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Le Mans / ALMS
ALMS: Inside The BMW Z4 GTE
John Dagys explores the newest ACO-spec GTE contender and gains insight into its development from BMW and Team RLL experts...
BMW's new Z4 GTE, destined for the highly competitive ALMS GT ranks, broke cover this week at Daytona International Speedway. (Photo: Chris Tedesco/BMW)
Following four successful seasons with its venerable M3 GT, which delivered back-to-back American Le Mans Series class championships, including the driver, team and manufacturer titles in 2011, BMW has opened a new chapter in its factory GT program with the Z4 GTE.
Unveiled during a press launch at Daytona International Speedway earlier this week, the newest GT class entry has already turned quite a few heads, not only for its clever design cues but also for being the first GT3-based car that’s set to be homologated by the Automobile Club de l’Ouest.
The arduous task of transforming the base car, a proven winner in numerous GT3 championships worldwide, into a top GT class contender for the ALMS, began last July as part of a joint effort between BMW Motorsport and its North American racing partner, Team RLL, which will be at the helm of the factory program for the fifth consecutive season.
"BMW wanted to start with their GT3 version of the Z4 because the engine was already in that chassis and the suspension had been developed,” explains BMW Team RLL technical director Jay O’Connell. “We had a list of requirements that we put together based on what we learned in the M3: Brakes, steering, cooling, aerodynamics, broken down system by system to give them specific targets. That really began the transformation."
Roughly 70 percent of the Z4 GT3 has been carried over into the GTE version, including nearly all of the major mechanical components. Central to that is the powerplant, a 4.4-liter 90-degree V8, originally derived from the production M3 engine. It’s coupled with a six-speed sequential transmission, also taken from the GT3 model.
Modifications, however, have been made to the intake system in order to accommodate the ACO-mandated sonic air restrictor, instead of the FIA GT3 style square-edged plate. There have also been further developments to the engine for optimization with IMSA’s E85R fuel, according to O’Connell.
"We have the GT3 car and wanted to obviously have a development program as efficient as we could, so we wanted to keep it as close to the GT3 to have synergies,” says BMW Motorsport director Jens Marquardt. “That was the reason behind going with that same engine and powertrain in the GTE car as well. That was the base of the discussions we had with the ACO and IMSA and they could follow that.”
While GT3 effectively offers an open rulebook, with cars equalized strictly through Balance of Performance measures, the GTE platform is controlled through a set of technical regulations, which enforces closer conformity to a car’s road-going counterpart. That includes having the same production-based engine block.
But with no V8 powerplant currently offered in the line of road-going Z4s, BMW has gone through the process of requesting a waiver from the ACO for its unique situation. It’s a similar arrangement to the recent homologation of the SRT Viper GTS-R, which received a waiver for its engine, which exceeds the category’s maximum displacement of 5.5 liters.
“We've had [the V8 engine] in the GT3 car for quite some time, so we know the engine very well,” Marquardt says. “And with needing a different restrictor system with the sonic restrictor, there was already enough effort that was needed to be put into that. Then, picking up on the engine that we already knew quite well was the logic step.
"We were very open [with the ACO] from the get-go and discussed it with them. If we were to make this happen, we really had to try and have it be as close to the GT3 [car] as we could."
The most noticeable difference from the Z4 GT3 to the new GTE variant are the aerodynamics. More restrictive technical regulations have resulted in re-shaped fenders, a smaller front splitter, the removal of the front dive planes and a single-element rear wing instead of the two-element version allowed in GT3. Additionally, the rear diffuser has also been heavily revised, per GTE rules.
It’s estimated the aero changes have resulted in a 30 percent reduction in downforce over the GT3 car.
"The biggest changes you can see are the bodywork from GT3 to GTE,” O’Connell explains. “The GTE car is even wider than the GT3 car in order to maximize the two-meter rule. Since Ferrari broke over the two-meter rule and the M3 was only 1.92 meters at the back, it's been a big change to re-configure it.
“[The Z4 GTE] is also about 75 mm shorter [in height] than the M3. So if you take that area that's in the cabin and put that into the wider flanks and the wider car, the frontal area is about the same as the M3. It's just been reconfigured to a better situation with more track width and more mechanical grip."
Unveiled during a press launch at Daytona International Speedway earlier this week, the newest GT class entry has already turned quite a few heads, not only for its clever design cues but also for being the first GT3-based car that’s set to be homologated by the Automobile Club de l’Ouest.
The arduous task of transforming the base car, a proven winner in numerous GT3 championships worldwide, into a top GT class contender for the ALMS, began last July as part of a joint effort between BMW Motorsport and its North American racing partner, Team RLL, which will be at the helm of the factory program for the fifth consecutive season.
"BMW wanted to start with their GT3 version of the Z4 because the engine was already in that chassis and the suspension had been developed,” explains BMW Team RLL technical director Jay O’Connell. “We had a list of requirements that we put together based on what we learned in the M3: Brakes, steering, cooling, aerodynamics, broken down system by system to give them specific targets. That really began the transformation."
Roughly 70 percent of the Z4 GT3 has been carried over into the GTE version, including nearly all of the major mechanical components. Central to that is the powerplant, a 4.4-liter 90-degree V8, originally derived from the production M3 engine. It’s coupled with a six-speed sequential transmission, also taken from the GT3 model.
Modifications, however, have been made to the intake system in order to accommodate the ACO-mandated sonic air restrictor, instead of the FIA GT3 style square-edged plate. There have also been further developments to the engine for optimization with IMSA’s E85R fuel, according to O’Connell.
"We have the GT3 car and wanted to obviously have a development program as efficient as we could, so we wanted to keep it as close to the GT3 to have synergies,” says BMW Motorsport director Jens Marquardt. “That was the reason behind going with that same engine and powertrain in the GTE car as well. That was the base of the discussions we had with the ACO and IMSA and they could follow that.”
While GT3 effectively offers an open rulebook, with cars equalized strictly through Balance of Performance measures, the GTE platform is controlled through a set of technical regulations, which enforces closer conformity to a car’s road-going counterpart. That includes having the same production-based engine block.
But with no V8 powerplant currently offered in the line of road-going Z4s, BMW has gone through the process of requesting a waiver from the ACO for its unique situation. It’s a similar arrangement to the recent homologation of the SRT Viper GTS-R, which received a waiver for its engine, which exceeds the category’s maximum displacement of 5.5 liters.
“We've had [the V8 engine] in the GT3 car for quite some time, so we know the engine very well,” Marquardt says. “And with needing a different restrictor system with the sonic restrictor, there was already enough effort that was needed to be put into that. Then, picking up on the engine that we already knew quite well was the logic step.
"We were very open [with the ACO] from the get-go and discussed it with them. If we were to make this happen, we really had to try and have it be as close to the GT3 [car] as we could."
The most noticeable difference from the Z4 GT3 to the new GTE variant are the aerodynamics. More restrictive technical regulations have resulted in re-shaped fenders, a smaller front splitter, the removal of the front dive planes and a single-element rear wing instead of the two-element version allowed in GT3. Additionally, the rear diffuser has also been heavily revised, per GTE rules.
It’s estimated the aero changes have resulted in a 30 percent reduction in downforce over the GT3 car.
"The biggest changes you can see are the bodywork from GT3 to GTE,” O’Connell explains. “The GTE car is even wider than the GT3 car in order to maximize the two-meter rule. Since Ferrari broke over the two-meter rule and the M3 was only 1.92 meters at the back, it's been a big change to re-configure it.
“[The Z4 GTE] is also about 75 mm shorter [in height] than the M3. So if you take that area that's in the cabin and put that into the wider flanks and the wider car, the frontal area is about the same as the M3. It's just been reconfigured to a better situation with more track width and more mechanical grip."
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