The topic of bump stops does not attract much interest. But especially in cars with lowered suspension, and in light-weight cars, bump stops form an important part of the springing system.

A bump stop is the (usually) rubber buffer that is compressed as the suspension reaches full bump. (Some cars also have full droop buffers as well.)

Traditionally, bump stops were impacted only rarely, but more and more often in current cars, the suspension is designed in such a way that the bump stops are frequently contacted.

Let’s look at light weight cars first.

In a light weight car, the variations in possible loads make up a greater proportion of the overall vehicle mass. This means that, to avoid bottoming-out, the suspension must be set up more stiffly to cope with the potential load variation.

Or – and here’s the key point – the bump stops can be designed to be increasing rate (but still relatively progressive) springs that are brought into operation when the car is carrying full loads over bumps. That way, the spring rate of the suspension during ‘normal’ load carrying can be set much softer, giving a better ride.

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Orville and Wilbur Wright were genuine engineering heroes. Despite their relatively humble beginnings, these men were the first to ever to build – and then successfully fly – a powered aircraft.

I’ve often read descriptions of their brilliance that damns them with faint praise: they were ‘just bicycle mechanics’, their work built heavily on the efforts of others, and so on.

In fact, they were simply brilliant engineers, with an astounding work ethic and the ability to both physically make things and also theorise about outcomes.

Unless you think I overstate the brothers’ abilities, consider these points… They built their own wind tunnel and tested in it almost 200 wing sections; they built an internal combustion engine with the then best power/weight ratio of any engine in the world; they made every part of their own aircraft – from that engine through to propellers to wing and control systems; they developed the concept of an aircraft banking into turns – and a lot more. 

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I’ve just returned from a week on the road.

The vehicle of choice was my recumbent pedal trike, a design that you can read more about here and here. (In the pic above I’ve just finished my ride, so explaining the wrong shoes.)

I left Gold Coast and went to Tallebudgera, Pottsville, Byron Bay, Lennox Head, Yamba and then Grafton – mostly in northern NSW. Carrying full camping gear, I stayed each night in local caravan parks, spending one night in each except at Yamba where, because of steady rain, I spent two nights.

My last stop was at Grafton, where I got picked up by car and trailer.

Including diversions, I rode about 350 kilometres.

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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.

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It’s perhaps the only car that I have always wanted – well, from the day of its release, anyway.

The year was 1988 and the BMW 750iL was an astonishing car – twin electronically-controlled throttles, 12 cylinders, a limousine that handled so well that contemporary magazine testers were able to triple advisory speed limit signs around corners. On just six of the twelve cylinders, it could still exceed 200 km/h…

I’ve watched and watched as their prices have fallen – in 1988 the cars were $216,000; each year since they’ve got lower. Now, they’re under $10,000.

Less than ten grand for what was amongst the very fastest of four door cars in the world, a superbly equipped, beautiful looking sedan from that long ago time when BMW styling still had grace and cohesion.

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I’ve been thinking about the way in which cars are heading. More and more these days you see driver-selectable modes. A sports mode – or even super sports mode – on a double clutch transmission. A button that sharpens throttle response, changes damping and alters auto trans shift points.

Two points.

Firstly, if the car drives badly when in standard mode, fitting a special button doesn’t fix the car. The ‘fix’ needs to be far more fundamental: at minimum, all modes need to drive well.

But the main point I want to make is this.

Why on earth are manufacturers giving only ‘digital’ control over this type of driver selection? Why an on/off switch when it would be far better to provide an analog knob that allows the driver to adjust the action of the system to their taste?

A knob for power steering weight.

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Look, I’ve tried to like it. I’ve admired its quite brilliant fuel economy, and its generally excellent ride/handling compromise. I mean, I was even very positive in the new car test I did on the car when it was first released back in 2003.

And when this family bought one with our own money, it was with the (stated) intention of making it an AutoSpeed project car, in much the same way that we did with the Peugeot 405 SRDT.

But I need to be honest. I just simply hate the Peugeot 307 HDi – I think it’s a car that in many ways is just rubbish.

Now normally to support such a statement you’d have an extensive list of shortcomings in its driving performance. But in fact, the Peugeot largely drives very well.

One clear negative is its dreadful low rpm management mapping and/or turbo sizing: this is one of the deadest off-boost turbo electronic direct injected diesels you can drive, especially in hot weather.

(I just checked the date of my original new car test – published November so probably tested about September. Just on the edges of the Australian summer – but not into it.)

But otherwise, the steering is largely OK (well, it kicks back when driving really hard); the ride is good; the handling is adequate and the brakes fine.

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Looking at how astonishingly badly the Australian-manufacturing car companies predicted car buying habits, one wonders if they should be rewarded by being given even more of our money…..

http://www.smh.com.au/news/opinion/car-subsidies-blow-good-money-out-the-exhaust/2008/11/10/1226165475381.html

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A while ago in a reply to another blog post, I wrote about the current Lancer Evolution that:

“The Evo should use far improved throttle mapping where blade angle is mapped against foot position and the calculated instantaneous tractive effort value. It should also use a smaller turbo. ”

At least one reader was so excited by this notion that he wished to “quietly roll up into a foetal position and rock back and forth on the floor”. However, leaving aside bizarre responses, it’s a concept sure to interest some.

I won’t discuss the ‘smaller turbo’ bit because most of you will have a good understanding of this idea. But what about the throttle mapping?

In electronic throttle cars, the relationship between the accelerator pedal position and the throttle blade opening no longer needs to be linear. In a linear system, the throttle blade would be half open at 50 per cent accelerator pedal travel, three-quarters open at 75 per cent accelerator pedal travel, and so on.

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