Be they BMW’s straight sixes, Porsche’s flat sixes, V12s from Ferrari, or Honda’s Vtec engines, automotive enthusiasts largely love high-revving naturally aspirated performance engines. The feeling and the sound coming from one of these machines flat-out at 8,000 RPM is hard to match with anything short of rocket power. Natural aspiration describes, simply, an engine that makes power without the aid of forced induction, like supercharger or turbos. Up until recent years, the vast majority of engines were NA, but the species is now steadily becoming extinct, especially in performance applications. Now, why are they going away, and what makes them so great in the first place? Keep reading to find out.
NA engines have gone back more than a century at this point, with forced induction methods trailing by only a couple decades. Early superchargers and turbos were fairly impractical, only finding their way onto things like millionaire Duesenbergs and fighter planes. In the burgeoning years of the American auto industry, manufacturers started boosting performance by offering larger displacement engines with more cylinders. This crude effective method of making power would culminate with the big block V8 muscle cars of the late 60’s. While those cars boasted some impressive figures, they didn’t really display the characteristics NA performance that we think of today. Those characteristics, however, would spring up out of Europe and Japan in the latter half of the 20th century.
These performance engines from across the pond were simply built different. Featuring smaller displacement, lighter moving parts, and overhead camshafts, these engines were smoother, more responsive, and had a wide, linear power-band up to much higher rev limits than the old pushrod V8s. This distinction would begin in the 60’s when Ferrari’s compact V12s would challenge, and often beat, Ford and Chevy around Le Mans and the Nurburgring. Around the same time, automakers were introducing turbochargers into their lineups, which widely suffered from an issue known as “turbo lag.” These early turbo models featured lower compression ratios than their NA counterparts, causing a lack of power low in the rev range. Until suddenly the turbo compressor built up enough pressure to feed back into the engine, and all of the power came on all at once. This unpredictability instilled fear in all but the most seasoned of drivers, and even earned the 70’s Porsche Turbo the nickname “Widowmaker.”
As the 70’s marched on, those big V8s were put into a chokehold by slapdash emissions equipment, and small displacement performance had its real moment in the sun. At this point, cars like the Nissan 240Z and Porsche 911 became the popular choice for enthusiasts. These engines could be much more economical at low RPMs, and absolutely wild when rung out to the limit, especially with the introduction of variable valve technology. In the 80’s, we saw the emergence of legendary models like the M3, and Toyota’s 4AG-powered Corolla. Then Honda’s dominance came in the 90’s, with the NSX, Civic Si, and S2000.
The advantage of high-revving linear power is all too apparent on a racetrack or a stretch of open road, allowing drivers to push their cars right up to the limit and pursue record lap times. Restrained by stop-and-go traffic, however, they lose some of their luster. With some drivers often complaining these performance engines felt gutless at low speed without the immediate torque push of higher displacement models.
Cars like the S2000, E46 M3, Z3M, and Porsche 993 remain popular choices for street and track.
It was in the last years of the 20th century that automakers like Porsche, Nissan, and Toyota started ironing out the kinks in turbocharging, offering much less lag, more torque, and progressive power delivery. These advancements were the beginning of the end for NA performance, as these new turbo systems could offer many of the advantages you get from a torquey V8 and a small displacement engine rolled into one. In the 2010’s, turbos began to supplant NA engines altogether, because they simply offer the best compromise between performance, practicality, and efficiency. That’s a perfect configuration for the average car buyer.
The Nissan GT-R, 300ZX, and Mazda RX-7 FD debuted in the early 90’s with sequential turbocharged power.
Nowadays, a large swathe of performance models are going turbocharged. BMW and Porsche are mostly turbocharged. Honda’s performance offerings are all turbo, and Ferrari has turbocharged it’s lineup top to bottom. There are plenty of good turbocharged engines out there, even great ones, but many enthusiasts will tell you that they don’t have the X-factor of naturally aspirated performance. They don’t sound quite as good. Don’t have the raw, edge-of-your-seat feel of the older models, despite being just as fast on paper. This trend has led to models from the peak of the NA era becoming very collectible and springing up in value.
For those wanting to purchase a new high-revving vehicle, there are a few last bastions of hope. Porsche still offers the 911 GT3 and Cayman GT4 in NA flat six trim. There’s bound to be a few Shelby GT350s available on dealer lots, although Ford has recently discontinued that model. Lexus still offers a few models with their growling five-liter V8, and Lamborghini has promised to keep its lineup naturally aspirated for the time being.
Also check out the inventory we have available at The Starting Line. As of writing, we have plenty of flat six offerings from Porsche, as well as a couple torquey Chevy SS sedans.