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.

News
Denny Miller in 1959 remake of Tarzan, the Ape Man
people
Arts and Entertainment
Cheryl despairs during the arena auditions
tvX Factor review: Drama as Cheryl and Simon spar over girl band

News
Piers Morgan tells Scots they might not have to suffer living on the same island as him if they vote ‘No’ to Scottish Independence
news
News
i100Exclusive interview with the British analyst who helped expose Bashar al-Assad's use of Sarin gas
PROMOTED VIDEO
Sport
Angel Di Maria celebrates his first goal for Manchester United against QPR
Football4-0 victory is team's first win under new manager Louis van Gaal
Arts and Entertainment
art
News
newsIn short, yes
Arts and Entertainment
Rob James-Collier, who plays under-butler Thomas Barrow, admitted to suffering sleepless nights over the Series 5 script
tv'Thomas comes right up to the abyss', says the actor
Arts and Entertainment
Calvin Harris claimed the top spot in this week's single charts
music
Sport
BoxingVideo: The incident happened in the very same ring as Tyson-Holyfield II 17 years ago
News
Groundskeeper Willie has backed Scottish independence in a new video
people
Arts and Entertainment
The Doctor poses the question of whether we are every truly alone in 'Listen'
tvReview: Possibly Steven Moffat's most terrifying episode to date
News
i100
Life and Style
Cara Delevigne at the TopShop Unique show during London Fashion Week
fashion
News
The life-sized tribute to Amy Winehouse was designed by Scott Eaton and was erected at the Stables Market in Camden
peopleBut quite what the singer would have made of her new statue...
Sport
England's Andy Sullivan poses with his trophy and an astronaut after winning a trip to space
sport
News
peopleThe actress has agreed to host the Met Gala Ball - but not until 2015
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

    Teaching Assistant for KS1 & KS2 Huddersfield

    £50 - £65 per day: Randstad Education Leeds: We are looking for flexible and i...

    Teaching Assistant for KS1 & KS2 Huddersfield

    £50 - £65 per annum: Randstad Education Leeds: We are looking for flexible and...

    Primary Teaching Supply

    £130 - £160 per day: Randstad Education Leeds: Qualified KS2 Supply Teacher r...

    Year 1/2 Teacher

    £130 - £160 per day: Randstad Education Leeds: Qualified KS1 Teacher required,...

    Day In a Page

    These Iranian-controlled Shia militias used to specialise in killing American soldiers. Now they are fighting Isis, backed up by US airstrikes

    Widespread fear of Isis is producing strange bedfellows

    Iranian-controlled Shia militias that used to kill American soldiers are now fighting Isis, helped by US airstrikes
    Topshop goes part Athena poster, part last spring Prada

    Topshop goes part Athena poster, part last spring Prada

    Shoppers don't come to Topshop for the unique
    How to make a Lego masterpiece

    How to make a Lego masterpiece

    Toy breaks out of the nursery and heads for the gallery
    Meet the ‘Endies’ – city dwellers who are too poor to have fun

    Meet the ‘Endies’ – city dwellers who are too poor to have fun

    Urbanites are cursed with an acronym pointing to Employed but No Disposable Income or Savings
    Paisley’s decision to make peace with IRA enemies might remind the Arabs of Sadat

    Ian Paisley’s decision to make peace with his IRA enemies

    His Save Ulster from Sodomy campaign would surely have been supported by many a Sunni imam
    'She was a singer, a superstar, an addict, but to me, her mother, she is simply Amy'

    'She was a singer, a superstar, an addict, but to me, her mother, she is simply Amy'

    Exclusive extract from Janis Winehouse's poignant new memoir
    Is this the role to win Cumberbatch an Oscar?

    Is this the role to win Cumberbatch an Oscar?

    The Imitation Game, film review
    England and Roy Hodgson take a joint step towards redemption in Basel

    England and Hodgson take a joint step towards redemption

    Welbeck double puts England on the road to Euro 2016
    Relatives fight over Vivian Maier’s rare photos

    Relatives fight over Vivian Maier’s rare photos

    Pictures removed from public view as courts decide ownership
    ‘Fashion has to be fun. It’s a big business, not a cure for cancer’

    ‘Fashion has to be fun. It’s a big business, not a cure for cancer’

    Donatella Versace at New York Fashion Week
    The fall of Rome? Cash-strapped Italy accused of selling its soul to the highest bidder

    The fall of Rome?

    Italy's fears that corporate-sponsored restoration projects will lead to the Disneyfication of its cultural heritage
    Glasgow girl made good

    Glasgow girl made good

    Kelly Macdonald was a waitress when she made Trainspotting. Now she’s taking Manhattan
    Sequins ahoy as Strictly Come Dancing takes to the floor once more

    Sequins ahoy as Strictly takes to the floor once more

    Judy Murray, Frankie Bridge and co paired with dance partners
    Wearable trainers and other sporty looks

    Wearable trainers and other sporty looks

    Alexander Wang pumps it up at New York Fashion Week
    The landscape of my imagination

    The landscape of my imagination

    Author Kate Mosse on the place that taught her to tell stories