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Source: Race Engine Technology

Publication Date: 26^th August 2008

The Ford fight-back

Last year Toyota marched into the fiercely contested Midget arena with a brand new race engine. This year GM has responded with a new Chevrolet, as described in our last issue. Now there is to be a Ford fight-back but this is not at the behest of the manufacturer itself nor is it through Esslinger Engineering, which develops the Blue Oval’s naturally aspirated 161 cu.in. (2.6 litre) in line four with the support of Ford Racing. Instead rejuvenation of the Pinto-based Ford is an initiative of Bret Conway’s Performance Research Inc, the North Carolina valvetrain specialist highly renowned for its work in NASCAR and NHRA and inother major arenas, including Formula One. As a first step Performance Research has radically re-engineered the Ford’s single overhead camshaft valvetrain to enhance performance and reliability.

The Pinto is a crossflow engine having two valves per cylinder, these sitting side by side with, as stock the intake port feeding in from the left hand side of the cylinder head and the exhaust feeding out to the right. The valves are angled at 7.5 degrees from each other, so that the tip of the intake valve is to the left of the single overhead camshaft, the tip of the exhaust to the right. In each case, on the opposite side of the head is the pivot point for a finger follower, through which the camshaft drives the respective valve.

As standard the finger follower is a stamped steel piece, with at its tail a splined ball pivot secured by a spring clip. A slot in its nose not only operates the valve tip but also provides for its lateral location, by forming a lug either side of the valve stem. The cam lobe operates directly upon a pad formed in the top of this simple steel stamping.

The Esslinger Ford Midget engine has a 3.94-inch (100.076mm) bore, a 2.100 inch (53.3 mm) intake and a 1.55-inch (39.4 mm) exhaust valve head diameter and uses, with only light modification the stock valve operating system, which is less than dependable in racing conditions. It uses the steel finger in conjunction with a 0.342-inch (8.7 mm) diameter valve stem, needing that dimension in view of the clumsy locating lug system. Performance Research has designed a replacement finger follower system, lighter yet stronger and better-located, which in turn allows the use of a thinner-stem, lighter valve and also reduces the valve spring pressure requirement. It has also introduced its own, superior quality camshaft. Throughout the valvetrain it has considerably reduced horsepower-sapping friction by its careful re-engineering.

The new finger follower is a billet aluminium piece that is shaft mounted and carries a mid-mounted roller wheel through which it interfaces with the cam lobe, in place of the stock stamping’s integral operating pad. The outboard pivot shaft, which is individually mounted to the cylinder head, provides lateral location so the nose of the follower can operate a lash cap atop the valve stem, with no need for locating lugs. The nose actually carries a fixed wheel with an eccentric mount that provides for valve clearance adjustment, following a system pioneered by BMW that is very neat and effective.

The lash cap and the fixed wheel that interfaces with it both are tool steel, the latter having a silicon nitride PVD coating. Also tool steel are the roller wheel, its shaft (carried by the finger) and the head-mounted shaft upon which the finger pivots. The finger itself is made from a rare aluminium alloy, which Conway tells us offers 100,000 psi tensile strength and is normally used for advanced airframe manufacture. It is stiffer as well as lighter than the steel stamping it replaces. The 0.950- inch diameter roller wheel runs on needle bearings on its axle shaft. A pair of tapered thrust bearings and thrust washers running on the finger pivot shaft locate the finger, ensuring that there is virtually no relative lateral movement between the nose of the finger and the valve lash cap. Compared to the established finger, the nicely engineered replacement provides a significant reduction in mass moment of inertia.

The valve itself is titanium and its 7 mm stem is hollow. It is a forging by Victory One, which is very cleverly produced in one piece by that North Carolina valve manufacturing company. It saves no less than 61 gm over the existing titanium valve on the intake side and 57 gm on the exhaust. Working in conjunction with the established aluminium/bronze seat and guide, the valve has an all-over titaniumnitride PVD coating, which is rated 2300¢ªF and consequently can withstand exhaust heat. Helped by the weight saved on the follower and on the valve and on its titanium retainer system, the valve spring stiffness requirement is 45% less and a single spring is sufficient to keep the valvetrain under control. Whereas the Esslinger Ford as standard requires dual springs on each valve, now to run 10,000 rpm there is only one spring of the type previously used for the exhaust outer spring. This is a Kobe steel production by PSI.

The total saving of weight beneath each individual cam lobe is in excess of 75 gm. That significant gain in turn reduces friction and with it power loss and also enhances precision of valve control (lift is 750 thou intake, 770 thou exhaust, with the valves just starting, by design to loft at the 10,000 rpm red line). The Performance Research valvetrain includes the use of its own, gun-drilled, hardened tool steel camshaft, which is micro-finished and runs directly in the head. Neither it nor the spinning roller wheel that it interacts with is DLC coated, to avoid the danger of the wheel skidding. Nosignificant cylinder head modifications are required to install this new Performance Research valvetrain, which once in place allows easier access to individual components than the existing system. Its design has been patented and it is available as a kit of parts to all Esslinger Ford runners, or it can be pre-installed by Performance Research at its base in Lincolnton, NC.

While for the time being at least the existing Ford toothed belt drive and camshaft location system are being retained, step two will be a new camshaft location system. The current approach is to slide the camshaft in through bearing holes in stanchions formed integrally with the aluminium alloy head whereas the new system will use removable caps. This will allow for the introduction of larger base circle lobes while retaining the existing journal size. There will then also be provided an individual oil spray for each cam lobe/follower interface. Currently there is simply a drilling through the lobe to introduce lubricant from a supply fed into the axis of the hollow camshaft, which is also used to lubricate the journals. Conway notes that by and large the current approach is that of the valvetrain running in a power-sapping bath of oil.

Conway reports that as a third step, Performance Research is looking at turning the Ford cylinder head through 180 degrees, which is quite feasible. Currently, when the engine is canted in a Midget chassis the intake slopes down to the left so that it has to feed from a low pressure zone behind the left front wheel, with no possibility for a ram air intake and with the mechanical injection system working against rather than with the aid of gravity. At the same time the heavier exhaust is highmounted, so a reverse head makes sense on a number of counts.

At the time of writing Performance Research had just finished manufacturing its new valvetrain for a trio of Beast cars that were set to debut it in the ‘Toyota Challenge Racing Classic’ USAC Mopar Midget National Championship race on the quarter mile at O’Reilly (formerly Indianapolis) Raceway Park, July 24th. Toyota, Mopar and GM rivals – and the other Esslinger runners – were set to get something of a shock when news of this major updating of the Ford broke at the event. At least the other Esslinger runners had the option of acquiring this exciting new technology!

Porsche’s DFI win - le mans

A month after convincingly winning LM P2 upon its debut at Le Mans, the Porsche RS Spyder took its first victory using direct injection. Third overall, first in LM P2 at July’s Mid Ohio round of the ALMS, Penske Racing was using for the first time a new ‘DFI’ version of the Porsche naturally aspirated 3.4 litre V8, (which runs on organizer-supplied E10 fuel).

Thomas Laudenbach, Head of Motorsport Development – Powertrain at Porsche says: "we believe our in house benchmark, the PFI V8 engine is already at a high level so we had to put a huge effort into the development of the DFI engine in order to improve performance and efficiency significantly. To run up to 11,000 rpm with DFI technology meant to enter unknown territory. At Le Mans we solely used the PFI engine – the DFI was introduced at Mid Ohio. Looking at the high level of competition in the LMP2 class, it was exactly the right time to launch the new engine."

The official output figure for the DFI engine is 503 hp (370 kW) at 10,000 rpm, up from 476 hp. That increase of 5.7 % in top end power is accompanied by a 4% increase of maximum torque, which is up from 370 Nm at 7500 rpm to 385 Nm at 8500 rpm. Fuel consumption has been improved also. We’ll have more information in the next issue of Race Engine Technology, which will include a major profile of the Porsche engine.

Peugeot’s package - le mans

Peugeot introduced a new aerodynamic package for its 908 LM P1 turbodiesel car at Le Mans, a key feature of which was a revised rear deck. The form of that deck took advantage of a lower engine plenum. The Peugeot 5.5 litre V12 twin turbo, like the superficially similar rival Audi engine has a plenum for each bank, fed by its respective turbo-supercharger, with the two plenums linked by a pressure balance bar. The accompanying photograph, of the Peugeot V12 on the dyno in 2008, shows us that there has been a move from the original ‘organic’ plenum form of 2007 (RET 022) to a more compact pair of cylindrical logs, albeit each with a (very difficult to manufacture) distinctive spiral pattern upon it.

The helical protrusions suggest that the individual cylinder runners are wrapped around the log section for something like 270-300 degrees before they break into the central volume. This provides the required runner length while keeping the overall height of the plenum system to a minimum to the benefit of car aerodynamics. A possible drawback of this approach is that there are additional bends in the cylinder intake run compared to a more conventional plenum, which on the face of it causes a loss of efficiency. On the other hand, could the spiral entry passage set up a beneficial axial swirl as the charge (which by regulation is compressed to as much as 2.94 bar absolute) enters the individual runner?

Contributing Editor David Wood says: "I would doubt that the aerodynamic influence of the spiral would reach the combustion chamber after such a long straight run from the plenum. Most of the swirl/tumble will be induced by the port shape and entry angles into the combustion chamber. Typically the two ports will be arranged to make a high and low approach to the valve face, plus the ports will be offset to the centreline of the inlet valves to create additional entry swirl. I think that here the design of the inlet runners and plenum is driven by packaging constraints."

Interestingly, observes Contributing Editor Jack Kane, this log-style plenum facilitates the deployment of a variable intake runner length, by rotating an inner cylinder set within the outer one so as to adjust the geometry of the spiral section. This system could be continuously variable, controlled by the engine control unit so as to maintain optimal port length as engine speed changes.

Variable length intake runners are no longer permitted in Formula One but there is no restriction upon their use at Le Mans. Mazda used variable length runners on its 1991 Le Mans winning rotary engine (RET 030) but to our knowledge the technology has not been employed since. There isn’t so much call for it in the case of a relatively slow running turbodiesel boosted to almost 3.0 bar absolute such as the 908 V12 but it is nevertheless not implausible that Peugeot would opt to exploit the potential of such a system. We shall see. Or perhaps we shall find the technology exploited by one of its rivals, most likely a naturally aspirated spark-ignition engine…

Aston Martin Project 14

The Aston Martin V12-engined Lola coupe run by Aston Martin Racing/Prodrive on behalf of Charouz was the sensation of Le Mans qualifying and but for an accident could conceivably have beaten one of the turbodiesels in the race. This car has an engine derived from the Aston Martin GT1 V12, which won its category at Le Mans again this year. Jason Hill’s engine design and development team at Aston Martin Racing/ Prodrive carried out some initial studies of an LM P1 engine during 2007. However, the Charouz funded Lola-Aston Martin project was only confirmed right at the end of the year, so Hill’s team did not start work proper until January 1.

The Aston Martin LM P1 engine first ran on the dyno in early February of this year then the rush-built car first tested at Snetterton circuit in England towards the end of the month. It helped that the initial engine was primarily an exercise in retuning around a larger restrictor area and in repackaging for a different car environment.

Not that the magnitude of these tasks should be underestimated. The permitted restrictor area increased from 1480 mm2 (1125 kg GT1 car with air con) to 1815 mm2 (GT1-homologated engine, again with air con concession). That is an increase of no less than 22% while the repackaging involved switching the engine from a front-engined production-based car (the DB9R) to a mid-engined sports prototype (the Lola B08/60).

The biggest issue in slotting the Aston Martin V12 into the B08/60 was its sheer length, which prompted a switch from the regular Lola transmission to a shorter Xtrac transaxle. Clearly a purpose-designed chassis would mount the engine further forward (one thinks of Tony Southgate’s Jaguar Group C cars, with the front of the V12 encroaching into the rear of monocoque area). However, new for 2008, the Lola coupe had been designed as a customer car, to accept a wide range of engines (at Le Mans in 2008 another version ran in LM P2 carrying EDL’s naturally aspirated, 3.4 litre Judd DB V8). By definition the layout of the Lola-Aston Martin B08/60 is not ideal.

From Hill’s perspective the main challenge was to modify the crankshaft and the front of the R9 GT1 engine, since here there was scope to shorten the overall package. This involved a new crankshaft, shorter at the rear to create a more forward flywheel position. The GT1 car actually runs its flywheel/clutch in its remote gearbox, whereas the new gearbox for the Lola-Aston Martin needed it on the end of the crankshaft. It also involved producing a new front cover and moving the water pump to a new location, away from this. Since an electric water pump is employed, that was not the issue it could otherwise have been. The sump also had to be modified, to marry up with the new front cover. The R9 already had its sump as low as feasible with oil pumps neatly packaged alongside, a layout that suited the Lola equally well. The oil system did not need to flow additional lubricant whereas the coolant flow was increased through an alternative specification pump.

Of course, the intake and exhaust systems had to be rethought, both from retuning and packaging perspectives. Aside from handling more air and thus more fuel, the LM P1 engine was permitted an electric rather than cable throttle. Each bank was consequently fitted with its own electric throttle controller. At Le Mans Hill noted that the powertrain control system was a considerable challenge, given the introduction of fly-by-wire throttles, which had to be married to the gearbox control and traction control systems. With this the switch was made to a newer Pi control system, providing more functionality.

For this LM P1 engine the fuel rails were new, as was the air box and plenum system. The exhaust was likewise redesigned. By contrast internally, initially at least there was no change. “Given the time frame we needed to be careful about what we modified,” remarked Hill. The compression ratio was unchanged and at first it was a straightforward instance of increasing engine operating speed to exploit the 22% greater quantity of available air.

In view of increased friction the increase in horsepower was less than 22%. Hill noted that by regulation the crankshaft journals must retain the stock dimensions and that those dimensions are not ideal for faster running. He also noted that the stock architecture is not ideal in terms of cooling efficiency at higher operating speed but again the rules do not provide scope for alteration. At 1480 mm2 the GT1 engine produces 570 bhp (unconfirmed RET ‘guesstimate’), by which token the LM P1 engine started life producing 700 bhp less an adjustment for losses – 670 or 680 bhp?

Without confirming an increase in horsepower of 100 bhp or more, at Le Mans Hill admitted that the peak torque speed was up by approximately 250 rpm, the peak power speed by approximately 1000 rpm, taking it to 6750 rpm. That was the red line speed for the GT1 car at Monza this year, whereas there the Lola-Aston Martin was run to 7750 rpm. The engine at Monza was still the prototype LM P1 engine, a modification of R9 engine number R926, which was the 2007 Le Mans GT1 winner. This was raced initially at Barcelona and then at Monza. Meanwhile, the first dedicated LM P1 V12, Project R14 engine number 01 was first tested on the dyno just before Monza, in late April.

R1401 had some internal modifications in the light of the increase in operating speed, although at Le Mans Hill reported that he was still developing a definitive LM P1 specification. "We have to retain the same 94 mm bore as we simply do not have room for a larger dimension but we have managed to squeeze in slightly larger intake valves. We also redesigned the piston/rod package for the higher operating speed. So far the compression ratio is still the same as for the R9, while valve lift is similar."

The upshot was a car able to outrun one of the Audi turbodiesels in qualifying. But that was as much to do with the Lola’s aero package as with the engine. Hill admits that he would happily trade the air restrictor advantage of this stock block engine, worth at best 30 bhp at the top end, for the opportunity to create a brand new gasoline race engine as the basis of a superior all-round car package.

Added to the database on 26^th August 2008