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Response

Some of this week's Letters to the Editor, discussion group posts and other feedback!

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Colour of Heat Exchangers

Regarding the letter from Kenneth Steinbach in the Response column, questioning the pros and cons of painting intercoolers/radiators black.

I have heard this debate on and off for years, so it's time to end it. Unfortunately the maths for determining accurately the heat lost by a radiator in a car is rather complex so I won't bore you with the details. The good news is that with a bit of simple calculation you can see that radiation heat transfer is irrelevant in this case anyway! However, the answer to the question 'to paint black or not to paint black' is easy.

As an example, consider a 1 x 1 m square radiator at 100 deg C radiating into an ambient temperature (in front of car) of say 20 deg C. The heat lost from radiation is only an absolute 680 W (less than 1 kW = 1000 W). Given that maybe 25 - 35 % of the fuel energy consumed by an engine is lost to the radiator system and maybe the same amount is converted to useful shaft horsepower, for a say 100 kW engine, you need to have a radiator system capable of transferring about 100kW to air. This is not accomplished via radiation if you look at the ratio between the above example and the required heat loss. Convection heat transfer is the dominant transfer mechanism by far for both intercoolers and radiators due to their low operating temperature. So paint (or don't paint) your intercoolers etc whatever colour you like - the effect is negligible simply because the radiation component of heat transfer for these items is negligible also.

If the above is clear as mud, pick up an engineering book on heat transfer and then you'll really be confused!

Julian O'Hara
Australia

Praise

Well done guys (and girls?) You are doing a great job of making AutoSpeed more reader-friendly and accessible. The new "E-mail Article to a Friend" buttons make it so much easier to win debates about which is the most relevant and in-tune auto magazine around; just hit them with AutoSpeed's contribution on the subject currently in contention. I know from responses that it has resulted in new subscriptions. It has to be the best automotive-specific-dollars I spend. Thanks again,

Ian Carter
Australia

Smart Technology

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Great article on the Black Boxes ["Inside the Black Box"], very enjoyable. Interesting to have something slightly different from an already captivating e-zine.

Craig Stampfli
Australia

Thanks for that. We've got lots more articles planned in the new Smart Technology category.

Old vs New

I am a great fan of your magazine, and even more so of your unabashed opinion. In a world where critical favour is bought and sold as readily as the products you review, it is refreshing to see you give your readers the same feedback as your friends. However, I have to call up your controversial article on the Tickford plant and its new car. I fully identify with your horror regarding waste of new parts, questionable product quality, and aberrant construction practices. There are few in the industry that would be so forthcoming on these issues.

In fact, the only way I take issue with your review is the criticism of their oversimplified and archaic suspension and engine design. My argument is this: cars in a production state have not fundamentally changed since their inception - 4 wheels motivated by an internal combustion engine. Despite experiments with other formats, this "archaic" method has been unchanged.

Not that I necessarily take up for Tickford - I have not driven one, so I cannot assess whether the engine and suspension are smooth, efficient, or capable, but I find their relative age of design to be of little importance in determining if these are the case.

A relatively recent example is the Honda CRX. The first generation si, of which I have owned three, has a 12 valve 4 cylinder motor that redlines at 6500 rpm, a rear beam axle, and torsion bar front suspension. The second generation has the next generation of Honda motors, featuring four more valves, 400 more rpm available, and about 15 more horsepower. The second generation is also equipped with four corners of double wishbones, coilovers, and a host of other more modern features.

Despite the obvious generation gap between the two cars, the first generation si continues to be a statistically more dangerous weapon for autocross, chiefly due to its lighter weight and lower torque. Even now drivers are winning stock class races by huge margins in this car. The second generation auto is the favourite of most enthusiasts because of its greater refinement of look and feel. More contemporary styling, parts and the resulting aftermarket selection. These are attributes chiefly linked to the greater complexity and more modern nature of the second generation, but the fact remains that when numbers are considered, the older car has many opportunities to embarrass its younger counterpart.

Perhaps this is an unfair cross section of a car's capabilities, but I feel that newness and complexity alone are not sufficient evidence of a vehicles' prowess in any situation. I don't disagree with your angle, just your evidence.

Grant Bailey
USA

We understand your point but in the Tickford case, we're talking about technology not just 10-15 years old, but fundamentally 30+ years old. It kind of changes the argument rather a lot! We don't think you'd be so happy autocrossing a Honda Life N600, for example....

Automotive Engineers

I heard that there is a society of automotive engineers in Australia. I was wondering are they the people that issue licenses to engineers to become a qualified automotive engineers to certify cars or do we have to go through the government bodies to obtain the certificates.

Julian Boudville
Australia

http://www.sae-a.com.au should be able to help you

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