Hillclimb racing is a very traditional form of motorsport – Shelsley Walsh, for example, is a closed-circuit venue in the UK and is the oldest motorsport venue in the world still running events on the original course. While the UK hillclimb championship is run on closed (and therefore short) circuits, in Europe the competition is run on closed roads, so the course length has the potential to be much longer.
This type of racing is very exciting to watch for many reasons, so it attracts enthusiastic fans who watch very dedicated and brave competitors. As with the famous Pikes Peak race on open roads, there are a lot of serious hazards for drivers in hillclimb competition. Typically, there are steel crash barriers lining the track, and no run-off areas. For anyone who appreciates variety in motorsport, hillclimb is very attractive because it has classes that accommodate a wide range of machinery, from quite lightly modified passenger cars, through production-based sportscars to specially constructed single-seaters and ex-endurance Prototypes. The magic ratio of one horsepower to one kilo, which is sometimes mentioned regarding very special – as in extremely expensive – road and racecars is routinely surpassed in hillclimb competition, sometimes even where the weight of the driver is included.
Cyrille Frantz in his Osella hillclimb car powered by the four-cylinder turbocharged Pipo PCC (Images courtesy of Pipo Moteurs)
The mix of machinery in terms of cars and their powertrains gives hillclimb a unique appeal, because it includes everything from modified saloon cars to open-wheel single-seaters. A leading competitor in European hillclimb racing is Cyrille Frantz who drives an Osella Sports Prototype in the French hillclimb championship, which is powered by an inline four-cylinder provided by Pipo Moteurs. I spoke to Pipo’s general manager, Frederic Barozier, who is the technical chief of Pipo and has been in charge during some of the company’s most exciting projects. It designs and manufactures engines for world championship competition in rallying, rallycross and at the pinnacle of endurance racing in the World Endurance Championship including Le Mans.
Compared to these disciplines, hillclimb is relatively obscure, but it is a challenging environment in which to run an engine competitively, and part of that challenge is supplying a reliable, high-performance power unit with a keen eye on cost. Claiming an overall Le Mans podium in 2022 shows the very high technical level of Pipo Moteurs and it thus has a valuable perspective on hillclimb. The link between the Le Mans V8 used in the Glickenhaus SCG007 and the four-cylinder (designation PCC) used by Frantz for hillclimb is an important one – they were in development at the same time and so share a large degree of design intent and actually some physical components. That makes the PCC one of the most recent hillclimb engines to be designed; many competitors race with ‘legacy’ products originally designed for other race categories. Pipo has a range of competition engines, from 1.6 to 2.0 litre fourcylinder units to a lovely 3.5 litre Le Mans V8 and a 5.0 litre Dakar V8. The company’s focus on cost means there is a wide degree of commonality of components between its engines.
The hillclimb engine is used as a semi-stressed structural member in the car: the engine is bolted to the chassis, the transmission is mounted to the engine and the suspension is mounted to the transmission. However, there is also a set of mechanically parallel connections from the transmission to the chassis in the form of a steel framework alongside the engine on both sides. The engine is a structural member, but takes only part of the chassis loads. I4 engines are notably narrow and package nicely, but they can lack torsional stiffness, so the additional framework adds very useful stiffness to the chassis as well as relieving load from the engine structure.
Left side of the Pipo PCC showing the cast aluminium plenum and drive-by-wire throttle
The engine capacity is nominally 1.747 litres; the regulations for this class allow a maximum of 1.75 litres. The reason for the engine not meeting this absolute maximum allowable capacity is based on a pragmatic approach to managing costs for customers, and is explained by referring to the engines already in production by Pipo. The 1.6 litre and 2.0 litre four-cylinders for rally applications and a range of 2 litre four-cylinder units for World Rallycross (WRX) competition are based on the Ford Duratec. The simple explanation for the 1.747 litre capacity of the hillclimb engine is that it takes the 85 mm piston from the 2.0 litre Ford-based engines, and the crankshaft with 77 mm stroke from the 1.6 litre rally engine. The commonality of parts is a feature of most of the engines produced by Pipo. The hillclimb engine has parts that are common to their rally, rallycross and endurance racing engines. This is not a parts-bin special though; it simply takes advantage of the most wellengineered parts that can be used.
This is a very pragmatic approach to the ‘cost engineering’ of race engines, and results in an engine being produced in very low quantities at an affordable price. Many companies simply do not have the range of competition engines to be able to provide a specific new engine at a sensible cost. Barozier notes that the commonality of components extends as far as the main structural parts of the engines, which means that the number of different dyno set-ups to allow all types of engines to be tested is kept to a minimum.
Inlet, combustion and exhaust
The combustion air is drawn from a forward-facing duct at the front of the car, and is delivered to the turbocharger’s compressor through fabricated aluminium pipework. The turbocharger is mounted on the right-hand side of the engine, and on exiting the compressor the air has only a short distance to travel to the air-to-air intercooler, which is mounted in the car’s right-hand sidepod duct. To maintain a low height, the intercooler is wider than the sidepod duct and is therefore angled and fed by a curved composite duct. The charge-air exit of the intercooler again connects to aluminium pipework that loops up over the engine behind the driver and then turns down towards the floor of the car before turning upwards again to join the downward-facing entry to Pipo’s bespoke cast aluminium plenum.
The plenum is used to mount the single throttle, which is a drive-by-wire type and thus offers the ability to be used for traction control. Port injection is used, with a single injector per inlet port, and the injectors are outside the plenum and therefore easily accessible in case of an injector fault. There are no ‘overhead’ injectors feeding the ports from above the trumpets. Although the engine is currently used with only port injection it can be used with direct injection, either alone or in conjunction with port injection.
Rear view of the Pipo PCC showing nine-bolt crank output and turbine exit
Given the commonality of this engine with those based on the Duratec, the combustion chamber necessarily retains a lot in common with it. There are a number of areas where there are options for components and systems, and the cylinder heads are no exception. There is a completely bespoke Pipo head or one based on the Ford casting. In order to allow them to be interchangeable on a ‘short engine’ – that is, one built up to the block deck face – there has to be a degree of commonality between the Ford-based and Pipo heads in terms of the valve positions and angles. This engine therefore isn’t any more adventurous than the standard Ford engine in these aspects, although we can expect the chamber to be very much ‘tidier’ and finished with much more care than a production car item. Where the Pipo engines are different from the Ford is the choice of bore and stroke. As mentioned in a previous article that discussed its Le Mans V8 (RET 128, December/January 2021) Pipo has experimented extensively with different combinations of bore and stroke, and has a preferred bore size of 85 mm for cylinder capacity.
The choice of bore is always a compromise – some companies like to use a small bore to create a compact engine and promote good combustion, while others follow the large-bore route to give a larger valve area and, for a given engine speed, a lower piston speed and therefore lower friction. While the hillclimb engine compression ratio is undisclosed, 12:1 is used in Pipo’s Le Mans engine. The exhaust system follows fairly conventional practice for turbocharged race engines, being made from Inconel. The exhaust headers are, as per normal practice for turbocharged race engines, insulated between the cylinder head and the turbine. The Garrett turbo features an integrated wastegate.
As per the Bourne Time Attack engine featured in RET 142 (October 2022), the PCC has phase/anti-phase wastegate control, with the wastegate valve being controlled for opening and closing by air pressure. That allows much more accurate control of the wastegate, and Barozier notes that such a system is “also good for the backfire condition”, when an explosion in the exhaust can cause the wastegate valve to come off its seat. One of the challenges of hillclimb as a discipline is the change in altitude. Pikes Peak is the extreme example of this, with naturally aspirated engines losing a huge amount of performance before they reach the top of the hill. In this situation, they are at a significant disadvantage to turbocharged cars.
View of the exhaust and compressor inlet. In the car, the exhaust primary pipes are insulated
Within the limits of operation of the turbochargers, the plenum boost pressure can be maintained so that there is no loss of performance. Provided the turbocharger shaft speed is not usually run at the maximum allowable speed, the boost pressure is maintained simply by getting the turbo to spin faster by controlling the wastegate. Barozier notes that the maximum turbocharger shaft speed is roughly 165,000 rpm, but by the top of a hillclimb course, at an altitude of 2000-2500 m, the turbo shaft speed required to maintain the boost target is 185,000 rpm. The choice of turbocharger is not straightforward, as with so many aspects of engine design. Barozier says, “You have to find a compromise – big turbo, big performance,” but a big turbo comes with greater lag and therefore worse driveability. A smaller turbo leads to a much better transient response and a greater sense of confidence for the driver. The aim therefore is to find a turbo that is as small and responsive as possible without limiting performance and, in the case of hillclimb, having some shaft speed in hand to compensate for a loss of air density at high altitude. Hillclimb courses often feature very tight corners and hairpins that reward responsive engines with predictable throttle response and a progressive torque curve.
The front of the Pipo PCC showing the drives for the pumps and alternator. The camshaft drive is by chain and is behind the machined-from-solid aluminium cover
The turbocharger is described by Barozier as a “low-cost option from Garrett”, and it has a wastegate integrated into the turbine housing. Barozier notes that the turbocharger is standard apart from Pipo modifications to the wastegate assembly. “The original wastegate shaft was not strong enough,” he says, which meant it had to be replaced with a stronger custom part, along with the use of the phase/anti-phase control, which requires only a very light return spring compared to a normal system, which is opened by pneumatic pressure and closed by spring force.
Mechanicals
As mentioned, the cylinder head on the hillclimb engine has two options – modified Ford or Pipo’s own casting. As both are compatible with engines originally specified for the other head, this has natural implications for aspects other than the combustion chamber. To maximise compatibility, the Ford and Pipo heads share the same cam drive and camshaft positions, and therefore very similar valve angles. The Duratec valvetrain is of a fairly standard design, having four valves per cylinder and double overhead camshafts. Drive to the cams is by chain, and Barozier says a damper is used in the timing drive, which he says is “good for the drive chain, valves and springs”. The optional head for the I4 is the left-hand one from the Le Mans V8, which is compatible with all the Pipo engines based on the 2.0 litre and 2.3 litre Duratecs, meaning that the engine shares the same 96 mm bore spacing as the Duratec and the Pipo Le Mans V8. The valvetrain is a little ‘old-fashioned’ in staying with inverted bucket-type flat-faced tappets, where many modern engines use finger followers. However, this is a design feature that is common to the Ford and Pipo heads and has also been demonstrated to be successful and competitive in Gibson/Zytek’s various Le Mans engines over the past 20 years.
Rear view of the engine installation in the chassis clearly shows the steel frames transferring part of the loads from the rear suspension through the transmission to the chassis around the engine
The limiting factor in terms of flat-faced followers is usually valve opening velocity, as there is an almost direct proportionality between the valve’s opening ‘angular speed’ in millimetres per degree and the size of the tappet required. The ‘almost’ is due to the effects of cam lobe width and cam lobe offset. The attractions and advantages of finger followers are less pronounced at the lower engine speeds currently typical of endurance race engines. In the Le Mans V8, Pipo uses domed tappets to produce some of the same advantages as finger followers through higher permissible valve opening velocities. It is interesting to note though that it doesn’t feel these are required in the I4 hillclimb engine.
single conical steel spring is used to close each valve; conical springs allow the use of a very small and lightweight spring retainer. In conjunction with the lighter spring, this gives a very useful reduction in valvetrain mass, making valve control much easier. The lower-load springs also reduce loads on the cam drive system compared with the heavier loads from a nested two-spring system. The valves themselves are hollow steel, sodium-filled items. It is common practice in race engines, particularly turbocharged ones, to have sodium-filled exhaust valves in order to reduce the valve head temperatures to improve reliability and remove hotspots from the combustion chamber. Reliability is improved by reducing the maximum component temperatures, which are often on the rear of the valve head, close to the area of minimum cross-section.
This view of the engine installation shows the insulated exhaust system and the wastegate actuator
The aim of filling the inlet valve head with sodium is different from that for the exhaust valves. The inlet valves rarely represent a hotspot in the combustion chamber, and the valves are cooled once per cycle by the charge entering the engine. By improving cooling to the inlet valve head, particularly to the back of the valve head, the component runs cooler and there is a reduction in heat transfer to the incoming charge. The result is that the trapped mass in the cylinder is greater, and higher performance should be found. Some readers will have seen Pipo’s engines at trade shows, and they are notable for their neatness and, especially in the case of those with billet cylinder blocks and crankcases, exceptionally nicely finished.
The cylinder block again has options. There is a modified Duratec block based on the production casting from a passenger car, or a billet machined block produced to Pipo’s own design. The block used on Frantz’s hillclimb engine is based on the 2.0 litre Ford. The block and sump are cast as a single component, with the crank secured in place with main bearing caps. That means the bottom of the engine is sealed with a closing plate rather than a sump pan extending down from the crankshaft’s centreline. Compared with a cast block, a billet block (which is machined from a single piece of wrought aluminium) is much stronger and more durable. Castings are much more variable than billet components, even if the production process is die-casting, as is usually the case with components produced in the tens or hundreds of thousands. The engine Frantz uses is still in its first period before a rebuild is required and, so far, it is proving reliable.
The fact that there is already an option for a billet block waiting in the wings means that, should any problems be discovered, a far stronger alternative can be used as a direct replacement. While the four-cylinder billet block has not been used in hillclimb competition, is does have some endurance racing pedigree – Barozier reveals that the billet block is “made from half of the Le Mans V8”. In effect, the 1.747 litre hillclimb block has many common design features with an engine designed for one of the most challenging endurance races. Barozier acknowledges that the billet block will be very expensive compared to the production car casting. Pipo has been producing engines based on billet blocks for some years, and the production method lends itself to low-volume projects. We featured its Fordbased billet-block WRX engine in RET 107 (December/January 2018) and Pipo also machined the crankcase assembly (block and sump) for its P21 Le Mans V8 from billet aluminium.
Left side view of the engine in the chassis shows the aluminium pipework taking air to the throttle and plenum
Continuing with the theme of options for many of the major components, there is a choice of dry or wet sumps. The oil system uses a single pressure pump and two scavenge pumps; the engine
is therefore not fully compartmentalised as with other dry-sump race engines, which have one scavenge pump per crankcase compartment in the search for minimum friction. The pistons follow endurance racing practice by using three rings rather than chasing absolute performance with a lower-friction tworing design. The rings seal against Nikasil-coated steel cylinder liners. It is notable that the pistons are also shared with the Le Mans V8. The con rods are steel and articulate at the small end on a DLCcoated steel piston pin. The Pipo-designed crankshaft follows usual motorsport practice in being a nitrided steel component produced from billet.
The chain drive to the camshafts is enclosed behind a billet aluminium front cover. On the front (non-drive) end of the crankshaft are mounted the crank trigger wheel, crankshaft damper and two concentric pulleys. The larger pulley, closest to the front cover, drives the alternator through a multi-rib (‘poly-vee’) type belt. The alternator is driven faster than crankshaft speed. The idler tensioner on the alternator drive has a second concentric pulley that drives the water pump via a second multi-rib belt. The scavenge pump assembly is mounted on the right-hand side of the engine and is driven by a toothed belt at approximately crankshaft speed. There is no connection to either chassis or transmission through the cam cover, and therefore no chassis loads pass through this component. This allows the Pipo engine to use the same inexpensive injection-moulded composite cam cover from the Duratec engine.
Performance
The performance of the Pipo hillclimb I4 is 550 Nm at 6000 rpm, and 600 bhp at 8000 rpm; the engine’s redline is at 8800 rpm. At peak torque that equates to 39.56 bar BMEP and 38.41 bar BMEP at maximum power. Pipo’s Le Mans engine, a V8 of broadly the same configuration, produces 715 bhp at an estimated 7250 rpm, which equates to a BMEP of 25.23 bar. Even without making the direct comparison of the two engines by calculating BMEP, we can see that the hillclimb engine has very high performance for a small-displacement engine. The 52% higher BMEP of the hillclimb engine compared with the Le Mans V8 is a measure of how highly stressed the engine is.
It is very unlikely though that the bearings in the I4 are 52% wider than the Le Mans engine, so we can conclude that the bearingspecific loads are much higher in the hillclimb engine; its stud and thread loads will be much higher too. Such increased stresses on components will be among the reasons why the hillclimb engine has a much shorter rebuild interval than its Le Mans stablemate. The Osella campaigned by Frantz in hillclimb is, like many hillclimb cars, very purposeful and lightweight, and hence, with 550 Nm available and drive through the rear wheels alone, there is a surfeit of performance. Again, to draw a parallel with the Bourne Time Attack engine, there is a great deal of vehicle performance to be gained by making the car and engine driveable and predictable. Owing to the low mass of the car, it is easy to overwhelm the tyres and get into a situation of significant wheelspin. As Barozier notes, “The car is very light, and it is difficult to find grip. We have massive over-torque.”
Controlling the excess of performance available in a light car is an important aspect of making the driver feel confident in the car and able to produce their best performance. With various systems under electronic control – such as ignition timing, injection, wastegate control and throttle opening – there are various options for controlling engine load and traction. The same control methods also allow the engine to remain responsive by increasing mass flow through the engine without producing significant drive. That has the effect of maintaining high turbocharger shaft speeds, so there is minimum delay in reaching the boost target when there is a torque demand.
Rebuilds
Cyrille Frantz is the only competitor using the Pipo hillclimb engine, and he has only one engine. Owing to the relatively short time that the engine runs during a typical race weekend, and the limited number of events, this single example of the engine is, remarkably, yet to have its first rebuild, even though it has been in use for more than a complete season. European hillclimb events typically have a run that lasts 2 to 3 minutes, although occasionally some runs are a little shorter than 2 minutes or much longer than 3. For instance, the Trento Bondone hillclimb is more than 17 km long, and the duration is around 9 minutes for the fastest drivers.
During any race event there are four runs for free practice and three race runs, with the fastest time being used to decide the winner. There is no ‘final’ or ‘run-off’ for the fastest competitors, as in some hillclimb series. Although speeds on the course can be high, the distances covered are modest during a typical meeting. The target 1000 km rebuild interval is likely to be ccumulated after two complete seasons of competition. The aim at the rebuild stage will be to replace the minimum of parts – pistons, gaskets, spark plugs and so on. Barozier notes that there will probably be a precautionary change of more parts on the first rebuild. At the same time, it will be possible to inspect all the parts carefully and to change anything that is a cause for concern. For instance, Barozier says the condition of the valves will be carefully noted and the springs loads will be checked. He also notes that many of the parts in the hillclimb engine are common to Pipo’s WRC engines, which usually accumulate 2000- 3000 km between rebuilds.
Summary
The PCC is an object lesson in producing cost-effective motorsport power units. A major part of the challenge for anyone supplying engines for this type of motorsport is at the design stage – the budgets for such engines are not the same as those for other motorsport series with much greater exposure. The basis of the design of Pipo’s hillclimb engine is a pragmatic decision to use components from existing race engines. Recycling is a very fashionable concept, and the re-use of design knowledge offers significant gains in design productivity. There is a focus on commonality of components throughout the company. Several significant parts from WRC, WRX, Le Mans and hillclimb engines are used for more than one motorsport discipline, allowing them to be manufactured in the most costeffective manner and minimising the need to design new ones each time. The overall effect is to produce competitive new race engines in the shortest possible time and at the lowest possible cost, while re-using designs that have already proven to be reliable in competition.
The PCC engine uses parts from Pipo’s existing WRC and WRX engines, while the PCC and P21 Le Mans engine (designed at the same time) share common parts. All these engines take significant design cues from the Ford Duratec. An ongoing advantage of this approach is that component design improvements can easily be introduced to other engines. The engine is quite modular in terms of construction, in that there are options for more durable cylinder blocks or heads with more performance potential which can be easily introduced and which are compatible with the rest of the engine assembly. Part of the challenge in an engine such as the PCC is to provide reliable, low-cost performance in an engine that can be run by a small privateer team at race and test events without requiring specialist attention throughout the season. Hillclimb is spectacular but not heavily sponsored, so the cost aspect is very important and is testament to Pipo’s design approach that a company supplying a competitive, successful engine in the top class at Le Mans can also supply – and make a profit from – a one-off hillclimb engine.