Taurus Sports’ Diesel V10
Interview With Dave Smith of Caterpillar
The concept of a diesel-powered sports prototype racing car has been under consideration by number of manufacturers for the past couple of years, but to date only the Norfolk, England based Taurus Sports team has actually built and raced such a car. The UK division of the American specialist diesel company Caterpillar has been a key partner in the Taurus project. Alan Lis spoke to CAT UK’s race engine project leader Dave Smith (right) about its involvement.

How did Caterpillar become involved in this programme?
“Ian Dawson of Taurus Sports approached Caterpillar UK at the end of 2003. He’d been looking for someone to do a diesel project with and had been to a number of agencies looking at the possibility of having a special engine designed and built. I think he came to the conclusion that a project like that would cost many millions of pounds because of the required investment in tooling. He came to us with the idea of using a road car engine as the basis of a project and converting it to a race specification. We liked that idea and it was at a level at which we could participate in the project for a fairly modest investment, in motorsport terms. We came up with this conversion of the Volkswagen Touareg V10 in which we’ve taken a basic road car engine and extensively modified it for racing.”

What is your role in the project?
“The project has been conducted with a very small group of engineers, of which I am the project leader: I’ve directed the developments associated with the combustion and fuel systems and the application of the engine to the car. I have a designer, Brian Payne, at our base in Peterborough who assisted with some of that work. James Reed is a development engineer who has been responsible for all of the calibration work on the dyno., with Mountune, who were contracted to do the engine building and dyno testing. That was because we didn’t have the resources to spare in Peterborough to do that work ourselves. Also Ian had brought Mountune into the project at the beginning as his preferred engine supplier. They have a huge amount of racing experience and have contributed greatly to the project, with things like procurement and the design of the dry-sump engine oil system. I guess we would have struggled with that, so in that respect they have been more of a partner than a supplier.

“Erik Olsen at Peterborough looks after the electronics and has worked closely with our partner Pi Research, whose Pectel division has taken Caterpillar algorithms for the electronics controller and actively provided hardware in terms of using our control technology. This is the first diesel engine project that Mountune and Pi have been involved in.”

What is the basic configuration of the engine and how has it been altered for racing?
“It’s a 5-litre turbocharged V10 with aluminium block and heads and an iron insert around where the crankshaft is mounted, to add strength in that area. Bear in mind that as a race engine it runs with cylinder pressures approaching 210 bar and fuel injection pressures of up to 2300 bar. So there are huge loads in the engine when it’s running and it stands up to them very well. The lubrication system has been converted to a dry sump, the pistons and other parts are different to allow us to run a lower compression ratio. The fuel system has been changed because of the feed required and that means different injectors. The crankshaft system is different, the balance shafts used in the road engine have been removed to take weight out of the engine. From there the rest of the work has largely been down to Ian in terms of adapting a racecar chassis to accept a diesel engine, which is significantly different. That required working with the transmission manufacturer because the torque from the engine is huge. On the dyno we’ve seen torque figures of up to 1200Nm, which is far in excess of what a standard racing transmission can handle. At Le Mans we ran the engine with just over 1000Nm of torque and about 530bhp.”

What advantages does a diesel race engine offer?
“The benefits of a diesel engine that one would traditionally expect – fuel economy and reliability. At Le Mans our expectation was that we would see a similar differential in economy between petrol and diesel cars on the road, in the order of 25%. So if the Audis with an 80-litre tank needed to refuel at 12 laps we were expecting 15-16 laps. Although our car was slower we were hoping for a tortoise and hare situation to develop as we made fewer pit stops. Having said that our expectations at that early stage of development were modest. A race finish was our primary target, to demonstrate the durability of the engine, but bearing in mind that the project only really started in January 2004, to get into the race at all was a huge achievement.”

What do you see as the future potential for this engine?
“Like all Le Mans Series engines we have to run with an air restrictor, but potentially we think this engine could generate about 600bhp, although not with the current fuel injection system. At the moment the dynamics of the injection system mean that we also have to run to self-imposed rev limit of just over 5000rpm. We’d like to get that up to 6000rpm if we can and doing that will require a new cylinder head and fuel system. That’s a development that could be done in time for 2005.

“Changing the cylinder head and fuel system will also help us address the weight of the engine. The car is significantly over the minimum weight limit with this engine installed. We can get some weight out of the engine but some will also have to come out of the chassis if we are to get anywhere near the limit. The engine weighs 190kgs before adding the turbo system: with all that plumbing it’s over 200kgs, which is heavy. It’s very beefy in the top end because of the current injection system and that’s what is limiting us at the moment. We can’t move this big heavy weight around at high RPM. There are things that we could do centred around changing to our own injection system and that could quite easily get 40kg out of the engine. That would mean a new head and a new drive train. Currently the camshafts are driven from the back of the engine by a fairly hefty gear train. We’d like to remove that and replace it with a chain drive. The crankshaft is very heavy and the top end of the engine is very heavy because of the high pressures. The base engine is engineered for road and off-road applications, not for racing. We would also like to go to a common rail fuel system driven by a simple high-pressure pump, with smaller and lighter electronically controlled injectors fed by the common rail. At the moment the system uses a mechanically driven electronic injectors.

“Another problem we need to look at is refueling the car. When you fill a car up with diesel the fuel froths quite significantly. We’ve talked to the ACO about adding some kind of anti-foaming agent, but that has not yet been resolved. Our concern is that we won’t be able to get the tank completely filled, which would have an obvious effect on our potential mileage per tank of fuel in race conditions. At the Silverstone race, where we had that problem, we should have been able to do 40 laps per stint based on measured fuel consumption in practice sessions, 12 more than the Audis. Our best run was 32 laps so we know there’s more to come.”

Will you also need to make changes to the transmission?
“The Hewland gearbox ratios available as standard are too long for use with diesel engine. That creates problems getting the car out of the pits from standstill and puts a heavy load on the clutch, as it slips a lot. Having said that the clutch problems we had at Le Mans have already been resolved. AP Racing has built us a new carbon clutch rated at 1700Nm and is working on another rated at 2200Nm.

“The engine runs at effectively half the speed of a petrol engine like the Judd V10, so there is a step down of about 2:1 to get the gearbox running at the right speed. For the same power there is a doubling in the torque and obviously that gives the gearbox bearings and gears themselves a hard time. The situation we are most worried about is during a gear change, where you have to get rid of the inertia of the engine in a gearshift as the speed comes down. That is translated into additional torque in the form of spikes that go through the transmission. We haven’t had a failure yet but that’s probably our biggest concern.

“The gearbox is a six-speed but from looking at the car data we think we could quite happily go with five gears. Reducing the number of gears might allow us to have stronger gears, which would be an obvious benefit. That again is a development for 2005, it’s not a quick fix.

“Having Caterpillar electronics on the engine has also been a big help with the transmission. We’ve used algorithms that have been extensively developed for truck and automotive engines that we’ve been involved with. We’ve taken complete control of the engine and we’ve got communication with the transmission so we can, for example, have different torque curves in different gears. That allows us to protect against some of the weaknesses in the transmission. During gearshifts we also slightly cut the fuel to make shifts smoother and to ease the general loading on the transmission.

“We are also looking at the shift system itself. At the moment it’s a sequential manual shift, but we think a paddle shift system could help to reduce the impact of gear shifting on the clutch and the rest of the transmission. The torque and power characteristics of the diesel engine mean that great precision is needed in gear shifting due to the narrow rev window, and making all or part the process automated should be a benefit. We’ve looked at the Piper system, but we’re also thinking about doing our own. CAT has solenoids powerful enough to shift the gears.”

Is this project Caterpillar’s first involvement in motorsport?
“No, in the past CAT has been involved in the European Truck Racing Series and actually won the championship, before withdrawing to concentrate on production programmes. Caterpillar is also active as a sponsor in NASCAR in the USA.”

Is Caterpillar’s expertise directly applicable to a racing programme?
“Caterpillar’s background is in making earth moving machinery but they also make engines for all their own machines and also for third parties, particularly truck manufacturers in the USA. In recent years they have led the way in America in truck engines because of the very stringent exhaust emission regulations that are being introduced there. CAT went away from the development route being followed by the other manufacturers and introduced new combustion technologies to their engines. This is called ACERT® Technology (Advanced Combustion & Emissions Related Technology) that involves a number things like turbocharger design, combustion chamber design and fuel injection strategies. These allow the engines that CAT produce to pass the US EPA emissions regulations and also provide advantages in fuel economy. Aspects of the ACERT development programme would be applicable to a racing programme. They are not currently being used but if we develop the engine further and apply a Caterpillar fuel system to it, we could take advantage of some of that technology. It would not be for exhaust emissions we would be concentrating on fuel economy. The same principles could be used to derive that benefit.”