Home Page

The early history of the High Speed Direct Injection (HSDI) Diesel Engine

by G L Bird CEng

Preamble

In 2010 the world production of diesel cars and light vehicles exceeded 10 million. All of these diesel engines are highly sophisticated designs with complex fuel and charge air systems controlled by electronics. These high performing, low emission fuel efficient engines owe their pedigrees to a group of engineers at Ford Motor Company at Basildon, Essex who against considerable odds and industry scepticism designed and developed the worlds first high speed direct injection diesel engine, based on the Austrian diesel engine consultancy, AVL Lists controlled swirl air inlet port.

The first production engines, introduced in 1984, were not emission friendly but the customers loved the performance, fuel efficiency  and reliability over the displaced pre-chamber engines. Emissions legislation quickly promoted a second generation engine, introduced in the 1987 Transit.  The new  engine had  extensive  combustion improvements to meet the first meaningful European emission  requirements of 15.04 legislation. The team then went on to develop a higher power turbocharged engine using the worlds first fully electronically controlled fuel injection pump from Lucas. From this point the acceptance that electronics were  the way forward for engines was established.

There have been many technical papers and other publications covering these engines, the narrative that follows is a small attempt to record the the history of how it came about and the struggles involved.  It is dedicated to all the engineers who's resolution  and determination to  solve the multitude of problems and overcome the many obstacles to get the engines into production.

The Story

The oil crisis of the nineteen seventies prompted the Automotive Industry to search for less fuel consuming power units.  In the USA the big three (GM, Ford & Chrysler) undertook extensive research programmes on gasoline alternatives.

In Europe, diesel was seen as the best alternative and engine production was increased especially on the continent. At this time diesel engines were divided into distinctive family groups. The Truck market was served by slow running, below 2600 rpm, direct injection engines while cars and light vans used indirect injection (IDI) pre-chamber engines mainly based on the Ricardo Comet IV pre-chamber system. While Mercedes Benz used their own pepper pot design and Perkins another pre-chamber design which had evolved from the original pre World War 2 design of Frank Perkins.. The IDI system enabled engine speed to be increased to 4000 plus RPM, but this was at the expense of a 15% drop in specific fuel economy, due to high pumping and thermal losses, when compared to the DI big brothers.
Ideally, what was wanted for passenger cars and light commercial vehicles was a high speed direct injection engine. Many in the industry at this time thought this was impossible because of the difficulties of achieving clean combustion at the higher engine speeds.  Contributing to the generic difficulties was that the air motion was generated by directional inlet ports with no air swirl in the ports, and as volumetric efficiency reduces at higher speeds air motion did not keep up with the engine speed. Also the injected fuel delay period, time between point of injection and start of combustion, becomes disproportionally longer.

However, the fuel crisis of the mid seventies prompted new research and following the publication of a technical paper  by AVL List, Graz Austria (author  Eng'r Cartellieri,  I was sent to Graz, in February 1976, by the Ford Motor Company (UK) to review their design and witness the demonstrator running on the test bed. AVL's concept was based on the principles of a swirling inlet port to provide controlled  air motion in the cylinder, minimum dead (parasitic) volumes, and higher injection pressures for the fuel. The high swirl was maintained in the cylinder by the vortex generated in the inlet port.  The higher injection pressures , by reducing nozzle hole diameters which give deeper penetration and faster atomisation and thereby shorter delay periods. In cylinder parasitic (dead) volumes  had been reduced by prepared and selected prototype build specification. These factors are easily achieved in the laboratory but the challenge was to make the systems work in production engines.

After reviewing the concept  design details I was invited to witness the engine on test.
The engine ran quite well although a little noisy with a smoke level below 4 Bosch. And as expected the specific fuel consumption (sfc) was in the range of 215-225 gms/kWhr akin to the heavy engines.

On my return I wrote a confidential report recommending that a larger study be carried out to assess the full potential of the design.
After internal reviews, a project was approved to convert twenty 2.36 litre york IDI engines to the AVL concept design for dynanometer test analysis  and vehicle drive evaluation. The engine conversion required a new cylinder head with the AVL controled swirl intake port (Fig.1) carefully positioned, with each inlet port being flow checked on  a Tippleman flow bench to ensure that the port design swirl coefficient had been cast and machined  correctly to new tighter tolerances. A  direct injection  piston and  reduced parasitic volumes in the cylinder completed the base build. The fuel injection was based on the Simms Mini mech inline plunger element  pump, and a multi hole injector provided  pressures in excess of 550 bar.

Fig 1: AVL Controlled Swirl Intake Port

The dynanometer testing, which involved two statistical analysis studies covering port location and cylinder dead volumes, showed consistent and promising results with the expected fuel consumption gains at full and part load, with the engine running comfortably at 4400 rpm without excessive smoke. With this confidence established  the project moved to the vehicle stage.

Ten vehicles were converted and prepared for a senior management appraisal over a chosen  hill circuit in Kent. Several competitor vehicles, including the Ford York IDI Transit, were set up as comparators. The evaluation team got to drive and compare the new power unit vehicles against the competition. Everyone was impressed by the big improvement in driveability and over the road performance. Two concerns were recorded, engine noise and smoke and these were set as development tasks. The final conclusion being that we seek US approval for a full  programme. Mr Ray Latimer the Truck Vice President (VP) at the time having thoroughly prepared himself went to Dearborn and got approval for a 1984 product introduction.

As the programme was being prepared, the Truck diesel design office was divided into a heavy (Dover) and light (York) engine groups. I was promoted to the light engine manager with Bill Bedwell as base engine supervisor and Derek Neil as performance and fuel injection  supervisor.   The specifications  for the engine were developed for a new  Transit vehicle scheduled for introduction in 1985 model year and approval for a new engine of 2.5 litre capacity 52 kW(70 PS) based on the current 2.36litre indirect injection engine was confirmed.

In 1979 and into the early eighties the emmission certification for light diesels were EEC  15.03 which was only a free acceleration smoke test with no requirement to measure gaseous emissions.

The base engine design and development progressed very much to plan with early testing proving out the expected improvements in durability and reliability over the IDI engine. Much of the base engineering effort was aimed at improving manufacturing process and control. The base engine was an all new design with particular attention being paid to the  cylinder head with the modelling of the  high swirl intake  port being the subject of intensive study and development of the port profiles. The introduction of swirl measurement of all inlet  ports prior to the cylinder head  being released for final assembly, required the design and build of a production Tippleman flow bench capable of meeting the planned production volumes.

The direct injection engine has significant durability advantages over the indirect injection engine. The thermal stresses in the cylinder head are greatly reduced due to the elimination of the separate pre compression chambers. This enabled the higher loading of turbo-charging to be considered at a later date.

Another benefit of deleting the pre-chamber is removing entrainment of carbon into the engine oil due to  impingement of combustion gases on the cylinder wall where the partly combusted gases exiting from the pre-combustion chamber passing the piston rings to the crankcase. These design changes  contributed to the objective extended oil change periods and major improvement in durability. To ensure that the long term reliability of the engine operated with minimum oil consumption during the target life span of 100,000 miles of vehicle operation, a new approach to piston, cylinder bore honing and piston ring compatibility was developed. Subsequent service experience showed that the  target 100,000 miles was several times exceeded.

Yet  another major benefit of the DI system is the cold start capability, due to the reduced heat loss from the compression generated temperature during cold cranking which enabled the deletion of glow plugs as the anciliary start aid.

The performance development of the engine was very complex and demanding. Having demonstrated the concept worked using inline pumping element fuel injection equipment, the programme choice was for the smaller more flexible rotary systems. The Bosch VE and the CAV Lucas DPS pumps were drafted in to support the  development programme. Neither of these systems had been used with direct injection systems running at high speeds, having been developed primarily to operate with IDI engines running at high speeds coupled with low pressure pintle nozzle injectors. We were now aiming to achieve this with the HSDI using multi holed high pressure nozzles. The rotary pumps also provided more flexibility of fuel injection timing and cold start settings. The ability to cold start the HSDI engine without costly electrical aids was another big benefit over the IDI engine.

For the high speed direct injection (HSDI) engine we required the highest line pressures attainable from these pumps to give short delivery periods to enable complete combustion of the fuel in the shortest possible period before the expansion of the charge slowed burning, resulting in high (black) smoke levels. The balance between legal smoke and acceptable noise was a continual battle for the Ford team and the fuel injection suppliers and in the end was only just won.

In the early 1980's legal  smoke was certified by a free acceleration test, which with preparation was achievable on a dynamometer. However, complexities arose with the need for production smoke  compliance and the newly introduced vehicle 7 metre drive-by noise certification together with a more demanding vehicle customer acceptance for interior noise. Balancing these conflicting demands, was as we termed at the time like a circus juggler keeping his five plates spinning on his sticks.

Further complications arose when in the winter the vehicles went to Finland for cold climate testing.The HSDI has lower combustion temperatures and consequently longer warm up periods especially when the ambient temperatures are below zero  degrees C. In these conditions complete combustion of the fuel is difficult and copious amounts of white smoke is generated. This can be over come by advancing the injection timing but this brings back higher combustion  noise levels  These opposing running conditions showed up the weakness of the two rotary pump systems under development which generically had a straight line advance mechanism giving an advance capability of about 10 to 12  degrees crank angle.

In summary we had at the mid programme stage an engine which was demonstrating all the projected improvements in durability and reliability, capable of a 15% reduction in fuel consumption, but without the flexibility of control to meet the vehicle demands of customer acceptable and certifiable smoke and vehicle driveby noise. At this stage threats of programme cancellation were common place and many previous supporters suddenly deserted the programme that was thought by many to be doomed.

Consequently the performance team and the fuel injection suppliers (Lucas & Bosch) had to go back to the drawing board!

All the combustion and performance related tolerances were re examined, especially the cylinder head valve porting and the piston/valve dead volumes. Closer tolerances were negotiated with some difficulty with suppliers and the engine manufacturing group, at Dagenham. The engine plant  fought  hard to keep their time honoured wide build specifications. But fortunately, at this time the Japanese were showing the Auto industry that statistical control was much better than max/min tolerancing and with the aid of some young enlightened manufacturing engineers we got the tighter build specifications we were seeking.

At this stage we would have liked to specify a re-entrant combustion bowl for the piston but the two vendors thought this to be too risky, for a high speed engine without more durability proveout.

The base engine team, supervised by Bill Bedwell did magnificant work during this period by relentlessly pursuing the requests of their performance team colleagues with the component suppliers and manufacturing. In summary the production specifications had been tightened significantly to give minimum dead volumes in the combustion chamber, tight control of inlet port location and air motion (swirl) as the charge entered the cylinder. The compression ratio (CR) was set at 19.5 :1 as low as possible without incurring white smoke during cold start, and engine  run up and warm up.

Having done the best possible job on the performance related hard points of the engine, the success or failure now depended on the ability of the fuel injection equipment to provide the flexibility of control needed for noise and smoke. Both pumps were limited in the amount of injection advance available, to about 10 degrees and this was normally a straight line progression.

To make the high speed direct injection engine work we needed a short high pressure injection period with improved control of auto advance and a start retard mechanism  to retain the inherent good cold start properties of the direct injection combustion systems.
The two fuel injection equipment (FIE) suppliers, Lucas and Bosch worked hard to provide new specifications to meet the demands set for the engine. Lucas in particular lead by Dr Frank Cunliffe took to the task and set about re-designing the standard  DPS pump to meet the demands of the HSDI. At Lucas, engineers had similar battles with their production colleagues to accept new practices for tighter control of the fuel injection pump build  tolerances and test methods.   Added features were designed and developed to manipulate  fuel delivery and timing until a fine balance of acceptability was achieved.

Development went through an extensive period of dynanometer, several  vehicle tests and drive appraisals with many heated arguments and disparaging remarks about engine engineers not meeting vehicle demands, with veiled  threats of programme cancellation.
However as engine sign off (ESO) approached we achieved the satisfactory balance we had been seeking with the Lucas  DPS fuel injection equipment being released for production   while the Bosch VE pump was dropped from initial production.

I was convinced that although the engine was rather raw in some respects, it would more than satisfy the buying customers demands of better fuel economy (24% in vehicle), consistent cold starting and much improved reliability and durability would make the engine a success in the market place.

Engine and vehicle  preproduction got underway with the usual panics eminating from production which had to be sorted out, but soon the validation programmes were running and confidence was building. Only minor changes were made to the vehicle ahead of a major face lift planned for 1986. The validations went very well, on dyno the engine romped through the extensive durability cycles  and the vehicle test drivers were filing glowing reports about power and response. The test figures confirmed the fuel economy returns against the calculated predictions. Power and smoke engine certification together with vehicle driveby noise were completed with some nervousness.

Press launch

A fleet of vehicles were prepared for the all important Press launch to the European Commerial Vehicle press. This took place in Portugal over the course of two weeks, with evening presentations preceeding a morning of drive appraisals, then a debrief lunch before the press boys left for home and we got ready to welcome the next group. All the organisation was done by Public Affairs and we covered the technical input and presentations. At one of the evening Dinners before I made my presentation, a German journalist stated that a HSDI engine was not possible because Mercedes had told him so! I replied that he would be able to see for himself in the morning when he would be able to drive several vehicles powered by these engines.

The resulting press copy was very complementary from all markets and I was requested to do several feature interviews. A crowning glory was the presentation of the Golden Molecule  award (Fig.2) made by the West German Automobile Club, for "Outstanding fuel economy and its overall contribution to energy conservation."

Fig 2: Gordon Bird (author) holding the Golden Molecule Award, surrounded by the Ford 2.5 HSDI development team 1985.

The engine also won the prestigious  British Design Council award presented in May 1985.  The citation stated "The new Ford HSDI diesel engine has pioneered a design concept which other manufacturers would follow as a means of improving the efficiency and fuel economy of their high-speed diesel engines." 

Following the launch of the engine in 1984  the Transit vehicle sales boomed, reversing a downward trend of the previous years, which had resulted from  the poor reliability of the replaced York  IDI engine.

As production settled down and with an increasing data-base of performance detail gathered from production assembly short test analysis   and our own extended validation of production units, we began to consider how we could reduce the engine's smoke levels.

These efforts were intensified when Germany announced their immediate intention to introduce the EC 15.04 emission legislation which required certification by a drive cycle on chassis rolls dynanometor . The 1984 engine and vehicle had been certified under 15.03 legislation which was purely a free acceleration smoke and power test. Germanys' intention for immediate introduction  of the 15.04 rolling road emission test was stifled when they realised that the EU Directive had not been passed by their National Government. This effectively gave us a 12 month window to re-develop the combustion system.
Direct injection combustion theory regonises that a centrally located injector gives good fuel distribution and therefore cleaner ( lower smoke) combustion. The 1984 engine layout was restricted to using the York (IDI) engine cylinder head machining geometry, which gave an injector tip offset of 10 mm, at an inclined angle of of 68 degrees, far from the ideal vertical position.



Series 2 Engine
The original injector was the standard 17 mm diameter unit from Lucas. Available from Stanadyne, the North American fuel injection manufacturer was a 7 mm diameter  "Slimtip" injector. (Fig 3) Using this injector on the same machining axis but moved to the maximum displacement possible within the casting would position the injector tip 4 mm closer to the combustion bowl centre.

Fig 3: Section View of the Slimtip injector positioned above the re-entrant bowl piston

To assess the potential of the "Slimtip", several cylinder heads were modified to accept the injector to enable performance comparison to be completed. Our expectations were sustained when a consistent 7 Hartridge smoke units (HSU's) reduction was recorded. A contributory factor to the smoke improvement was was the smaller sack volume under the injector seat of the Stanadyne injector compared to the Lucas unit reduced the amount of post injection fuel drible. Respecifying the injector together with other minor improvements in performance was just what was needed to provide the basis for our development programme to meet the emission challenge of 15.04

A new programme was approved to give the Series  2 engine  an introduction with the all  new 1987 model year Transit. Other component refinements were introduced to improve performance and lower emissions, most notable being a re-entrant combustion bowl in the piston. (Figs. 4).  These changes enabled the re-specification of the fuel injection equipment with the Bosch VE pump being released for production as second supplier  to the Lucas DPS pump.

Fig 4: Right: Series 1 Straight bowled piston. Left: Series 2 Re-entrant bowl piston

The advent of rolling road emission testing for light commercial vehicles necessitated a phase change in the performance process where every cycle of change had to be validated on the rolling road. The development and verification programes went well and the certifications sessions were successfully completed. A pleasing aspect of the new specification was the softening of the combustion noise.

The new 1986 Transit was launched with much acclaim, the reputation of the 2.5 HSDI engine boosting sales so much that production volume expansions were put in at Dagenham engine plant.

Ford had successfully demonstrated to the world that a HSDI diesel engine was indeed feasible and that fuel economy improvements of 15 to 25% with low CO2 emissions made it a prime contender for the European Car Market.

However, at Ford there was a reluctance to take the development of a DI engine based on the Kent 1.8 litre petrol engine beyond concept studies, whereas Volkswagen saw the potential immediately and designed a 1.9 litre  turbocharged engine and in so doing energised Bosch to commit to furthering the development of the VE pump.
This I consider was a major missed opportunity for Ford of Europe.



Turbo-charging the engine
However, on the back of the Transit's success and their desire to increase market volume there was a need for a higher output engine. The naturally aspirated engine was rated at 52 kWs.  To meet the demands of the Transit  higher gross vehicle weight (GVW) vehicles and the expanding 15 seat bus market an engine with rated power of 70kWs was required.

The proposal was therefore, to turbocharge the 2.5 litre HSDI  engine. On the face of it this was a fairly easy challenge. But with the advent of rolling road emission testing of light commercial vehicles and with the forecast that the European legislation projected to get more demanding in future years, it was essential to consider the specification carefully.

Turbo-charger design had  progressed significantly in the preceeding years with down sizing and improved efficiency over a border speed range which  was essential for flexible engine control and the KKK unit was selected for the task. (Fig.5)

Fig 5: KKK Turbocharger

The selection of the fuel injection equipment  was more difficult and as it turned out ground breaking. Our expanding knowledge of the naturally aspirated 2.5 HSDI indicated that the limitations of the mechanical manipulated equipment would not meet the demands of a low emission turbocharged engine. After due consideration and a leap of blind faith, we proposed to the company that the best solution for this engine was electronic control.

At this stage in the development of electronically controlled fuel injection equipment (EFIE)  was in its infancy. There were samples of electronically control timing regimes but only one pump with both fuel and timing control and this design  was in its early stage  of development.  This was the CAV Lucas Epic pump.(Fig.6)

Fig 6: Lucas CAV EPIC, the World's first fully electronic fuel injection pump.

The application of electronic control to vehicle power units requires the programming and installation of an electronic control unit (ECU), speed and timing sensors plus the associated wiring looms. All new components for diesel engineers and still in their early stages for gasolene engine engineers. We were all at the start of a steep learning curve. The routines of the performance development engineers changed from considering angles, stops and screw settings to using laptop computers with layers of timing and fuel maps.

The Ford Management were still un-easy about the prospect of introducing the first all electronically controlled fuel injection system on a diesel engine, decided that we should present our proposals to our North American parent company and take on their experience, although purely based on gasolene engines and limited, at this stage, to a small number of applications.  A team made up of Chris Best (CAV), Chris Jones (Lucas CAV. Micos) and myself set off to present our system proposals. A series of  presentations with Q & A sessions with the Dearborn technical staffs were arranged over a period of three days. The concept proposals were favourably supportive and we returned home feeling that we have covered all the possible problem areas.

The development programme progressed with many changes to the fuel pump and the supporting electronic equipment. The burden of these new to diesel engine development processes were performed superbly  by Philip Bostock and Laurence Cooper.  As the engineering sign off (ESO) approached another new facet arose "How to validate" the newly created engine control software for vehicle operation safety. This was particulaly demanding because there was no industry comparator or recgonised standards to provide guidance. Lots of debate and head scratching ensued for several weeks, until finally confidence was established, and we moved forward to engine and vehicle sign off and production validation.

The vehicle testing started well but as more vehicles became available some "Glitches" were  reported which were soon identified to be associated with the engine wiring loom. Wriggle testing became the order of the day to identify the offending contacts. Analysis of the  problem showed that the multi pin connectors were not maintaining continuity under all driver controlled changes. The very low voltages in the circuitry needed high conductivity contacts and a change to gold plated terminals resolved the problem.

The production validation programme was satisfactorily  completed without further incident and engine production got under way. The Ford Transit vehicle gained another "World first" by introducing the first fully electronically controlled fuel injection system on a diesel engine.(fig.7) This event laid the foundation for the future development of all the high performing high speed direct injection diesel engines which were progressively introduced across the world. Electronic control enabled the increasingly severe gaseous emission regulations to be met and with the application of catalitic converters to tackle particulates the diesel established itself as a major automotive engine.

Fig 7: Ford 2.5L 90PS HSDI Turbo-charged Engine

Conclusion
This period of diesel engine development in the 1980's was extremely exciting and rewarding. It encouraged other engine makers and fuel injection manufacturers to push forward the development which has kept the diesel as the most fuel efficient vehicle engine.

In later years the advent of common rail and electronically controlled injectors with the much higher injection pressures and the flexibility to provide accurate multiple pilot injections improved combustion by reducing the delay period. Engine specific outputs and emission control have been pushed further forward, ensuring that the high speed direct injection diesel maintains its position as a major automotive power unit.

Looking back at the early days of the high speed direct injection diesel development it is a compliment to the determination and dedication of a small team of engineers in the early nineteen eighties who set the foundation for the design and development of all the World's current car and light vehicle high speed direct injection diesels and the explosion in electronic controlled fuel systems, which are universally manufactured across the globe,

Gordon L Bird  2014

Acknowledgements;-

This brief narrative is dedicated to the team of engineers whose persistence and ingenuity  overcome all the problems and challenges to turn the concept engine into a production reality and set the foundation for all the high speed direct injection diesel engines that grace the world today.
To Derek Neil  who kindly reviewed and added important detail to the original draft.  

Reference publications:
1. Cartellieri W & Schukoff.H-AVL Graz Austria -  Direct injection as a combustion system for light duty diesel.FISITA Congress 1978
2. Tippelmann G.A  - A new method of investigation of swirl ports. SAE Paper No 770404,1977
3. Bird G.L C.Eng, MIMechE. Ford Motor Co , Britain  - The Ford 2.5 litre direct injection naturally aspirated diesel engine. I MechE 50/85 1985
4. Bird G.L Ford Motor Co.The Ford 2.5 litre High Speed Direct Injection Diesel Engine-Its performance and future possibilities. SAE ref: 850262 
5. Bird G.L CEng,MIMechE & Tolan L.E BSME - Stanadyne Automotive  
 Development and application of the Stanadyne new slim tip pencil injector.
6.Bostock P.G MSc,CEng MIMechE & Cooper L.Turbocharging the Ford2.5 HSDI