A few months back we put together a list of the road cars that produced the most power per litre of engine capacity. There were some truly unbelievable numbers coming from the likes of McLaren, Mercedes, Bugatti and many more. We even called the numbers that NA cars used to produce ‘poultry’. On reflection, forced induction is just cheating isn’t it? Any old lump with enough boost can put in the numbers, at least for a little while. So we thought it high time now to celebrate the free-breathers. These are the naturally aspirated road cars with the most power per litre.
The naturally‑aspirated cars with the most power per litre
125PS per litre
A champion of the NA power per litre arena has to be the Honda S2000. In amongst all these six- and seven-figure supercars and hypercars is an everyman sportscar with one of the most highly-strung engines homologated for road use. It bests the likes of the Lamborghini Huracan STO, Ferrari F12tdf and Ferrari 812 Superfast. At least, it does in its most powerful Japanese specification, which produced 250PS from a 2.0-litre 9,000rpm-revving four-pot. That made for a heady 125PS per litre… in 1999!
Commiserations to the Porsche 911 GT3 RS 4.0 of 2011 and subsequent 4.0 GT3s. All matched the S2000’s figure but the later engines feature further up the list on even better form...
Ferrari 458 Italia
126.6PS per litre
Ferrari had been champions of power output per litre since the 360 Challenge Stradale. It wasn’t until the 458 Italia of 2009, however, that the incredible show of strength that Ferrari is still on in this arena began. From 4.5 litres the 458 produced 126.6PS per litre. Good gravy, what a screamer and one anyone with enough money could own! Okay, not ‘everyman’ like the Honda, but still!
126.8PS per litre
Before the tdf and the Superfast, the LaFerrari extracted what was until recently, the most potential from that V12. 6.3 litres as in the tdf but in this instance, capable of 799PS, for 126.8PS per litre. We might add, just 0.2PS per litre more than the 458...
Porsche 911 GT3 (992)
127.5PS per litre
The recent 4.0-litre flat-six Porsche 911 GT3s are just a sensation, aren’t they? In the latest 992 form, the engine has ITBs and produces 127.5PS per litre, from a 510PS total. Like that Ferrari V12 that we’re shortly to get back to, surely this motor will go down as one of the last-great free-breathers? Hell, it could go down as one of the all-time great combustion engines full-stop. We wonder what the RS version will bring.
Ferrari 812 Competizione
127.7PS per litre
Just pipping that is Ferrari’s latest and greatest iteration of its incredible Tipo F140 V12. The 812 Competizione produces 830PS from 6.5 litres, revving to 9,500rpm, for 127.7PS per litre. Yes, it even pips the LaFerrari, by 0.9PS per litre and supposedly, this isn’t the last we’ve heard of this engine. Good lord.
Porsche 911 GT3 RS (991.2)
130PS per litre
The 991.2 GT3 RS is evidence that highly-strung as it is, there’s more for this incredible engine to give. On release four years ago, the 991.2 bumped power to 520PS, for 130PS per litre. What on Earth can we expect from the 992 GT3 RS…
Porsche 918 Spyder
132PS per litre
The second of the so-called ‘holy trinity’ to feature in this list is the Porsche 918 Spyder. It’s also arguably one of only two hypercars we’ve seen on this list so far, given that most modern examples have moved on to forced induction to create their neck-breaking numbers. Derived from the flywheel-less V8 found in the Porsche RS Spyder LMP2 car, this incredible 4.6-litre motor produces 608PS, for a 132PS per-litre figure.
133PS per litre
But for all of the might of Stuttgart, they couldn’t best a rattly old Caterham, could they? The R500 of 2008 was Caterham at the height of its powers, using thinner alloy and carbon-fibre to make a light car lighter. The 266PS 2.0-litre Ford Duratec made a fast car faster, too. Yes, almost 270PS from two litres. That makes for 133PS per litre. Anecdotal in this context, of course, is that the R500 also had a power to weight ratio of 530PS per tonne, besting the Bugatti Veyron. It won’t be the last hardcore underdog to make this list… Brap!
Ferrari 458 Speciale
134PS per litre
Far from being the most potent naturally-aspirated prancing horses, the Competizione and indeed the LaFerrari are easily cleared by the amazing 458 Speciale of 2013. It had a 605PS 4.5-litre V8, for a scarcely believable 134PS per litre. While the Speciale is rather pricey these days, it still sits proud as a comparative bargain in among seven-figure hypercars. Live with that, Porsche… Is this Ferrari’s greatest ever engine?
BAC Mono R
Ah yes, here we go again. More boutique track-focused performance that’s technically legal for use on the road. The BAC Mono R is as single-minded as it is single-occupant. It features, as celebrated by BAC, 347PS from its 2.5-litre Mountune four-cylinder engine. Yes, that means the Ferrari 458 Speciale is bested, with the Mono R sporting 138.8PS per litre.
Aston Martin Valkyrie
156PS per litre
We’re really on to the unobtainium now and arguably, what will be the crescendo of the combustion engine as a whole. Both the last entries are V12s and come courtesy of all-time great engine masters Cosworth. This is of course the Aston Martin Valkyrie, the most uncompromising, most-advanced hypercar yet made. Vac-packed within that incredibly tight bodywork is a 6.5-litre V12 producing 1,014PS, as it revs to a redline of 11,100rpm. We’ve known these numbers for years, we’ve now seen and heard it in action but it’s all still difficult to believe. Oh, the per-litre output. 156PS per litre. Surprise surprise, another unbelievable number.
Ariel Atom V8
160PS per litre
You thought we’d move on to the T.50 and be done? Think again. Like a family member that you’re slightly scared of at Christmas, the absolutely absurd Ariel Atom V8 is here to remind you of what true madness is. It packed a 482PS 3.0-litre V8 that revved to five figures and came to be by welding together two bike engines. Yes, that made for 160PS per litre. No, we still can’t believe it was road legal.
166PS per litre
Finally, we’ve arrived at the end. As spoiled above, it’s the Gordon Murray Automotive T.50, with its 3.9-litre 663PS V12, that makes the 918 Spyder’s race-derived V8 look like a pushrod small-block. It revs to 12,100rpm and on the way, produces a staggering 166PS per litre. Unrelated to the Valkyrie, this engine is also a Cosworth development. The key difference? Engine size. Gordon Murray wanted it to be compact, free-revving and weigh as little as possible. On top of all that, owners will be controlling these biblical numbers with a manual transmission. Internal combustion? Cosworth completed it.
There are countless legendary NA engines we will have missed. A number of BMW M engines (including that in the McLaren F1), AMGs, Lamborghini V12s, the Lexus V10. When you do the maths – trust us, we did – they just don’t do the business to the standard of the cars above. Commiserations also to the Ferrari 812 Superfast, F12 TdF and Lamborghini Huracan STO, which fall only slightly below the Honda S2000, at around 123PS per litre.
We researched, we iterated but we’re sure we might have missed some. Let us know in the comments.
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