The days of the naturally aspirated six-cylinder engine look to be running out amidst the forced induction revolution. High-end performance cars like the Ford Mustang and the timeless E46 M3 CSL all used throaty naturally-aspirated sixes. The extreme boost in power made possible with the addition of a turbo means non-forced-induction engines simply can't cut it in the performance car market these days.

The only vehicles that tend to have them are luxury brands such as Lexus and Infinity, as well as lower-end trucks and commercial vehicles. HotCars embarked on a quest to find the naturally-aspirated six-cylinder with the most torque ever created, a trip that culminated with a lesser-known European car manufacturer.

TVR's Speed Six Is A Naturally Aspirated Powerhouse

TVR Sagaris Specs

(Source: TVR)

The torquiest six-cylinder engine ever produced was not some ultra-high-tech homologation special built in an air-sealed lab in some underground bunker, quite the opposite in fact. British sports car maker TVR's mighty Speed Six inline-six engine takes the title on this occasion, the brand having continuously developed the powerplant over nearly a decade.

The engine first debuted in 1999 under the hood of its Cerbera coupe, though this was not the last we'd see of it. TVR wasn't exactly the most flush manufacturer in history, so to help save cash it used the engine on every model it produced following its debut. It was available in 3.6 and 4.0-liter flavors, the former available as a base engine on vehicles like the terrifying Tuscan Speed Six and T350c.

The Origin Story Of The TVR Sagaris

TVR started to run into chronic financial difficulties during the mid-2000s and was eventually sold off to Russian businessman Nikolay Smolensky. Looking to try and turn its fortunes around, Smolenkey ordered the design of a new halo car, which would later be christened the Sagaris. It was in this that the Speed Six would take its final, most powerful form.

The car, which featured a more aggressive design than its predecessors, also got a boost in power as TVR's engineers extracted every last drop from the venerable engine. The 4.0-liter unit made 400 hp according to TVR, and 349 lb-ft of torque. This was enough to make it the torquiest naturally aspirated six-cylinder powerplant ever made when the Sagaris was released in 2004, a title it still holds today.

The Speed Six Engine Was Designed To Be As Light As Possible

While TVR had carved out a reputation for offering crazy vehicles that made just reaching a destination a victory for their owners, the brand wanted to ensure the Sagaris was more focused. One of the biggest elements of making a balanced-handling car is to ensure weight distribution is as close to 50-50 as possible, something difficult to achieve unless a car is mid-engined.

Powerplants are inherently heavy, though TVRs have always been front-engined. While this tradition continued with the Sagaris, the lightweight Speed Six helped to reduce the problem as it was made primarily from aluminum. This consisted of the block, cylinder heads, and pistons all being constructed from the material.

The connecting rods were made from forged steel to make them stronger, while the overall size of the engine was further reduced as it used a dry sump oiling system. This allowed the oil reservoir to be placed to the side of the engine and out of the way, which allowed TVR to mount the engine really far back in the chassis.

It was so far back that the manufacturer refers to the Sagaris as being 'front mid-engined', a crucial ingredient to achieving its final weight distribution figure of 53:47, as per a 2005 issue of Autocar magazine. The engine was rev-happy as well, featuring a redline of 7,800 rpm.

Light And Powerful Speed Six Helped Sagaris Achieve Blistering Pace

The 400 hp and 349 lb-ft of torque available from the lightweight engine, which when combined with a composite body resulted in a weight of just under 2,400 pounds, meant the Sagaris was pretty brisk.

It could hit 60 mph in just 3.7 seconds and 100 mph at a click over 8 seconds, before carrying on to a top speed of over 185 mph. The engine was mated to a five-speed manual gearbox, while a trick limited-slip differential helped put the power to the road. The Sagaris was also afforded independent suspension all around, giving it the agility and poise to match its straight-line performance.

The 2022 Porsche 911 GT3 Offers Huge Torque From Its NA Flat-Six

Porsche 911 992.1 GT3 Specs

(Source: Porsche)

It may be a surprise to gearheads that Porsche didn't come out on top in terms of building the torquiest naturally-aspirated six-cylinder engine. After all, it's been developing its flat-six engine since the 911 made its debut back in 1964. The German manufacturer got to within touching distance of the rapid TVR with the 2022 992.1 version of its 911 GT3 offering.

The car, essentially a stripped-out and track-focused version of the standard 911, featured a more powerful version of the 4.0-liter flat-six. Despite producing more power than the Sagaris at 502 hp, and revving higher to 9,000 rpm, its torque figure falls a little short. At 346 lb-ft, the 911 GT3 comes within a whisker of stealing away bragging rights from the Blackpool Rocket.

How Porsche Tweaked Its Well-Developed Flat-Six

The all-aluminum engine construction helps keep weight down, a design Porsche has perfected over decades. For the 992.1 evolution of the GT3, the automaker managed to find yet more areas to enhance to squeeze a bit more from it.

Essentially the same engine as in the GT3 Cup racer, the powerplant was given brand-new pistons to help bring a little more grunt to the party. It was also given a new advanced dry sump lubrication system, which consists of seven suction stages that rapidly bring oil back to the sump to prevent oil starvation.

An advanced seven-speed PDK semi-automatic transmission ensured that the driver could quickly bang through the gears, the unit helping to carry the GT3 to 60 mph in just 3.2 seconds. A six-speed manual gearbox was also available as an option for customers looking to have a more engaging and old-school driving experience.

While the technologically advanced Porsche is arguably a better option for a track blast than the slightly unhinged TVR, the Sagaris' meaty torque figure allows it to eclipse the 911 in this challenge. Despite failing to turn around TVR's worsening financial foundation, the Sagaris' Speed Six remains the torquiest naturally-aspirated six-cylinder engine ever produced.