Some BMW sports cars have been good, and others haven’t quite made it as sports cars, but the BMW Z4 is different. Sure, BMW can produce superb sports sedans and coupes – some outperform two-seater supercars – but some of its shots at producing sports cars have missed the mark.
The forerunner to the Z4, the Z3, was more a boulevard cruiser than a sports car. But at last they’ve done it! The BMW Z4 is a real sports car. Now, you can get a slick coupe version as well, with similar performance to the roadster. If you want more power, there is an M version.
Z4 a cracker of a sports car
The Z4 is a cracker of a sports two-seater. You sit well down in the car – almost an inch lower than in the Z3 - the engine is up front, behind the front wheels where it belongs, you’ve got 50% of the weight on the front and 50% on the back. The basics are right. Performance is quite good, too: the 3.0 liter model will reach 60 mph in about 5.8 seconds, and top speed is 155 mph.
But does it look right? Not quite right to me, although the basic shape is not far off. The front end, with the trademark grille works fairly well, but the hood could be a bit lower – looks as if it would be more at home on a sedan. BMW is proud of those chiselled lines running down the side. The knife-edge highlights along the tops of the fenders work well, but the stylists had to work in those extra lines around the door. Pity.
The back, too, starts well but doesn’t quite pull it off. The hump in the center of the tail looks like a parody of the subtle Ferrari back end. Still, the overall impression, especially in dull light is pretty good and so much better than the Z3.
Superb six-cylinder engines
But the Z4 scores not just over the Z3 but over many competitors in many ways. To start with you’ll get a superbly smooth but powerful in-line six-cylinder engine. Almost everyone else has switched to V-6s to reduce the size of the engine room, but not BMW.
BMW believes in gradual development rather than revolution, so once it found that its in-line sixes were smoother than V-6s it decided to stick with them. They’re pretty compact as in-line sixes go, and because they’re narrow they fit well in front-engined, rear-drive cars.
You can either get a 2.5 or 3.0 liter engine in the Z4, and most opt for the extra power and torque of the three-liter mill. It is a slightly undersquare engine because it shares the same bore as the 2.5 liter unit, and turns out 231 bhp at 5,900 rpm. Peak torque is 221 lb ft (330 Nm) at 3,500 rpm. Good without being exciting.
Like most modern sporty engines, these sixes have variable valve timing, but with the addition of adaptive knock sensing. This means that the engine can run very close to the point when it would start to knock. Engine knocking or pre-ignition is dangerous, but running close to conditions that would cause it without it actually happening, results in greater efficiency.
You get the engine noise you’d like
The intake manifold is designed to give ram air at low and high speeds, and the whole air intake system is designed to send an increasing roar into the passenger compartment in the way a sports car should.
Also new is the electronic butterfly in the intake system. This is more sensitive at low speeds, smoothing out jerks, but when high performance is called for, it responds very quickly. BMW integrates all the various sensors and controllers so each knows what is happening – nothing simple and direct for them.
Engine response modified to suit conditions
So, the controller knows which gear you’re in – manual or automatic – and when you press the accelerator it modifies the butterfly opening according to the gear – you get more power quicker in a higher gear. It also smoothes out transitions between acceleration and the overrun, which actually you may not want, should you be backing off to shift some weight onto the front of the car as you enter a corner.
DDC for the ambitious driver
There are pluses and minuses with many electronic systems, but here’s a bonus: DDC (Dynamic Drive Control), designed for the ‘very special, ambitious driver’ and that could well be you – it’s certainly me. Anyway, DDC has a sports mode which provides even more rapid engine response, which is exactly what we want.
On top of that, it also makes the steering more direct – more about that later - and if you've got the sequential gearbox – recommended – you’ll shift up at higher speeds as well. Sounds good to me.
SMG gearbox for best performance
With the Z4 you have three choices of gearbox: A six-speed manual, a six-speed SMG (sequential mechanical gearbox) or a five-speed automatic. Like other sequential boxes, the SMG can be operated either by a pair of paddles at the steering wheel or by using a lever. Gearshifts are made in 150 milliseconds – one-sixth of a second which is so darned quick, I doubt you’ll compete.
Again, BMW has added some electronic features – not necessarily unique, but good. For example, you can shift up without lifting your foot from the gas pedal, and you can do a racing start. You select the Sports program, press the gas pedal quickly and completely. The engine speed rises to 4,000 rpm, the clutch is engaged and you hurtle off like a dingbat, and will attain the 0-60 mph time BMW claims, whatever your driving experience. Hmmmm.
To match the power of the engine, BMW has developed its strut suspension, which has forged aluminum arms at the front, and the multi-link system at the rear. Most components are aluminum to reduce unsprung weight.
Electric power steering
Electric power steering is used for the first time on a BMW two-seater, and this us why it is possible to alter the steering response rate. In Sports mode, less power assistance is provided, so the steering feels more direct and responsive.
It doesn’t stop there, though. There is this DTC (dynamic traction control) program which works in conjunction with the stability control. The stability program either brakes or reduces engine power when you get cornering too fast, but with DTC you get DSC acting as a wise uncle not doing much but ready to help if really needed.
DTC ensures you get good traction at low speeds and low cornering speeds. At higher speeds, and cornering force, DTC allows some slip to make your cornering more exciting, but still maintains traction. Sounds cool.
Electronics play an important role in the Z4 – maybe too important – but the basic car is clearly pretty good. And it isn’t overweight either, despite that rag top – a hard top is available, by the way. It’s a bit lighter than its obvious rivals - the Chrysler Crossfire, Mercedes-Benz SLK 350 or Nissan 350Z, although these all have slightly larger engines.
Oh, and you can have an automatically opening and closing roof – it works at the press of a button, and BMW claims that it’s the fastest in the world in 10 seconds. Drive into a sudden downpour and you’d be glad it took 10 instead of 20 seconds!
