Original Article Proc IMechE Part D: J Automobile Engineering 1–11 Ó IMechE 2018 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0954407018760935 journals.sagepub.com/home/pid Benefits of wonder process craft on engine valve train performance M Usman Abdullah 1 , Samiur Rahman Shah 1 , M Usman Bhutta 1 , Riaz Ahmad Mufti 1 , Muhammad Khurram 1 , M Huzaifa Najeeb 1 , Waseem Arshad 1 and Kiyo Ogawa 2 Abstract The performance and durability of tribological components in roller follower valve train is governed mainly by the roller rotational behaviour. Pure rolling of roller on the camshaft surface is essential to achieve the optimum valve train effi- ciency. The increase in roller slip can lead to high valve train power loss due to increase in sliding friction and can increase the wear rate of mating surfaces of camshaft and roller. In this research work, a modern gasoline engine having end-pivoted roller finger follower valve train configuration has been instrumented to investigate the effects of Wonder Process Craft surface treatment on roller slip. Comprehensive test programme has been undertaken at transient cam- shaft speeds by employing the New European Drive Cycle under different oil temperatures and pressures. Remarkable reduction in roller slip was recorded for Wonder Process Craft surface treated roller as compared to the original unmo- dified roller indicating its strong potential of employment in engine valve train. The test rig, surface treatment of roller, instrumentation, experimentation, results and discussion have been presented in detail in this paper. Keywords Engine valve train, roller sliding, surface treatment, Wonder Process Craft, drive cycle, cam roller interface Date received: 26 September 2016; accepted: 29 January 2018 Introduction The automotive industry is in continual pursuit to pro- duce cars having lower emissions, higher power output, greater fuel economy and a longer service life. These requirements are forcing the modern original equip- ment manufacturers to design and manufacture engines that are more complex and compact. The engine valve train design is one of the critical issues as it is often operated at high temperatures, varying contact loading, varying oil film thickness and lubrication mode. However, the use of low viscosity oils to reduce shear friction has become common. Such low viscosity lubri- cants in severe operating conditions has raised concerns about the reliability, robustness, life and performance of engine valve train components. The direct acting mechanical bucket-type valve train configuration is the most common type of valve train configurations being used in the automotive industry. However, the use of roller follower valve trains, Figure 1, particularly the end-pivoted configuration is becoming more common in modern passenger cars. This is due to its improved fuel economy and higher performance. Staron and Willermet, 2 Sun and Rosenberg 3 and Bair et al. 4 have all demonstrated the reduction of friction in engine valve train with the usage of rolling contact in place of sliding contact. Roller rotation in roller follower valve train helps in even distribution of surface wear and avoids fatigue failure. Compared to the fixed pad-sliding follower, the wear in roller follower is much lower. 5 These models clearly show the higher efficiency of the roller follower valve train configuration. Theoretical studies showed that during most of the cam cycle, roller is rotated with the same surface velocity as that of the cam relative to the point of contact. However, at high camshaft rotational frequencies, sliding may take place on the cam flanks where the acceleration of the surface of cam is high. 6 Relative sliding of mating surfaces oper- ating under marginal lubrication conditions can result in 1 School of Mechanical & Manufacturing Engineering (SMME), National University of Sciences and Technology (NUST), Islamabad, Pakistan 2 Fuji Manufacturing Co., Ltd, Japan Corresponding author: Samiur Rahman Shah, School of Mechanical & Manufacturing Engineering (SMME), National University of Sciences and Technology (NUST), H-12, Islamabad 44000, Pakistan. Email: samiur.rahman@smme.nust.edu.pk