, and that’s not good for rotation speeds. The lighter a crankshaft is, the easier it will spin, therefore making flat-plane versions a lot more “racing-prone.”

They can spin up to incredible RPMs, and the GT350 is one such car, with a redline of 8,200 RPM. Don’t think that’s something new in the industry. After all, as Jason does point out, the Audi RS4 had a similar engine a long, long time ago.

Being lighter, these V8s can also be used in racing applications more easily because that’s where even a couple of ounces can make a huge difference. Even exhaust gasses are better handled by flat-plane units, offering better performance and efficiency using less complex manifolds.

The thing is, this is a rare bird today, and that’s what makes it so desirable. It’s also incredibly enthralling to use on the track, where you can play with a broad range of revs, to keep your seam of the pants happy and your adrenaline rush at a high level.

Yes, flat-plane crank V8s don’t offer a lot of pulling power at lower revs, but once you get them up into the range, they are extremely rewarding. The thing is, they are expensive to make.

It’s not the construction process per se, but the development needed to make them refined. As we stated, big-displacement V8s are hard to balance when they are using a flat-plane crank, and that’s an expense most manufacturers aren’t willing to pay for.

However, with the advancements in lightweight materials made lately and new ways of handling vibrations, the V8s of today can be turned into purring kitties from roaring lions regarding vibrations.

In the end, we’ve come to learn that a car’s value can be judged by the smiles it brings to the face of Randy Pobst, and looking at the man in the video below, we think the GT350 is indeed hard to beat in this department.

If you liked the article, please follow us:  Google News icon Google News Youtube Instagram Twitter

Would you like AUTOEVOLUTION to send you notifications?

You will only receive our top stories