The sound is unmistakable—rich, complex, cultured, yet ferocious. Even among Ferraris, the noise emanating from the F355 is unique. After a recent opportunity to drive a manual F355 Berlinetta, fulfilling a childhood fantasy, the noise burnished itself in my brain. I walked away with two wants, a manual F355 Berlinetta—ideally in blue—and to drill down into its specific sound.
Seeing as I can't afford a 355, I'll write about the sound for now. We should start with the fundamentals. Literally. While in carbureted sports cars intake noise might mean everything, and for certain luxury cars ultra-quiet valvetrain noise might be paramount, for cars like the F355, the dominant sound is the exhaust. The exhaust sound is specifically the pulses of air that run from exhaust valve to tailpipe. The dominant frequency made by these pulses can be determined with simple math. Divide engine speed by 60, and you get a value in hertz, or cycles per second. As a four-stroke engine only fires twice for every rotation of the crankshaft, multiply that number by half the cylinder count. So for an eight-cylinder engine running at 3000 RPM, 3000/60 is 50 hZ; multiply 50 by 4 and you get 200 hZ. (For musicians, that's around the G#/Ab just below middle C, and how I verified my math.)
Chances are you've heard of the two types of crankshafts used by V-8s, flat-plane and cross-plane. The vast majority of V-8s use a cross-plane crankshaft, which has pairs of crankpins offset by ninety degrees. This gives an uneven firing order between cylinder banks of left-right-left-left-right-left-right-right, which presents audibly as the distinctive V-8 burble you know and love. A cross-plane crank is best for minimizing vibrations, though this comes at the expense of weight, and thus maximum possible engine speed.
A flat-plane V-8 uses a crankshaft with crankpins offset by 180 degrees. Unlike a cross-plane V-8, a flat-plane V-8 fires evenly between cylinder banks, which incidentally, means it behaves a lot more like two four-cylinders with a common block and crank. This also gives it quite a different sound, a lot more four-cylinder-esque, as the exhaust pulses from each side of the engine arrive at our ears at evenly spaced intervals. Flat-plane V-8s aren't as smooth as cross-plane V-8s, but their crankshafts are much lighter, allowing for higher revs. Ideal for, say, a Ferrari sports car, but not a Chevy pickup. While these two types of V-8 sound very different, the math to calculate the primary pitch for a given RPM is still the same. With flat-plane vs cross-plane V-8s, we're talking about a difference in tone here, not pitch, though given a flat-plane crank allows for high revs, the engine is therefore capable of producing a higher-pitched sound.
Still, the timbre or tone of a flat-plane V-8 is distinctive to its cross-plane brethren, and that's why the F355's V-8 sounds different from, say, a 1995 Corvette's small-block. But while a lot of Ferrari V-8s–all of which are flat-plane—are tonally similar, the F355's, and by extension, the 360 Modena's mechanically similar 3.6-liter, are still unique. And unique among all flat-plane V-8s, except one from Detroit.
That Detroit V-8 is, as you may have guessed, the new Corvette Z06's LT6 V-8, a 5.5-liter flat-plane unit designed specifically for this model. Early last year, Chevrolet held a virtual briefing for the media where they pored over the details for the LT6, and it's proven instrumental—no pun intended, at least not consciously—for my understanding of the Ferrari F355's V-8. The engineers tried to emphasize two frequencies above all, the fourth and eighth order.
The fourth order is another name for the dominant frequency produced by a running V-8, so called because the frequency is four times the frequency of crankshaft rotation. (The sound a four-cylinder makes is a second order, a six-cylinder a third order, and so on and so forth.) What I find particularly interesting is that eighth order. You can calculate the eighth order frequency by using the same formula to determine dominant frequency, but just multiply your engine speed in hZ by eight. In the case of an engine of any cylinder count spinning at 3000 rpm, you get an eighth order frequency of 400 hz. With both our Z06 and F355 V-8 at 3000 rpm, the 200 hz fourth order and 400 hz eighth order blend to provide an octave, the same note at two different frequencies. (Think "do-re-mi–fa-sol-la-ti-do," if we want to relate this back to Western 12-tone equal temperament.)
It's this octave that defines both the 355 and Z06 V-8s. An octave is a so-called perfect interval, or one of a handful of pairs of notes that are not considered dissonant in Western music. Perhaps I'm letting my musical training run wild here—basically know that this blend produces a very pleasing sound.
Listen to this clip of editor-at-large Travis Okulski lapping the new Z06 during our Performance Car of the Year test. You get that smooth flat-plane V-8 sound, and both the dominant frequency—the fourth order—and the eight order are very present. As I explained in my column about helmholtz resonators, the tone of a sound is made up of more than one pitch. The volume of each of those pitches defines the quality of the sound, and it's why a piano and a guitar playing the same note sound different, and why a C8 Z06 and an F355 spinning at 3000 rpm sound different too.
Different, yet similar. After watching many YouTube clips of F355s with stock exhausts and otherwise—the one I drove had a Kreisseig exhaust from Japan, which was amazing—you can hear that same octave, that blend of fourth and eighth order that dominates the sound of the Z06. Other flat-plane V-8s, including other Ferrari flat-plane V-8s seem to deemphasize that eighth order, for better or for worse, likely via exhaust tuning. The way one responds to tone is, of course, subjective, but I think a lot of people respond to that specific timbre of the 355 and the Z06.
STEPHANE FOULON
Ferrari
It's worth looking back at the state of the sports car when the F355 debuted back in March of 1994. This was a time when auto manufacturers were looking at exhaust tuning not just as a way to optimize airflow, but to actually create an aural signature. The Mazda Miata is commonly accepted as the first to do this, with engineers trying to ape the sounds of the classic sports cars that inspired it. For Ferrari, the F355 was an opportunity to flex its engineering muscles, to wrest back the spotlight from the upstart Honda/Acura NSX.
There are all sorts of ways to emphasize different frequencies in an automotive exhaust system, too numerous to get into here. The shape of the manifolds and the rest of the system downstream has a huge effect, especially muffler design. Those helmholtz resonators that Porsche uses to cancel out certain intake noises? They can be used in an exhaust, too. Unfortunately, there's not much out there on what Ferrari did specifically with the F355, but it's easy to see that its engineers put a lot of time into creating an aural signature, just like Chevy's did with the Corvette Z06.
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Of course, the sound a car makes is more than just whatever comes out the exhaust pipes. From the driver's seat, depending on how the car is built, you can hear intake and combustion noise, possibly the resonance of the engine bay and bodywork itself. In the new Porsche 718 Cayman GT4 RS, you can hardly hear the exhaust over the amazing racket coming from the intake tracts that run directly through the cabin. This isn't the case with the F355 or the Corvette Z06, though. Their sound is all about exhaust.
I mentioned earlier that my background is in music, and there's a fun parallel between the study of music and the subject of this article. It's not that we're talking about notes specifically, we're talking about things that are subjective. You don't need to analyze or understand music theory to appreciate a great song. At the end of the day, the details don't need to matter to the listener. Perhaps it's my education and interest in engineering that led me down this Ferrari F355-exhaust-sound rabbit hole, but, I wouldn't have gone there if I hadn't heard the thing first. Let the engineers (and hardcore nerds, like me) worry about harmonics. Just enjoy the noise.
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May 06, 2023 at 12:17AM
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