| Back to: AutoSpeed | Shopping: Cars | Musical Instruments |
Julian Edgar, 50, has been writing about car modification and automotive technology for nearly 25 years. He has owned cars with two, three, four, five, six and eight cylinders; single turbo, twin turbo, supercharged, diesel and hybrid electric drivelines. He lists his transport interests as turbocharging, aerodynamics, suspension design and human-powered vehicles.
Today’s AutoSpeed article on electric vehicles is, as the box in the article states, based on a seminar given by Dr Andrew Simpson.
Dr Simpson produced the paper that we used as the foundation for the Assessing the Alternatives article we ran about a year ago – it’s amongst the very best of articles you’ll find in deciding which fuels vehicles should be using.
Andrew Simpson has just returned to Australia from four years in the US, where he worked at the US Government National Renewable Energy Lab in Colorado, and then was a Senior R&D engineer at Tesla Motors.
I found his seminar quite riveting: it changed my views on a host of subjects relating to electric cars.
The boom in GPS-based navigation systems must have seen a diminution in sales of book-based street directories. I haven’t seen the figures to support that, but it’s certainly what you’d assume to be taking place.
But the companies that produce street directories (and of course in many cases also supply the software for the nav systems) are fighting back.
The more you think about turbo boost control, the more implications there are for any given system.
Let’s just refer to a traditional wastegate system.
(That’s where there’s a bypass passage – the wastegate – around the turbine. Open the wastegate and exhaust can bypass the turbine, slowing turbo speed and so dropping boost pressure. Remember – the less open the wastegate, the higher the boost pressure.)
In this discussion it doesn’t matter if it’s an electronically controlled system or a simple pneumatic system.
Let’s say that boost pressure is sensed from the compressor outlet of the turbo. If the maximum desired boost is 10 psi, the maximum outlet pressure of the compressor will also be 10 psi.
But the situation changes if the boost pressure is sensed from the intake manifold. If 10 psi is again desired, the boost pressure at the manifold will be 10 psi, but the boost pressure being developed by the turbo will need to be higher.
When modifying cars, everyone conducts some sort of cost/benefit analysis.
That might be as informal as weighing-up the likely cost of the modification against the guessed benefit, or it might be a more detailed analysis.
A friend of mine, Paul, has a rule of thumb that goes like this:
Back in 1998, on naturally aspirated cars, he budgeted $100 per kilowatt for a power improvement. Any more than that and he thought the value poor; any better than that and – well, he thought that was pretty good.
That $/kW ratio was for mods like intake, exhaust and chip.
I am writing this sitting in the Maryborough (Queensland) caravan park’s camp kitchen. My wife, Georgina, and our little boy and I are camping here, having driven up from the Gold Coast, a distance of about 350 kilometres.
I have stayed on and off in caravan parks since about the age of 16; camping in tents or staying in cabins or on-site vans.
Over that time, the biggest change has been in the nature of typical caravan park guests. Once, the people staying in caravan parks comprised almost entirely families with young children. But now, especially in non-holiday periods, caravan parks are dominated by ‘grey nomads’, older, retired people who have hit the road.
As we covered in Analysing Road Car Drag, most aerodynamic drag of current vehicles is created by separation pressure drag. Put simply, this is reflected in the size of the wake – the cross-sectional area of the disturbed air dragged along behind the car.
The most slippery vehicles in the world – the solar race cars – have reduced separation pressure drag to the extent that the other types of drag (eg viscous drag, induced drag and interference drag) become more important.
But in all conventional cars, it’s separation drag that remains the big one.
Now this gives rise to a rather interesting idea. Imagine you’re standing alongside an empty road. The day is a still one – there’s not much wind blowing. A car is rocketing towards you along the road, travelling at perhaps 100 km/h. It will pass close by to you. It grows in size and then roars past.
Now – what do you feel?
Clearly, you will be able to feel the wake – the eddies and turbulent air indicative of the aerodynamic disturbance of the car. This disturbance will take into account the separation pressure drag and the frontal area of the car – the two when multiplied form the vast majority of the actual aero drag that’s experienced by the car.
And, equally clearly, the smaller the air disturbance that you can feel, the greater the slipperiness of the vehicle.
I’ll let you into a secret.
I think it quite bizarre, but some people actually believe that the greater the driver skill needed to operate a car, the better the car must be.
The corollary of this is that is if a modification makes it easier to get more out of a car, the modification must be bad.
Now put this way you can see why I called the notion bizarre. But in the time I’ve been writing about car modifications, I’ve come across it quite a few times.
Here are just two examples.
This week we have the first in a two-part series, one that I am very pleased with.
The series is on how to use cheap and simple electronic kits to monitor the output of the oxygen sensor.
The first story I did on this, way back in the mid 1990s, resulted in the development of the ‘Mixture Meter’ kit – thousands have since been sold.
Now we both re-introduce the narrow band sensor display, updating the story to additionally discuss what many people want from such a display (and that’s improving fuel economy) and also, in Part 2, look at how a similarly cheap and easy-to-build display can be used with wideband sensors.
The latter is especially significant: while there are plenty of aftermarket air/fuel ratio meters that use wideband sensors, we’ve never seen a description of how to tap into the standard wideband sensor fitted to many of today’s cars.
Here in Queensland the State Government has issued a discussion paper entitled Improving Sustainable Housing in Queensland.
The paper canvases a range of requirements the government is considering implementing for the construction of new houses and units.
I think it astonishing how little government regulation has been applied to the energy efficiency of housing. Especially in the context of the media attention given to fuel-efficient cars, there seems to have been a deathly silence on what is surely the far more important area of housing.
After all, a typical house is going to be consuming energy for something in the order of five to ten times as long as a car, and will be doing so most hours of the day and night.
Perception of any crisis in world affairs has always followed much the same pattern.
Those who say it isn’t happening and never will happen; those cautious but observant who say it might happen; those early adopters who say it is happening well before a majority agree; and those who like to see it unambiguously demonstrated before acknowledging it is actually happening.
Or – and this is really important – not happening.
Trouble is, at the ‘it might happen’ stage it’s difficult to decide on the right course of action. Do nothing and any action might be too late.
Or, conversely, do nothing and in fact the action might later prove to have been correct.
Think CFCs in aerosols and the ozone layer for the first; think Y2000 bug in computer software for the second.
And the eminence of the ‘early adopters’ counts for little: remember the 1970s predictions of a world overpopulation crisis, and how widespread famine would result in a catastrophic reduction in the population by the year 2000? Despite some very highly credentialed experts arguing vehemently – and with apparent logic – that we were doomed, it didn’t happen.
And now to global warming.
Copyright © 1996-2008 Web Publications Pty Limited. All Rights Reserved
RSS|Privacy policy|Advertise
