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Exclusive! C8.R Corvette 5.5L DOHC V-8 Pic and How the Flat-Plane Crank Alters Its Iconic Sound

HOT ROD logo HOT ROD 28/01/2020 04:14:57 Steven Rupp

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There's a new engine in the C8.R Corvette, and it sounds nothing like its predecessor.

They say beauty is in the eye of the beholder, and although that's true, it can also be in the ear of the listener.

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Since the Corvette first hit the streets back in the 1950s, it was imbued with the beautiful and nearly magical sound of V-8 performance. It was a deep, bass-filled rumble that just oozed a feeling of power. Over the years, the sound emanating from Corvettes, both on the street and at the track, had a distinctive note that became synonymous with the car. When the Corvette moved to the LS1 in 1997, the firing order was tweaked a bit, and although the sound did change, it still had that deep rumble that we all love.

Chevrolet is super secretive of its new mill for the C8.R, so much so that it covered up the back hatch to keep out prying eyes. About all the team will say is that it's a 5.5L DOHC V-8 fitted with a flat-plane crank. Power numbers are limited to 500 hp and around 475ish lb-ft of twist, but that's all it will say. In fact this picture is about as close as you're going to get to seeing the new C8.R engine.© Hot Rod Network Staff Chevrolet is super secretive of its new mill for the C8.R, so much so that it covered up the back hatch to keep out prying eyes. About all the team will say is that it's a 5.5L DOHC V-8 fitted with a flat-plane crank. Power numbers are limited to 500 hp and around 475ish lb-ft of twist, but that's all it will say. In fact this picture is about as close as you're going to get to seeing the new C8.R engine.

In terms of racing, it was even more apparent. When a C6.R Corvette was running, it sounded unique among its peers. You could tell a C7.R Corvette was coming around the corner or over the hill based on that distinctive pushrod V-8 sound.

But the only thing constant in the world is change. For the C8.R, Chevrolet Racing really changed things up with its new mid-engine marvel, but it wasn't the engine placement that ended the car's iconic sound signature. It was the engine itself. Gone is the deep baritone exhaust note, replaced instead with a high-pitched Ferrari-like sound. Think puberty in reverse. And although we love the sound of a wound-out Ferrari or other Italian supercars, having that pitch emanate from the back of a Corvette is something that will be hard to get used to. We're not saying the sound is bad-it's actually pretty badass-but it's not even close to the sound signature we've come to associate with Corvettes.

a drawing of a face: A cross-plane crank has two consecutive exhaust firings on one bank, which is what helps give the rumble associated with American V-8s, though it makes exhaust scavenging less efficient. It also means cross-plane crankshafts have to use large counterweights to properly balance the engine, helping to keep it from rocking up and down but keeping rotational mass high, making for a slower-revving engine.© Hot Rod Network Staff A cross-plane crank has two consecutive exhaust firings on one bank, which is what helps give the rumble associated with American V-8s, though it makes exhaust scavenging less efficient. It also means cross-plane crankshafts have to use large counterweights to properly balance the engine, helping to keep it from rocking up and down but keeping rotational mass high, making for a slower-revving engine.

The real culprit here isn't the new 5.5L DOHC V-8 that Chevrolet moved to. Instead, it was the choice to go with a high-revving flat-plane crank. This drastically changed the firing order of the engine and eliminated the classic American V-8 sound that's typical with the firing sequence of a traditional cross-plane crank. But we know what you're thinking: "Well, this is just the race car, so I'm going to be able to get my V-8 rumble fix from the production car!" Well, yeah, for now. You see, for Chevrolet Racing to run this new DOHC flat-plane crank mill in the C8.R, it has to, according to the rules, run a similar engine in at least 300 production cars. So does this mean that an eventual C8 Z06 variant will lose its iconic exhaust note? Only time will tell, but that sound that we've all grown to love is gone from the C8.R Corvette.

Flat-plane V-8s, no matter the firing order, will always alternate between banks. That makes for efficient exhaust scavenging without needing to have header primaries cross over from one bank to the other. Flat-plane cranks don't require massive counterweights and consequently rev very quickly, though they tend to have a noticeable secondary vibration. This vibration is why the displacement on is kept smaller, and we're dying to find out how Chevrolet addressed this with the 5.5L engine in the C8.R.© Hot Rod Network Staff Flat-plane V-8s, no matter the firing order, will always alternate between banks. That makes for efficient exhaust scavenging without needing to have header primaries cross over from one bank to the other. Flat-plane cranks don't require massive counterweights and consequently rev very quickly, though they tend to have a noticeable secondary vibration. This vibration is why the displacement on is kept smaller, and we're dying to find out how Chevrolet addressed this with the 5.5L engine in the C8.R.
28. tammikuuta 2020 6:14:57 Categories: HOT ROD MTV

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