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BMW Z4 chassis secrets March 22, 2009

Posted by Richard Aucock in Launch fever.
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Heinz Krusche is BMW’s chassis guru. I’ve met him several times, and always enjoyed top insight from him (not least his tales of how he keeps DSC turned on for the road – but ‘always’ turns it off when on track…).

bmw-z4-chassis-secretsSuch people exist in every car company, but they don’t always have the power of Krusche.

He wields the same sort of influence as Jost Capito at Ford. There’s another genial genius – and look at how well Fords drive. Lotus, too, has Matt Becker, ensuring that every model drives sublimely.

So, speaking to Krusche is always enthusing. Here, then, are five reasons why the Z4 is another tick against his name.

1. Stiff Body In White
The basic bodyshell is 25 percent stiffer than before. Vital, said Krusche, for the entire driving experience. This torsional rigidity is the starting point, the vital gear in the cog. Without such a good starting point, he said, it is impossible to make cars drive well.

‘It is a big step down if the tolerances are too great.’ You can’t turn a fundamentally bad car into a good one with tweaks alone.

2. 3 Series front axle
The new Z4 uses the 2-joint front axle from the E90 3 Series (and also the various iterations of 1 Series). It’s vital, said Krusche, not least for improving feedback to steering.

With it, BMW can independently tune directional stability, steering feel and lane change stability. Curing a major flaw of the E85 Z4: its wearisome camber steer.

The rear axle, incidentally, is a development of the old Z4 (and is also on the X3). ‘There was no reason to change it,’ said Krusche.

3. Axially parallel layout electric power steering
The new Z4 also uses the axially-parallel EPAS system from the 3 Series. It means the engine isn’t sat on the steering column, so mass is reduced and a purer feel from the road is allowed. The electric motor is in parallel to the steering rack.

The EPAS system has also allowed Krusche to tune the frequencies from the road surface. Basically, you want to isolate high frequencies, but allow through low frequencies. Cumulative learning from the old, oft-criticised Z4 EPAS has allowed BMW to do this.

‘You can vary steering torque with the switch in the car,’ said Krusche. It means it can be (over) light in normal mode, meatier in Sport +.’

He’s tuned it so there is no resistance for when you need to make steering corrections – tidying up snap oversteer, for example. ‘We also vary the feel for when you come to the limit, adjusting the Servotronic function for more feedback.’

4. Greater understanding of run-flat tyres
The E85 Z4 was a run-flat pioneer, and earned much criticism for being so. The tyres’ necessarily stiff sidewalls, and greater weight, both counter ride fluidity. Almost a decades’ learning, plus BMW’s close collaboration with tyre maker Bridgestone (the rubber’s bespoke for the new Z4) mean big improvements.

The evidence of this learning is illustrated by driving the E60 5 Series alongside the newer E90 3 Series, for example. But for greatest contrast, feel how the E85 and E89 Z4s deal with impact harshness and sudden surface imperfections.

Krusche makes a further revelation here, though: again, close work with the Body In White team has led to yet more improvements. By working out the intricacies of where run-flats need compliance in the structure, and where they’ll benefit from extra stiffness, BMW’s been able to tune and filter the natural frequencies of the bodyshell to dramatically improve ride quality.

It’s all about incremental understanding, he said.

5. Change in BMW setup philosophy
Since the 1 Series Coupe, BMW has subtly tweaked its basic chassis setup to improve comfort. Spring rates are slightly softer, and dampers a little stiffer. This has been influenced, again, by knowledge from the characteristics of run-flats.

The secret to doing this well, says Krusche, is in damper tuning. By playing with internal baffles, the size of the holes within them, the rates of flow between the three internal champers – goodness, even the material of the plunger on the strut! – depth is engineered in. Fine art? Call it black magic…

Despite all this, though, Krusche says he doesn’t get the final sign off. It’s always down to the BMW Board – who, at least thrice a year, will drive test cars and give the final say-so.

Krusche can only do so much. The final Z4 we drove on the launch was not one chosen by him, but the good Dr. Ings. You have to say, all have not done a bad job…


NEW: BMW Z4 photo stream on Flickr March 21, 2009

Posted by Richard Aucock in Launch fever.
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Want to see what I’ve been up to on the BMW Z4 launch? Well, check out my Z4 photo stream on Flickr.

bmw-z4-2009-launchAnd be sure to come back here over the next few days, as I plough through all my notes and feed back to you…

… clicking on the images should give you a taster, though!

Pre-launch impressions: BMW Z4 2009 March 21, 2009

Posted by Richard Aucock in Pre-launch impressions.
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Sitting on the plane, going through the press information for the Z4, writing this, I’m really rather intrigued.

See, I have a fair impression of what this car is going to be like. Fast, very crisp and agile. Sublimely cultured and smooth. Bigger and more grown up than the old one. And, vitally, smoother riding.

I don’t expect it to have lost the original’s alacrity and rear-balanced precision. Indeed, I expect this to be enhanced, as there’s surely no way the new one can tramline and follow the road surface as badly as the old?

pre-launch-impressions-bmw-z4-2009And, with the improvement in ride quality, it’s going to be a much easier car to drive on rough surfaces.

There should be a sat-back, powerful feeling, judging by how close the seats are positioned to the rear axle. That will be enhanced by an engine I adore – the 3.0-litre twin-turbo. 306bhp, 62mph in 5.2 seconds… it’s just dawning on me how fast this is likely to be.

Negatives? Well, I reckon they could have done more with the interior which, apart from a Z8 style centre console, lacks the special style of Audi’s TT. The instrument panel also looks a bit cheap, still, despite apparent improvements elsewhere.

Back to ride, though. They’ve got to, got to, have improved it, surely? In fact, I can guess they have. The press pack tells me the optional electronic damper’s stiffest setting is only as stiff as the old car’s standard set-up…

I have doubts over the price, though. The sDrive35i I’m driving today is £4400 dearer than the sDrive30i – that car’s almost as fast. What are the benefits of the sDrive35i? I’ll be grilling them to find out the intricacies.

My aim now is to always record these pre-impressions, then to see how the reality fares. You can follow my thought processes, and any preconceptions I take into the road test, for a more accurate representation of how a car actually is.

More on the mighty Alpina D3 Bi-Turbo March 18, 2009

Posted by Richard Aucock in What I learned today.
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Matthew Kidd, sales chief for Alpina GB, dropped me a line after reading my post on the new Alpina D3 Bi-Turbo. It’s even more of a machine than I first thought!

more-on-the-mighty-alpina-d3-bi-turboAs he says, ‘this is no simple chip-tune’. Engine software, for example, is completely bespoke to Alpina – written from scratch by the tech guys, and downloaded into the car on the regular BMW production line.

It even has its own engine wiring loom.

All this is why the 123d’s 2.0-litre twin-turbo enjoys such a power boost. But, here’s something: the bigger Bi-Turbo actually weighs less than the 123d! What’s more, at 1480kgs, it’s also 25kg lighter than the 325d.

Where it matters: up front.

It also has those distinctive big Alpina wheels, but they hide far more besides. The suspension comprises:

· Stabilisers from M Cars

· Secondary springs from the 335d

· Unique camber, caster and rolling radios

· Unique primary springs

· Bespoke settings for each variant – saloon, Touring and Coupe D3

Less than 100 saloons will be sold a year. The Touring and Coupe will be even rarer – ‘just a handful’.

Matthew’s invited me up to Sytner HQ in Nottingham, to test drive it for MSN Cars and Car Dealer Magazine (Alpina’s 14-strong UK retailer network will certainly be interested!).

When I can get up there, look out for more on how it fares on the road!

The Alpina that’s greener/faster/rarer than a 325d… March 16, 2009

Posted by Richard Aucock in What I learned today.
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BMW usually covers all bases, but a hole in its range was highlighted today. OK, it’s a small hole, but nevertheless…

What’s the 3 Series diesel buyer to do, who finds a 320d too slow, but a 325d too, well, you know, ‘not quite a 330d’?

Well, you’d think, the 1 Series comes in twin-turbo four-cylinder 123d guise. With 214bhp, it’s got bags of go. It’s obvious, then. Chuck this into the 3 Series, revive a classic nametag from the past, and bingo. Yet another niche filled.

rarer-than-a-325dNot so fast. Earlier today, BMW told me there are no plans for a 323d. Pity. The engine is a gem, and the lighter 2.0-litre engine would help create a wonderfully balanced high-performance diesel.

Help, however, is at hand! See, Alpina GB clearly shares my thinking. And has just started importing the Alpina D3 Bi-Turbo. Yes, it’s a 3 Series saloon, with a 123d engine transplant, and the usual hardcore Alpina makeover.

It looks great. But if, like BMW, you think ‘hey – why not just buy the peachier six-pot 325d’, here’s some stats:

Alpina D3 Bi-Turbo/BMW 325d M Sport

Price: £29,950/£30,825

Power: 214bhp/197bhp

0-62mph: 6.9secs/7.4secs

MPG: 52.3mpg/49.6mpg

CO2: 143g/km/153g/km

Compelling, aye? Furthermore, with the Alpina, you get a stackload of ‘in the know’ kudos to boot. Those stripes, those badges, those wheels, that ALPINA sticker on the front splitter…

But is it any good? Are pace and economy fair substitute for the loss of six-cylinder smoothness?

A test drive request has duly been sent. Watch this space.