Upgrade the existing Land Rover Defenders powertrain
The design teams project aim:
To propose a program and new engine design to upgrade the existing Land Rover Defenders powertrain
The following report discusses weaknesses of the current LR Defender along with a subsequent review of advanced engine technologies. Finally the design targets for the new proposed engine are defined with all necessary parameters calculated and justified. The design team have also considered the cost, manufacturability and marketing affects of the new engine as well as the performance requirements.
The current LR Defender engine will be critically analysed in-relation to the vehicles main competitors in the market place. This will allow the weaknesses of the current engine model to be determined and thus rectified for the new specification engine.
The engine throughout the following section will be critically analysed in the following main areas;
Acceleration & speed performance
Engine power & effectiveness (MEP and power density)
Emissions of harmful gases and particulates
The potential customer perception of vehicles engine and other performance criterion (including value for money).
The following competitor vehicles were researched and compared to the current LR Defender to establish baseline requirements for the new spec engine;
Jeep Wrangler Unlimited (regarded as the main competitor)
Mercedes-Benz G-Class G550
Nissan Patrol GR
Toyota Land Cruiser 3.0 D
For a table of the above vehicles full specifications, benchmarked with the existing LR Defender, refer to Fig.4.7 in Appendix.1.
Analysis & Discussion
By reviewing the benchmarking table, Fig.4.7 in Appendix.1, it becomes apparent that the current LR Defender is slower than its competitors by taking 14.7 seconds to reach 0 62 mph compared with the Jeep Wranglers time of 11.7 seconds. Although the LR Defender is not expected to have a very fast acceleration time, as it is an off-utility vehicle, potential customers may be discouraged by the Defenders slow acceleration characteristics compared to the Jeep and its other competitors.
The fastest acceleration time is achieved by the Mercedes-Benz G550 which can go 0 62 mph in an impressive 6.1 seconds with its supercharged 5L V8 petrol engine. The cost of the Mercedes-Benz G550 however is 50,250 (compared to 27,610 for the Defender) and has twice the engine capacity of the Defender, so is expected to be far more powerful with its petrol engine compared to the 2.4L turbocharged diesel Defender engine.
The design teams proposal is that the current LR Defender engine should at least match or beat its rival the Jeep Wrangler in areas such as acceleration time from 0-62 mph as the Defender is more expensive than the Jeep and approximately 230kg lighter.
Another issue is that the Defenders top speed is the lowest out of all its competitors. This low top speed has also attracted criticism from motoring journalist Jeremy Clarkson (2006) who stated that the biggest drawback of the LR Defender is its weak engine and thus corresponding slow acceleration and top speed. The new LR Defender engine must eliminate these same criticisms to become more competitive in the market place and thus more appealing to potential customers.
Power per cylinder (kW/cylinder)
Power Density Ratio (kW/L)
LR Defender 2.4L D 4inl
Jeep Wrangler 2.8L D 4inl
Mercedes Benz G550 5.5L V8 petrol
Nissan Patrol GR 3.0 D 4inl
Toyota Land Cruiser 3.0D 4inl
Fig.1.0 compares the effectiveness of the engines that were benchmarked in detail. It shows that the Defenders current engine has the lowest power density in terms of engine capacity. This is a big weakness as it shows that the when not taking into account the Defenders relatively small engine capacity, its engine is vastly underpowered. The Mercedes Benz G550 as expected displays the best power density as it is a gasoline engine. The Defenders regarded closest rival in terms of target market and image, the Jeep Wrangler, also shows a much greater power density ratio.
Or group propose to increase the engines the power density to be comparable with the Jeep Wrangler with at least a ratio of above 43kW/L.
LR Defender 2.4L D 4inl
Jeep Wrangler 2.8L D 4inl
Mercedes Benz G-Class G550 5.5L V8 petrol
Nissan Patrol GR 3.0 D 4inl
Toyota Land Cruiser 3.0D 4inl
A weakness of the current Defender however is highlighted test drive of the vehicle by motor journalist Jeremy Clarkson (2006) for the Times Newspaper. He stated that the vehicle simply did not have enough torque to pull a horse trailer behind it at a reasonable speed. This can be backed up by the data seen in Fig.1.1 above which shows that the current Defender engine produces the least amount of torque out of all its competitors. This weakness is heavily compounded by the fact that the vehicle is marketed as an off-road vehicle and thus needs high torque requirements to be-able to navigate through steep and loose terrain effectively. As a consequence customers may be off put by the fact that the current Defender has less torque than its competitors and thus this issue will have to be addressed when upgrading the existing engine.
The new engine must be made more environmentally friendly than the current engine as January 2013 will see the current Euro 5 emissions targets replaced by the Euro 6 legislation and thus stricter emissions targets. The Defender is third best out the five competitors the vehicle was benchmarked against in regards to CO2 emissions, which is an indicator for overall total emission performance.
The current Defender comes second best to the Jeep Wrangler in regards to fuel economy, by achieving a combined fuel economy of 28.3 mpg. However the other diesel engine competitors, the Nissan Patrol and Toyota Land Cruiser are less fuel efficient than the Defender.
When purchasing an off-road vehicle such as the Defender, fuel economy may not be the most important factor but it has become more important to potential customers over the last decade. The same could be said for the greater importance of emissions performance that potential customers may look for. The new Defender engine is likely to be more powerful and thus a better fuel economy target (comparable to 32.8mpg of the Jeep Wrangler) may be out of reach. However through reviewing and selecting technologies, the fuel economy performance could be improved slightly or at least kept the same.
From analysing the Defender, by using the data displayed in Fig.4.7 (Appendix.1), it can be seen that the vehicle is neither the best nor worst performing vehicle in regards to fuel economy, but averagely in relationship to competitors.
The balance of the current Defenders inline four engine configuration, according to Nunney (2006), has perfect primary balance because when one pair of pistons are moving up, the other pair are moving down at the same time. Inline four engines however do not have perfect secondary dynamic balance. This is because piston acceleration varies depending on its vertical position within the cylinder head in relation to the crankshaft that it is connected to. This leads to one pair of pistons moving faster than the other, which creates a secondary imbalance and results in the engine vibrating vertically. Nunney (2006) also explains that at low power configurations the secondary imbalance (vibration) is not too severe but can get considerably worse with increasing size and powerful engines. This may explain why the current inline 4 Defender engine has a lower displacement than its competitors, to reduce secondary imbalance vibration in order to appeal to potential customers and save costs on designing a crankshaft to damp heavy engine vibration.
The following strengths are also exhibited by the current engine;
Highest MEP value out of the competitors benchmarked against
Best strength to weight ratio (could be due to basic interior making vehicle lighter)
Potential customers may overlook the apparent power and torque shortfalls as the highly regarded Land Rover brand may persuade people to buy the vehicle anyway.
Summary of existing Defender engine (compared to competitors);
- Slowest acceleration from 0 62 Mph
- Best Mean Effective Pressure of 1.885Mpa, better than competitor vehicles
- Lowest top speed of only 82 mph
- Highest Power to weight ratio (kW/kg)
- More expensive than Jeep Wrangler by >4000 even with poorer speed performance.
- Fuel economy is not the worst
- Lowest Power per cylinder produced (kW/cyl)
- Emission of CO2 is not the worst
- Secondary imbalance of straight inline four engine configuration (rivals also have this weakness)
- Long history of Defender may appeal to potential customers, thus engine shortcomings may be overlooked
- Lowest torque produced out of competitors
- Not the best in either fuel consumption or emissions, even with smallest capacity engine
- Lowest Power Density Ratio (kW/L)
Current Vehicle Performance Trends
Fig 1.3 shows the performance trends for Jaguar engines up to 2010. While exact performance targets cannot be extrapolated from the graph, The design group can see that the new Defender engine needs to have an increase in specific engine power. However with the increase in power, increased emissions and fuel consumption will occur. This in conjunction with Fig 1.4 below from Richardson (2010) shows how CO2 emissions have decreased despite the trend of engine power also increasing.
While the trends from Figs 1.3 and 1.4 show that performance trends increase and emissions trends decrease, the group is concluding that potential customers for a LR Defender will be less likely concerned about the vehicles emissions or fuel economy compared to non-SUV vehicles customers. Thus increasing the torque (and power) of the current engine to match its competitors is prioritised. It is conceded that any improvement in fuel economy and emissions departments will be limited, but in the interests of Land Rovers image, any improvement on these characteristics will be beneficial.
Advanced Engine Technology
Supercharging & Turbo-charging Technology
Superchargers (mechanical drive driven)
This is a device comprising of an air compressor to force more air into the engine. Forcing a greater amount of air (under positive pressure) into the engine provides more oxygen for the combustion process than without a supercharger. As a result more fuel can be thus provided for stoichiometric combustion reaction to occur and allowing more work per a cycle to be done. This thus increases the power output of the engine.
The advantage of supercharging according to Daniels (2001) is that it multiplies the engines BMEP and torque by the amount the air compressor increases the atmospheric pressure into the engine. Supercharged engines also experience better throttle response than naturally aspirated engines.
The disadvantage of using a supercharger is that it is generally less thermally efficient than the more common used turbocharger (which uses energy from otherwise wasted exhaust gas). Another drawback highlighted by Harris (2002) is that supercharging (particularly mechanical-supercharging techniques) puts extra strain on the engine and its components as they are required to withstand extra strains provided by the supercharging boost. This requires the engine to be made stronger, thus thicker, heavier and more expensive. Daniels (2001) also explains how the noise generated by a superchargers mechanical drive components can contribute to extra passenger discomfort.
These devices consist of a turbine and a compressor and are a type of supercharger. The difference is that instead of mechanically driving a compressor to force more air into the engine, turbochargers uses the engines own exhaust gases (which would have been otherwise wasted). It does this by converting the kinetic energy from exhaust gases into rotational energy to turn a turbine. The turbine is connected to the compressor on the same shaft, thus this powers the compressor to draw in atmospheric air and pump it pressurised into the engine.
The advantages of a turbocharger are same as for a supercharger as previously described of increasing engine BMEP. This is appropriate for the LR Defender which will need the extra power if being used off-road or in mountainous steep roads, which is the market the vehicle is targeted to. Turbochargers are also more thermally efficient than superchargers due to use of the otherwise wasted exhaust gas. This thus decreases exhaust emissions and fumes expelled into the atmosphere. Daniels (2001) also explains that for mainly diesel engines variable geometry turbochargers can maintain an appropriate exhaust gas speed though the turbo turbine when the engine is at low load.
Disadvantages include the need for a cooler to cool exhaust gas before it enters the turbine therefore adding weight and bulk to the engine. During operation turbochargers also experience a turbo lag when the throttle is applied.
As previously explained the LR Defenders competitors (particularly its main rival the Jeep Wrangler) have more powerful engines than the current Defender 2.4litre 4 cylinder engine. If upgrading the engine by increasing its cylinder capacity, more air (particularly oxygen) will need to be supplied to the cylinders for combustion. Thus the use of twin-turbochargers may be required to force more air into the cylinders to make the combustion process stoichiometric. Also the advantage of using two smaller turbochargers (twin-turbo), instead of a larger single turbocharger, is that turbo-lag is reduced. Usually a small turbocharger provides boost at low engine speeds and the second kicks in and supplies boost at higher engine speeds. There are two widely known types of twin-turbochargers called Parallel and Sequential types.
When comparing the advantages and disadvantages of mechanically-driven superchargers and turbochargers it was decided to use turbochargers as they are more environmentally friendly and fuel efficient to run. The current engine for the LR Defender uses a variable geometry turbocharger and it is likely the new spec engine will also be turbocharged by the same type of unit.
Variable Valve Timing Systems
Camless Valve Systems
Autoweek Magazine (2005) states that camless valve systems were tested in 2005 by Valeo on two Peugeot 407s successfully under extreme weather conditions and intensive testing. The valves were controlled by individual actuators and powered through solenoids to open and close valves.
The advantages of camless systems, explained by Daniels (2001), include the following;
- Valve timing can be altered to as desired
- In theory some cylinders could be shut off (at low load) to allow others to run more efficiently
- Valve timing and lift can be matched to the needs of the engine with an estimated saving of up to 20% on fuel saving.
- The mechanical design of the engine can be simplified as the usage of a camshaft and other associated valve gear become redundant.
The advantages however are currently overshadowed by the power needs of the camless system and the associated complexity and reliability issues if the vehicle has electrical problems. Peter Brown who is vice president of powertrain engineering and design for Ricardo stated in Autoweek Magazine (2005) It comes down to complexity and cost which sums up why camless systems are still not (although many think they eventually will be) utilised in passenger vehicle engines. For The new LR Defender engine camless systems will not be used for the disadvantages described above.
Variable Valve Timing Technology
Mechadyne International (2006) states that that the use of variable valve train systems can substantially reduce both fuel consumption and exhaust emissions. The amount by which the variable valve train systems reduce fuel consumption and emissions is going to be approximated to 10%. This is because, as the Bosch Automotive Handbook (2007) states, BMWs VALVETRONIC system reduces fuel consumption and exhaust emissions by over 12%.
According to the Bosch Automotive Handbook (2007) the following types of variable valve timing technology are available;
- Camshaft phase adjustment
- Camshaft-lobe control
- Fully variable valve timing with camshaft
- Fully variable valve timing without camshaft
- Camshaft Phase Adjustment
This type of variable valve timing adjusts the phase that the cams are in contact with the levers that open and close the valves. To change the phase of the camshaft small adjustments are made, by electrically controlled actuators, to the camshaft as a function of engine speed. Typically the camshaft can only be controlled to move to two pre-calculated extreme positions.
Advantages include greater power, torque and efficiency being experienced for a wider range of engine speeds. Disadvantages to other valve timing methods include the limited range in which the valves timings can actually be altered.
Fully Variable Valve Timing with Camshaft
These types of systems can vary both valve lift and timing. The lobes on the camshaft have a curved profile which in conjunction with the camshaft being able to move freely laterally, this enables the valve lift and timing to also be varied independent to each other, which is an obvious advantage to the previously limited valve control systems mentioned above.
Fully Variable Valve Timing without Camshaft
These types of systems are very different, to the previously mentioned, as it replaces the use of a camshaft with either the following types of control methods solenoid (electromagnetic) or electro-hydraulic actuators.
The biggest advantage of these systems are that operate independently from the crankshaft and thus this allows the valves to be opened at any time period of the engines cycle. This, as stated by the Bosch Automotive Handbook (2007), offers the greatest degree of freedom for valve timing and thus the greatest potential for reducing fuel consumption. Also deactivation of certain cylinders can be achieved thus allowing the active cylinders to work more efficiently at lower engine speeds. Disadvantages are however that superchargers cannot be installed (without very expensive and complicated design), and while space is saved from not using a camshaft, electrical components can be bulky and hazardous. Also the cost of fully variable valve timing systems means it is unlikely they will be incorporated into The new engine design.
In these types of systems it becomes possible for a valves timing to be controlled by three separate camshaft lobes depending on the engine speed. According to the Bosch Automotive Handbook (2007) the one lobes profile is tailored so that valve timing and lift is optimised for the lower to mid engine speed range. Another lobes profile is optimised for higher engine speeds by maximising valve lift and opening times. Systems such as Hondas VTEC and Toyotas WTI use camshaft-lobe control method. Camshaft-lobe shifting types of variable valve timing also share similar advantages and disadvantages to the camshaft phase adjustment method.
This type of variable timing (camshaft-lobe control) will be used for the new engine design. This is because it doesnt cost as much (or weigh as much) as the other variable valve timing systems while still being hugely advantageous in terms of performance, fuel economy and emissions control gain.
Fuel Injection Systems
Common Rail Fuel Injection
These fuel systems consist of a common rail tubing system maintained at constant high pressure via a pump. Injectors for each cylinder in the engine are in turn connected to the common rail tubing. The injectors have solenoid valves which are electronically controlled via an engine ECU (Electronic Control Unit) to open and close at the desired timings as explained in detail by DENSO (2005).
An advantage of common rail fuel injection is that control of fuel injection (according to Daniels, 2001) is at the injector itself and not at the pump which is the case with other fuel injection systems. Higher pressures can also be achieved thus more fuel can be injected into the cylinder in a shorter amount of time with better fuel atomisation, as described by DENSO (2005), leading to high combustion efficiency and a reduction in emissions. This is important as new emissions targets will have to be met in 2014 with the Euro 6 legislation when the vehicle will be on the market.
The main disadvantage of this type of injection technology according to Daniels (2001) is that the injectors are expensive to manufacture and inherently complicated in design.
Piezoelectric Injectors (For Common Rail Systems)
Instead of using solenoid valves which are more frequently used in common rail fuel injection system, piezoelectric injectors can be used in higher performance engines. These injectors work by using piezoelectric crystals that expand when supplied with an electrical charge and thus opening and closing fuel injection valves. The following attributes of piezoelectric type injectors are common;
Greater compact dimensions than solenoid valve injectors.
More accurate control over injection timing and fuel volume.
Piezoelectric injectors can be used with Accelerometer Pilot Control (APC) to minimise diesel engine vibration at low engine speeds. This is achieved by injecting a small quantity of fuel before the main injection quantity.
Piezoelectric injectors can also operate faster with more frequency than solenoid valves (approximately five times faster), which allows greater control over fuel consumption and emissions.
The Bosch Automotive Handbook (2007) states that the use of piezo-injectors for common rail fuel systems can reduce emissions by up to 20%.
Emissions Reduction Technologies
Stanton (2009) from roadtransport.com explains how the European Parliament (EP) and European Commission (EC) have agreed new targets for comply with Euro-6 emission legislation. The new Euro-6 targets will have to be met by vehicle manufacturers and thus the new spec LR Defender by 1st January 2013. This is before the new LR Defender model will reach Job 1 (mid to late 2013). It is therefore important that new and existing technologies are reviewed in Emissions control to meet these targets. In recent years the environmental performance of vehicles influences potential customers more than ever in their buying decision. It is therefore important we maintain Jaguars highly regarded brand image and compete with competitors by meeting the existing (Euro-5) and future Euro-6 emissions targets.
Diesel Particulate Filters (DPF)
This is a device which is responsible for removing small particulate particles and soot from the exhaust gas of a diesel engine. A DPF is not 100% but is normally found to be over 50% efficient most of the time. A good feature of a DPF is that its function according to torquecars.com (2008) is independent to a catalytic converter thus ensuring a fault in the DPF will not affect overall emissions critically.
The advantages of particulate filters are much publicised including removing dangerous small particles from an engines emissions. The two types of DPF, active and passive, have their own advantages and disadvantages.
The main disadvantages of DPF, explained by torquecars.com (2008), are highlighted below;
- The filters can get very hot causing a possible fire safety hazard.
- To remove a DPF very technical changes have to be made to the affected ECUs to change the sensitivity of sensors in the vehicles engine and exhaust.
- A DPF can decrease engine performance by at most 10% Bhp.
- Other Technologies
Accelerometer Pilot Control (APC)
Diesel engines are known to display harsh chugging and vibration at low engine speed, which can now be minimised through technology called Accelerometer Pilot Control (APC). An APC system, described by Delphi (2008) consists of an accelerometer (microphone) attached to the engine block which listens to the nature of the combustion which may have caused vibrations occur throughout the engine block. An engine management system then minimises the unwanted vibrations and noise by optimising the amount of fuel pilot injected for combustion, in a closed loop system, until acceptable noise and vibration levels are reached.
According to mobilechiptune.com (2007), when we remap an engine ECU we are fine tuning the program that deals with engine performance. Remapping or upgrading an ECU could therefore potentially increase the available engine power and torque. Mobilechiptune.com (2007) also states that remapping a diesel turbo engine ECU will produce 30 – 50% BHP on exact the specification, where diesel engines give the most impressive power and torque gains available. A remap of the ECU will definitely be required be a twin-turbo (or other technologies) are added to the new engine, however the ECU itself is only likely to achieve small gains in efficiency, fuel economy and emissions.
Summary of Chosen Technologies
Fig1.5 below shows the selected technologies the group is proposing for inclusion into the new Defenders engine. Fig1.5 also shows estimates of the expected improvement over engine performance, emissions and fuel economy. Also see Section.3 for justification to estimates below.
Twin-Turbo (reused exhaust gas
Variable Valve train
Diesel Particulate Filter
Improved ECU Mapping
Emissions, CO2 g/km
Fuel Economy, mpg
*Piezo injectors as opposed to solenoid controlled injectors in a common rail fuel injection system.
3. Selection of Engine Arrangements
Modified engine parameters:
Total engine capacity 3000 cc.
Capacity per each cylinder 500 cc.
Number of cylinders 6
Type of engine Diesel engine
The target is to improve engine performance (mainly torque) by increasing the number of cylinders from 4 to 6. Although there is a reduction of capacity per cylinder, a net increase in total engine capacity of 600 cc will not only compensate it, but also increases total horsepower produced. Kayne (2009) states that 6 cylinder engines are more suited to towing, off-road, hilly and mountainous areas while experiencing greater throttle response. Bore size is thus reduced from 89.9 mm to 82 mm while retaining the same stroke length. Bore/stroke ratio is 1.15, which is within the range of 1-1.3 for diesel engine. The weight of the current engine is estimated as being 180kg taken from a BMW 2.5L inline 4 diesel engine (plus weight added for turbo) from data compiled by Williams (2006), which is a similar spec to the current Defenders 2.4L turbo inline 4. The new engine is estimated as being 25% larger thus heavier by the same margin, and an additional 50kg for the additional technologies added. The new engine weight is thus taken as approximately 300kg.
4. Determination of Design Targets
This section of the report provides estimations for the new engines power, torque, fuel economy and emissions characteristics. Below Fig1.7 Shows modifications to the Defenders current engine will affect the new engines power performance.
Estimated affect on engines Performance
BHP (%) affect from current Defenders 121 BHP engine
Increasing engine capacity by 600cc
+ 25 %
+ 30 BHP
Upgrading current Turbocharger to a Twin-turbo charger
+ 20 %
+ 24 BHP
Installing a Variable valve train system Camshaft Lobe Control
+ 10 %
+ 12 BHP
Decreasing the bore from 89.9mm to 82mm
– 10 %
– 12 BHP
Adding a Diesel Particulate Filter
– 10 %
– 12 BHP
Piezo-electric injectors (instead of solenoid valves) in common-rail system
+ 6 BHP
-Accelerometer Pilot Control (APC)
-Improved ECU Mapping
-Improved intake air flow
+ 5 %
+ 6 BHP
Total affect in BHP =
+ 50 %
60 BHP Increase
Given the maximum power for previous engine is 121 bhp. Therefore, the new engines maximum power is:
Power = (121 + 30 + 24 + 12 – 12 – 12 + 6 + 6)bhp
= 181 bhp
Torque and Power at 3 operating conditions:
T = 368.5 Nm @ max power (3500rpm)
T = 400.0 Nm @ max torque (2000rpm)
T = 120.0 Nm @ idle (1000rpm)
The Torque at various engine speeds were calculated via using the following equation:
Engine power: Pe=2*? *N* T
Figure 1.8 shows the estimated power and torque curves for the vehicle.
Justification of Targets & Estimations
While the decision has been taken to increase the engines capacity, increasing the engines power to increase the vehicles acceleration and torque characteristics, the fuel economy and emissions of the engine also has to improve. This is due to more stringent legislation and targets, as well as the expectations from potential customers who expect the engine to improve in every department.
It may be said that that increasing the engines capacity from 2.4L to 3L means that the targets of decreasing the fuel consumption and emissions will be difficult. The group would argue however that the current Defenders engine is underpowered compared to its competitors and was consequently the recipient of bad reviews from motor journalists (such as Jeremy Clarkson, 2006).
The Defenders potential customer market also may not require huge improvements in fuel consumption and emissions. This is because the Defender is going to be utilised for and marketed as an off-field vehicle with specialist applications such as towing and rough terrain excursions. These categories of vehicles are expected by customers to have poorer fuel economy and emissions than other smaller vehicle types. These customer expectations will therefore be beneficial when designing the engine as while emissions and fuel economy is targeted to at least stay the same, the issue of increasing the Defenders torque can be prioritised.
The increase in engine capacity naturally means the emissions and fuel consumption will increase. To overcome this advanced engine technology will be utilised in order to decrease the emissions and fuel consumption. Estimations will be made regarding how much saving (in terms of percentage) the addit
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