Belt vs. Chain. Study on the Potential for CO2-Saving by the Timing Drive
 

Belt vs. Chain
Study on the Potential for CO2-Saving by the Timing Drive

The well-known German car research and development company FEV Motorentechnik GmbH has conducted a study to quantify the lower friction losses of timing belt drives. The independent study, sponsored by Gates, Conti and Dayco, uncovered a significant potential for CO2-Saving by timing belts.

The primary target of the study was to evaluate the differences between chain and timing belt drives with respect to friction and dynamic behaviour as well as the noise relevant excitations. Therefore, FEV used a state-of-the-art European combustion engine. In addition, FEV Motorentechnik GmbH evaluated and quantified the impact on fuel consumption, engine dynamic and NVH.

The study demonstrated a significant reduction in friction losses of 0.04 bar through the use of a toothed belt in comparison to the chain drive for the investigated 1.6 l in-line Gasoline engine. The resulting fuel consumption reduction results in a CO2 saving potential from 1.29 g/km to 1.45 g/km depending on the vehicle mass.

Next to the CO2 saving potential, the study also detected that the dynamic behaviour of the prototype belt drive was much more favourable than that of the reference chain drive in almost the entire speed range. Structural vibration measurements indicated that an improvement of the engine's acoustic behaviour could be demonstrated.

The presentation of the results of the study at the Aachener Kolloquium 2008 was attended by more than 200 engine engineers from all over the world. Prof. Dr. Fritz Indra, a former engine Chief engineer of GM, noted three additional advantages of the belt drive over chain:
- Almost no belt elongation versus up to 7 degrees change of cam angle with chain, eliminating emission problems over vehicle life when designed with belt drives;
- Weight reduction with belt drives;
- Cost reduction with belts.


To conclude, in view of ever more stringent CO2 emission standards and higher customer expectations with regards to comfort, it can be safely concluded from this study that timing belt drives constitute many advantages over chain drives and need to be considered as the better design option for future engine developments.
Comparison Dynamics Measurements - Angular Vibration
 
Comparison Friction Measurements
 
Prediction of Differences in Fuel Consumption
 
Prediction of Differences in Fuel Consumption