My sack is so packed this week, I almost didn’t have room for the nuts. But don’t worry - three nuts after the regular weekly Q&A…

Coming up in the sack: Suck, squeeze, bang and blow - inside your engine - the definitive guide to power, torque, and forced induction, plus a classic car sales con, and the truth behind how I get to be such a bastard saying exactly what I think about car companies and their products.

My fun car...

My fun car...


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I'm curious: What vehicles do you own personally? And did you purchase them or are they supplied by a manufacturer? (I’m referring to your previous answer stating you don't take payments or kickbacks from car companies.) - Jesse Webber

I own a 2011 RenaultSport Clio limited edition (my fun car) and a 2011 Kia Sportage Platinum Diesel. I bought the Sportage because it was the best compact SUV in the market at the time - as both a consumer proposition and as a vehicle per se, at about the $40k price point. Actually I was recommending the Kia on air all the time to callers on Radio 2UE and we needed that kind of vehicle. I felt I would be a hypocrite if I didn't put my money where my mouth was - and it's been great. The Clio's been great too - I just don't get to drive it often enough, because I'm always road testing something else.

And no, I don't take kickbacks or inducements from car companies.

Power and torque are the two key engine performance characteristics

Power and torque are the two key engine performance characteristics


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Power and torque figures get quoted all the time. (You quote them all the time.) What do they really mean? And, anyway, what’s the difference between power and torque? - Sarah

In a nutshell, torque is how hard the engine turns, and power is torque multiplied by revs. Another way of looking at this is simply torque is turning effect (like a spanner on a bolt) and power is the time rate of change of that turning effect. This means that torque doesn't include engine speed (although engines do have a particular speed where the torque is maximised at wide-open throttle) and power is a product of both torque and engine speed.

It's also worth remembering that the quoted figures are the maximums for a particular engine, and most of us hardly ever exploit those maximum figures. However, when you look at those maximums, you should also look at the revs. It's generally harder to access the peaks when they are higher up in the rev range (unless you drive like a cut snake, or on a racetrack) and manufacturers often cook the books by pumping up the revs to make a little more power than the competition. For a road car, low-rpm power is generally what you're after.

See also: What is direct injection >> and petrol versus diesel >>

Video blogging is easy - and you don't have to be uncomfortable doing it...

Video blogging is easy - and you don't have to be uncomfortable doing it...


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I run a small business, and I wouldn’t mind blogging on video like you. How do you shoot these reports? What kind of setup do you use? - Jessica

Video blogging is easy. I shoot these reports on a green screen and then zip in a custom background - but you generally don't need to go to that trouble to get the point across professionally. I've got a background in TV, which helps, but anyone can do it. Here are the main tips:

  • Set aside an area in your home, office or workshop. De-clutter it a bit, but keep relevant props in there (like tools of the trade)
  • You can get a good result with a cheap Canon DSLR and a kit lens but you'll need a plug-in microphone like a Rode Videomic
  • Learn enough about photography so you can set everything to manual and get a useable result (manual exposure, manual focus, manual sound levels)
  • Make sure the area is reasonable brightly lit, with soft light
  • Frame yourself to one side of the shot, not dead centre
  • Talk to the camera as if it's one person
  • Talk in soundbites - work out what you want to say in bullet points, then just expand on each bullet point on camera, and cut out the dead space between

Remember, nothing engages personally like video.

A car dealer bullshitting you, yesterday

A car dealer bullshitting you, yesterday


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I’ve been to three dealers, and instead of actually giving me a better quote than the quote I walk in with, they want me to provide them with a dollar figure I’ll accept before they consider giving me a written quote. An example from the last dealer is here:

I am happy to ask my Dealer Principal to request extra support from Hyundai Australia we would love to supply your New Santa Fe Highlander, but he will ask for a figure that will secure the business. So please let me know if there is a figure and payment budget that will secure your business.

This statement seems to suggest that the price the dealer pays for the vehicle from the manufacturer is also negotiated. If this is the case then what does the recommended drive-away price from the manufacturer really mean and can it be used to calculate whether you are getting a good deal or not? - Tariq

Here are the top 20 ways to beat a car dealer >> for reference.

My strong suggestion here is that this dealer is conning you. There is no referral to head office for greater consideration on the table here - that's bullshit. The dealer is framing the debate for his tactical advantage. He wants you to set a price so that he can come back to you with a counter offer and talk you up. He is also going to use this purported representation to head office as justification to get you to spend more. (The logic works like this: 'Head office said no - but we can do business at $[X - higher price].' Super-convenient for the dealer because he's suddenly not the roadblock between your offer and the sale: head office is, and you cannot negotiate with them.)

Get the dealer to offer a price first. Then counter-offer 10% below that. If they don't go for it, walk away, and tell them the offer is good for the next 72 hours, after which time you intend to buy elsewhere. You might be amazed how malleable the price suddenly becomes.


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I love your reviews - they helped me buy my last car. But how do you get away with saying the things you say about some cars? Don’t some carmakers hate you? Why don’t they sue you? - Karen

On car companies hating me: I'm sure they do. However, I'd suggest that if you are a reporter and you care about what the organisations you are reporting on think about you, then you are in the wrong line of work. There is generally a very unhealthy relationship between carmakers and so-called motoring journalists. The car industry spends a lot of money manipulating the motoring press - and they are spectacularly successful at it. I just decided to put consumers first (and have some self respect).

On getting sued: We have freedom of speech in Australia. In practice this means that under Australian law, companies with more than 10 employees cannot sue for defamation. So basically you can say whatever you want about a carmaker and they have to cop it on the chin. Individuals in those organisations can sue you, however. (This means you have to be careful about what you say in relation to individuals.) Even then, however, defamation law strikes a balance between protecting the reputation of individuals and the freedom of speech. The balance is: truth is a defence against a defamation lawsuit, as is honest opinion.

Turbochargers force more air into an engine. More air means the engine can burn more fuel, delivering additional performance without fitting a bigger, heavier engine

Turbochargers force more air into an engine. More air means the engine can burn more fuel, delivering additional performance without fitting a bigger, heavier engine


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What are the differences between a turbo and supercharged engine? What are the benefits as well as drawbacks of each? And what is biturbo? - Dominickson Peter

Both are examples of forced induction - methods of jamming more air into an engine than it can suck in naturally. More air means you can burn more fuel, and if you burn more fuel you can deliver more performance without increasing the displacement. 

A supercharger is an air pump that's driven by the crankshaft. These tend to boost performance at low-to-medium revs, but lose efficiency at high revs.

A turbocharger is a pump that's driven by the flow energy of the exhaust gas exiting the manifold. There's more energy at high revs and wide throttle openings, so turbochargers tend to boost performance at medium-to-high revs.

One of my favourite turbo cars is the Subaru WRX STI >>

Biturbo just means 'two turbos'. Tow turbos often deliver more than a single larger turbo, as well as responding faster to changes in engine speed, which reduces the characteristic of 'lag' - where the turbo takes a while to respond to demand, typically at low speeds. Biturbo installations come in a few different flavours:

  • Parallel - these are common in V-configuration engines (V6, V8, V10, V12, etc). Basically they bolt a turbo into each bank of cylinders and each one works in parallel to pump air into the inlet side of the engine.
  • Sequential - where one turbo is designed for low-speed boost, and a second is designed for high-speed boost, so you get more performance across a wider range of revs.
  • Staged - where one turbo feeds into a second, and then that goes into the engine. This is more common in aircraft than cars, because the stages setup doesn't respond well to changes in revs. (Aircraft tend to cruise for hours at constant revs.)

Turbochargers sometimes use 'variable geometry' to increase low-rpm boost and to prevent the turbo from choking the engine at high rpm. Variable geometry effectively makes the turbo more efficient across a broader operating range. It's achieved by changing the flow dynamics of the air on the way into (and sometimes also out of) the turbo. A series of movable vanes in the inlet (and - sometimes - outlet) to the turbo are used to change the flow characteristics in response to operating speed. 


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I will probably buy a new Hilux or NP300 Navara. Which one would you suggest? I go outback a fair bit and I'm a little worried about the reliability of the twin turbo Nissan. Is the twin turbo setup just another thing that could go wrong. - Tony

Above: New Toyota Hilux (left) and NP300 Nissan Navara (right)

Frankly I think the new Hilux is under-done and over-priced. I wouldn't be too worried about the NP300's twin-turbo engine - I suspect they've done this to appease Mercedes-Benz. (The new Navara will be the Mercedes-Benz pickup in a few years' time - and the platform and powertrain have been designed from the ground up to conform to Mercedes-Benz's as well as Nissan's design requirements. I suspect there's no way Mercedes-Benz would have agreed with a big, lazy diesel.)

See also: Mitsubishi MQ Triton review >> and my ute market breakdown >>

When you look at the specific power output of the Navara engine it's not outrageous. It's up there with other leading diesels in Europe. Furthermore I don't think you can say that a twin turbo installation is going to be less reliable than a single turbo. The bottom line is that either setup could be reliable or unreliable, depending on the calibre of its underlying engineering R&D.