The automotive tuning world is known for developing innovative pieces of kit, released and sold to interesting customers around the globe. In the BMW-tuning world, AC Schnitzer are a perfect example of this. The Germany-based third party tuning company sells upgrades for numerous cars and is focused on transferring the world of motorsport onto the road and into packages for day-to-day use.

These kind of steps are normally linked to increased performance and sportier drives, and not typically to increased efficiency and lower CO2 emissions. In fact, when tuning is mentioned, many people would consider this to be the opposite effect. Not wanting to look completely unfriendly to Mother Earth the technicians at AC Schnitzer came up with the 99d Concept, their definition of efficient performance, with only 99g of CO2 emissions.

Despite this, driving pleasure seems to be guaranteed thanks to the 190hp diesel engine lifted from a 320d and fitted to the setup of a Z4 two-seater roadster, a car that is a true pleasure to drive on the street or on the track. The 99d accelerates from 0-100km/h in 6.9 seconds and has a top speed of 235km/h. So it is a vehicle with all the sporting potential, but with a fuel consumption of just 3.8 liters diesel per 100km. Enough ingredients we thought to give it a try.

Road Test AC Schnitzer 99d Concept 01

The way AC Schnitzer have combined these ingredients is the key to this concept. Eight single steps were used by the design and engineering departments at AC Schnitzer to come up with the concept we now have in front of us. At the nose of the car, they fitted the most efficient engine available at the beginning of this year, the diesel engine used in the 320d EfficientDynamics Edition. The power was optimized by the Aachen specialists to 190hp at 4,000rpm and 420Nm of torque between 1,900 and 2,250Nm. This gives an overall increase of 27hp and 80Nm.

Accompanied by an efficient engine, shedding weight is the next way to save on fuel consumption. The battery for example is a lightweight lithium ion battery instead of the usual lead accumulator. The use of lightweight materials such as carbon, magnesium and titanium achieved further savings. The most noticeable difference to the stock Z4 is the absence of the retractable-hardtop mechanism. The 99d instead has a fixed carbon fiber roof.

But the weight savings didn’t stop here. A 35kg weight reduction in the parts directly connected to the wheels. Weight loss from the wheels, tires and brakes, provides for a noticeably improved handling setup. As a basis to save weight the latest forging techniques using materials from the aerospace industry were used. This also guaranteed increased strength. The lightweight four-pot high performance brake system with retraction system fitted to the front axle, and the lightweight brake discs on the front and rear axles, are another example of this. The same can be said for the Type VIII one-piece high-strength forged rims. They weigh in at just 7.9kg per wheel and are connected to the vehicle with titanium wheel bolts.

The rims are fitted with Continental BLUECO tires size 225/35 ZR19 developed in conjunction with AC Schnitzer. The tires help optimise rolling resistance. The design is a refinement of the Conti Sport Contact 5P tire, offering high levels of cornering stability and a ZR speed rating of over 240km/h. In the end they saved a total of 230kg, making it the lightest current BMW.

Road Test AC Schnitzer 99d Concept 02

To achieve an additional level of sportive potential, the sports car concept is lowered by 30mm. The racing suspension with adjustable dampers reduces the residual spring travel to a sporting but still comfortable level, especially when driving at lower speeds. The lowered setup also helps in reducing the drag of the vehicle together with specially developed carbon fiber aerodynamic components, like the front spoiler, sport wings, rear skirt insert, boot lid and rear spoiler. Other parts added to the exterior trim are the bonnet vents, an anodized matt silver front grille and an intriguing paint job themed “eco-friendliness”.

On the inside, you get the typical BMW interior refinements with an AC Schnitzer touch. The seating is more driver-focused than many other roadsters, but it cannot match the Porsche’s driving position. The two-seat cabin is quite cozy, which might be a problem for especially tall drivers. The seats are snug but the lateral support they provide is appreciated when cornering. The side bolsters are adjustable if needed. The sports steering wheel is definitely an improvement over the standard unit. It has a better grip, and complements the new AC Schnitzer gear knob, foot rests, pedals and foot mats with their 99d logo.

Our afternoon inside the 99d left us with a smile. The minute you get behind the wheel of the 99d, you feel that it has been designed to deliver responsive performance. You sit just in front of the rear wheels and you look out over a long hood ready to go. The most interesting part of the whole experience awaits when you turn the key. The sound track is unknown to any Z4 in the world, because a diesel engine erupts under its colorful hood. Up to the moment you turn it off, it will tell you what you are dealing with via a lightweight silencer which produces a moderate growl.

Road Test AC Schnitzer 99d Concept 03

The overall balance of the car has not changed significantly. The 99d feels lighter and more nimble than a stock Z4, but AC Schnitzer did not change anything with respect to the favorable characteristics of the two-seater. The 99d is still a cornering champion, exhibiting little body roll and plenty of grip. There’s no waiting for the rest of the car to make it through the turn because you’re practically sitting at the back of the roadster. The only penalty for this sublime handling is the ride quality that can be quite rough on patched asphalt roads. Comfort is not something you would immediately search for in the 99d, but the ride is far from bumpy or hard.

Complementing all the weight saving and technical improvements is the diesel engine providing a decent amount of acceleration and an adequate straight line speed while being linked to a six-speed manual gearbox offering quick shifts and precise throws between your fingers. The overall experience of the 99d is a successful marriage between agility, performance and efficiency. Exactly what AC Schnitzer set out to achieve with the concept. Do not expect any future sale plans, it will remain the only diesel-powered Z4 in the world for the moment. This colorful 99d Concept is an one-off, and not for sale.

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