Taurus Sports’ Diesel V10
Interview With Dave Smith of Caterpillar
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
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.”
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
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.”
is the basic configuration of the engine and how has it been altered
“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.”
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.”
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.
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.
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.”
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
“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.
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.”
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.”
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.”