Super Eta Analysis And Report

With the purpose of designing an efficient engine which provides a larger amount of torque at lower RPM, BMW increased the stroke of their existing 2. 5l engine (from 75mm to 81mm) and redesigned the head and camshaft. The new design proved to be very effective for general driving, however, the design was very limited in terms of outright. This new engine configuration provides a high revving, larger capacity engine (2. 7lt as opposed to 2. 5lt) that produces significantly more power.

This report revolves around the BMW Super Eta motor and the use of varying connecting rods. It intends to decide whether utilizing the original Eta bars has any difference in performance/running of the BMW Super Eta motor as compared to the bars used in the 2. 5i arrangement. The significance of the decision of conrod in the Super Eta, while apparently insignificant, could conceivably influence the motors in terms of general power yield and life expectancy. Through kinematic and kinetic analysis, it was found that the use of shorter connecting rods (130mm) applied a slightly greater force on various components of the engine such as the journal bearing, the gudgeon pin, and the cylinder wall, as well as generating a greater piston-cylinder acceleration as compared to the longer connecting rod(135mm) used in the 2. 5i arrangement.

Since there is a prominent contrast between the conrods in terms of the subsequent speeding up of the cylinder, and the additional loading, the distinction in terms of performance and engine wear is noticeable. On using the original eta connecting-rod will adversely affect the engine’s running as it will result in increased wear on the entire piston-cylinder system increasing the likelihood of engine failure. It is this report’s recommendation that the 2. 5i conrod is a more acceptable and more viable option.

Introduction

With the constant shrinking supply of natural resources, it is of great significance that we humans design and manufacture vehicles with the basic concept of conserving fuel and move towards an eco-friendly plan, but we must also make sure that such vehicles whilst providing an environmentally friendly experience also provide an acceptable and competitive level of power. This issue is especially obvious in the outline of the Super Eta motor. Eta motor made by BMW in the eighties concentrated highly on eco-friendliness, but however, had to give up terms of outright power. On the contrary, the Super Eta planned to keep up the first Eta's effectiveness while delivering essentially more power, adequately adjusting the drop-in fuel utilization with increased power output.

The report specifically revolves about deciding the choice of connecting rods to be used. While both connecting rods work the engine, information regarding the loadings on critical parts of the motor, as well as the resulting acceleration of the piston associated with each conrod. The information gathered from testing both conrods are then compared to highlight any significant differences to quantitatively conclude if there are any notable adverse impacts from using both different conrods.

About the Internal Combustion Engine (ICE)

The INTERNAL COMBUSTION ENGINE is a device in which a mixture of fuel and air is burned inside a confined space called a combustion chamber. This exothermic reaction of a fuel with an oxidizer produces gases of high temperature and pressure. The gases produced from the exothermic reaction is therefore used to carry out useful, for example by acting on pistons, rotors, or even by pressing on and moving the entire engine itself. Internal combustion engines are seen mostly in transportation. The advantages of these are the portability and mainly its reliability. Hence these types of engines are preferred over electrical engines. However, unlike electrical engines, they do produce a lot of pollution such as noise, air, and waste pollution.

Brief Description of the Eta Engine

The “Eta” engine is a stroked-out 2. 7-liter variant of the famous M20 inline-six. The e stands for efficiency. The engine is designed to be a low-revving, high on torque, low on horsepower, not unlike a V8 from the era. It manufactured with the idea to be a more fuel-efficient choice. It provides an unusual 121 horsepower and 171 lb-ft of torque. The engine, however, produced revs that were found to be really low: the car’s redline tops off right around 4, 700 RPM.

Assumptions

For the following analysis, the following assumptions are considered as the entire analysis is down based on theoretical and mathematical results, hence will not consider certain parameter which does appear in real-world conditions

• Factors such as frictional force, gravitational force, gas pressure and combustion forces are not considered.
• The piston-cylinder system will not be subjected to any wear or tear or any deformation.
• System fails will not occur.
• Mass of piston-cylinder system is constant (unless in the case of reciprocating mass).
• Forces are analyzed neglected the effect of weight and inertia of connecting rod.
• Energy-mass, momentum are considered to be conserved.
• No energy loss due to heat at joints.

Kinematic Analysis by Analytical Method

Analysis of the system is carried out using the following single slider crank mechanism which is shown the figure. The details of the system such as piston mass, con-rod mass, the con-rod moment of inertia, con-rod length, the location of the center of gravity and crank radius are provided for the analysis. Using mathlab software, it will be used to produce graphs from which the results will be obtained. Using the following Free body diagram of the single slider crank mechanism the piston velocity and piston acceleration equation will be derived. Here the crank OC is driven with uniform angular velocity ω, r being the crank radius, l is the length of the connecting rod, x being the position of the piston pin P from the crank center, θ being the crank angle and φ representing angle OPC.

Analysis of Forces Experienced By Gudgeon Pin

The gudgeon Pin is an integral part of the internal combustion engine which connects the connecting rod to the piston and provides a bearing for the con-rod to move about as the piston moves inside the cylinder from TDC to BDC. This small part operates under high temperatures and pressure, lubrication plays a major role in helping the movement of the pin. The Piston Pin is subjecting to both shear and bending loads. The Pin, however, to found to fail mostly due to fatigue loading. The eta configuration was found to have the highest connecting rod force hence it applies the most force on the gudgeon pin as compared to the other two configurations, hence we can safely state that the eta rod which has the smallest length will cause more wear and tear on the gudgeon pin as compared to the 2. 5i configuration and the M3 configuration.

Analysis of Side Loading Force

The variation of Side Loading Force was observed over an interval of 3 cycles and it is found that the eta configuration possesses a greater Side Loading force as compared to the others, the M3 configuration having the least Side Loading force among the three. Over the duration of three cycles it has been observed that the peak values of all three configurations fluctuate at both TDC and BDC positions. The eta configuration was calculated to have a Side Loading force 5. 5% more than the 2. 5i configuration and 9. 1% greater than the M3 configuration at the TDC. Similarly, the eta configuration was calculated to have a Side Loading force 5. 9% more than the 2. 5i configuration and 10. 1% greater than the M3 configuration at the BDC.

Analysis of Forces Applied On The Cylinder Walls

The walls of the piston-cylinder system are subjected to high temperatures and under constant pressure due to the fast up and down movements of the piston due to combustion. For proper functioning of the piston, the bore diameter of the piston must be just smaller than the piston-cylinder diameter but must not be too small that it will allow the combustions gases to escape. The small gap between the piston and the cylinder wall must be well lubricated to allow smooth movements and prevent the wear of the cylinder wall and the piston due to friction. If the cylinder wall is damaged due to excessive wear and tear or due to excessive force, cracks tend to form on the walls that inhibit the pistons movements which lead to engine failure.

From the results tabulated for the Side Loading forces, it can safely be stated that the eta configuration was found to apply more force on the cylinder wall as compared to the 2. 5i configuration and the M3 configuration, the M3 configuration applying the least, Hence the eta would tend to cause the most damage over the long run if used as compared to the other two configurations.

Analysis of Tangential Force

The variation of Tangential Force was observed over an interval of 3 cycles and it is found that the eta configuration possesses a greater Tangential force as compared to the others, the M3 configuration having the least Tangential force among the three. Over the duration of three cycles it has been observed that the peak values of all three configurations fluctuate at both TDC and BDC positions. The eta configuration was calculated to have a Tangential force 2. 05% more than the 2. 5i configuration and 5. 7% greater than the M3 configuration at the TDC. Similarly, the eta configuration was calculated to have a Side Loading force 1. 98% more than the 2. 5i configuration and 5. 671% greater than the M3 configuration at the BDC.

Analysis of Bearing Force

The variation of Radial Force was observed over an interval of 3 cycles and it is found that the eta configuration possesses a greater Radial force as compared to the others, the M3 configuration having the least Radial force among the three. Over the duration of three cycles it has been observed that the peak values of all three configurations fluctuate at both TDC and BDC positions. The eta configuration was calculated to have a Radial force 1. 78% more than the 2. 5i configuration and 5. 22% greater than the M3 configuration at the TDC. Similarly, the eta configuration was calculated to have a Radial force 1. 09% more than the 2. 5i configuration and 5. 15% greater than the M3 configuration at the BDC.

Analysis of Forces Applied On The Journal Bearing

The Journal Bearing also called the main bearing are parts on which the crankshafts rotate, they are located at the location where the connecting rod is connected to the crankshaft, the purpose of this part is to prevent the piston force to be transmitted to the crankshaft through the connecting rod so as to prevent the crankshaft from dislodging and force the crank to convert the reciprocating movement to rotational motion. If the Journal Bearing does failure due to excessive wear due to friction or excessive force it will ultimately lead to engine failure and damage which will be very tedious and expensive to repair, mostly will require a completely new crankshaft and engine.

On observing the results tabulated before, we can safely state that stated that the eta configuration was found to apply more force on the Journal Bearing as compared to the 2. 5i configuration and the M3 configuration, the M3 configuration applying the least, Hence the eta would tend to cause the most damage to the Journal Bearing as compared to the other two configurations.

Final Analysis of System and Recommendations

Engineers are always looking for new ways to design and change the way engines are built to give an edge over their competition. In this report, we observe the effect of changing the length of the rods with respect to the stroke of the crankshaft.

On using the shorter connecting rod of length 130mm, do have many advantages. Overall height and weight of the engine can be reduced, the engine will provide a better throttle response. Having shorter connecting rods will allow the user to add modifications to the vehicle such as turbochargers, supercharges and even nitrous applications as the shorter connecting rods are able to produce a higher RPM as compared to the longer connecting rods. These points make the use of shorter connecting rods best suitable for high performance or racing engines.

However, due to the excessive forces applied by the shorter connecting rods on the piston-cylinder system, it cannot be utilized for a long period of time due to the quick wear and tear caused by the pistons. Hence are not suitable for everyday driving From results of piston velocity, the connecting rod with length of 135mm which is to be used for the 2. 5i/M3 configuration is found to have a maximum velocity of around 30. 686 m/s while the shorter connecting rod of length 130mm which is to be used in the eta configuration was found to have a maximum velocity of 31. 089 m/s.

Using the following equations, the RPM of both the longer and shorter connecting rod can be tabulated: For the shorter rod, we find it to have a peak RPM of 7018 and the longer rod has peak RPM of 6950. Using longer connecting rods with the same stroke length reduces the forces experienced by the cylinder walls, the Gudgeon Pin and the Journal Bearing as compared to the shorter connecting rod. It also applies less friction during its movement and hence causes less wear and tear and can be utilized for a longer duration as compared to the shorter connecting rod. Using longer rods will require lighter pistons hence the additional weight of longer rods is compensated. However, the usage of longer connecting rods will results in less RPM production hence will not be suitable for high-performance engines but it suitable for everyday driving or street performance.

Conclusion

Since we are required to provide a connecting rod which will provide a high RPM along with a right amount of power, it is recommended to use the M3 connecting rods of length 130mm. Although the eta connecting rod of length 130mm do provide a greater amount of RPM, The M3 connecting rod will provide close to the same amount as well as last longer due to the fact that it will result in less wear and tear of the piston-cylinder system and can be utilized for a longer period of time as compared to the shorter eta connecting rods.

M3 Connecting rods are also lighter and will benefit the movement of the piston movement. Although the M3 connecting rods are expensive and a bit difficult to source, the user will be less burdened by the pressure of maintenance which will not be the case if the shorter eta rod is used. From all the results and graphs produced we can clearly state that if the shorter rod is used, a greater force is applied to various parts of the piston-cylinder system as compared to the longer connecting rod. In terms of velocity and acceleration, the values of velocity and acceleration for the shorter rods differ very little to the values of velocity and acceleration for the longer shorter, hence can be neglected. In conclusion, I prefer that the M3 connecting rods be used despite being expensive as they will prove to be a better solution for the consumer if it is used for everyday driving and not for high-performance conditions.