Hamish McRae: A British invention gives Otto the elbow

Cars are inevitably a compromise. This was brought home to me the other day when we hired a Mercedes A-class. On paper, it is a genius of a design, cramming a mid-size interior into the length of a super-mini by dint of putting the people on top of the mechanics instead of among them. So there is a flat floor and if you have a crash, the engine evidently slides underneath the people instead of chopping off their knees. It is solidly made, quiet and well finished, as you would expect from Mercedes.

Only snag: it was horrid to drive. Or at least it was on the bumpy, twisty roads of Galloway, though it may be fine on the billiard-table surfaces of German suburbia, where it was designed. The problem is that the original design failed the Swedish elk test: it rolled over when the driver swerved as if to avoid an elk. So the Mercedes people had to redesign the suspension to give the car greater stability. They succeeded - elks all over Sweden are breathing sighs of relief - but at the cost of a very bumpy ride. A tall car is inherently less stable than a low one and suspension is a compromise between stability and comfort.

We accept these compromises as inevitable. They occur at every level of vehicle. A Ford Ka is lovely to drive and easy to park but is tiny inside for four. A Porsche 911 is exquisite but it is not really even a 2+2, as the back seats are strictly for children (lucky ones, too). The Citroen Picasso people carrier is hugely successful because it is roomy and cheap but it is profoundly unsatisfying to drive because of the sacrifices needed to give it space and keep the cost down.

Clever engineering can reduce the scale of the compromise but it cannot eliminate it. There is, however, one advance now taking place that is radically reducing the compromises in engine design. Nearly all engines, petrol and diesel, operate on the Otto four-stoke cycle, called after the German inventor Nikolaus Otto: induction, compression, ignition, exhaust. They can be tuned to give maximum top-end power, or bottom-end torque, or maximum economy. But there is always an element of compromise. If, however, you don't have to worry about either power or flexibility but just want economy, designers are largely released from such constraints. Indeed, they are released from the Otto cycle.

The new hybrids, such as the Toyota Prius, use an electric motor to provide additional overtaking power and starting-off torque. So the petrol engine can be tuned to give maximum economy because its main job is to provide steady power for cruising and topping up the battery.

The designers have found that an engine running on the Atkinson cycle is more efficient than on the Otto one. James Atkinson was a British engineer who invented a different type of crankcase design and different valve timing about the same time as Otto. It is the valve timing and an element of his crankcase design that both Toyota and Ford are using for the engines of their hybrids. (Put the names of the two engineers into www.google.com for stuff about the differences, which I find fascinating but which do get a bit anoraky.)

The result, at any rate, is a very sweet and extremely efficient engine. It does not have to produce much power or much torque so it can spin away quietly running at its most efficient pace. Hybrids seem likely to become the most important innovation in car design in the last half-century because they can combine efficiency with very low pollution. So here is one area of automotive design where there is a sudden leap forward - and where design is becoming much less of a compromise than ever before.

Sport
wimbledonScot will face Ivo Karlovic next
Sport
football
News
Hillary Clinton comments on viral Humans of New York photo of gay teenager
Arts and Entertainment
The gang rape scene in the Royal Opera’s production of Gioachino Rossini’s Guillaume Tell has caused huge controversy
music
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

ES Rentals

    iJobs Job Widget
    iJobs General

    Recruitment Genius: Sales Administrator - Spanish Speaking

    £17000 - £21000 per annum: Recruitment Genius: This is a fantastic opportunity...

    Recruitment Genius: Sales Administrator - German Speaking

    £17000 - £23000 per annum: Recruitment Genius: This is a fantastic opportunity...

    Recruitment Genius: Sales Administrator - Japanese Speaking

    £17000 - £23000 per annum: Recruitment Genius: If you are fluent in Japanese a...

    Recruitment Genius: Graphic Designer - Immediate Start

    £16000 - £25000 per annum: Recruitment Genius: This is a fantastic opportunity...

    Day In a Page

    Is this the future of flying: battery-powered planes made of plastic, and without flight decks?

    Is this the future of flying?

    Battery-powered planes made of plastic, and without flight decks
    Isis are barbarians – but the Caliphate is a dream at the heart of all Muslim traditions

    Isis are barbarians

    but the Caliphate is an ancient Muslim ideal
    The Brink's-Mat curse strikes again: three tons of stolen gold that brought only grief

    Curse of Brink's Mat strikes again

    Death of John 'Goldfinger' Palmer the latest killing related to 1983 heist
    Greece debt crisis: 'The ministers talk to us about miracles' – why Greeks are cynical ahead of the bailout referendum

    'The ministers talk to us about miracles'

    Why Greeks are cynical ahead of the bailout referendum
    Call of the wild: How science is learning to decode the way animals communicate

    Call of the wild

    How science is learning to decode the way animals communicate
    Greece debt crisis: What happened to democracy when it’s a case of 'Vote Yes or else'?

    'The economic collapse has happened. What is at risk now is democracy...'

    If it doesn’t work in Europe, how is it supposed to work in India or the Middle East, asks Robert Fisk
    The science of swearing: What lies behind the use of four-letter words?

    The science of swearing

    What lies behind the use of four-letter words?
    The Real Stories of Migrant Britain: Clive fled from Zimbabwe - now it won't have him back

    The Real Stories of Migrant Britain

    Clive fled from Zimbabwe - now it won’t have him back
    Africa on the menu: Three foodie friends want to popularise dishes from the continent

    Africa on the menu

    Three foodie friends want to popularise dishes from the hot new continent
    Donna Karan is stepping down after 30 years - so who will fill the DKNY creator's boots?

    Who will fill Donna Karan's boots?

    The designer is stepping down as Chief Designer of DKNY after 30 years. Alexander Fury looks back at the career of 'America's Chanel'
    10 best statement lightbulbs

    10 best statement lightbulbs

    Dare to bare with some out-of-the-ordinary illumination
    Wimbledon 2015: Heather Watson - 'I had Serena's poster on my wall – now I'm playing her'

    Heather Watson: 'I had Serena's poster on my wall – now I'm playing her'

    Briton pumped up for dream meeting with world No 1
    Wimbledon 2015: Nick Bollettieri - It's time for big John Isner to produce the goods to go with his thumping serve

    Nick Bollettieri's Wimbledon Files

    It's time for big John Isner to produce the goods to go with his thumping serve
    Dustin Brown: Who is the tennis player who knocked Rafael Nadal out of Wimbeldon 2015?

    Dustin Brown

    Who is the German player that knocked Nadal out of Wimbeldon 2015?
    Ashes 2015: Damien Martyn - 'England are fired up again, just like in 2005...'

    Damien Martyn: 'England are fired up again, just like in 2005...'

    Australian veteran of that Ashes series, believes the hosts' may become unstoppable if they win the first Test