Why Your Daily Driver Can't Rev Like A Supercar

Reaching supercar revs is a complicated casserole of ingredients that includes the reciprocating mass, balance, lubrication, type of valvetrain, valve timing, and the engine's ability to breathe. Listen to a Lexus LFA winding out its V10 and you'll hear what that casserole is supposed to be. Thanks to the magic chefs in the engineering department, LFA owners get to enjoy a 9,000 rpm redline. All that careful design and matching of parts is why the Bugatti Tourbillon's 8.3-liter V16 and the Porsche 911 GT3's 4.0-liter flat-6 also redline at 9,000, but your 1989 L98-powered Camaro tach shows a 5,500 rpm redline. 

Your average everyday commuter cars just don't need to rev to the stratosphere. Most street engines are happy at low rpm, where they make good torque and little noise. High rpm power trains typically cost a lot to build and maintain because they need light, strong internals with stupidly tight tolerances. It's not cheap to make a Le Mans racing V10 sound like a dental drill for hours on end. Do you want your Kia K4 to redline at 10,000 rpm? 'Cause that's how you get your Kia K4 to cost $40,000 or more. Case in point, building a reliable engine that revved to 8,900 rpm is why the Honda S2000 had a suggested price of $32,740 in 2001, or nearly $60,000 in today's dollars.

To paraphrase the definition of inertia, objects at rest stay at rest unless acted upon by outside forces, and the less mass something has, the easier it is to move. Light crankshafts, connecting rods, and pistons can simply spin faster than heavy ones, especially when properly balanced to prevent unwanted vibrations. It's why Porsche 911 GT3s have titanium connecting rods. Heck, Top Fuel dragsters use even lighter aluminum connecting rods. Even though steel handles reciprocal forces better, aluminum connecting rods can still withstand eight to 10 drag races, according to Engine Labs, but let the rpm reach 8,000 or more. 

Of course, light and strong reciprocating parts are only as good as their ability to move. Since friction is an enemy to be defeated, lubrication is paramount. High-rpm engines need modern synthetic oil that flows freely and stands up to extreme temps. You can't dump some "Beverly Hillbillies" bubblin' crude into your engine and hope for the best. 

Many high-performance cars use dry-sump lubrication rather than traditional wet-sump systems, meaning the engine doesn't store its oil in a pan under the crankshaft. Instead, oil gets pumped into and scavenged from the engine, resulting in lower overall temperatures, less drag on the reciprocating mass, more consistent oil supply, and no oil starvation under heavy g-loads. For example, the C8 Corvette's LT2 small block has a dry-sump system so when the 0.4% that get driven by skilled drivers on tracks are there, the engine stays lubricated. 

Then there's the valvetrain. You might expect that's about overhead valves (OHV) vs. overhead cams (OHC), and you're mostly correct. But it's not just the type of valvetrain that lets supercars rev so high, it's also the materials and techniques used. The vast majority of hot exotics do have single overhead cams (SOHC) or double overhead cams (DOHC), but that's not the whole reason they can spin like a pathological liar trying to run for office. 

OHV engines, which use a single camshaft pushing on thin rods to actuate the valves, can be made to rev, it's just harder and more expensive to do so. Performance-oriented OHV engines such as the C6 Chevrolet Corvette Z06's LS7 can hit 8,000 rpm. It's just that there's more inherent inertial mass thanks to that pushrod middleman, so OHV engines need more exotic, lightweight materials to achieve high revs, meaning supercar makers typically just design engines with the cams on top in the first place. Plenty of everyday Hondas and Subarus use OHC setups and can get up to a decent 7,000 rpm, but they still can't rev like a Formula 1 car or even that Porsche 911 GT3. The key here is that the valvetrain in supercars is light with strong, stiff components.

The final component of high-rpm supercar-ing is the breathing. There's a reason supercars have vents large enough to ingest small birds, pets, and pedestrians. Lots of air flowing quickly translates to high revs. It's why they also have huge, minimally restrictive exhaust systems. In other words, you have to get air into and out of your engine as quickly as possible if you want more revolutions than the country in a young-adult future-dystopia novel.