Today Ulrich Baretzky, Audi Sport’s head of engine technology, retires from his post after over 30 years with the company, a stint that has seen success in Trans Am, DTM, and in unprecedented fashion, at Le Mans.
Whilst his days designing and fettling the 5 cylinder and 8 cylinder petrol engines that scored multiple successes for the marque brought huge success, for many the project that defines him within the Audi sporting legend was the move to diesel technology in the R10 TDI.
Back in 2007 Alan Lis spoke with Ulrich Baretzky about the TDI V12 engine that powered the R10, we reprint that interview here in tribute to a man who has done more than most to shape modern sportscar racing:
How did the diesel race engine project begin?
“The TDI V12 race engine ran on the dyno for the first time in mid-May 2005, but early exploratory tests were carried out using road car diesel engines from the Audi product range. The engine we used was a 3.7-litre version of the 4-litre TDI V8 road engine. Of course, the V12 engine is more powerful and efficient but with the 3.7 litre V8, we were able to achieve performance good enough to help us in the early stages of the diesel race engine programme. Among other things, these tests helped to establish the bore: stroke ratio for the V12 race engine.
“It proved to be a very cost-effective way to begin our development work and we ended up running the 3.7-litre V8 engine for more than 800 hours on the test bench. That’s impressive compared to a high-performance gasoline engine that would fail well before 800 hours.”
What were the main challenges of the diesel race engine programme?
“Packaging the V12 engine in the R10 chassis was a real challenge, but we knew about this already from the R8 which was also a turbocharged car. It’s always a compromise in terms of the cooling requirement, weight and aerodynamics. When everything is packaged very tightly it makes it a nightmare for the mechanics, because there is no room to work. That puts the onus on the engine designers and engineers to make a faultless and reliable engine. The moment you have to repair it you have lost.
“Another unusual aspect of the engine that was a surprise to us, and I’m sure it will have been a surprise to Peugeot too, is that the diesel race engine requires about 30% more cooling than the gasoline V8 engine used in the R8. The received wisdom is that a diesel engine is very efficient and it most ways it is, but it nevertheless needs more cooling, which compromises the car package.
“There was also the important issue with the R10 of racing a diesel-engined car without generating smoke. At the rear of the car, we have particulate filters supplied by Dow Automotive.
“We used production filters for the early testing of the R10, but they were very large and very heavy, so we were very happy to find a partner like Dow that was able to come up with new technology to create new ceramic filters with good porosity. This meant that they could be very compact. They are only about 130mm (5in) long and about 90mm (3.5in) high. Being able to make the filters small was important because they were in a location where they would block the flow of heat out of the engine bay if they were too large.
“The particulate filters are a fully self-contained system. The only real difference between the ones we use for racing and those used in a production car is that there is no regeneration system because it’s not necessary. The engine does not run at idle and there is no stop-start driving, as you would have in a city. The race engine runs pretty much constantly at full load and this helps to regenerate the filter. When the driver backs off the throttle there is a lot of oxygen in the filter, which helps to burn out the soot, and when he goes back on the throttle the process is complete. The filters generate a lot of heat and during the night at Le Mans, you could see them glowing at the back of the cars as they went by.
“Another reason we were happy to use the Dow filters was the lower back pressure they generated in the exhaust system. Compared to a conventional Silesium filter, the backpressure was 50% lower. The Dow filter technology is a development that we hope will find its way onto Audi road cars in the near future.
“In addition to being completely reliable, we have not had a single problem with them up to now, they also work very well. At the end of the race at Le Mans, I wiped the exhaust of the winning car with a paper towel and it was absolutely clean.”
Being a turbocharged diesel engine, the loads and pressures that the TDI is subjected to for racing must also have been a challenge?
“Yes of course, and because of the loads and pressures that it must withstand, the TDI race engine must be very compact and very stiff – at least as stiff as the R8 engine, and of course the TDI has four more cylinders. We had to do some very hard work to achieve the required stiffness without compromising the weight of the engine. We set a target weight of 260kg or lower.
“By way of comparison, combustion pressure in a highly loaded gasoline-fuelled engine reaches something like 140 bar, in our TDI engine, it is over 200 bar.
In the past diesel road car engines have been relatively simplistic in terms of electronics. I assume that this is not the case with the V12 race engine?
“Not at all. Today electronics are a very important issue for diesel engines. In the old days, you didn’t need anything apart from a starter: when the engine heated up it could run without any electrical input. This has all changed dramatically. For today’s high-performance diesel engines you need a lot of electronics.
“On the sides of the race engine, we have gathered all the connection points for the sensors in single boxes, in order to make it easy to change something if it’s failing. As you can imagine, the wiring loom for the TDI V12 engine is very complex. The electrical supply for the injectors is completely separate from the rest of the electrical system because the injectors need a high level of current as they are required to react very quickly.
“The Bosch ECU was specially developed for the TDI V12. There are a lot of existing ECUs for diesel engines and race engines, but not a combination of the two. We sat down with Bosch to work out a good compromise of what is needed for a diesel engine and what is needed for a race engine. The MS14 is what we came up with.
“The engine is equipped with Piezo electronic inline injectors supplied by Bosch, who also supply the common rail fuel system and the hydraulic system. Before they were used on the TDI V12, Piezo inline injectors had only been used up to a pressure of 1600 bar in a road car. We have successfully used them at 2000 bar and they will be used in this way in Audi road car engines in 2007. Of course, we have already taken another step with the race engine in this area.”
“The alternator is driven by a vee belt by the gear train, and that takes its power from the crankshaft. This allows damping between the engine and alternator. The starter is also a very important part and is mounted in a location on the engine that allows it to be changed, through a hole in the undertray of the car, in about 30 seconds. This is necessary because you are not allowed to push start a car at Le Mans, it must start under its own power.”
Did the TDI V12 require a new design of turbocharger or were you able to use the same system from the R8 engine?
“The turbochargers are a special development we made with Garrett, which has been our turbocharger partner for the past eight years. To date, we have never had a turbo failure, which is remarkable given how highly they are stressed.
“The wastegate is very simple and is pneumatically controlled, there are no electronics in the system. You will note that the exhaust system has insulation on it but this is not to protect the rest of the car from the heat. We try to keep the heat energy in the system to keep the turbines spinning in the turbochargers. You need to capture as much energy as you can, but a diesel exhaust system cools down very quickly, hence the insulation.
“From the R8 we knew that the snorkel air intakes for the turbochargers were a benefit, because the pressure created inside them gave better filling of the inlet than you would have from a normal turbocharger without a snorkel. From the snorkel, the air goes through a filter and into the compressor stage of the turbocharger. When the air leaves the compressor its temperature has risen to more than 200 deg C and has to be cooled down in the intercooler before it enters the plenum. The plenums on the R10 are made from carbon fibre and I was surprised how light they were and yet they were still able to handle pressures of 2.94 bar. We tried to make the air package very short to avoid having dead volume in the plenum. That was done to minimise the turbo lag and improve the responsiveness of the engine. Of course, there is still a small amount of throttle lag in the system because it will always take a little time to fill up the volume of the plenum.”
One of the biggest challenges that the Taurus Sport team found with their diesel engine in 2004 was with the transmission’s ability to handle the greatly increased torque. Evidently this has been resolved by Audi Sport?
“Yes, diesel road cars tend to have a turbo boost limit to avoid damaging the gearbox, whereas with the race engine we are able to make as much torque as is required to achieve the performance we want to have and that the gearbox can stand. In fact, we were able to use a clutchless power shift system with the diesel engine – and I was personally very surprised that we were able to improve on the shifting times that we had achieved with the FSI V8 engine by about 30%. If you imagine the inertia in the masses that are turning inside a diesel engine, it is hard to conceive that gear shifting could even be done as quickly as with the R8, let alone faster. With 15,800 gearshifts during the race at Le Mans, it adds up to a benefit that can be counted in minutes.”
How does the R10 compare with the R8 in fuel consumption?
“In terms of lap time, the 2006 R10 TDI and the 2002 R8 FSI are nearly the same – around 3m 30s whereas the consumption of the TDI is improved by around 10%, even taking into consideration that the length of the track has increased, that the R10 is 25kg heavier than the R8 and that the changes to the aerodynamic regulations on safety grounds have resulted in a much lower cD.
“Nevertheless the R10 reached a top speed of 330km/h and a lap time of 3m 30s with this improved consumption. If we had the same aerodynamics as in 2002 the figures would be even better. The absolute consumption figure that the R10 achieved during the race at Le Mans was 41 litres per 100 kilometres, that’s a figure that can be compared with a high consumption road car such as a 4×4. In a racecar lapping Le Mans at 3m 30s, it’s impressive.
“We ended up with an advantage of 2-3 laps over the best gasoline-engined cars. The longest run by a gasoline car on a tank full of fuel was 13 laps, we could do 14-15 laps without a risk and during the race, Kristensen managed one run of 16 laps, on a 90-litre tank of diesel. Of course, this will change for 2007.”
One of the most striking aspects of the R10 TDI is that you can hardly hear it when it’s running on the track. Some people have said that quiet cars are not spectacular. What is your opinion?
“Personally I hope this is the future of motorsport. Some people complained about the reduced noise, saying that it’s boring if racing isn’t noisy. If a race is thrilling only because of the noise, then that’s a shame because I think the show is wrong.
“Noise is also a form of energy and we wanted to avoid wasting it. We already made progress in that area with the R8 with the high-efficiency turbocharger system that we used on that car. The R10 is a quiet car because it also has a high-efficiency turbocharger system that absorbs most of the energy coming out of the exhaust.
“In a race, you will only hear an R10 it if it’s alone, as soon as there are other cars nearby you don’t hear it at all. We haven’t actually measured the noise level but we think it is below 100db. That’s important because in 2007 the ACO has said that it will require the cars racing at Le Mans to pass a noise test. Any car over 113db will be excluded. To reach that some cars will need a silencer system and that will cut performance.
“You could drive the R10 through the streets of London and no one would turn his head because of the noise.”
A lot of people believe that the fuel that Audi used at Le Mans was a special fuel. Is that a fair comment?
“In that, we used it in a racing engine it was a special fuel, but it is within the EU norm for diesel fuel. The most important aspect of the fuel for Audi and for Shell, who supplied it, is that a significant part of the fuel is made by the Gas to Liquid (GTL) process. This produces a synthetic diesel fuel that is made from the natural gas that occurs in oil fields and that in the past was just burned off. Now it is collected and transformed into liquid by the Fischer-Tropsch process. The end product looks like water, is completely odourless and burns very cleanly, almost without smoke. The fuel we use in the R10 has a GTL content of 20-30%.
“We want to use the R10 programme to develop combustion technology for a future target for us in the VW Audi Group, which is to go a step beyond oil and gas-based fuels. As soon as possible we would like to use Biomass to Liquid (BTL) fuel. That means that we will be using synthetic fuels made from renewable sources. The best part is that the transformation process can be CO2 neutral. All of the C02 absorbed by the plant is burned. That’s environmentally friendly motorsport and we hope to introduce BTL fuel in 2008.
“Some people in Formula One have are finally waking up to the fact that you can’t waste energy, time and money like hell, just to go quickly round in circles. You need to take care of what the planet needs and what it needs are really efficient engines – not engines that run at 20,000rpm. In motorsport, we need to make reasonable use of resources, not waste them. We are trying to show that this can be done with the R10 programme.”