Front wheel disconnection is seen as the best choice to decrease fuel consumption for all-wheel-drive vehicles. This trend comes from the USA and seems to be founded on corporate average fuel economy (CAFE) regulations. Initial calculations have led to the suspicion that lifetime fuel saving may not justify the higher cost of front wheel disconnection. The aim of these investigations is to identify and isolate the factors which are responsible for the drag losses and to quantify their influence on the total losses. Furthermore, the economic benefit of front wheel disconnection must be determined. The measurement methods described and used in this report are methods to measure spin losses, which are load independent losses. The results are rather representative because a high percentage of power losses are only speed dependent, for example, loss due to splashing. Spin loss measurement is a low-cost and simple method to start with loss measurement. The used methods are the Retardation Test and the Direct Torque Measurement. The results of the fuel consumption simulation show a maximum of 0.33 mpg more between 4WD and 2WD operation with a base fuel economy of 16 mpg in 4WD. This extreme fuel saving can only be achieved by comparing a rigidly connected all wheel drive system to a rear driven system with a zero loss multi-plate clutch and a fixed (non-rotating) front powertrain. The smallest increase of fuel economy is 0.07 mpg at freeway speed, but a realistic increase of 0.15 - 0.19 mpg can be achieved for a transfer case from our company. However, the data shows that the fuel savings of an optimized transfer case in 2WD is still better than one in 4WD even under low speed conditions. As a result, rear wheel drive has to be recommended. Front axle disconnection for financial reasons only makes sense for simple all-wheel-drive systems with activation via dog clutch, because these systems cause high powertrain distortion and increased fuel consumption in 4WD. It seems that the fuel consumption advantage of a rigid fourwheel-drive system over an advanced all-wheel-drive system has been assumed without having been proved. This is why every four-wheel-drive strategy should be proven with regard to the optimal operating mode, ecological effects, and business and political economic benefits.
Advanced efficiency analysis for a four-wheel-drive powertrain
Wirkungsgradanalyse für einen Vier-Rad-Antriebsstrang
2001
7 Seiten, 10 Bilder, 4 Quellen
Aufsatz (Konferenz)
Englisch
Advanced Efficiency Analysis for a Four-Wheel-Drive Powertrain
British Library Conference Proceedings | 2001
|Advanced efficiency analysis for a four wheel drive powertrain
Kraftfahrwesen | 2001
|ADVANCED EFFICIENCY ANALYSES FOR A FOUR WHEEL DRIVE POWERTRAIN
British Library Conference Proceedings | 2001
|Hybrid-electric four-wheel drive vehicle and powertrain therefor
Europäisches Patentamt | 2016
|Four-wheel-drive powertrain models for real-time simulation
Kraftfahrwesen | 1991
|