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.

• » Comments (3)

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.

• » Comments Comments Off on You can write books!

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….

• » Comments (2)

My major job – training people in business and government writing skills – takes me all over the country. Usually that involves lots of flights, but recently I chose to take the Greyhound bus between Coffs Harbour and Port Macquarie.

The bus travel was actually very pleasant – though I didn’t envy the driver threading his way through the dusk traffic on narrow roads constrained by constant roadworks.

When I was sitting in the bus, I started analysing its ride quality over the often poor road surfaces.

To cope with the large variation in possible load while still giving the best ride quality, long-distance buses typically use air suspension. (This also lets the bus ‘kneel’ as people get on and off.)

The air suspension stiffness is set to give a natural frequency of about 1Hz – the best frequency for ride quality.

And, in the bus, the ride felt about right for a 1Hz natural frequency – the absorption of large bumps was superb.

However, sitting back and admiring the flowing scenery outside the window, I thought I could feel another ride quality characteristic – and this one was not so pleasant.

Superimposed on the soft suspension movements was a higher frequency judder. It was like riding in a conventional car travelling on a road that had long wavelength bumps – but a corrugated surface.

Rather than guess any longer, I whipped out my iPhone and, using the ‘Vibration’ app, recorded the ride accelerations being experienced by the bus body. The seat next to me was empty and so I put the phone down on the cushion and gently held it in place.

Ten seconds later I had a record, and a moment after that I used the software to perform a Fourier analysis, giving the dominant frequencies in the waveform.

This showed a peak at 1Hz (the air springs) but also another peak at about 10Hz. The latter was the juddering “corrugations” I could also feel.

But what was causing this higher frequency of vibration?

The higher speed juddering was caused by the natural frequency of the unsprung mass – the weight of the suspension acting on the “springs” that comprise the tyres.

But it gets more complex. How do the 10Hz unsprung weight vibrations get through the 1Hz air spring isolation? With the forcing frequency (10Hz) so far from the natural frequency (1Hz), wouldn’t the transmission be almost zero?

I am not completely sure, but I think it has to do with the massiveness of the unsprung weight. Was that rapid shaking of the huge tyres and suspension arms feeding a vibration through the suspension mounts that I could feel?

Reflecting on this, I realised that I’d felt all this before – but to a lesser degree. In 4WD passenger cars using solid front and rear axles (ie a high unsprung:sprung mass ratio) you can feel something similar… it’s a bit like the car is being shaken by the suspension. So the soft main springing was being subverted in ride quality by the high unsprung weight bouncing on the tyres.

Here’s another point: dampers need to control suspension movement at both the suspension and tyre natural frequencies…. but the requirements for controlling each mode are quite different. One requires damping of large amplitude, low frequencies (the movement on the body springs) – and the other damping of high frequency, low amplitudes (the movement on the tyre springs).

It would be interesting to talk to a damper manufacturer about the decisions in damper design that they must be making.

• » Comments (4)

I’ve always enjoyed having lots of gauges in a modified car. Even in my first car – an air-cooled, 2 cylinder Honda Z – I fitted an oil temperature gauge. Subsequent cars have had gauges that show everything from exhaust gas temperature through to air filter restriction.

So it’s not surprising that I have been enjoying the MoTeC CDL3 digital dash that I have fitted to my Honda Insight.

What has surprised me, though, is how much my enjoyment of the car revolves around the dash. These days, where driving fast means that you get locked up, having the ability to be entertained by the dash rather than by just the driving is a major advantage. And being able to program the dash to show the parameters you want adds another layer of enjoyment.

So I have the dash displaying on the main screen:

– Engine rpm (bar graph)
– Speed (derived from the dash’s GPS input)
– Gear (worked out by the dash based on road speed and revs)
– Fuel level (using the standard Honda fuel tank sensor, with the result calibrated in per cent)
– Engine temp
– Lambda number (showing mixture strength, where Lambda 1 = 14.7:1 AFR)

Then, on the bottom line of the screen and able to be scrolled through by pressing the standard Honda FCD button on the dash, I can further bring up:

– Manifold pressure
– Inlet air temp
– Fuel injector duty cycle
– Engine oil pressure
– Engine oil temperature
– Ignition advance
– EGR valve duty cycle
– Water/air intercooler pump duty cycle
– VTEC on/off
– Lambda short term trim
– Lambda long term trim

The dash is also able to be configured to display different text-based warnings. I currently have warnings displayed for:

– Seatbelt
– Door open
– Engine hot
– Engine cold
– Oil pressure
– Lean
– Battery level
– Inlet air temp
– Fuel level
– Change up
– Change down
– ECU hot
– Dash hot

These warnings are all ‘smart’ – eg the seatbelt warning shows only when the car exceeds 5 km/h with the seatbelt off, and the ‘change up’ warning shows only when a certain combination of throttle position, gear, manifold pressure and road speed occurs.

The CDL3 dash is now part of the old range of MoTeC dashes that use a B&W LCD (rather than the newer models’ colour displays) and cannot be configured with anywhere near the versatility of the current stuff. However, the major advantage from my perspective is that the old dash shape fits perfectly into the Honda’s instrument binnacle.

So what can’t the CDL3 do, things that I’d really like? The answer is not what I would have thought before buying it: more than anything else, I’d like the dash to be able to perform maths functions. For example, to be able to show trip fuel economy, where fuel used is divided by distance travelled. And I’d also like it to be able to show maxima and minima of all readings, and….

In fact, the CDL3 has been such a success that I am upgrading to the ADL3 dash – same footprint and display, but the ability to do maths functions… and a whole lot else. Luckily, like the original CDL3 dash, I have found one second-hand – as I write, it’s on its way.

• » Comments (2)

Never have I had such fun when playing with a car! So what am I excited about?

Tuning programmable management on the road.

Regular readers will be aware of our Honda Insight series. As you’d expect, the publication of the articles in that series lags well behind where I am actually up to with the car. (I don’t want to run into a problem and have a big gap in the middle of the series, so it’s best from a publishing perspective that I take this approach.)

So I am around three months ahead of the series in what I am actually doing – so explaining my recent tuning of the MoTeC M400.

In the last month I’ve been tuning crank and start, fuel, ignition, idle speed control, turbo boost, exhaust gas recirculation, acceleration enrichment, wide-band closed loop feedback and lots of others.

All has been done in my shed, driveway or on the road.

It has been an immense learning curve – I’ve never before tuned a programmable management system – with some problems to overcome along the way.

But what I have found so rewarding is the degree of control that you can have over how the car drives. Tuning an interceptor (that I have previously done) or making minor tweaks to factory ECU inputs and outputs allows you to do lots of things, but tuning programmable management allows you to do so much more. (The same would also apply to factory ECUs where the software has been cracked – not the case with the Insight.)

Having so much control means that you can stuff things up absolutely mightily. I am not talking about blowing the engine (though that of course isn’t difficult with wrong timing or fuel figures) but how the car can be made to drive so badly, so easily.

Or, more positively, you can tweak and tweak and tweak until you achieve things that appear initially impossible.

The Insight is running without its hybrid electric assist at this stage, so the bottom-end torque normally provided by the electric motor is missing. With just a 1 litre engine, very high gearing (especially in first and second) and 4800 rpm peak torque, getting the car tractable around town has been no mean feat.

That’s especially the case when no ‘start-up’ map exists for this car – the MoTeC has had to be programmed literally from scratch.

The excitement of activating and then mapping exhaust gas recirc that boosted part-throttle low-rpm torque to a major degree was sensational; getting acceleration fuel enrichment sorted so the turbo boosts much more quickly after a throttle movement was fun; mapping the control of the water/air intercooler pump so that the pump works only when needed was intriguing; and designing the boost table in three dimensions to give exactly the boost behaviour I want was exciting.

I can now see better why a friend of mine years ago talked about driving to work each day, laptop on the passenger seat and making tuning tweaks at every set of traffic lights! With literally thousands of data points able to changed, and often interacting with each other in the driving, getting the perfect tune could be a lifetime pursuit.

But in the mean time, it’s a helluva lot of fun.

• » Comments (2)

We will be covering in a later issue of AutoSpeed what I am about to write about – so this is just a quick heads-up.

If you are developing a custom water/air intercooling system, here are some critical questions for you.

1. How can you bleed all air out of the system? Nearly all commercially available aftermarket water/air heat exchangers don’t have bleed fittings. If you are mounting these heat exchangers conventionally, eg horizontally, about one-third of the internal volume will stay full of air – not water!

2. How are you measuring pump flow? If your answer is to pull off a hose and direct it into a bucket, then almost certainly the amount you measure will not be correct. Why? Because pumps will often work differently when they are part of a closed system versus an open system.

3. Finally, is the pump flowing effectively – or is it cavitating? Of the three pumps I tried in my system, only one was effective in circulating water without any apparent cavitation.

Looking around the web at pics of custom water/air intercooling systems, I’d guess that many (most?) of these systems are operating below par because of these issues.

• » Comments (3)

When is enough clearance sufficient?

If you’ve modified a lot on cars, you’ll have come across this question. It might be the clearance between the exhaust the bodywork, clearance of a driveshaft at full suspension bump with a chassis member or subframe, or even clearance between a large turbo and bodywork.

Years ago I read an excellent book written by an automotive suspension engineer working in the 1950s. In it he made the (almost throwaway) line that there’s no need to provide tyre clearance at full suspension bump AND full steering lock – the idea being that this situation almost never occurs, and if contact did in fact occur in that situation, the car would be moving so slowly that it wouldn’t matter much anyway.

These thoughts are intruding because at the moment I am massaging a turbo dump pipe so that it clears a steering tie-rod, with the greatest potential conflict occurring at full suspension droop and with full right-hand steering lock.

At full droop but with the wheels pointing straightahead – no problem. And at full steering lock and with the wheels at normal ride height – again no problem.

It’s just at that particular combination – one that again is very unlikely to ever occur – that I have the issue.

I am concerned because if the car has to undergo full engineering approval, I can just imagine an engineer saying something along the lines that conflict should not be able to occur at ANY combination of lock and suspension movement….

And even if clearance is achieved, how much clearance is enough? If I were ornery enough to throw in maximum engine torque reaction movement at just that moment, perhaps another 10mm of clearance would be needed.

But hold on! How could the engine be developing maximum torque if the suspension is at full droop? After all, in that situation there’s very little – next to none in fact – of the car’s weight on the tyre… so how could it transmit the torque anyway? No torque transmission means no transverse engine rocking!

Hmm, what about if the car has an LSD, and a very stiff front anti-roll bar, and is cornering hard enough (at full lock!) to lift a wheel? Then I suppose one could imagine a situation where something like contact could occur.

Aaaagh!

• » Comments (5)

It’s not often that you get a clean slate in terms of designing an instrument panel.

With my Honda Insight project, where the standard instrument panel is being ditched and replaced with (primarily) a MoTeC CDL3 digital dash, to some extent the type of display becomes obvious – it’ll be dominated by the MoTeC unit.

But what about the factory-fitted warning lights – things like ABS, EPS (electric power steering) and airbag malfunction indicators? And how will high beam, low beam and the action of the indicators be shown? And will there be data that I will want to be able to see but the MoTeC dash won’t easily show?

Despite the dash not likely to be installed for many months, I’ve been mulling over these ideas.

At this stage – and things may well change – this is what I am thinking I’ll need:

Warning lights for:

 – high beam

 – low beam

 – left indicator

 – right indicator

 – EPS

 – ABS

 – airbag

 – handbrake / braking system fail

Small backlit numerical LCDs for:

 – high voltage battery voltage

 – electric motor current flow

MoTeC dash display of:

 – engine rpm

 – coolant temp

 – fuel level

 – road speed

 – manifold pressure

 – intake air temp

 – gear

 – oil pressure

 – oil temperature

 – turbo exhaust back-pressure

 – water/air intercooler pump drive voltage

 – 12V battery voltage

Some of these MoTeC-displayed parameters (eg intake air temp and rpm) will be communicated via the CAN bus from the M400 ECU.

One parameter (selected gear) will be internally calculated in the dash, while other parameters (like oil temp and pressure) will require dedicated sensors.

Note that the MoTec dash allows different data to be displayed depending on the mode selected – so not all of these things will be available all at once!

On the list above there are a couple of unusual ones.

I want to be able to see turbo exhaust back-pressure because, in order to provide low rpm torque, the turbo that is being used is small. However, if as a result of its small size, the exhaust back-pressure is overly high, then fuel economy will suffer. It’ll be good to be able to see this figure.

So why show the water/air intercooler pump drive voltage? The pump will be varied in speed by the ECU. This is needed because I want to control the intake air temp, rather than just keep it as low as possible. For much of the time, I would expect that the pump will be operating at less than full speed. Displaying pump drive voltage will allow me to see at what speed the pump is being driven. Not only will this be interesting in itself, it will also allow me to assess how effective the control strategies are that are being used to operate the pump.

As I said, all still a long way off, but I need to start sourcing bits and installing sensors right now.

• » Comments (12)