BMW Z4 has 3 Series Convertible to thank May 29, 2009
Posted by richard in : Uncategorized , 5commentsLEARNING how to do folding hard-top roofs with the 3 Series Convertible served BMW well.
It meant it could launch a folding hard top Z4 relatively easily – simply because it had acquired so much knowledge.
What’s more, the shift over to the folding tin top is another reason for the car’s production relocation to Germany.
The Regensburg plant where it’s built has now become BMW’s official ‘centre of excellence’ for folding hard-top roofs.
It’s so well geared up, the supplier is even located there on site, an engineer insider told me.
‘This gives us the best possible means of achieving high quality levels.’
Engineering a folding hard top isn’t the work of a moment. Even one such as the Z4’s, whose lower 2-panel count reduces the number of joins and joints to worry about.
The problem come in areas you probably don’t even think about. Such as?
• Packing the roof into the boot without the lardy bum of a Peugeot 307 CC. ‘A close working relationship with the designers is vital.’
• Making it watertight – ‘this is the key. The biggest challenge is not to get the roof moving, it’s to keep the water out.’
• The need to like coffee. ‘I was able to work closely with the expert from the 3 Series Convertible project – we could have coffee, chat about our weekends, and how to get the Z4 roof watertight. We did this a lot…’
‘Once you’ve got it watertight the first time, you then need to do it again. Repeatability is of huge importance.
‘Our approach is to always take one car at random and test it for water tightness.’
Passing the tough BMW test involves putting the car in a high-pressure shower. Literally. ‘It’s a severe test. At the moment, every car is being tested. In time, tolerances will be such that we can test a certain percentage.’
What’s a watertight test pass rate for BMW? 95 percent ‘right first time’. Which means that, basically, every single Z4 has to be built to be watertight.
‘We’re almost there…’
BMW Z4 development background April 3, 2009
Posted by richard in : Uncategorized , 5commentsSo, there we were in Alicante. Heinz Krusche opened his technical discussion on the E89 Z4 with a little background behind the project. This was revealing in itself.
We spoke in the lobby of the launch hotel. Once we’d got drinks (Krusche: cappuccino. Me: OJ. PR men: water), it was down to business. When did development of the E89 start?
3 years ago, said Krusche, but they only started drilling down to production finites 18 months ago. Prior to that, they were assessing 2 types of car – both ‘flexible’ roof and hard top. Interesting… as was the revelation that there was a philosophy change with the E89, towards ride.
This had to be balanced with an internal BMW edict, that every single car has a different concept to one another. Crucial point, this: just as the 5 cannot simply be a shrunken 7 or a big 3, so the Z4 should not be a quasi-M, or a 135i Coupe with 2 less seats.
Much of the on-road testing happened in Munich – specifically, the country roads around the factory. They’re twisty enough to be a good base. Sweden’s Arjeplog was for low-friction testing, while Miramas was the base for dynamic stuff.
‘We also visit the Italian Dolomites 4 times a year, for big department handling tests.’
Specifics on that new chassis philosophy, explained Krusche, centred on a shift in thinking within BMW, that has been in place since the 1 Series Coupe. In a nutshell, to go softer on the springs, but stiffer on the dampers.
The ICM chassis controller helps, especially on cars with Adaptive M suspension. Krusche says that here, ICM is not as all-encompassing as on the 7 and X6, but is still a trick bit of chassis software centralisation. Bosch’s latest ESP 8.0 also brings finer finesse than ever.
2 different chassis setups were engineered; standard and Adaptive M. the fact that ‘Comfort’ Adaptive M is even more comfortable than the standard suspension, yet ‘Sport +’ even sportier than the E85 Z4, is crucial to its appeal.
‘It widens the breadth of the car’s abilities,’ says Krusche. For just £930? Tick the box for me, definitely…
Before we got into the real deep stuff, I asked Krusche who’s responsible for testing it all and pulling it together. Driving gods, such as him? Partly, he answered.
‘But we also have people who are not such good drivers. They are brilliant engineers, yet drive more like the average guy on the street. Their input is crucial, too.
‘This is how we make cars that are great to drive by everyone, not just race car drivers.’
Krusche. The most savvy dynamics engineer in the industry?
NEW: BMW Z4 photo stream on Flickr
Pre-launch impressions: BMW Z4 2009
BMW Z4 chassis secrets March 22, 2009
Posted by richard in : Uncategorized , 4commentsHeinz 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…).
Such 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 single 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 by 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 also 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 iterative 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 in : Uncategorized , 3commentsWant to see what I’ve been up to on the BMW Z4 launch? Well, check out my Z4 photo stream on Flickr.
And 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 in : Uncategorized , 1 comment so farSitting 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?
And, 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.
