The Best Compromise in the Z4 Range: The 3.0 Si Version

During the 2006 facelift, concurrent with the introduction of the coupe variant, the Z4 received an update to its 3.0-liter six-cylinder engine, increasing power from 231 to 265 horsepower. The Roadster variant is the Z4 E85. The coupe variant is the Z4 E86. The E86 coupe was only available in the 3.0 Si and 3.2 M 6-cylinder versions. This limited E86 range, restricted to the largest engines and produced for only two years, makes it a relatively rare model. The Z4 3.0 Si represents the perfect balance within the BMW Z4 line-up. With 265 hp from the naturally aspirated inline six-cylinder, it offers excellent performance without the complexity and maintenance cost of the more powerful Motorsport variants.

An Excellent Engine-Transmission Package, as is Often the Case with BMW

In March 2006, BMW replaced the M54B30 3.0i inline six-cylinder (231 hp) with a new 3.0 Si engine (265 hp) designated as the N52B30. This new N52 engine is substantially lighter than its predecessor because it features an aluminium block, whereas the older M54 had a cast iron block. This weight reduction benefits agility, giving the front axle a more lively feel. The N52 features Double VANOS (VALVETRONIC II) for variable lift on both intake and exhaust valves. This grants it great power and torque availability from the lowest revs. However, it remains eager all the way up to 7,000 rpm. You never get the impression of lacking power in this Z4 (unlike the Cayman 2.7, one of its competitors). The ZF 6-speed manual gearbox contributes to this feeling of power through its very well-chosen gearing. The manipulation of the very short shift lever is highly satisfying. The sound is a great quality of BMW’s six-cylinders, and the N52 is particularly successful in this regard. Very guttural at low revs, it reaches for high-pitched notes at the top of the tachometer. Overall, mechanical pleasure is maximized in this car, which feels like its heart is this glorious naturally aspirated 6-cylinder. With a 0-100 km/h time of 5.7 seconds, performance is very close to that of the Motorsport variant and even slightly better than the Porsche Cayman 2.7. Excellent acceleration across all rev ranges and very reasonable fuel consumption are the signature of a highly efficient engine.

On the Road

The chassis is balanced, though the electric steering was often criticized in press tests. When first launched, these models were equipped with stiff-sided RunFlat tires as standard. Nowadays, the owner would be well-advised to equip it with modern, sporty Non-RunFlat tires. This will greatly improve driving precision, as well as suspension and acoustic comfort. While the Z3 had archaic suspensions and limited rigidity, the Z4 benefits from advanced suspensions and good structural rigidity. This, combined with a contained mass, provides it with very good road holding and agility. The handling is typical of a rear-wheel-drive car: playful at the rear but very controllable. Sport driving enthusiasts will prefer a model equipped with the optional sport suspension and 18-inch wheels, which feature wider rear tires than front tires. These options further enhance the Z4 3.0 Si’s handling to the point of approaching that of the Z4M. The only regret is the absence of a limited-slip differential, which is reserved for the Z4M. As a modern car, the Z4 3.0 Si features electronic aids (DTC and DSC) that protect overly optimistic drivers (within the limits of physics). They can be disconnected for those who know what they are doing or for track use. Compared to its successor, the E89 coupe-Cabriolet, the E86 coupe is much more engaging in sporty driving. With a better mass distribution, being lighter and more agile, it is globally sportier without truly sacrificing comfort (with non-RunFlat tires). Compared to its predecessor, the Z3 3.0 coupe, the Z4 is more effective, more rigorous, easier to drive aggressively, much more comfortable, and safer. Objectively, across all generations of BMW Z, this Z4 3.0 Si offers the best compromise between sportiness, feel, and modern handling.

Road Trip Comfort and Enjoyment

The Z4 3.0 Si is not a car intended for daily use. It should be considered a car designed for road trips on weekends or holidays. With only two seats, the boot is sufficient for two people’s luggage, and the coupe version is very well provided for loading space thanks to its hatchback. The driving position is very comfortable. The optional sport seats are recommended (the same as in the Z4M) as they add exclusivity and provide very good lateral support during spirited driving. The build quality is much better than on the Z3, even if some details could be perfected. The layout is very original, with a small but legible instrument cluster. The automatic climate control illustrates the positioning of this generation of cars, which offer sufficient comfort and safety while remaining simple.

Reliability and Maintenance Costs

The Z4 3.0 Si is a reliable and simple model to maintain. It uses a timing chain. Unlike the Z4M, there are no issues with connecting rod bearings. The N52 does not require regular valve clearance adjustment because the valve lifters are hydraulic on this modern engine (the Z4M does not have hydraulic lifters). Unlike the Motorsport models, the recommended oil is not excessively expensive. Compared to the Porsche Cayman 987.1 2.7 and 3.4, which risk engine failure due to the IMS bearing or bore scoring, the Z4 3.0 Si is truly a simple and reliable engine. This mechanical simplicity will suit those who wish to maintain their youngtimer themselves. If you buy a model that has been well-maintained, you should not face major unforeseen expenses that could ruin your investment (as happens when the engine of a Cayman 987.1 needs replacement).

Investment Perspectives

Rarity

According to several sources, the Z4 3.0 Si Roadster was produced in approximately 14,500 units, and the Z4 3.0 Si coupe was produced in approximately 12,500 units. Production estimates for the Cayman 987.1 2.7 are between 15,000 and 20,000 units. Ultimately, the Z4 3.0 Si coupe is an uncommon car that you don’t often encounter on the road.

Value Evolution

The market value has already hit its low point and has been rising for some time. The value has slightly increased in recent years, with a constant upward trend for examples in excellent condition. A well-maintained example, with a clear history and low mileage, will quickly find a buyer. Transaction prices vary, but the highest are achieved for cars in perfect condition and well-configured. For now, this car is in the period where it is no longer modern enough for some, but not old enough to be considered a “classic” by vintage car enthusiasts. When they are considered “classics,” the value will likely benefit and climb significantly.

Market Liquidity?

The Z4 3.0 Si coupe is in a small niche market. This means that for the seller and the buyer to meet at the right time, patience is required for both selling and buying. With that said, these cars sell without particular difficulty provided they are well-maintained and well-configured. Therefore, liquidity is good, and it will improve once this car is considered a “classic.”

coupe or Roadster?

Which one will gain the most value between the coupe and the Roadster? The Z3 Roadster has been universally liked since its introduction. This is not the case with the Z4 Roadster, which has its fans but also those who dislike it. For the coupes, it’s the opposite: the Z3 coupe is not universally appealing (its nickname “clown-shoe” testifies to this), whereas the Z4 coupe is renowned for its design. Thus, we recommend the coupe, whose lines appear to be more consensual.

Manual or Automatic Gearbox?

The Z4 is clearly not a practical car, but rather a pure pleasure car that is very analog and tactile in its feel. The manual gearbox elevates these sensations, and we believe it is preferable to choose it this way.

Why the Z4 3.0 Si E86 coupe?

In the shadow of the M: The M 3.2 is more powerful but demands a solid maintenance budget. The 265 hp 3.0 Si is sufficient for the Z4 chassis. The BMW 3.0 Si is a better engine than the 2.7 in the Cayman or Boxster: reliable (no bore scoring or IMS bearing issues at BMW), more torque, more powerful, and never gives the impression of being underpowered, unlike the Cayman 2.7. Reasonable maintenance costs and moderate fuel consumption. A very successful line and style. Cars of this generation are in the trough of the wave: not yet classic (unlike the Z3) and no longer modern enough. This is the time to put one in your garage!

Buyer’s Guide

Regarding the choice of your specific car, be aware that these cars fell quite low in value around 2015. Consequently, some passed into the hands of owners who did not have the means to maintain them. Often, these examples were resold from owner to owner, each avoiding maintenance costs. Avoid these examples with a difficult-to-trace history. Prefer a car that has been held for many years by its last owner.

As they are often second or third cars, they sometimes have not been used for long periods. Mechanics do not like long periods where seals dry out. Therefore, check if the mileage has been accrued regularly.

Choose an example in genuinely good condition. Since these cars are destined to become collector’s items, they must be very well preserved.

Regarding mileage, it is not necessarily a problem as these engines are very robust. However, the wear condition of the seats, steering wheel, and pedals will allow you to guess whether this high mileage was accrued on the highway or in the city. In the former case, the car should be well-preserved, and high mileage is not a problem, provided the price is consistent.

Regarding the mechanical condition: Demand a documented maintenance history with invoices stamped by BMW or a recognized BMW specialist. Check that it does not emit blue smoke (a sign of excessive oil consumption). The timing chain should be silent. Hydraulic lifters may be noisy (clattering) when cold, meaning they are losing pressure, but they must not make noise when hot. The valve cover gasket should not leak. The ignition coils deteriorate with heat. The water pump and thermostat should be replaced around 120,000 km. In rare cases, the VALVETRONIC system can be faulty (the engine will not deliver its full power or torque). Try hard braking: If you feel a vibration in the steering wheel during braking, a disc is warped (endurance is not the strong point of BMW braking systems of this era).

Bring a companion when viewing the car you desire: We advise you to ask a friend to accompany you on the day you go to see and test drive your dream car. Indeed, on the day the configuration you’ve dreamed of appears (after being patient for many weeks), you risk getting carried away and overlooking certain clues or signs that mean it is not a good deal. Since your friend is not the buyer, they will be able to remind you to be wary of these signs, which sometimes mean you should wait for the next opportunity, even if it requires more patience.