More than anything else, BMW are known as the producers of the world’s best inline six cylinder engines. Sure, there are plenty ready to challenge that claim. But BMW’s commitment to the layout has produced some of the world’s great engines – anyone who has driven an S54 powered car would surely agree.
However, BMW are certainly not on their own. The layout boasts particular inherent characteristics, and several manufacturers have exploited the type to brilliant effect over the years. A good straight six is silky smooth, has a torquey delivery and provides strong power across the rev range.
The inline-six was once the engine format of choice for many manufacturers. Aston Martin’s classic DB5 had a 4.0 Litre straight six, and Datsun followed suit with one in their early Z cars. Mercedes fitted them to decades worth of luxury sedans and sports cars, and of course, who could forget that magical lump installed in the beautiful Jaguar E-Type.
Even as technology advanced, the inline-six kept its grip as the platform of choice for luxury and performance cars. Nissan and Toyota developing two of the most famous straight six engines to date; RB series from Nissan and the JZ family from Toyota. Both coming in either naturally aspirated, turbo charged or twin turbo charged formats, and could be tuned in the aftermarket to devastating effect.
In the late 90’s there was a shift in the tide and more pressure was put on manufactures to become eco-friendly and pedestrian safety also started to become more of a concern, the age of downsizing had begun. As a result we started seeing less and less inline-six options as manufactures swapped to a smaller V format engines or efficient four cylinders.
Soon enough, if you wanted an inline-six, BMW was your last bastion; they never put the straight six to bed. BMWs stubbornness meant they kept developing it as it fitted into their modern modular inline engine template. Each cylinder in a BMW engine is 500cc, meaning all engines use the same internal parts like valves, bearings, pumps and even pistons keeping costs down and design times to a minimum. The inline-six has become a staple in the BMW arsenal and is part of the brands heritage and history.
But it appears they aren’t the only one who can still see an advantage in the format. Mercedes announced last year that they will be putting a new inline-six into production over the next few years. As technology has advanced we have seen small displacement engines putting out some incredible power figures while still delivering over 40mpg and meeting new tighter environmental guidelines. Ford’s 3 cylinder 1.0 Litre Eco Boost set a new standard, not only can it fit on a sheet of A4 paper but can be had from factory running a staggering 140bhp! Aftermarket tuners have even claimed to get them up to a safe 205bhp with a few modifications and a remap.
These advancements in technology have meant manufactures have now been able to return to the straight six format, while still being able to match the performance of larger V8s while delivering the economy of smaller 4 cylinder units.
Mercedes aren’t the only ones to make the shift to the inline-six either. JLR have recently announced that they will stop buying their V6 and V8 engines from Ford, leading people to speculate that there are plans afoot to develop and produce their own straight six replacement unit. Following the same Modular format that BMW use, it would be much easier and cheaper to add another pair of cylinders to their 3 and 4-cylinder engines.
It’s looking increasingly likely that the inline-six could be the last configuration of the performance internal combustion engine before we all start to make the switch to electric and hybrid technology.