Archive for category: Technical

It’s now 57 years since the introduction of what would become the most successful Formula 1 engine in history. The Cosworth DFV engine won on its debut at the Dutch Grand Prix in 1967 and would go on to dominate in Formula 1, racking up 155 victories. No other engine has come close. Using notes that were prepared by company founder Keith Duckworth and chief designer Mike Hall, along with feedback from one of Cosworth’s long serving employees Malcolm Tyrrell, we take a look at the birth and technical spec of the early iterations of this incredible power plant.

Cosworth had already become an established name in the motor racing world with its successful Formula Junior, Formula Three MAE, Racing Lotus Twin Cam and Formula Two SCA engines, based on standard cylinder blocks with bespoke cylinder heads. But then, at the end of 1965, Cosworth embarked on a completely new project that would establish its name in racing for ever. In exchange for £100,000 from the Ford Motor Company, Cosworth would create a four-cylinder Formula Two engine, the FVA (Four Valve Type A), which would then be ‘doubled up’ to create a V8 for Formula One, the DFV (Double Four Valve).

For nine months in 1966, Duckworth entrenched himself in a room at his house, working every day from 9am until past midnight. Once a week he would visit the factory to hand over schemes and drawings, and get feedback on the progress of the manufacture of his designs. Chief designer Mike Hall joined Cosworth from BRM in October 1966, and was instrumental in the detail design of the major components and all auxiliaries, working from Duckworth’s layouts. The engine was completed in April 1967, winning first time out at the Dutch GP in June in Lotus’ new Type 49 chassis.

As per the contract with Ford, Duckworth and his team started with the FVA, incorporating the lessons learnt on this four-cylinder engine into the design of the DFV. Duckworth set a power output target for the FVA of 200 hp, reasoning that the DFV would need 400 hp to be a winning engine. As it turned out, both these performance targets were comfortably exceeded.

Engine Mounting and Layout

The oval shape of the Lotus 49 monocoque meant it would be difficult to extend the sides of the chassis down past the engine, resulting in the dictate from Lotus’ Colin Chapman that the engine should be a stressed member of the chassis from the outset. Part of the suspension would also mount directly to the engine; schemes and handwritten notes still at Cosworth show that the layout of the suspension went back and forth between Duckworth and Chapman before settling on the final positions.

The engine was bolted to the bottom of the rear of the monocoque bulkhead by a wide-based bracket on the sump, with the intention that these lower mounts would transmit the shear loads between the chassis and engine. Anecdotally, Duckworth would remark that the distance between the two engine mounting bolts at the front of the engine was chosen to match the width of Jim Clark’s posterior! At the top of the engine, the left- and right-hand cam covers were connected to the top corners of the rear bulkhead with thin triangular shaped steel plates, so as to take the tension and compression loads. The plates were also intended to deflect under the thermal expansion of the engine, calculated at the time to be 0.015 in (0.4 mm).

Duckworth was intent on keeping the engine as compact as possible, so to keep the front of engine flat and uncluttered he positioned the water, oil and fuel pumps along the sides of the cylinder block underneath the exhaust pipes. That would also allow for a lower centre of gravity, recorded at 4.6 in (116.4 mm) above the crank centreline. The left- and right-hand pump pulleys were driven at the front of the engine using a Uniroyal toothed rubber belt, driven from a pulley connected to the second compound gear running at half engine speed.

The overall dimensions of the Cosworth DFV engine showed that it was wider and higher than it was long – the height of the engine from the bottom of the sump to the top of the trumpets was 23.3 in (590 mm), the length measured at 21.6 in (550 mm) and the overall width between the extremities of the cam covers was 26.8 in (680 mm). With no clutch or starter motor fitted, the dry weight of the engine came out at 350 lb (159 kg).

Crankcase

With the rules stating that the DFV had to have a capacity of 3 litres, the individual cylinder capacity was reduced from 400 cc on the FVA to 375 cc on the DFV. The DFV copied the FVA’s bore diameter of 3.373 in (85.67 mm), with the smaller cylinder capacity achieved by a shorter stroke of 2.550 in (64.77 mm) to give a total capacity of 2993 cc.

Like most of the other major castings, the cylinder block was created from fully heat-treated 7% silicon LM 25 aluminium. At the time, this material was considered to be the best commercially and readily available alloy in the UK, with the highest proof stress and Brinell hardness, and good casting and machining capabilities.

In the cylinder block were wet liners machined from centrifugally spun castings, made from chrome vanadium alloy iron. They were interfered into the block with two O-rings at the bottom of each liner to seal off the crank case chamber. The top of the flange on the liner had a recess for a Coopers sealing ring.

The sump was made up of box sections that ran from front to rear and across the engine to try to maximise stiffness. The box section at the front also carried water to connect and balance the two water pumps on either side, while the rear box section carried the scavenged oil to an outlet on the left-hand side of the engine.

Water Pumps

The first iteration of DFV engines had a single water pump, mounted on the right hand side, directly in front of the oil scavenge pump. Later DFV iterations featured two water pumps mounted on either side of the engine, so that each bank of the engine was cooled by its own water pump.

These later water pumps used 2.5 in (63.5 mm) diameter centrifugally bladed impellers contained within a volute spiral casing. Each pump had a maximum flow capacity of 45 gallons per minute (204 litres per minute), and the water flow from each pump was sufficient to restrict the temperature rise from the water pump inlet to the engine outlet to 7 C.

Fuel Pressure Pump

A mechanical fuel pressure pump was positioned at the front of the left-hand side auxiliaries. This gear-type pump was capable of delivering 40 gallons per hour (182 litres per hour) at maximum engine revs against a back pressure of 120 psi (8.3 bar). An electrically driven high-pressure pump was activated for starting purposes; this auxiliary pump was then switched off when the engine speed reached 2500 rpm.

The fuel pump was positioned as far out as possible so that it would be cooled by the air stream around the engine, in a bid to keep the fuel cold and prevent fuel vaporisation. A further measure to reduce fuel temperature included isolating the pump from its supporting bracket with a Tufnol insulator.

Oil Pressure Pump

At the rear of the left-hand auxiliaries sat the main oil pump incorporating an integral filter. The oil pump contained a 0.8 in (20.3 mm) wide Hobourn Eaton lobe-type rotor, which at maximum engine revs could displace 11 gallons per minute (50 litres per minute) against a 100 psi (6.9 bar) pressure relief valve setting.

A transfer pipe fed the filtered oil from the pump to the crankcase main oil gallery. From here the oil was fed to the five pairs of main bearings, and then through the cross-drillings in the crankshaft into the eight pairs of big-end bearings. It was estimated that at 11,000 rpm a minimum oil pressure of 68 psi (4.7 bar) was required to force the oil into the centre of the crankshaft due to the centrifugal head generated at this speed.

Oil Scavenge Pump

On the right-hand side of the engine were the scavenge pumps, two pairs of Hobourn Eaton form rotors with a separator between them, drawing oil in from the scavenge chambers in the sump. (Later pumps would feature Roots type rotors.)

Each cylinder head featured two head drains, one at the front and one at the rear, which fed down to the scavenge chambers. Finally, oil from the oil pump pressure relief valve was also fed directly into one of the scavenge chambers.

Early DFV engines suffered serious issues with bad draining of oil from the cylinder heads. The first engines only had a scavenge capacity of twice the oil pressure pump, so the scavenge pumps were unable to handle the oil and the blow-by gases. As a result, the blow-by gases would go up the head drains, preventing oil from coming down the other way, which caused the heads to fill with oil, eventually venting the oil to atmosphere and draining the oil tank.

Unable to increase the size of the head drains, a temporary sliding vane-type pump was fitted to take care of the blow-by. However, this in turned caused more problems, as the conventionally scavenged oil, which measured 11 gallons per minute (50 litres per minute), was now mixed with the equivalent of 40 gallons of air per minute (182 litres per minute). The resulting aerated oil led to the design of a centrifuge which ensured that the mixture returned to the oil tank contained 90% oil and only 10% air. This centrifuge was included in the new design of scavenge pump, which now had a capacity of 55 gallons per minute (250 litres per minute) – five times the capacity of the oil pressure pump.

Geartrain

Behind the front cover was a geartrain consisting of 14 gears. Assembled to the front of the crankshaft was the crank gear, which turned the first compound gear, an assembly of two gears. The smaller of these two gears drove another gear assembly, termed the second compound gear. This assembly was made up of three gears; a large central driven gear sandwiched between two smaller gears. To the left and right hand side of the second compound gear were the first of two head idler gears, driven from the outer gears of the second compound gear. On each bank, the first head idler gear turned the second head idler gear. Finally, the left and right hand second head idler gears drove the respective bank’s inlet and exhaust cam drive gear.

All the gears were made from forged vacuum re-melted EN39B steel blanks, case hardened to a depth of 0.020 in (0.5 mm). Considerable effort in production engineering and quality control was made to ensure that the teeth were accurately ground to ensure concentricity of their pitch circle diameters to the gear bearing bores, resulting in the required backlash and correct involute profiles.

However, despite the great attention to detail given to the design and manufacture of the geartrain, gear problems blighted the first race engines. At debut race of the Cosworth DFV engine, Graham Hill retired with cam gear failure, and broken gear teeth were found in the winning engine of Jim Clark. In addition, the gear failures were compounded by catastrophic valve spring failures when the engines were run at more than 9000 rpm. Cam lobes profiles were redesigned to bring down their maximum torque requirement from 36 lb-ft (49 Nm) to 26 lb-ft (35 Nm); however, even though the valve spring life improved, there were still gear failures.

Using strain gauges, instantaneous stab torques of 300 lb-ft (407 Nm) where recorded – far higher than the original torque calculations used for the gears. What was needed was a way to absorb the shock loading from the camshafts that was destroying the gears.

In a typical moment of Duckworth ingenuity, the answer came in ‘cushioning’ the second compound gear, which up to this point had been a rigid assembly. The new design of second compound gear contained 12 small quill shafts that allowed the two side gears to rotate over a limited angular displacement relative to one another, thereby storing some of the huge energy from the cam loadings to successfully reduce the loading on the geartrain.

Crankshaft

Although the first crankshafts were machined from billets, Cosworth quickly switched to fully forged blanks supplied by Smith Clayton Forge. The material for the crankshaft forging was heat treated EN40C 3% chrome molybdenum nitriding steel. After the crankshaft was machined, it was nitrided in an ammonia atmosphere at about 500 C, resulting in a hardened case depth of around 0.015 in (0.38 mm).

The main journals had a diameter of 2.375 in (60.325 mm) and the crank pins were the same as the FVA at 1.938 in (49.2 mm) in diameter, with the crankpins arranged to give a flat-plane layout. The crankshaft weighed 32 lb (14.5 kg), coupled to a flywheel weighing 8 lb (3.6 kg).

Calculations made during the design of the crankshaft showed that the maximum load would be on the centre main journal, creating a bearing pressure of 6600 psi (45.5 MPa) at 10,500 rpm. The big-end bearing pressures were estimated to be nearly 8000 psi (55.2 MPa). Both the main journal bearings and the big-end bearings were made by Vandervell, from a steel backing with a bronze intermediate layer and a lead indium overlay.

During the early 1970s a Holset-manufactured crank damper was situated on the nose of the crankshaft to reduce torsional vibration. Analysis by both Holset and Vandervell proved that the principal resonance peaks lay between 8,000 and 11,000 rpm. The largest of these peaks was the eighth harmonic excitation of the first order, which occurred at 8,594 rpm, unfortunately in the middle of the running range of the first engines of between 7,000 and 9,500 rpm. The maximum alternating torque was +/- 2,122 lb-ft (2,877 Nm) on the third crankpin, creating a maximum amplitude of +/- 0.95°. The crank damper was removed on later engines in the mid 1970s when the running range was increased away from this peak to 9,000-10,500 rpm.

The crankshaft proved to be an extremely reliable component, but in 1970 there were a series of widely known crank failures. Investigations pointed to a relatively simple grinding error. The corner radii of the crankpin journals were ground both before and after nitriding, but unfortunately the radius on the pre-grinding wheel was too large, which led to the post-nitride grinding wheel going through the nitrided layer, drastically reducing the life of the crankshaft.

Piston & Rings

DFV piston forging material was chosen to be RR58 aluminium alloy (developed by Rolls-Royce). Although this material had a slightly higher thermal expansion coefficient when compared with the high-silicon alloys used on production engine pistons of that era, it remained consistent from 20-200 C. The skirt profile featured tapering along the length of the skirt combined with ovality around the diameter, to provide a diametral skirt clearance of 0.003 in (0.076 mm).

Duckworth sought to minimise the weight of the cast-iron top compression ring, such that the thickness was only 0.030 in (0.76 mm) thick. This would ensure that the ring would stay seated on the bottom face of the piston groove under deceleration and thereby prevent gas leakage past the ring. For the record, the ring gaps were set at 0.017-0.022 in (0.43-0.56 mm).

The gudgeon pin was made from heat treated EN39, case hardened all over, with an outer diameter of 0.813 in (20.6 mm) and an inner diameter of 0.47 in (11.9 mm).

Connecting Rod

Both the rod and the cap were supplied as separate stamped forgings by Smethwick Drop Forgings, using re-melted EN24 steel. The cap was secured to the rod with a pair of 3/8 in (9.525 mm) 12-point big-end bolts, with location provided by two dowel pins. The small-end bush was a steel-backed bronze bearing supplied by Vandervell, finish-bored and honed after assembly. The rod centre distance was 5.230 in (132.84 mm), as Duckworth tried to keep the rod length as long as possible to reduce the secondary out-of-balance forces inherent in a V8 configuration.

Cylinder Heads

The FVA cylinder head featured an included valve angle of 40⁰. Duckworth reduced this further on the DFV to 32° to give a shallower pent-roof chamber and hence a further reduction in surface area and hence less heat loss.

Both the left- and right-hand heads were machined from a common casting. These heads contained 1.32 in (33.5 mm) inlet valves and 1.14 in (29 mm) exhaust valves, both with 7 mm diameter stems. In the middle of the combustion chamber was a 10 mm spark plug. The valve seats and guides were made from aluminium bronze alloys, with 0.003 in (0.076 mm) interference in the head when cold.

The shape of the inlet ports was kept as straight as possible by Duckworth, with a diameter of 1.02 in (25.9 mm). The ports were fully machined; straight sections were bored, while curved and flared sections into the throats were copy milled. The exhaust ports were completely curved and so had to be copy milled throughout. After machining, the heads were given to the fabled finishing section, where the ports would be polished using a process known as ‘broddling’ within the organisation. It was not uncommon for the finishers to stamp their initials on the side of their cylinder heads so that they could compare dyno test results with each other.

Duckworth had a very rational approach to port design. “I have never believed that there is any point in having a gas flow rig and measuring the flow,” he once said. “I think it is possible to look at the shape of a hole and decide whether the air would like to go through it or not. A hole that looks nice and smooth and has no projections will generally flow easily. Most people start with something so horrible that to create an improvement should be very simple. I would claim that I could arrive at something close to their results from gas flowing just by putting my finger down the hole and seeing what it feels like.”

Camshafts

The camshafts ran in steel-backed white metal shell bearings, again supplied by Vandervell. The bearings were held between dowelled caps and one-piece cam carriers, which like the heads were made from a common casting. Oil was fed up from the main engine gallery into grooves in the middle bearing pairs and then into the hollow camshafts, where it would be directed through drillings in the other cam journals to lubricate the other bearings. The oil from the cam bearings also splash lubricated the tappets, after initial tests showed that feeding oil through holes in the cam lobes was not necessary.

The selected material for the camshafts was EN16T steel, which was liquid nitrocarburized (Tuftride) all over after machining to provide an anti-friction coating. Tappets were machined from EN40, fully ground all over and lapped on the tappet face. The tappets ran directly in the cam carrier, and were 1.25 in (31.75 mm) diameter by 0.9 in (22.9 mm) long.

Understandably, Duckworth paid a lot of attention to the profile of the cam lobes. The Cosworth DFV engine copied most of Cosworth’s other engines of that era and had a lift of 0.410 in (10.4 mm), and symmetrical valve timing with inlet valve opening at 58° before TDC and closing 82° after TDC, exhaust valve opening 82° before BDC and closing 58° after TDC, giving 116° overlap. During build, the tappet clearances were set to 0.010 in (0.254 mm) on the inlet side and 0.015 in (0.38 mm) on the exhaust side.

The ‘Bomb’

In the centre vee of the Cosworth DFV engine lived what Cosworth termed the ‘bomb’, a set of auxiliaries driven from the second compound gear. Within a magnesium centre casting was a Lucas rotating magnet alternator that produced 10 A at 12 V. Also in this assembly was the Lucas Opus ignition system (Oscillating Pick-up System), a plastic drum rotating at half engine speed into which was moulded eight ferrite rods running against a stationary pick-up.

Within the ignition system was a thyristor speed limiter set to 11,300 rpm. This was a standard Lucas product, which Cosworth would then wire into a rubber-mounted box before subjecting it to numerous rig tests to ensure consistent operation over the required speed range, with an overspeed test to check that the speed limiter operated correctly. The trigger disc for the ignition system was mounted on the nose of the crank.

Finally, also in the centre vee was the fuel injection metering unit, again supplied by Lucas. The unit consisted of a stationary hollow sleeve containing a series of radially drilled holes, some of which would feed fuel in from the high-pressure pump and some which would allow fuel out to the injectors mounted in the inlet trumpets. Within the sleeve ran a rotor that also had a corresponding array of radial holes, at selected angles to give the required timing of fuel delivery. Along the centre of the rotor were fuel metering shuttles that oscillated back and forth. A fuel cam that pivoted at the end of the unit controlled the length of the stroke of these shuttles, thereby determining the amount of fuel being delivered. The cam lever was driven by the throttle slides, so that when the throttles were fully open the shuttles could operate a maximum stroke and hence provide maximum fuel delivery to the injectors.

In some of the early races in the late 1960s the Cosworth DFV engine was plagued with fuel vaporisation issues, especially at races in South Africa such as those held at East London and Kyalami. The solution was the rerouting of the return fuel line from the fuel PRV to help cool the fuel.

The Launch of an Icon

The DFV was unveiled by Walter Hayes, public relations director of Ford, at a function at Ford’s Regent Street showrooms on 25th April 1967. In attendance were Keith Duckworth, Lotus founder Colin Chapman and Lotus driver Graham Hill.

Autosport had this to say about the launch of a new Ford Formula 1 engine: “The announcement this week of the Cosworth-designed and developed Formula 1 engine must be a cause of concern for Lotus’ rivals in the Grande Epreuve field. The compact V8 is extremely light and, as it is designed to do the work of the chassis frame at the rear of the car and carry the suspension, the new Lotus that has been designed around the engine can also be expected to be light and compact. With minimum weight, 400 bhp and Jim Clark and Graham Hill as their drivers, Team Lotus and Ford must be very strong contenders for World Championship victory once they have got their new car sorted out.”

Autosport’s words would prove to be very prophetic – Jim Clark won the first race that the new Lotus 49 powered by the DFV entered in 1967, and Graham Hill took the driver world championship the following year.

Lasting Legacy

The DFV would become the most successful engine ever in the history of Formula One. It went on to win 155 Grand Prix races, 12 driver world championships and 10 constructor championships. It spawned several other winning engine types – the DFW (Tasman Series), DFX (CART/IndyCar from 1975), DFL (Group C), DFY (Formula One from 1983), DFZ (Formula One in 1987), DFR (Formula One from 1988) and the DFS (CART/Indycar from 1988). And its DNA could be traced through subsequent Cosworth Formula One engines and even in the current generation of race engines.

Although numerous developments of the DFV were pursued by Cosworth – including shortened stroke, new cam profiles, changes to the ignition system, redesigned pumps and larger valve diameters – its basic layout never changed. Perhaps this is even more remarkable given that the DFV was the first entire engine designed by Cosworth.

The DFV is still very much alive in historic racing. We continue to support customers rebuilding these engines, supplying a wide range of genuine Cosworth parts along with parts that we’ve been able to reverse engineer and develop. You can find these parts in our on-line shop here: https://modatek.co.uk/product-category/dfv-parts/

This feature on the Cosworth DFV is based on an article written by Modatek’s Matt Grant for Race Engine Technology, issue 84. You can purchase a back copy of this publication here: https://www.highpowermedia.com/Product/race-engine-technology-issue-084

OK, so this might not be the most exciting of subjects, but understanding the conventions of Cosworth part numbers can save a lot of time and effort. If you’re trying to identify a part then the part number that might be marked on it can give you several clues as to what engine it came from.

To understand the history of Cosworth part numbers, let’s go back 65 years to when Cosworth was first formed. Cosworth’s first foray into engines centred on modifications to the Ford Anglia engine, producing components like camshafts. They soon progressed to building cylinder head assemblies, followed by complete engines that were designated Mk I, Mk II, Mk III, Mk IV, etc, followed by engines such as the MAE, SCA, FVA and DFV.

One of Cosworth’s early strengths was that every part was identical from batch to batch, so it was easy to swap parts between engines. There were minimal modifications required prior to fitting each part, and this made engine build a lot quicker and far more reliable. They achieved this through very detailed drawings and technical specifications that would give the manufacturer all the information they needed to produce the part. Cosworth would then book the part into stores when it was either manufactured in-house or bought in. Then all Cosworth had to do when building the engine was to book out the required parts and assemble them into the engine.

The production and tracking of components for these engines necessitated a system to keep track of the parts that would be required – the parts list. Hence each part needed its own unique part number, one that could be used to track the life of the part through design, manufacture and assembly. Cosworth quickly realised that random part numbers wouldn’t work, and that they would need to have a system to follow to generate each part number.

The Project Codes

The system that Cosworth devised was fairly simple (remember KISS – Keep it Simple, Stupid!). Every part number consisted of two letters that designated the project code followed by four numbers, for example YB1429. With the amount of engine projects rapidly expanding as the company developed, this system meant that one could instantly identify which engine the part was intended for.

There were over 50 different project codes, and some of these never saw the light of day, but here are some of the more common ones, arranged in alphabetical order:

Cosworth also used other project codes in their part numbers, especially for parts that might be used on one or more projects. These included:

PP/PR – ‘proprietary parts’, these were for parts that were bought in

LL – ‘liner length’, these were bought in parts that were supplied by length, such as O-ring cords

DE – electronics parts

PA – this code was used for pistons

KK – these were kits of parts, like piston rings

The codes were supposed to be unique for each project, but occasionally the same code was used for two different projects. For example, CA was meant to be the code for the Cosworth 4WD Formula 1 project in 1969, but it was also used for the V8 Formula 1 engine in 2006.

The Casting Codes

Cosworth also had another set of project codes, called the ‘casting’ code, that were specifically for parts like castings, forgings and billets. Again, these codes were linked to the engine project, and Cosworth instigated a clever way of defining the casting code. The first letter was the same as that for the project code, and for the second letter, just go 13 letters along in the alphabet. So, for example, the casting code for YB was YN.

There were some exceptions, and there was also a rule that letters like I and O had to be skipped as they could be confused with numbers, but on the whole the casting codes followed this pattern.

This brings us to an important point. Many people incorrectly identify a part by the casting number, but this only identifies the part when it is in its part-finished form. For example, in the photo below, YN0627 is the part number of the YB head casting, not the finished machined component.

There will be a number of different types of cylinder heads that are machined from the YN0627 casting, so knowing just the casting number doesn’t completely identify the head. Here are the part numbers for the heads for the different types of YB engine:

Another example of a common misconception comes with pistons, which had a forging code of PM. Cosworth would imprint the forging part number into the forge tool, and this would be visible on the piston. But the PM part number only referred to the part number of the forging, not that of the machined piston. Given that the same forging could be used for a variety of different pistons, it is the finished part number that is required.

The Four Numbers

As mentioned, the part number consisted of two letters followed by four numbers. For most projects, four numbers would be enough, as it would be extremely unusual for a project to need more than 9,999 part numbers.

At first these four numbers were sequential, starting with 0001. Usually each project had its own folder that listed these numbers so that there could be no duplication. Over the years, Cosworth started to instill some ‘intelligence’ into these four numbers. The four numbers would begin with an 8 for assemblies, and numbers beginning with 05 were reserved for schematic drawings.

At one point Cosworth also introduced a rule that said that the last number would odd for left hand components and even for right hand components.

Certain projects stipulated more rules for the four numbers, such as reserving 0001 for the cylinder block, 0002 for the LH cylinder head, 0003 for the RH cylinder head and 0010 for the crankshaft. However, this rule was fairly short-lived.

Cosworth used the part number on all documentation, including drawings (as per the example of a drawing excerpt above for our YB1429 WRC head gasket), purchase orders and invoices.

SAP & Sequential Part Numbers

These fairly simple rules for defining the part number with the project code and four numbers ran fairly smoothly for a number of decades. However, all this came to an end when Cosworth launched SAP at the beginning of 2007 as its new ERP (enterprise resource planning) system.

SAP was essentially a giant database that contained virtually all of the company’s records. It enabled Cosworth to be able to keep track of the entire life of a component, from design through to manufacture, assembly and usage. But one of the problems of SAP was that it was no longer possible to allocate part numbers that followed Cosworth’s rules. (Actually, this proved not to be true, but by the time a solution had been found, it was too late.)

Instead, the company switched to sequential numbers starting at 20000000. There was a central computerised database that would supply the next number available, but without the intelligence that the old part numbering had provided.

To make matters more confusing, for the first few months Cosworth used numbers starting at 10000000 to identify raw materials and kits. You’ll notice that some of our piston sets follow this pattern, such as 10001487 for our BDG Hoyle piston sets.

If you’ve survived to the end of this article, then congratulations. It is definitely not the most riveting of subjects, but will hopefully help to shed some light on how to identify Cosworth components.

The Cosworth DFV and the CA engines represent bookends of nearly half-a-century of normally aspirated Formula One engines. These two engines allow for a discussion of how Cosworth was able to double both engine speed and power output, as well as guarantee a staggering threefold increase in engine life. In this special tech feature we’ll compare these two engines, taking a closer look at some of the critical components.

An Icon in F1 History – the DFV

Very few companies can survive more than 60 years of trading and still follow the founders’ original mission intent. In the cut-throat world of motor racing this is an exceptionally rare feat, and one only has to look at a race report from half-a-century ago to see that most of the teams and engine suppliers of the time have since disappeared, falling foul of financial setbacks, changes in regulations and necessary diversifications away from motorsport.

Yet one company has flourished since its inception in 1958 and can still claim to be true to its roots. That company is Cosworth, built on the foundation that “it must be possible to make an interesting living messing around with racing cars and engines”, as decreed by founders Keith Duckworth and Mike Costin.

In 1967 Cosworth launched the DFV into Formula 1, initially for Team Lotus, and it instantly became a race winner. The following year the DFV was made available to other teams, and it went on to become the most successful engine ever in the history of Formula 1, scooping 155 wins, 12 drivers titles and 10 constructors titles.

The first DFVs might only have been able to delivery just over 400 bhp and reach 9,000 rpm to start with, but as each failure mode was methodically overcome (starting with the valve spring, then torsional gear drive problems), power and speeds gradually rose. By the time the DFV had finished active service in 1985, peak speed had topped 11,000 rpm and power was in excess of 500 bhp.

Working in conjunction with Lotus, the DFV was the first successful Formula One engine designed to be a fully structural member of the chassis, with mounts on the heads, cylinder block and sump connected to the chassis and gearbox bulkheads.

The DFV had a V8 configuration, with the two banks separated by a vee angle of 90 degrees, and for various reasons had the air intake to the two cylinder heads in the centre vee and the exhausts on the outside of each bank, running down either side of the engine below the heads.

The auxiliary water, oil and scavenge pumps were housed on either side of the cylinder block, tucked away underneath the exhausts and driven by a belt that in turn was driven by the nose of the crankshaft. The drive to the camshaft gears was via a series of gears at the front of the engine, again driven from the crankshaft nose. In the centre vee sat the alternator and fuel pump assemblies.

The Need for Speed – the CA

Some 40 years later, Cosworth launched what would turn out to be their final V8 Formula 1 engine, codenamed the CA. Formula 1 engine regulations had gone through many changes since the advent of the DFV, with brief interludes of turbocharging in the mid-80s, followed by a return to normally aspirated 3.5 litre engines up until the end of 1994, and then 3 litre engines in various configurations.

When the CA was first launched in 2006, and with no regulations capping speed, a mind-boggling and class-leading 20,000 rpm was attainable in qualifying, and by the end of that same season the CA could run up to that speed over an entire race distance. Frustratingly though, regulations aimed at reducing soaring development costs had capped the maximum engine speed to 18,000 rpm when Cosworth returned to Formula One with a modified CA in 2010.

Even so, peak power of 780 bhp was attainable, almost twice that of the DFV when it was first launched, despite a reduction of 14% capacity. Perhaps more impressively, there was a huge jump in engine mileage. The DFV competed at a time of unlimited engine changes, and hence only had to be capable of completing one race distance. Fast forward to the 2010-2013 era, and drivers were only allowed 8 engines for the entire season, which meant that the CA had to be capable of completing around 1,500 miles between rebuilds.

Comparing the DFV and CA

What is perhaps surprising is that the CA’s overall architecture was almost identical to the DFV’s, save for the removal of belt drives and the repositioning of the alternator and fuel pump (in subsequent Cosworth Formula One engines the alternator was relocated to the back of the left-hand auxiliaries, while the fuel pump ended up submerged in the car’s fuel tank and driven by a quill shaft from one of the drive gears on the front of the engine). While Duckworth would certainly never claim to have pioneered this layout, it is interesting to note that most Formula One engine manufacturers later followed a similar approach.

A comparison of DFV and CA engine weights wouldn’t necessarily be fair, as in addition to the reduction in capacity, the CA’s weight was mandated by the regulations, which specified a minimum dry weight of 95 kg. However, it is worth noting that the corresponding weight of the DFV would have been around 168 kg when it was first launched.

The regulations that governed the design of the CA also defined a minimum height of the centre of gravity from the bottom of the sump at 165 mm. As this figure was easily achievable on the CA, any weight-saving requirements were rendered unnecessary, hence extra material in the heads and cam covers could be used to improve the engine’s overall stiffness.

Cylinder Block Comparison

The most striking difference between the cylinder blocks is in their respective sizes. The DFV block stands almost twice as high as that of the CA, due in part to the height of the sump. The distance from the crank centreline to the bottom of the sump for the DFV was more than 133 mm; for the CA that fell to just 58 mm (the minimum allowed by the regulations).

Some of this reduction was made possible by gradually miniaturising the bottom-end geometry over successive engine designs, such as shrinking the crank counterweights following the shift to bolt-on tungsten weights. Of equal significance was lowering the piston stroke (64.77 mm for the DFV versus 39.77 mm for the CA) thanks to an increase in cylinder bore size and a reduction in capacity.

There was a marked increase in bore size from the DFV to the CA, 85.67 mm for the DFV compared with the CA’s 98.0 mm, as dictated by the regulations. Despite this, the CA block is slightly shorter in length, as both engines have almost the same bore spacing. The distance between the walls of the bores could be reduced on the CA because it ran with coated parent metal bores, whereas the DFV block was an open-deck variant containing cast-iron cylinder liners.

Both blocks were cast from aluminium alloys, LM25 TF for the DFV and a similar in-house derived aluminium alloy for the CA. Cosworth actually experimented with magnesium cast blocks and cylinder heads for the DFV during the 1970s, but that was soon abandoned owing to the increased complications that came when using magnesium. In essence, the magnesium blocks and heads were problematic because of the large difference in thermal expansion coefficient values for the magnesium material, the steel main bearings and the nickel-aluminium bronze alloy valve seats.

Cylinder Head Comparison

Duckworth famously remarked that the DFV was the first race engine to incorporate a narrow included valve angle (the angle between the inlet and exhaust valves). At the time, rival engines had valve angles of around 60 degrees, but Duckworth sought to reduce this to give a shallower pent-roof chamber. The DFV was designed with an included valve angle of 32 degrees – compare this then to only 18 degrees on the CA.

Actually, the CA had compound valve angles, with both the inlet and exhaust valves also inclined 6 degrees apart along the crankshaft axis. The switch to a compound valve angle improved the shape of the combustion chamber on the CA, plus an opportunity to make a small increase in inlet and exhaust valve diameters.

Like the DFV, the CA cylinder head featured a separate cam carrier – in the case of the CA, this was necessary to be able to package the compound valve angles. The CA heads featured a pneumatic valve return system instead of conventional wire springs, which allowed the engine to run at such high speeds.

Piston Comparison

Thanks to the tightening up of the included valve angles in the cylinder head, the CA piston crown didn’t need deep valve pockets, as seen on the DFV. Instead, the crown was almost flat, with shallow pockets to clear the valve heads. The lack of sharp edges and pockets in the crown had a huge beneficial effect on good flame propagation and the elimination of detonation.

Piston material was largely unchanged from the DFV to the CA, thanks to the CA’s regulations banning the use of exotic materials such as aluminium beryllium and metal matrix composites. The DFV piston forging used a grade of RR58 aluminium alloy that had originally been developed by Rolls-Royce. By the time the CA was designed, Cosworth had already defined a confidential proprietary blend of aluminium alloy.

Another change that was quite noticeable when comparing the two pistons was the undercrown design, which on the CA was an elaborate arrangement of highly polished ribs and buttresses, optimised using various design techniques. The net effect was a piston that, although bigger on bore size, was almost half the weight of that from the first of the DFVs.

One other note was the amount of oil cooling supplied to the CA piston, via an array of squirt jets fed from the main oil gallery in the block. The correct cooling of the piston was a critical factor in achieving the required durability while also withstanding increased gas pressures and speeds.

DFV & CA Continuation

Whilst both engines might have ceased active service, they can still be heard roaring around race tracks today. The DFV is a popular engine for historic Formula 1 race categories, and some of the Formula 1 cars from the end of the V8 era are still being run by privateers with power from the CA.

Modatek actively supports customers with rebuilds of both engines, supplying genuine parts such as pistons, bearings, seals and countless other critical components. We even have an on-line shop for DFV parts.

We also sell race-used Cosworth CA engine parts in our Memorabilia section of our on-line shop.

This feature on the Cosworth DFV and CA engines is based on an article written by Modatek’s Matt Grant for Race Engine Technology, issue 100. You can purchase a back copy of this publication here: https://www.highpowermedia.com/Product/race-engine-technology-issue-100

Have you ever wanted to take a peek inside a Formula 1 engine? Up until now the insides of a Formula 1 engine have remained a guarded secret – until now! Take a look inside one of the best engines from the mid-2000s, the Cosworth TJ.

We stock race-used parts from Cosworth’s TJ and CA engines that can be displayed for all to see. Just keep an eye on our Memorabilia section of our on-line shop to see what’s currently available. Each part can be bought directly from the website shop and delivered straight to your door.

The Cosworth TJ

The TJ was the first used by Jaguar Racing in 2003. The team continued to use this engine when they morphed into Red Bull in 2005. It also saw active service powering the Jordan and Minardi teams in 2004 and 2005, respectively. Its final year of racing was in 2006, when Torro Rosso (formally Minardi) ran the engine against the V8’s.

It was a clean sheet design, learning on the lessons from the successful CK engine that had been used by Stewart Grand Prix / Jaguar Racing from 1999 to 2002. There were several important concepts copied from the CK, such as the unique central-beam cylinder head philosophy.

The TJ received an extensive amount of development, eventually allowing the engine to reach a maximum speed of 19,000 rpm and peak power in the region of 900 bhp.

Last of its Era?

When it was introduced in 2003 the TJ was the epitome of the “anything goes” regulations from that era. Devoid of rules that restricted the number of engines that could be used by each driver, the emphasis was very much of extracting the maximum out of each engine in just one session or race.

It wasn’t uncommon back then for teams to get through over six engines in one weekend (and that’s not allowing for unscheduled engine changes!). As a result, engines like the TJ were designed with performance over reliability in mind.

Midway through the life of the TJ, rules aimed at extending engine life started to creep in. In 2004 the FIA introduced the “two race” requirement that each engine had to attain. Engines like the TJ that were designed for outright power and performance had to be re-engineered to last longer.

In addition, restrictions in later years on low density materials plus minimum weights and centre-of-gravity heights meant that the lightweight features seen on the TJ became redundant in subsequent engines.

In its final year of service with Torro Rosso in 2006, the TJ’s maximum engine speed was capped at 16,700 rpm amid fears that it would outpace the newly-introduced V8 engines (including the 20,000 rpm CA from Cosworth).

However, the TJ lives on, and can be seen (and heard) running in the back of numerous historic Formula 1 cars.

Modatek are pleased to be able to help keep these engines alive for historic race series and demonstration events. If you need assistance then get in touch.

All of our Cosworth production pistons start life as a piston forging to ensure that they are as strong as possible.

Put simply, the forging process involves pushing a bespoke die under great pressure into the billet. As a result, the billet material flows into the required shape of the piston. The forging process gives us the finished machined shape in the undercrown. This reduces the amount of machining that is required. Further, the orientation and distortion of the grains in the material is optimised to give superior mechanical strength. Aligning the axes of the material grain in a certain way can have a significant impact on the structural properties of the piston.

Temperature Effects

Our pistons begin their life as a billet of extruded aluminium alloy bar. This billet is heated to a pre-determined temperature to ensure that the billet is soft, but not at melting point. When the billet is at the correct temperature, it is placed into the forge and shaped by the die. The forging temperature needs to be carefully controlled. This temperature will have a significant effect on the homogeneity of the microstructure. If there were localised changes in the billet temperature then this could lead to inconsistencies in the material properties of the finished piston. For example, if the die was cold then the outer surfaces of the piston would cool rapidly. This would lead to a varied grain structure in the finished piston.

Hence the die is heated to the same temperature as the billet, creating a process known as isothermal forging. This process  that keeps the billet at its maximum elevated temperature throughout the entire forging operation. During the forging process, any cooling at the interface between the die and billet is eliminated, which can greatly improve the flow characteristics and hence the grain structure of the finished item.

If you’d like to know more about our genuine Cosworth pistons and how they can provide you with the performance and reliability that you need from your engine then please get in touch via our Contact page.

One of the most important aspects of any IC engine is the correct timing of the rotational movement of the camshafts relative to the reciprocating movement of the pistons. Any errors in this timing will result in detrimental performance, and could in the worst case lead to contact between the valves and pistons, which could prove to be both catastrophic and costly. There are a number of ways that this meticulously choreographed movement of valves can be achieved, such as with gears or chains. But one of the most common methods in a road car is with the use of a timing (or cam drive) belt. The timing belt is normally driven by the crankshaft, and then turns pulleys that drive the camshafts.

Timing Belt Construction

The majority of automotive timing belts are constructed from an elastomer body that contains tension cords, with a fabric backing and a tooth jacket.

Looking at these four ingredients one by one, then the first is the elastomer body. This is normally a high temperature spec rubber such as HNBR (hydrogenated nitrile butadiene rubber) or EPD (ethylene propylene diene). HNBR is more suited to engines, as it can handle exposure to lubricating oils. The elastomer body can sometimes be reinforced with aramid fibres, which help strengthen the belt and provide extra protection for the teeth. Aramid is a heat-resistant and strong synthetic fibre that is sometimes referred to by the tradename Kevlar. Our heavy duty belts for the YB engine contain this aramid reinforcement, which helps make them three times stronger than a conventional automotive timing belt.

The tension cords help to give the belt incredible levels of tensile strength without compromising on flexibility. Tension cords are typically manufactured from high-strength glass fibre, and the individual strands of fibre are bundled together and twisted for added strength. It is the presence of glass fibre that means that a timing belt should never be ‘crimped’, which is the action of over-bending or twisting the belt that then shears the glass fibres.

Next up we have the tooth jacket, which is a temperature-resistant polymide fabric that helps to protect the teeth from abrasion as well as shear forces. The last ingredient is the fabric backing, which is usually another type of polymide fabric. This fabric backing is used on the smooth face of the belt that will run against the belt tensioner, so resistance to abrasion and wear is a must for the fabric.

Toothed Belts

In the majority of cases the timing belt is driven by teeth on the belt that engage with matching teeth in the pulleys on the crankshaft and camshafts. It is these teeth that provide the accuracy in timing, and hence toothed belt drives are often terms ‘synchronous belts’, as the keep the movement of the cams in synch with the crankshaft.

Keeping the teeth engaged at all times is vital. If a tooth jumps out of position then this is called ‘ratcheting’ (some people might use stronger language when this happens!). It is normal for the belt teeth to try to escape from the adjacent teeth in the pulley – when this happens the belt tension increases, which pushes the teeth back together, but this can lead to long lasting damage of the tension cords inside the belt. Complete slippage of the belt teeth out of the pulley teeth usually happens because either the tooth engagement is poor, or because of lack of belt tension.

The profile of the teeth is an important factor for the performance of the timing belt, and there are generally three categories for the profile – trapezoidal, curvilinear or modified curvilinear. Curvilinear profiled belts are sometimes called High Torque Drive (HTD), and modified curvilinear profiled belts are often called Super Torque Drive (STD), S-type Tooth Profile Dual-sided (STPD) or GT.

Tooth Profiles

The trapezoidal profile is the oldest of the three, introduced over 80 years ago. The shape of the profile is a trapezium, with straight flanks that are angled inwards towards the tip of the tooth. When the teeth revolve around the pulley, these flanks create an involute curve that matches the involute tooth profile on the pulley.

One disadvantage with the trapezoidal tool profile is that it has sharp corners at the root of the tooth, and this can create high stress concentrations that can weaken the belt. To overcome this, the curvilinear has fully radiused corners, which helps to even out the stresses. Also, the curvilinear tooth profile is taller than the trapezoidal profile, making it more difficult for the teeth to jump out of position and also giving a larger contact area, which in turn helps to reduce both stress and noise.

The last of these three profiles, modified curvilinear, is today the most popular type with timing belt manufacturers. As the name suggests, this profile is based on the curvilinear profile, but has a shallower tooth height along with an increase in flank angle. These changes help to give the modified curvilinear profile the ability to withstand higher amounts of torque.

Cosworth Engine Belts

Want more information on the belts that we stock for Cosworth engines? Then get in touch via our contacts page.