The top 10 greatest straight six engines
TVR SPEED SIX
PRODUCED: 1999-2006 DISPLACEMENT: 3996cc INDUCTION: NA
Britain’s TVR was ambitious to name its inline-six after Bentley’s own famous 6.5- litre. But its resulting engine honoured the legendary name well. The story goes TVR had dreams to build a road version of the 7.7- litre V12 GT1 Cerbera Speed 12 – until company boss Peter Wheeler decided it was too dangerous. It then derived an alloy, dry-sumped 4.0-litre six from the project that unleashed 268kW/420Nm. The engine went on to find its wildest form in the 2005 Sagaris, making 303kW/473Nm at 7500/5000rpm, the zenith for a production atmo straight six.
PRODUCED: 2016-... DISPLACEMENT: 2999cc INDUCTION: Turbo, s/c
Mercedes-Benz’s M256 returned to lining six pots in a row after it ditched the layout in 1999 to focus on vee engines. Found today in AMG’s 53-badged variants, the M256’s genius lies not in V8-upsetting grunt but hybrid integration. The 48V battery system powers ancillaries like A/C and the water pump, as well as the electric supercharger, to not only free up the engine from parasitic belt drive but aid turbo spool as well. The electric motor on the output shaft then plays both starter motor and power booster, helping deliver 320kW and sometimes as much as 770Nm. The result is an incredibly smooth, strong feeling engine that is as refined as it is ground breaking.
PRODUCED: 2000-2006 DISPLACEMENT: 3246cc INDUCTION: NA
The E28 M5. The M1. BMW has relied on the inline-six to power its most iconic performance heroes for decades and the S54B32 that debuted in the E46 M3 is a particular highlight. In regular M3s it delivered 252kW/365Nm thanks to its individual throttle bodies and double VANOS, while a reworking of its valvetrain and a new carbon-fibre air intake in the CSL’s HP version unlocked a further 13kW and 5Nm. Besides the incredible noise emitted when spinning the S54HP to 8100rpm, it also extracted 83kW/115Nm from each of litre of its 3246cc capacity. An achievement that an engine like Ford Mustang’s 5.0-litre Coyote V8 would need 415kW/575Nm to match.
MERCEDES BENZ M198
PRODUCED: 1954-1963 DISPLACEMENT: 2996cc INDUCTION: NA
Engines usually find their ultimate form on the racetrack but the roadgoing Mercedes-Benz 300SL bucked that trend when it debuted at the New York International Auto Show in 1954. Its donk was based on the M186 found in the brand’s W186 300 limo, which was then dry sumped for duty in the W194 SL racers. They produced 125kW, or enough to propel them to first place at the 24 Hour of Le Mans enduro in 1954. In road trim, engineers developed the engine further as the M198 with a Bosch direct mechanical fuel injection system (a production car first), to produce 148kW and 275Nm. To top it off, the block was then upgraded to a far lighter alloy in 1962.
CHRYSLER HEMI 6
PRODUCED: 1972-19773 DISPLACEMENT: 4342cc INDUCTION: NA
Aussies first tasted a six with true V8-crushing grunt when Chrysler Oz rolled up its sleeves on the 1972 Charger E49. While the Aussie overhead-valve Hemi engine was fairly simple, locating exhaust and intake ports on the one side, it proved there was no replacement for displacement. Reworking the 4.3- litre used in the 1971 Charger E38, the E49’s engine sucked air through its triple Webers to put out 225kW/441Nm. Forget the Holden Torana GT-R XU-1, this Chrysler covered Ford’s fabled GT-HO Phase III’s V8 for kilowatts. Although the E49 did not win Bathurst, it cut the quarter mile in 14.4sec and earned local legend status.
PRODUCED: 1949-1992 DISPLACEMENT: 3442cc INDUCTION: NA
Decorated and versatile, the XK6 has powered everything from modern tanks to the gorgeous E-Type. Its legend kicked off with the 3.4-litre crossflow DOHC six that pushed the XK120 to 205km/h and a production car speed record in 1949, before claiming the 24 Hours of Le Mans in 1951 and 1953 in the nose of the C-Type. The succeeding D-Type took the great race in ’55, ’56 and again in ’57 when a privateer raced the larger 3.8-litre version. But it’s in the 1957 XK-SS, a road going D-Type, where the 3.4-litre truly flexed its muscle with 195kW.
PRODUCED: 1991-2002 DISPLACEMENT: 2997cc INDUCTION: Twin-turbo
Toyota’s Aristo might have wielded the 2JZ-GTE first but it will be remembered as an engine that belonged to the Supra. Strength was key in the 2JZ-GTE’s cleansheet design that, surprisingly, reverted to a cast-iron block. It also used a closed deck, forged crankshaft and a square bore and stroke. Sequential turbos could push 243kW and 431Nm through its 3.0-litres, enough to propel a delimited Supra to 290km/h, but the engine quickly found its calling in the aftermarket that discovered it could easily reap 745kW with choice modifications.
PRODUCED: 2019-... DISPLACEMENT: 2993cc INDUCTION: Twin-turbo
Turbocharging the F80 M3 might have given it serious grunt, but it’s the new M3’s S58 engine that has found manners to go with it. The engine still spins high to 7200rpm. And not only does its 3D printed cylinder head, forged pistons and a lower compression ratio squeeze a hefty 375kW/650Nm from just 3.0-litres, it’s docile and smoother in delivery – as we’ve found in the X3 M. A small weight saving also paves the way for duty in the new M4 GT3, replacing the V8 M6. It confirms its closed-deck block and forged crank as sturdy enough to handle serious motorsport.
PRODUCED: 2002-2014 DISPLACEMENT: 3983cc INDUCTION: Turbo
The Barra showed Aussies could build a world-beating six as good as anyone else. It was FPV engineer Gordon Barfield’s inspired idea to bolt a large turbo to Ford’s all-new DOHC 4.0- litre six, producing 220kW/450Nm on a measly five psi. Later Ford and FPV versions showed the cast-iron block’s true potential, culminating in the Falcon XR6 Sprint that put all the best bits into a 325kW/576Nm swansong that could thump out 370kW and 650Nm on overboost. Unsurprisingly, tuners have also flocked to the engine, revealing 1000kW as achievable on a stock block.
PRODUCED: 1989-2002 DISPLACEMENT: 2568cc INDUCTION: Twin-turbo
While Nissan’s RB engine had been around for a while, it reached its peak when it was called up for the R32 Skyline GT-R. Debuting the new ‘26DETT’ suffix, it used belt driven dual overhead camshafts, a cast-iron block, individual throttle bodies and twin ceramic turbos to punch out 205kW/355Nm. While that was plenty for its day, the Japanese gentleman’s agreement on a 206kW limit grew increasingly restrictive as the GT-R evolved into R33 and R34 guises. The engine’s Group A racing record with the R32 hinted at its capability, as do tuner examples, while Nismo showcased its production potential when it bored them to 2.8-litres for the 2004 GT-R Z-Tune. These made 368kW/540Nm.