19MTZ 04|2006 Volume 67

Authors:Werner Bauer, Rupert Baindl and Ewald Mayer

Leistungsstarker Zweizylinder-Dieselmotorfür Motorräder

You will find the figures mentioned in this article in the German issue of MTZ 04|2006 beginning on page 270.

Powerful Two-Cylinder Diesel Engine for Motorcycles

A completely new diesel engine design has been proposedfor top class motorcycles by Neander-Motors GmbH. Theengine, which is equipped with numerous innovative solu-tions, has very compact dimensions for its displacement of1.4 l and output of 74 kW. In this article the engine is de-scribed and test results from the engine test bed at theUniversity of Munich will be shown.

1 Introduction

The corpulent torque development and lowfuel consumption of the diesel automobileengine has earned it its high praise. Up untilnow, the unfavorable vehiclepackage, theloud combustion noise and the high devel-opment expense for a motorcycle diesel en-gine has prevented broad acceptance of thisdrive concept. The motivation of providing amodern, powerful diesel engine in a motor-cycle has prompted Neander Motors to hirethe motorcycle developer Rupert Baindl tostart a development product for a motorcy-cle with a direct injection turbodiesel. Thegoal for the drive unit was to achieve a peakoutput of 74 kW and a torque of 200 Nm at2500/min. In the combustion engine labora-tory of the University of Munich, under thesupervision of Prof. Dr. Werner Bauer, thedevelopment work was carried out for thediesel engine using an engine test stand.

By using and modifying a classical auto-mobile diesel drive in the motorcycle, thetarget specifications were not able to be met.

Through a consistent development for mo-torcycles and some unconventional at-tempts, a more powerful, larger volume two-cylinder diesel engine was developed. In thisarticle, the engine is illustrated in some de-tails, along with the results of the first testengine.

2 Engine Concept

This new drive is an in-line two cylinder en-gine installed transverse (360° paralleltwin). This concept permits a vehicle pack-age to be provided that does not require themotor to extend beyond the frame width aswell as a centre of gravity low enough toprovide good handling. The engine is oil-cooled with dry sump lubrication. Other in-novative design features include two gear-driven, counter-rotating, coupled crank-shafts that almost completely neutralisethe first order inertial forces and a dohc 4Vcylinder head with valve actuation throughcam followers and diagonally opposite inletand outlet ports. The base engine affects the

DEVELOPMENT Diesel Engines

20 MTZ 04|2006 Volume 67

stroke/bore ratio of the engine. This is ex-tremely unfavourable for a diesel engine.Through an asymmetrical piston motion,this disadvantage can be alleviated. A com-mon rail system is used as the injection sys-tem, which is made by Bosch. To meet theperformance data, turbocharging with VTGis required and to meet the emission values,an EGR is required with DPF. Figure 1 showsthe engine-transmission unit in both views.The Table shows the characteristic parame-ters of the test engine

3 Base Engine

The upper section of the aluminium cast en-gine housing contains the Nikasil coatedaluminium cylinder liners. The connectionof the cylinder head to the crankcase, to-gether with the cylinder head gasket andthe cylinder, is accomplished using eighttensile rods to withstand the high peak pres-sure loads. The crankshaft bearing is locatedat the bottom of the crankcase, along withhydraulically actuated multiplate dry clutchand gearbox behind it as well as auxiliarysystem for the alternator and the diesel highpressure pump. This is enclosed by a flat alu-minium oil tank at the bottom with a gear-driven oil supply system that operates onthe dry sump principle.

4 Crank Drive

An extremely narrow, gear-coupled, dualcrank drive design is used that has can-tilevered connecting rod bearings, Figure 2.The drive is accomplished via the rear gearof the crankshaft segment. This arrange-ment of extremely shifted crank operationis the cause of asymmetric piston strokebehavior, which has resulted in longer suc-tion and expansion strokes in the direc-tion of rotation selected. Since the pistonsare practically free of side forces, they wereable to be designed extremely short andlightweight, i.e. without a piston skirt,which has positively effected the frictionalforce of the drive. Another advantage ofthis crank drive is that both rotational aswell as oscillating 1st order inertial forcescan be 100 % balanced by the two counter-rotating shafts using counterbalances onthe cogwheels. This meets the engine re-quirements of low vibration excitation inthe motorcycle. The cylinder skirt as acomponent that controls the design spacespecifies the stroke-bore ratio of 0.72,which is unconventional for a diesel en-gine, and which puts a high requirementon combustion optimisation (see engineconcept).

the acoustic behavior of the engine and thegearbox were initiated for the next extensionstep of the engine design.

8 Engine Management

Engine control is provided with the EDChardware of Bosch, which has been provenin automobile engines. This allows all re-quired basic functions in the operation of acommon rail injection system to be used ina motorcycle as well. The peculiarities ofdual cylinder characteristics and the adjust-ment to dynamic requirements of a motor-cycle were successfully overcome with theINCA application tool, which is made byEtas. The data gained from the stationarytest rig are being supplemented with themeasured values recorded from the test ve-hicle. A datalogger made by Motec with aCAN connection to the engine control de-vice is being used for this purpose; the data-logger also operates as a functional display.

9 Functional Results

The power and torque values fixed in the tar-get specifications were fully achieved in thefirst two prototypes, Figure 5. The best valuefor specific fuel consumption were at2700/min at an mean pressure of 15.5 barand came to approximately 221 g/kWh.Load-dependent injection pressure can beused to optimise partial load injection peri-ods. Likewise, in the next step combustionprocess development will focus on achiev-ing lower exhaust emissions. The emissionspackage includes a high-pressure side ex-haust gas regeneration system and an openparticle filtrations system with an upstreamoxidation catalyst.

10 Summary

With the new Neander diesel engine, a pow-erful, compact direct injection turbo dieselhas been presented for the first time for amotorcycle [1, 2], Figure 6. Its most impres-sive feature is its layout as a flat, paralleltwin with many innovative solutions. Thisallows the characteristics most known forautomobile diesels, such as high torque,good elasticity, low fuel consumption andhigh driving enjoyment to be conveyed to amotorcycle as well.

References

[1] Pfeiffer, M.: Fahrbericht Neander 1400 Turbodiesel-Direkteinspritzer. In: Motorrad 6.2005, Nr. 14, S.36-43

[2] Pfeiffer, M.: Der Hightech-Turbodiesel der Neander1400, In: Motorrad ( 8.2005), Nr. 17, S.40-43

5 Cylinder Head and Valve Drive

The four-valve cylinder head has two diago-nally opposite inlet and outlet valves, respec-tively, which is why there are two exhaustmanifolds, one at the front and one at theback of the engine; these manifolds com-bine prior to the turbocharger, Figure 3 andFigure 1. The two camshafts are driven by acentral chain and cogwheels. One verticalinlet port was designed as a filling port andone was designed as a swirl duct. To opti-mise the charging swirl, swirl inserts thatwere designed previously in the flow teststand were applied in the inlet ports. Thisport arrangement exhibited excellent flownumbers in the flow test on the test rig. Nomap-specific port shut-off was performed.The valves, which are positioned at a smallvalve angle of 8°, are actuated via an over-head bucket-tappet assembly.

6 Steel-Piston

For realisation a short compression heightof only 37 mm, new steel-pistons withoutpiston-shirt, Figure 4, where designed andused in the engine. The substantial higherstrength with regard to an aluminium-pis-ton allows clearly shorter wall-thickness. Sothe piston-bottom-thickness could be re-duced to 2,2 mm and disadvantages in thepiston weight could be avoided (pistonweight 608 g). For heat dissipation a pistonoil spray cooling is used.

7 Combustion Process

The new Neander diesel engine contains atypical ω-combustion chamber with a bowl-diameter of 64 mm and a centrally posi-tioned 8-hole injection nozzle, as well as aswirl of cu/ca = 1.2. Fuel injection is donethrough a Bosch common rail system whosehigh-pressure pump is driven by a toothedbelt. The engine is furthermore equippedwith a Garrett turbocharger and variableturbine geometry as well as a charging aircooler. To improve the acoustic behaviour, apilot injection is applied near idle speed.

A compression ratio of 15.5:1 improvesthe rotational pavement irregularity andprovides reserves with regard to componentstresses as a result of high peak pressures. Forsufficient cold-start ability, ceramic sparkplugs are used. The combustion chamberpeak pressure of max. 140 bar and the cylin-der pressure increase of 8 bar/°KW is moder-ate, but leads to clearly audible engine noisein connection with the oil-air-cooled, finnedcylinders and the high number of vibration-sensitive components. Measures to optimise