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Goose bumps under the skin

BMW's makeover of Z line goes deep beneath surface

The last time BMW's Z cars got a makeover it was all about the skin. They went from bulbous and Rubenesque in their lines to having edges honed like a knife.

Not everyone liked the look, which became a BMW trademark as its fleet was overhauled.

Now comes the first big change since that 2003 redesign. This time, the big news is what lurks beneath the surface.

Today's test car, the 2006 BMW Z4 roadster, features two new power plants, derived from the new 3 Series cars: the 3.0i, as tested, and the 3.0si.

The test car's engine replaces the 2.5i and the heftier 3.0si trumps the old 3.0i.

In the test car that meant 215 horsepower (up from 184 in the original), and 255 horsepower (up from 225) in the pricier version. Both are powered by in-line six-cylinder engines and can be had with a choice of transmissions, both six speeds: a manual, which is standard, or an automatic with paddle shifters behind the steering wheel.

On the outside, only subtle changes have been made to the bold design, which features sharp edges along the fender lines, deep scoops from front quarter panels to rear panels along the side, and a flip for airflow at the trunk.

The changes include new fog lamps and tail lights, both given crisper edges.

In addition to the engine upgrades, the latest BMW technology has been added to improve the standard stability control system, brakes have been updated, and xenon headlights are now standard.

All of this, of course, does nothing to take away from the designers' harkening back to the 315/1 and 319/1 classics of the 1930s, or the car's resemblance to the costly Z8 and -- most spectacularly -- to the 507s of the mid- to late-1950s.

So how does a car that already carved corners smoothly handle this new setup?

Faster, tighter, and with more rigidity.

First, in the test car, you get nearly the same horsepower that the old upper-end delivered. Second, the six-speed manual makes the extra power more accessible.

The result: a noticeable difference at launch and, particularly, in pulling out to pass on highways. To a resonant burble, it leaps forward when asked, and the wider range of gears allows more room for fun. The extra power could also be felt when adding gas at the apex of corners.

The car (given that it came with an optional sport package that included upgraded suspension) felt even more stable than its predecessor, which was no slouch when it came to handling weight transfer, side-to-side or front-to-rear-and-back. Yet the last model did seem a bit softer in hard handling.

But now, no body roll and no nose dives or back-end dips in hard braking or rapid acceleration. This is a sure-footed, plenty powerful roadster that delivers the fun you expect from a performance drop - top.

And it comes with plenty of standard features, many aimed at safety: stability control, dynamic brake control, dual front-mounted side air bags, advanced front bag system, automatic brake drying, and rollover protection.

Our test car's base price was boosted, from $35,600 to nearly $40,000, by the addition of such items as the sport package ($1,000), upgraded seating ($1,350), automatic soft top ($750), and heated front seats ($500).

This is largely an under-the-skin tweaking. But it's enough to give you goose bumps.

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