How Does the Z4 M40i Differ from the Boxster?

I switched to manual mode and tried the paddle shifters. Personally, I really like recent BMW automatics, and I’m almost convinced there’s no need for twin-clutch transmissions anymore.

The Z4 M40i’s automatic transmission is called the Steptronic Sport Transmission, but it’s hard to believe it’s a torque converter automatic given how crisp the shifts are. The shift speed is quite fast, especially on upshifts.

In feel, it’s comparable to the PDK found in Porsche 991.1 and 981 models.

The exhaust note on upshifts is powerful, and the afterfire pops on throttle lift-off are very satisfying. At low to mid RPMs, the sound is deep, but at high revs, lifting off the throttle produces a loud and exciting “crackling, popping!” This will be a matter of taste, but I like it.

Regarding engine feel, it’s the silky six as expected. Having known naturally aspirated engines from the past, I can detect a slight roughness or micro-vibration from the turbocharging, but this is truly an engine made by the “Bavarian engine masters.” It’s very easy to drive even at low speeds and delivers strong torque and exhilarating acceleration when you push it.

This time, I intentionally avoided researching detailed engine specs beforehand to keep an open mind. While driving, I honestly guessed it was around 350 to 380 horsepower.

Later, I checked the specs: 340 ps (250 kW) at 5000 rpm, and torque of 500 Nm (51.0 kgm) from 1600 to 4500 rpm. My guess wasn’t far off, but the power feels stronger than the numbers suggest. This is likely due to the massive 500 Nm torque available from very low revs.

In Japan’s traffic environment, it’s certainly not slow, but it’s not violently fast either. I think it’s just about the upper limit you can comfortably push on Japanese winding roads.

Once I got used to driving it, I raised the pace a bit. At that point, in terms of handling precision and road grip, it honestly doesn’t quite match the Boxster. Other car friends who joined that day shared the same impression, so I don’t think I’m far off.

For example, on the Royu Driveway, the gentle S-curve leading from Arima Corner to the tunnel at Juhatcho Corner is a pleasant mid-speed section. You approach it in 2nd or 3rd gear, pressing the accelerator on the uphill. It’s satisfying to cleanly and linearly pass through the S-curve, and I believe this spot clearly reveals handling precision and ease of control.

When driving the Boxster through here, it feels great, running almost without any slip in a straight line. But with the Z4, there’s a slight feeling that the line in your head and the car’s path don’t quite match when you flick it right and left. It’s hard to analyze exactly why, but comparatively, I think the Z4’s slightly larger body roll and softer suspension rebound damping cause this difference.

On the other hand, comfort and ease clearly go to the Z4. After this test drive, if I had to sum up the Z4 in one word, I’d say it’s a ‘Z5.’ It feels like a luxurious ride with strong GT car qualities.

Often, Z4 reviews compare it to the Boxster and treat them as rivals. But my impression is that these two cars are quite different.

I used to drive a Mercedes SLK350, and if I were to consider a rival, I’d compare the Z4 to the SLK (SLC).

At first, I thought the Z4 and Boxster were rivals, but after driving both on the same course on the same day, I feel their directions are quite different. This isn’t about which is better or worse, but rather they aim for different things, and depending on driver preference, they could be judged completely opposite.

The Z4 is a GT-style open sports car. For example, if you want a fast open-top car for weekend mornings to the golf course, the Z4 is definitely more suitable. But if you want a car purely for enjoying winding roads and touring, the Boxster is probably the better choice.

Also, for city driving with lots of traffic jams and stop-and-go, the Z4 is more practical, while for weekend circuit track days, the Boxster is preferable.

Since these two cars appear to be in the same category, it’s tempting to compare and find which is superior or inferior, but that’s not the right approach. When considering these two, it’s best to choose based on the situations and uses you expect from the car.

This test drive made it clear to me just how different their directions are.