Posts Tagged ‘vs’

I wonder what will be the popular fuel of choice in 20 years time?

In Europe, 2011, it’s safe to say that diesel is currently most popular.  The ACEA winter report 2008 claims 70% of all new cars purchased in France, Italy and Belgium were diesel.  This trend is continuing to further favour diesel.  So what will be top in 2031 then?

Twenty years ago, 1991, diesels were not nearly as popular as they are now.  They were slow, smelly and uncouth!  The tides did start changing around this period however.  The diesel engine was now turbo charged, relatively high revving, refined, cheap to run and best of all it offered respectable performance.   Any petrol head would still be repulsed by this engine, but for the masses, this was just the thing.

Of course, low fuel consumption equates to low CO2 emissions.  Now the European governments are keen to encourage low consumption of foreign oil, this is achieved by heavily taxing fuel, justified by claims on environmental grounds.  Great, we are saving the environment, less fuel burnt means less CO2 released which means less global warming, (that’s what they want you to think anyway)!

Europe is no doubt a leader in diesel tech, but why?

In the late 80’s through to the mid 90’s when Europe was developing and manufacturing diesels, the rest of the world still loved petrol.  There are some good reasons why America didn’t share the same enthusiasm for reducing CO2 as us Europeans back in the 90s, ultimately it comes down to cost!

North America's most popular automobile of all time

It would appear that the American domestic market is driven by lazy advertisers.  Fashion trends dictate that the bigger the car the better.  The consumer is told they want low cost powerful engines, so thats what is made and thats what they buy, a chicken and egg situation.  The only thing to change that attitude will be fuel cost.

Well in days gone by, North America have had little interest in saving fuel, as they are not completely reliant upon foreign oil- they have their own domestic production.  Another big player in the auto industry, the Japanese, appear to have focussed alot of their attention on American requirements.  The Japs always tend to play it safe, not noted for innovation, they could have implemented Rudolph Diesel’s invention on a mass scale but opted out, it seems they still regard diesel as a dirty, noisy fuel and shy away from using it in their heavily crowded cities.  This leaves the  European market left hankering after frugle little cars that sip as little of the heavily taxed black gold as possible.

Lowering fuel consumption requires expensive research & development as well as increased material and manufacturing costs.  This is what holds back the rest of the world from investing.  In Europe fuel is so expensive the consumer is willing to pay more for their vehicle than an American.  However, recently opinons in the US are shifting, $4 per gallon fuel prices have been hitting the headlines for example.  Take a look at what the likes of GM and Toyota are offering.  GM has a brand image built on the American dream of large trucks, so they can’t go building small town cars, instead they are now offering hybrids as part of their lineup.  Toyota have small eco cars as their foothold and again offer hybrids.

Why do Americans generally not have diesel cars then?  The answer is simple, California!  The state of California has the strictest emissions laws in the world.  That’s right, stricter than ‘green’ Europe.

They require that the following emissions are within a strict defined limit:

  • Carbon monoxide, the highly toxic gas.
  • Hydrocarbons, a large contributor to smog air pollution and disease.
  • NOx, the nastiest of all, acid rain, smog illness and ultimately death.
  • Particulate matter, cause of asthma, cancer and found chucked out of London busses at about the height of a baby in a pram.

Now the state of California is leading the way in emissions regulations.  Diesels are essentially outlawed in California, where limits are set out in three simple classes, low emissions vehicle (LEV), ultra low emissions (ULEV) and super ultra low emissions!… (SULEV).  The majority of diesels are incapable of even meeting LEV, (note that all petrols are SULEV or better).  So in Europe we demand SULEV for our petrol vehicles and then it’s a case of one rule for petrol, another for diesel!  The European governments are essentially making special allowances for dirty diesels.  The only emissions that diesel emit less of, is the harmless gas that plants use to respire, CO2.

So, will Europe eventually come to it’s senses and outlaw diesel like California and the rest of North America?  The alternative is to ignore the problem and keep fooling people into thinking that diesel is a fine alternative to petrol.  In the background Euro 6 standards are being agreed, this will force diesels to be less efficient as they are engineered to battle against all of the emmisions equipment required to clean up their exhaust.  In times gone by, standards have been made and manufactors have responded by failing to achieve the goals, so governments simply move the goal posts!

Ultimately it is down to money, in 20 years time oil will still be lying around and it will be sourced from the same places it is found today, hence, I don’t see any shifts, unless Europe decides to actually be green and then petrol really will be the only sensible solution.

Personally I would hope to see lots more use of electricity and innovative hybridisation and down sizing for the forthcoming 20 years.

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I’m talking about that age old argument between diesel fans (who like to talk about torque) and petrol heads who claim power is most important.  My vote is power all the way, and here is why…

Torque:

Say we need to tighten a nut up.  Doing this without a spanner will not get you very far, why? because you need lots of torque.  Torque includes two things-  force AND distance.  For example, slamming a door by pushing on it next to the hinge will not make it slam, that is because the force may be large but the distance between point of rotation and acting force is small, so the torque is low.  Infact even an incredibly strong man with no tool will not be able to tighten a nut as much as a child with a spanner.

So our strong man ‘Arnie’ tightens the nut using only his very strong fingers.  Now a child comes along to undo the nut, without a spanner he’s helpless.  With a spanner, the child now applies a comparitively small force to the spanner but this force acts a long way away from the centre of the nut the longer the spanner is, the easier (or less forece) required to undo the nut.  Try this with a door.  See how hard it is to close the door if you push near the hinges, compared to if you push near the handle.

Taking this example and applying it to a car, the engine has now become our strong man/weak child and  the car’s gearbox is considered to be the length of the spanner.  The nut we were tightening is of course the road applying an opposing force on the car’s wheels.

Power:

Say we need to tighten up 100 nuts, engineers refer to this job as ‘work done’ (which is equivalent to ‘energy’).  Doing this without a spanner would probably be a lot quicker, why, because you don’t have to tighten the nut up by travelling through a large arch/distance.  Speed is the relationship of distance : time.  If we have less distance to cover and we turn nuts at the same rotational speed it will always use less time.

If you don’t believe me, drive 10 miles at 10 miles an hour and then do only 1 mile at 10 miles an hour- the latter surely won’t use up as much time!

So if Arnie and the child both complete the same amount of work in the same amount of time, they are said to have the same power.

Transition to the car example.  Two cars of equal weight have to tow a caravan up a hill.  One car has a lovely (sarcasm) torquey diesel engine, the other has a racy motorbike engine.  The work done will be the same, (same hill, equal weights).  So which one will get there first?  Well it’s all about power.  Power is of course, work done per unit time.  So if you get your work done quicker you finish first.

Interestingly, these vehicles make power in very different ways.  Rember Arnie and the child, well the diesel engine is our strong man- he can afford to spin things slowly because he has lots of torque (strength).  The motorbike engine and child have relatively little strength but a gearbox/spanner provide a torque/strength multiplication.  Like all things in engineering, if you fix one issue, another one is introduced.  By using the gearbox as a torque multiplier you must operate more quickly to keep your work output high.  This is why motorbike engines have to rev so much.

For those interested, a new school SI unit engineer like myself uses the following formula to work out power in kW:

Power [kW] = Torque [Nm]  * EngSpeed [RPM] * (2*3.142/60000)

In the brackets above we are converting engine speed into radians per second and watts into kilo-watts.

To convert kW into brake horsepower, BHP = kW * 1.34

So, What’s Best?

If you want to win a drag race, you need lots of power.  Simple, that is the answer to the question.  If you want to tow your caravan to the top of the hill before all the other caravans you still need to have the most power!  The subtly is the gearbox that denotes the relationship between road speed and engine speed.  Towing caravans up hills requires lots of torque at the wheels even to get rolling.  This can be done by a weak or low torque engine geared to do many more revolutions for each turn of the cars wheels.  Or perhaps a high torque engine, geared to do similar revolutions as the wheels it is driving.  In a towing race, the higher powered engine will always win!  And it doesn’t matter which engine produces more torque (provided they both have a suitable gear box) .

Most diesel fans will claim that this means lots of revving of the less torquey engine to keep up.  Yes this is true, but so what- thats why you have a gearbox and a red line almost double that of the average diesel!  Also, in favour of the smaller less torquey petrol engine is the weight advantage.  By minimising weight you reduce the amount of work needed to complete a race/sprint.

The only real advantage of high torque is longevity.  By creating  power at low engine speeds, service life is dramatically enhanced.  It is also possible to observe fuel savings by keeping engine speed low, as frictional losses are less significant at low speeds, and are zero when the engine is stopped!

In Summary

Cars, trucks boats have all been designed to speed things up.  Whether it’s getting to work quicker in a car compared to walking.  Or perhaps transporting building materials from A to B.  These jobs took a lot longer before the benefit of powerful engines.  Low power means less work done for a given period.