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perhaps due to some stifling regulations, polymers and composites have not offered the revolution in engine and transmission materials technology that was. Race Engine Technology is full of highly technical articles by experts on all aspects of race engine technology. Race Engine Technology Magazine. PRINT Like Father, Like Son (August PDF). Racer Engine Cover omyrkasuba.cf July 16, by Danny Thompson.
Obviously, for this optimization process to be reliable, the baseline engine model has to have been carefully validated.
Baseline engine AD valve lifts only All AD optimum parameters An optimum engine design was found after analyzing 75 engines, which took over 4. This software has been extensively used to in Table 3, the best torque gains could be achieved from analyze valve train dynamics and scrutinize the effects of modifying the valve lift profiles as predicted by the particular lift profiles and components used [17, 18, 19 optimization process. Table 3 shows that this would and 20]. The software can be provided with existing During the automated design AD process, the virtual valvetrain geometry and valve lift profiles.
These profiles model reduced the negative effects of reverse flow by can be manipulated such that the cam profiles meet the reducing the valve overlap period. This was done by design criteria and fall within the limitations of the decreasing the intake and exhaust valve durations by existing components and cylinder head layout.
The automated design also proposed lift profiles are more aggressive this can invoke found that both the intake and exhaust valve peak lift effects such as valve float and bounce, generate higher optimum positions were ten degrees earlier than the stress, and have tribology and geometric implications.
The closing angle of the inlet valve is then also advanced by this ten degrees therefore reducing the Therefore to conduct this analysis, the valve-train and reverse flow of fresh charge out of the cylinder during the associated components within the engine needed to be initial phase of the compression stroke. The optimized valve lift profiles are shown in Figure 7, in valves, buckets, springs and the masses for each were comparison to the stock engines valve lift profiles, and measured as shown in Tables with the respective the reduction in valve overlap period along with the component images from the 4stHEAD software.
The earlier closing of the intake valve can be clearly seen. Automated Design and Stock Valve Lift Profiles Table 4 — Valve Dimensions This thermodynamic optimization gives no consideration to the mechanical viability of these valve lift designs. Therefore it was necessary to check not only the Dimension mm mechanical feasibility of this new design, but also to determine whether it was possible to manufacture Db There is a complex design relationship between both of these variables, the valve lift profiles Tbp 2.
To assess the mechanical implications of the proposed lift profile, a mechanical analysis was required using valvetrain mechanical analysis software called 4stHEAD Table 6. Valve Springs - Progressive Coil Spacing cam and the valve-lift acceleration i.
The bucket diameters and the base circle radii of the cams could not be changed and therefore the new narrower valve lift profiles had to be manipulated within 4stHEAD to ensure that feasible cam profiles could be manufactured based on the aforementioned constraints.
Other factors that are constantly checked in this iterative process are the cam to follower Hertz stresses and oil film thicknesses to ensure that they remain within recommended limits.
Figure 8 shows the finalized intake valves lift profiles with its associated velocity, acceleration and jerk characteristics. The key points to note here are the shape and smoothness of the acceleration profile as it is this that is manipulated to achieve the goals described previously. The Intake Spring Outer This shows that the valve lift profiles had to be slightly more aggressive than the original shortened Exhaust Spring It was therefore Exhaust Spring Retainer 5.
Figure 10 shows the torque Bucket The narrower valve lift profiles produced by the optimization process were input to the 4stHEAD software. These profiles were matched precisely within the software, but the ensuing cam profiles could not be directly produced for two reasons. Firstly, the original shortened valve lifts had maximum velocities that were not compatible with the bucket follower diameters in the R6 cylinder head.
The simple fact is that bucket diameter is a function of valve-lift velocity i. Secondly, there is a complex relationship between the radius of curvature of the ensuing cam profile, the base circle radius of the AD Intake Int Mech Analysis AD Exhaust Exh Mech Analysis 10 9 8 7 Va lve L ift m m 6 5 4 3 2 1 0 0 Degrees after TDC Cyl 1 starting comb stroke Figure 9 — AD and Mechanical Analysis Profiles Figure 12 - Exhaust Camshaft Profiles It can be seen that there is not as great a gain in The 4stHEAD software was also used to check that the predicted torque with the mechanical analysis valve lifts new valve lifts and their respective timing events would but still a substantial improvement upon the baseline.
In addition, it was necessary to check that the new valve lifts would not cause any problems to the dynamics of the valvetrain. First of all the dynamics of the valvetrain with the original valve lift profiles were modeled and these were then compared to the dynamics of the valvetrain with the new valve lift profiles.
There were no anomalies with float, bounce or separation of the valvetrain components in the relevant speed range and the maximum stresses were within acceptable limits. The modified camshaft profiles could be manufactured by regrinding the stock camshafts. The modified camshafts were then placed in the engine and the valvetrain was re-shimmed due to slight changes in the camshafts base circle diameters due to the manufacturing process.
The valve lift profiles of the modified camshafts were measured and compared to the lift profiles that were provided by the mechanical Figure 10 — AD and Mechanical Analysis Torque analysis software to ensure that the manufacturing process was successful.
The modified camshaft valve The outputs from the mechanical analysis software also lifts are shown in Figure 13 in comparison to the stock include the camshaft profiles, shown in comparison to profiles.
The reduction in valve overlap and the earlier the stock camshaft profiles in Figures 11 and IVC timing are clearly visible. Stock and modified inlet camshafts are shown in Figure The engine was mapped at full load throughout the speed range between to rpm with fuel adjusted to leanest for best torque and ignition timing adjusted to Figure 14 — Intake Stock and Modified Camshafts minimum advance for best torque for both the standard camshaft and the modified camshaft configurations.
The camshafts when then fitted with vernier pulley Figure 17 shows the full load corrected brake torque wheels so that their timing could be adjusted to the curve comparison between the two tests. Using the VE model of the baseline engine with the 4stHEAD camshafts, a simulation was conducted to examine the changes the camshafts had made on the reverse flow effects.
A comparison of air purity and the mass flow rate for the stock and modified camshaft engines at rpm are shown in Figures 15 and These show an increase in charge purity and a decrease in the reverse flow using the modified camshafts. There are smaller gains at speeds greater than rpm due to the the airflow becoming increasingly choked through the restrictor.
Figure 15 — Comparison of Air Purity at Intake Valve During the optimization process, the Automated Design feature found that an optimum runner length would be mm. It was decided to investigate this factor by increasing the length in the direction indicated by the analysis but not to the extent recommended due to difficulties in packaging such a long runner length within the FSAE car.
Therefore an extension of 50mm in runner length was implemented and the engine Modified Cams remapped at full load.
A comparison of the engine with the extended runners and modified camshafts is shown compared to the standard runners and modified camshafts in Figure Formula SAE Rules [online]. Jawad, M. DeGain and A. Young Jr. As expected mid-range torque was increased but the 4.
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