In tuning, what are standard conditions?

Posted on August 16th, 2016 in Driving Emotion,Economy,Engine Management,Honda,testing by Julian Edgar

It’s been cold hereabouts, and I have been doing some more on-road tuning of my MoTeC-equipped, turbo Honda Insight.

(But before I get to the subject of this column, a point on the DIY tuning of programmable engine management. In short, it’s the best fun-for-$ expenditure you can ever make on a car.

Why? Because after you’ve bought and fitted a system, you’ve just gained a pastime you can do for literally ever. There is always – always! – a tuning change you can make that will cause the car drive fractionally better in a given situation, or to develop slightly more power, or to use a little less fuel.

In short, buy programmable management and you’ll never need another hobby or leisure activity!)

So anyway, this time I had the car on 98RON and there was an ambient temp of 5 – 10 degrees C.

Over the last two years I’d have tuned the ignition timing maps on this car for literally hundreds of hours. That might seem to indicate that I’m rather slow at it, but in fact more accurately reflects the statements above about gains always being able to be made – and also the fact that the little Honda is very sensitive to ignition timing variations.

As an example of the latter, it’s one of the very few cars that I know of that requires some negative timing figures if it is to avoid detonation. That’s especially the case at low revs and when only one intake valve per cylinder is working (ie VTEC is off), so giving very high combustion chamber swirl.

I do the on-road tuning of the ignition timing using a microphone temporarily mounted in the engine bay (clipping it to the throttle cable works well). This microphone feeds a small amplifier and I listen on headphones. With this system I can not only clearly hear detonation, but I can also hear the harsher edge the engine develops just before detonation.

In addition to the headphones – and the laptop on the passenger seat – I also have another trick up my sleeve. A dashboard-mounted knob allows instant variation in ignition timing of plus/minus 10 degrees.

So I drive along (lots and lots of empty country roads around here), listening to the engine through the amplified headphones. I might be at 2000 rpm, full throttle in 4th gear, the engine just coming onto boost and lugging hard up a hill. VTEC is switched on. (So that the engine will readily accept boost pressure, I have the engine switch to two-valves-per-cylinder operation from 1750 rpm upwards at full throttle. The engine doesn’t like it so much if only one-valve operation is occurring as it comes onto boost – in this non-VTEC mode, I have heard turbo compressor surge.)

Anyway, in these conditions, where change is occurring relatively slowly, I manually advance the timing with the dash knob and listen carefully. If the car clearly goes harder (almost always) and there’s no sign of detonation (or its precursor sounds), I pull over and add some timing at that spot overall ignition timing map. Then repeat the process….

Now you know why it takes me so long!

Anyway, finally to the point of this column.

As with all programmable management systems, the M400 has a base timing map (it uses RPM and MAP axes) and then a series of correction maps. These corrections include coolant temperature and intake air temp. Because, as I’ve said, the Honda is very sensitive to timing variations, I use all these correction maps.

Let’s take a look at intake air temp – and how I influence it.

I regulate intake air temp by using a water/air intercooler and variable pump speed. If the intake air temp is below 35 degrees C, the pump stays off. Depending also on throttle position, as the intake air temp rises above that figure, pump speed increases. Together with the effect of the thermal mass of water within the heat exchanger, the upshot is that in nearly all conditions of ambient temperature and boost, the intake air temp stays within the range of 20 – 50 degrees C.

Initially, I’d intended to aim at an intake air temp of around 45 degrees C (the higher temp better for fuel atomisation and so fuel economy), but I found that to avoid detonation, timing had to be retarded at this intake air temp. I then reconfigured the water/air intercooler pump map (ie I turned the pump on earlier) to aim at an intake air temp of around 35 degrees C.

So, all well and good. On this basis, the main ignition timing map would be configured optimally for 35 degrees C, and the intake air temp correction map would knock off timing as the temp rose above this.

Hmm, but what about when it is very cold, like it has been over the last few days? I’ve seen intake air temps lower than I’d ever planned – around 25 degrees. The intercooler water pump is off, but the air entering the turbo is so cold that even with spurts of boost, the water within the intercooler heat exchanger is staying at less than 35 degrees.

And in these conditions I’ve been hearing precursor sounds of detonation through my headphones.

Is it because the density of air (and so cylinder filling charge) is greater, resulting in higher combustion pressures? That is, the greater mass of air (more likelihood of detonation) is more than offsetting the colder air (less likelihood of detonation)? And so do I pull back timing at lower intake air temps (ie less than 35 degrees C) as well as at higher intake air temps (above 35 degrees C)?

And do I therefore accept that, in the real world, the engine will probably never be running the timing as specified in the main chart – after all, while intake air temp might occasionally be at 35 degrees C, stopped at traffic lights in might be 40 degrees, and down a long country road hill it might be 30 degrees – and so on…

And how do I correctly tune this intake air temp correction map? After all, to do it accurately I’d need road test ambient temps that range from -10 degrees C to plus 50 degrees C.

And, thinking about that, I have in fact tuned at the high intake air temps. Early in the tuning process, in the middle of summer and with an ambient of about 35 degrees C, I can remember doing repeated 0 – 160 km/h runs, flat out and working the little car as hard as I dared. I was tuning the high temp ignition timing correction chart (and also revising how much boost gets pulled out in these conditions – another variable!).

Looking out the window as I type this early on a Sunday morning, it’s frosty and foggy, about 0 degrees C. I should, I think, get away from this desk and hit the road for some tuning…

It’s a process that will literally never be finished.

 

The trap of load index

Posted on August 2nd, 2016 in Safety,testing,Tyres by Julian Edgar

This issue we have a story on understanding (and varying) gearing, based primarily on changing tyre diameter. The prompt for the story was the availability of a wide variety of on-line calculators that allow you to very easily correlate road speed with selected gear and engine rpm, and to see how overall gearing changes can be made by changing diff ratio or tyre size.

And there’s nothing at all wrong with those calculators – in fact, it’s easy to spend a few hours trialling all sorts of different combinations of numbers!

However, when looking at making major reductions to tyre rolling diameter, there is a trap that I wasn’t aware of.

And the trap?

Load index!

Load index is the rating given to a tyre that describes the maximum weight that should act through that tyre. The rating is indicated by a number that correlates to a vertical load (in kg or pounds). So for example, a tyre with a load rating of 89 has a maximum load of 580kg per tyre. (And at what tyre pressure does that apply? Again this is an area that most people don’t think about, but that load applies only at a specified inflation pressure – often 36 psi.) Load index tables can easily be found by a web search.

And what governs load index? Most references talk about the strength of the tyre (ie how many layers of steel reinforcement are used, for example) but in fact it also depends to a large extent on the volume of air trapped within the tyre.

And, as you go smaller in rolling diameter, that volume decreases!

Thus, changing gearing by reducing tyre diameter may be difficult if the load index of the smaller diameter tyre has decreased a great amount.

The minimum load index is a legal requirement as stated on the tyre placard. For example, my little Honda Insight, with 165/65 14 tyres, requires a minimum load index of 79 (or 78 in some markets). A load index of 79 means the tyres can cope with 437kg per tyre. That seems really high for this small car – the highest static load the Honda tyres would ever have to deal with is about 330kg – but that’s what the placard says.

If I wished to lower the gearing, changing the wheel size to 13 inch and going with 165/55 tyres (which would give about 10 per cent lower gearing) sounds good – until you realise that the load index of such tyres is only 70, or 335kg. A load index of 335kg is some 23 per cent lower than legal!

In fact, I found it impossible to find a tyre with a legal load index that gave a smaller rolling diameter on the Honda. To go further, I also found it hard to find any cars where these small tyres would be legal, their load indices being so low.

So if you’re thinking of reducing the volume of air inside the tyre (eg a by using a lower profile but keeping the same width, or a combination of smaller wheels and smaller tyres), check the load index of the available tyres first.

It’s honestly not an area I’d ever given much thought to.

You can write books!

Posted on July 5th, 2016 in books,Electric vehicles,Opinion,Technologies,testing by Julian Edgar

Earlier this year I published my 15th book.

Now that might sound impressive, but you can do the same.

Yes, you!

How? Read on…

My first book, 21st Century Performance, was published in a very traditional manner in 2001. A print magazine publisher (who I’d done quite a lot of work for) suggested to me that he’d be interested in a book on car engines. I asked if that could be broadened to all things car performance, and he agreed.

I put a huge amount of work into the book – not just its content, but also working with its graphic designer. The production quality turned out to be excellent – the photo reproduction (off quality 35mm slides in those days) was outstanding and the general presentation of the hardback darned good.

I also think – and forgive my arrogance – that the content was very good. There are perhaps only one or two points in the whole book I’d now change – though of course I could now add a lot more to the content.

I negotiated a small up-front payment for the book and then sat back and waited for the royalties to roll in. I think that history records it as the best-selling automotive modification book ever published in Australia, but getting royalties out of the publisher wasn’t quite what I’d expected. Cheques arrived, but there were never any statements of sales, and the cheques were all round figures…

Maybe everything was above-board (I still don’t know), but it didn’t feel right.

And the royalty amount? I’d have to look it up but I think the book sold (15 years ago!) for around AUD$70 each copy – and I got AUD$3 a book. That’s a royalty of 4 per cent. (Incidentally, second-hand copies of the book now sell for up to US$350.)

I resolved then never to do another book on the basis of traditional publisher royalties.

My next book – in 2004 – was Performance Electronics for Cars, written with John Clarke for the publisher of Silicon Chip magazine, Leo Simpson. At that time, I was a major contributor to Silicon Chip and, while I subsequently decided that writing for Leo was the last thing I’d ever do on Earth, the book deal was fine. I asked for my normal up-front ‘article rate’ for each chapter of the book, and I was free to use the material elsewhere as I wished.

The book sold well – I think – and probably made the publisher a tidy profit. I got paid a decent amount, so we were all happy.

Time passed…. a lot of time.  In fact, it was about early 2013 when I started thinking about book writing again. I’d just read a really interesting book (On a Cushion of Air: The Story of Hoverlloyd and the Cross-Channel Hovercraft) and the authors had self-published it. I wrote to one of the authors (Robin Paine) and asked him about the process. At the same time, I also wrote to a few other authors currently publishing tech stuff.

Self-publishing, it appeared, meant stumping up lots of cash to pay for everything, while the authors publishing through traditional publishers (like I’d done) did it more as a ‘labour of love’ than a money-making deal.

Then I did some more exploring… and discovered CreateSpace, Amazon’s publishing arm.

At first I couldn’t believe it – just upload a properly formatted pdf and they’d publish the book (complete with ISBN) and list it on Amazon. As people ordered, they’d print on demand (POD). There were no upfront costs, the author could set their own price (above a certain minimum that took into account the printing costs and some profit by the publisher), and royalties would be sent to the author monthly…  And that was it.

To say it again: I just couldn’t quite believe it.

I developed a template (actually the biggest effort of the process) and put together a book from my published articles – it was Amateur Car Aerodynamics Sourcebook, published in 2013.

I followed that up with Inventors and Amateur Engineers Sourcebook, Home Workshop Sourcebook and DIY Car Electronic Modification Sourcebook, again all published in 2013.

I then wondered about a smaller book, and did DIY Testing of Car Modifications, also in 2013.

In 2014 came Tuning Programmable Engine Management, Hybrid and Electric Cars Amateur Sourcebook and Thoughts about Driving, Car Modifications and Life (the latter based on these columns – and bought by basically no-one!).

In 2015 I wrote DIY Suspension Development and then, putting on my other hat as a trainer in high-level writing, I produced Writing Effective Arguments: How to Write Strong Arguments in Business and Government.

Also in 2015, I wrote Using the Brilliant eLabtronics Modules!

This year, in 2016, I have written DIY Loudspeaker Building.

As a contributor not just to AutoSpeed but also to UK magazine Everyday Practical Electronics, I have lots of material available to me. That makes it easier to assemble books, although the effort in doing so cannot be understated.

But the advantage is amazing – it costs me nothing in terms of cash… absolutely nothing at all.

And the royalties can be set as you, the author, wish. Remember the royalty I got with 21st Century Performance – 4 per cent? I typically set my CreateSpace royalties at about 40 per cent (but it depends on the distribution channel that the customer buys through). Therefore, sales can be much lower for the same income.

The downsides? There’re no publisher promotions, no placing of books on booksellers’ shelves (they can order it to sell, but often they won’t). On the other hand, eBay sellers often list your book, and you can buy copies of your own book at a discount and flog them off wherever you want… but you soon tire of that.

Me? I am happy writing books (good for my CV!) and receiving royalty cheques that result in monthly trips to the bank (CreateSpace won’t do direct bank transfers to Australia, so they’re always mailed cheques).

Am I making squillions? Absolutely not (though I would if more people bought my books!).

Is it worth it? – unquestionably yes.

If you have a story to tell, I think it’s the way to go.

If you’re interested, see my Amazon listed books here.

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Incredible car aerodynamics resource… and it’s free!

Posted on June 28th, 2016 in Aerodynamics by Julian Edgar

Over the years I have bought nearly all of the major books published on automotive aerodynamics. In fact, a quick glance at my bookshelf shows more than 20 of these books. To assemble the same collection, however, will take you a lot of time and a fair amount of money.

But today I found an incredible free resource that summarises the vast majority of information that you’ll find in all those books.

The resource comprises the presentations used in the Master of Science programme at the Budapest University of Technology and Economics, and the lecturer is Dr. Jen Miklós Suda, assistant professor in the Department of Fluid Mechanics.

Dr Suda appears to have put together almost every significant picture, diagram, graph and text snippet you’ll ever find on car aero – and it’s pretty well all in English.

It’s a simply extraordinary presentation. You can find the six downloads here – grab them while you can!

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Manufacturing decline not always as analysed

Posted on June 18th, 2016 in Economy,Ford,Holden,Mitsubishi,Opinion,Toyota by Julian Edgar

I have just finished reading a book on the manufacturing decline that has occurred over the last 60-odd years in the UK. It’s called The Slow Death of British Industry and is subtitled A Sixty Year Suicide 1952 – 2012. It covers, decade by decade and industry by industry, the decay in making things in what was once a great manufacturing country.

The industries it covers include car manufacture, ship building, aircraft design and construction – and also more obscure industries like pharmaceuticals. It describes the companies that fell by the wayside, were absorbed by others, or ended up being split into so many entities that their whole reason for existence simply disappeared…

Companies like Dorman Long (builder of the Sydney Harbour Bridge), Parsons (the inventers of the steam turbine) – and car brands like Wolseley, Triumph and Jowett.

The book catalogues in excruciating detail the union bloody-mindedness, the inept management, the worthless interventions of government, the confusion in direction and execution.

And visiting Britain’s wonderful technological museums (as I have done) where you can see Concorde; the SR.N4 hovercraft; the remains of one of the crashed Comets; the beautiful Jaguar E-type; the fastest steam locomotive in the world (the Mallard); the world’s first code-breaking electronic computers; the Sinclair electronic calculator – it makes this whole story of UK manufacturing success and decline come alive.

But there are some things missing in the analysis. They’re the same things missing in many analyses that occur here in Australia of our similar (but smaller scale) decline in domestic manufacturing.

Firstly, quoting massive reductions in the share of employment that manufacturing comprises in the economy is to miss the point that such changes have occurred in all first world countries. For example, that’s the even the case in countries like Germany and France that are often cited as manufacturing powerhouses we should be emulating.

In much the same way as primary industry (farming and mining) once dominated employment, these days, tertiary (service-based) industries now create most employment. That decline in the share of employment held in manufacturing jobs is exactly what you’d expect with greater mechanisation, use of robotics and so on. We wouldn’t want to be hand-building all our cars, one at a time, as was once done. Productivity would be terrible and cars would be unaffordable. So, of course machines will replace people, manufacturing productivity will improve and employment in the sector will decrease as a proportion of total employment.

Secondly, ignored is that the decline in local manufacturing is based entirely on a reduction in demand for those goods. If the pubic, the buyers, choose not to buy locally made goods – and instead buy imports – then of course (unless they are competitive in exports), local manufacture will decline.

In other words, to be brutal about it, uncompetitive domestic companies go broke. They may be uncompetitive in technology, in branding, in price, in innovation – in all cases, consumers vote with their wallets.

So we hold a major collective responsibility for manufacturing in our country declining. The person who blames the Federal Government of Australia for the loss of car manufacturing in this country – that is, the loss of Toyota, Ford and Holden – often has a Nissan Patrol in their driveway, or a Honda, or a BMW. The person who complains that the last Australian-built washing machine recently came off the production line is the same person who has never bought an Australian-made washing machine.

Thirdly, and as an extension of this idea, globalisation, free trade agreements and geographical shrinking of the world through information technology has increased the flexibility with which consumers can make choices. I source electronic modules on eBay from China; they’re bought from either the manufacturer or wholesaler of these products. I can remember when some such modules, able to be sourced only from local retailers, cost me over ten times as much and would take a month to be delivered.

I can very much empathise on a technological history level with the loss of once great companies, once great manufacturing enterprises.

But that’s a completely different perspective from saying that we should all have paid more for inferior goods– and so on a societal level have had a lower standard of living – to prop up manufacturing companies that had become uncompetitive.

I think that in the future, commentaries on the decline of manufacturing will appear to be as relevant as those that bemoan the fact that most people no longer till farms for a living.

 

 

A shortwave radio

Posted on May 2nd, 2016 in Opinion by Julian Edgar

It seems that about every 10 years or so I get excited about radios. No, not radios that can receive only AM and FM, but radios that can hear broadcast signals from all around the world.

They’re called shortwave radios.

In days gone past, shortwave radio stations were the main ways in which governments attempted to spread their gospel: Voice of America, Radio Australia, and so on. These days, streaming on the Web has replaced the need to listen to these broadcast stations – but there are still literally hundreds of stations on these frequencies.

This time I got excited when I saw how prices have come down for really exceptional radios that can work on these frequencies. Specifically, I bought a Tecsun PL-880, a radio with excellent reviews that can receive all the shortwave bands, in addition to being a very good (ie long distance) AM and FM receiver.

I can remember when a radio of this calibre would have cost around AUD$500: mine cost just over AUD$200, including delivery.

So what can it do? Well, there’re too much to cover here but the radio has 3500 station location memories, signal strength and signal/noise ratio meters, excellent sound quality and very good sensitivity.

It also has a built-in whip aerial, but as has always been the case for shortwave reception, better results are achieved by using an external aerial. Which is where this column comes in – yesterday, I spent most of the day putting up that aerial.

Antenna theory is complex – what with resonant modes for different frequencies and so on – but the simplest approach is to just put up a long wire, positioned as high as possible. I live on a few acres on the edge of a little country town, so there is room to put up a big aerial. Easing the process, there are also two tall gum trees on the block, located about 50 metres apart.

My tree-climbing days are past (especially when one of the trees drops boughs occasionally!), but I figured it would be easy enough to get a rope up into the trees from which the aerial could be strung. I ended up using a bow and arrow, the arrow weighted with sand (and then a bolt). A light line was shot upwards and over a tree branch, then this was used to haul up a heavier nylon rope.

At one tree, the nylon rope connected to an insulator I made from an offcut of high density polyurethane.

At the other tree, I hauled up a pulley through which another rope was passed. The rope holding the pulley was tied off. The rope running through the pulley connected to the insulator (and so aerial) at one end, and to a suspended weight at the other.  This weight keeps the aerial taught, even with the tree boughs moving in the wind.

Said quickly it all sounds easy, but it was actually quite a job to get the ends of the aerial positioned in the trees. (And, even then, they’re nowhere near as high as I’d like.) The end result is an aerial just over 50 metres long that is 6-7 metres in the air.

The aerial connects to a copper feed that in turn connects to a coaxial cable, which in turn plugs into the PL-880’s aerial socket. A ground connection is provided by an earth stake.

And does it work? Yes! Night time is best for receiving shortwave signals, and last night I reckon I could hear at least 100 stations.

But were they interesting? Well, not as much as they once were!

These days, with the rise of China in this part of the world, many stations are transmitting in Chinese. In fact, last night I think perhaps only one-fifth of stations I could hear were in English.

It still gives me a thrill though, listening to other countries on a radio.

(And, incidentally, the PL-880 is so effective that, using only its inbuilt aerial, on the AM domestic broadcast band you can hear at night a station on nearly every frequency – pretty good in Australia.)

No it’s not for everyone, but the idea you can hear the other side of the world using just a long piece of wire and a portable radio remains to me a thrilling idea. Yes, even with the Web.

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Brilliant woofer testing hardware and software

Posted on March 26th, 2016 in Reviews,testing by Julian Edgar

This week I have been having a great time playing with speaker stuff. About a week ago I bought Woofer Tester 2 from the US, and I’ve since been blown away by what you can achieve with it.

But first, a step back.

If you’re into sound systems (either car or home), you’ll be well aware of the famed Thiele Small speaker parameters that are especially important when designing woofers and subwoofers. These parameters are the speaker specs that you plug into software (or an on-line calculator) to allow you to design the speaker box. That box design includes aspects such as internal volume, length and diameter of any ports, and so on.

Without the Thiele Small (abbreviated to TS) specs of the driver, you’re just guessing the box design – and the chances are overwhelming that your guess will be less than optimal!

So to design a good speaker enclosure, the TS specs are needed. Which is fine if you’re buying a new driver or one that is second-hand but still has specs available on it.

But what if you’ve sourced a speaker that is literally an unknown? For example, a quality driver from a late model car being sold off cheaply? Or even the speaker from a salvaged TV or surround sound system? (Don’t laugh: some of these consumer goods speakers are small and high quality – perfect for enclosures built into car doors or under seats. And people just throw these speakers away…)

In those cases, the driver’s specs need to be measured.

And, if you do a search online, you’ll find plenty of DIY techniques for measuring TS parameters. You’ll need a precision resistor, an AC multimeter that measures over a wide frequency range, and a frequency generator. And a lot of time spent doing very finicky measurements and plugging numbers into lots of equations. It’s certainly possible, but who wants to spend the time and effort doing all that? Especially if you’re sorting through a whole bunch of drivers to find one suitable for an application?

Well, now you now longer need to do so – just use Woofer Tester 2.

Woofer Tester 2 is a complete speaker test unit. This incredible piece of hardware plugs into the USB port of a PC or laptop and connects straight to the speaker under test. Open the software, press a button and within literally seconds many of the TS specs are measured. Do some more testing (eg by weighting the cone by a known amount) and the rest of the important specs are there in front of you – it’s that easy!

You can then import those specs into the provided Thiele Small program that will allow you to model sealed, ported and band-pass enclosures.

Build the enclosure, and then you can use Woofer Tester 2 to test it to see if it matches the predicted response. (Woofer Tester doesn’t include a microphone, so you cannot directly measure frequency response – but, indirectly [eg by impedance plots] you can get a good idea of what is happening.)

So does the system work? Does it ever!

So far, I have measured about 15 pairs of salvaged speakers. Picking the best of these, I have built two different types of enclosures to suit.

In one case, using just an 8 litre ported enclosure and a 5-inch woofer, I have clearly audible (and smooth) response down to 50Hz. In the real world, that’s a stunning result from such a small driver in a very small enclosure. Especially when the woofer (bought as a pair of second-hand speakers) cost $5!

In another case, I had some ex-Sony home surround sound drivers that were originally mounted in tiny (200cc!) boxes. For these drivers, I modelled and then built 2 litre ported enclosures, made from short lengths of 125mm heavy-wall plastic pipe, with MDF ends cut to suit. The drivers are just 3 inches in diameter (and have an effective piston diameter of only 2.4 inches) and yet in these easily built enclosures, sound very good indeed. I am thinking of using them as outdoor speakers for a BBQ area – they’d fit nicely under the house eaves.

Using Woofer Tester 2 hardware and software, you can now measure all those speakers for which proper TS specs are not available (and that’s almost all car sound speakers) and then model enclosures to suit. You can even build enclosures that work for individual drivers (useful, because even apparently identical drivers can have different measured specs).

I think that this approach represents a revolution in how bass / midrange speakers can be installed in cars, and how speakers can be sourced.

I paid US$160 for Woofer Tester 2 – and think it’s incredible value for money.

We’ll be covering in much more detail in AutoSpeed how to use the Woofer Tester 2 hardware and software, and what it can achieve in DIY speaker design and installation. But to say I am impressed is a vast understatement….

My new (old) car

Posted on January 12th, 2016 in BMW,Driving Emotion,Opinion,Skoda by Julian Edgar

It wasn’t that there was too much wrong with my 2006 Honda Legend, but maybe I was just getting a bit bored with it.  While I think the Legend is a fantastically under-rated car – what with its silky 3.5 litre V6 and active all-wheel drive – after three years I was also starting to hanker for something else.

The buying criteria varied on the day of the week: one day something spacious and frugal like a Skoda Superb wagon; the next day something fast and fun like a Jaguar XJR. Or, more conservatively, a Falcon G6E, Camry Hybrid or Subaru Outback. But in all cases, the budget was under AUD$35,000, and the car had to be brilliant on the 150km round trip that I do when, for work, I go into Canberra. (This trip might occur two or three times a week.)

Out here, the roads are rough and demanding; you need big lights and the ability to out-brake a kangaroo hopping across the road in front of you. And you also need a car that is easy over long distances – when you’re feeling tired, you want the car to do most of the work for you.

So I looked and looked.

The X350 model Jaguars (2003 to 2007) greatly appealed. These cars are aluminium-bodied, riveted and glued together. They also all have air suspension, and are available with a 3-litre V6, a 4.2 litre naturally aspirated V8 or the mighty supercharged V8. Incredibly, the massive differences in price as new cars is not reflected 12 years down the track… depending on condition and kays, you can buy any of them for much the same money.

Three years ago, when I was deciding on the purchase that eventually led to the Legend, I also considered these Jaguars. However, the pick of the bunch – the supercharged XJR – was then around $50,000. Nowadays, they’re around $32,000. Unfortunately though, there were none available on my side of the country.

[And why have a budget of under $35,000 – in relative terms, not much money? Basically, I think that it’s now enough to buy a very good car. Why? Well, I am not convinced that there have been huge gains in new cars in the last decade or so. For me at least, the major technological improvements of the last 20 years were really good engine management (electronic throttle, variable valve timing, etc) and safety (lots of airbags, electronic stability control).  From a convenience point of view, I like navigation and a good sound system. Pick a prestige car of the last 10 or 15 years and you get all these. Pick a diesel and you’ll also get good fuel economy…]

So Jaguars were off the list, for now at least. So what about BMWs then? If old prestige cars fall badly in value, then 7-series BMWs fall catastrophically. We had a good look at one – huge diameter rims, massive interior space, very comfortable seats… and lots of broken bits and pieces inside. High kilometres too: this BMW reeked ‘money pit’.

And then suddenly one morning I made a decision. We were going to buy a 2010 Skoda Superb wagon, with the 125kW 2-litre diesel and all the fruit. There was one in Sydney (about three hours away) and it looked mint. At $22,000 (but negotiable) from a private seller, I figured twenty grand would get it. Roomy, reliable, reasonably quick point-to-point, well-equipped… yes, this was it.

We went and got $20,000 out of the bank, and off we went to buy the car. My wife, ten-year-old son and I, all very excited.

And in the metal, the Skoda looked really good. We already have a Skoda in the family – a diesel Roomster – so we’re familiar with the practicality built into these cars. The Skoda was huge inside and had lots of thoughtful touches – but it didn’t have navigation. Hmm, for me that’s a downer. (And yes I know I can use my phone but I much prefer inbuilt navigation.)

But what about on the road? I am unconvinced about the driveability of twin clutch autos and, as we moved away from a standstill, I could immediately feel the slightly unprogressive behaviour of this one.

“The transmission has been replaced by Skoda,” said the owner helpfully. He saw it as a positive, but with only 100,00km on the odometer, I just wondered.

The drive was around an industrial area, relatively new with well-surfaced roads. But even on these good surfaces, I could feel the bump-thump of the low profile tyres, and beyond that, the impact harshness was also high. Worse, the car pitched: in ride quality, it didn’t feel well sorted at all. Last time I considered buying a car, I deleted the Superb from the list because a local person with one has experienced dented rims on our bad roads….and driving this car, that wasn’t surprising.

So we said no, and off we went.

It had taken ages to get the money out of the bank (aren’t banks supposed to have money? – they never seem to make cash withdrawals easy) and my wife suggested that, rather than driving home, we stay the night in Sydney. I agreed: that meant we could spend the next day looking for cars – and so we hit the hotel.

That night, I browsed the web, creating a ‘must see’ list of Sydney cars for the next day.

There was a 2004 Mercedes E500 (V8 and air suspension), a 2004 Jaguar XJ8 (this one with the smaller 3.5 litre engine); a 2002 BMW 735i (perhaps this one would be in better condition); a 2004 Mercedes S430 (with V8 and 7 speed auto); a BMW 530 diesel from 2006; S350 and E320 Mercedes (from 2003 and 2004); and another Mercedes E500.  That’s right: no Camry Hybrids or Falcons or Subarus… they’d kinda gone from the list without conscious decision.

Incredibly – well, it seems incredible to me – all the prestige cars were at or lower than the $20,000 we’d got out the bank for the Skoda. I know that expensive cars have always dropped in value fast, but I don’t think in my whole driving life I have ever seen the quality of car now available for the price of an old Falcon or Toyota!

The next morning we were up bright and early – off to see the first on the list, an E500 Mercedes. From the W211 series (2002 to 2009), the E500 was the top of the W211 line (the supercharged AMG E55 excepted). It used a 5-litre V8 with 225kW (and an exceptional 460Nm from 2700 to 4250 rpm) and the first cars had 5-speed autos.

The car we were looking at was dark blue and had a black interior. It also had a panoramic sunroof and an interior that was mint. It also had full Mercedes Benz service history and had travelled just 127,000km over its 10 years of road registration. Surprisingly, it had the 7-speed auto – it must have been among the first E500s in Australia delivered with the better trans. Factory navigation, six stacker CD, nice mix of analog and digital instruments in the dash, superb woodgrain, full memory everything on both front seats. Even a split-fold rear seat (useful for us) and a large boot.

But what would it be like on the road? We took it for half an hour, allowed out with the car sans salesperson.

And the E500 was simply a revelation.

It had three settings for the air suspension; most of the time we left it on ‘comfort’. You could hear the impact of the tyres on small irregularities but could feel nothing. On large bumps, the capacity of the suspension to absorb vertical accelerations was extraordinary. And handling? Hard to find out on a half-hour city test drive, but I threw the car around a few roundabouts and it stuck well, body roll surprisingly low for the apparent softness of the suspension.

But I think that my wife and son were sold the minute I put my foot down: for the V8 cars with the 7-speed auto, the quoted factory time is 6.0 seconds for the 0-100 km/h… and it felt just like that.

We kept staring at each other in disbelief.

How could this old car, that inside felt and looked so modern, a car that went like a cut snake and rode like a limousine – how could this car be stickered at just $18,500? Hell, even if in the future you needed to replace the air struts, or the air compressor, or – well, whatever – you’d still be getting an incredible machine… even for the total outlay.

We offered $18,000 of our cash and the car was ours. That’s less than the price of a new Toyota Yaris….