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Audi R18 TDI – Click above for high-res image gallery

Take a look at the beast that is the new Audi R18 TDI and you'd be forgiven for assuming it has a big, rip-roarin' V10 with at least two turbochargers. Right? Wrong. Although the previous R15 TDI packed in ten oil-burning cylinders, new regulations – implemented to diminish the advantage the last generation of diesel-powered Le Mans Prototypes over their gasoline-burning competitors – forced Audi to go with a single-turbo V6 for the new R18. That didn't stop Audi from finding some unique ways to make the best of the new engine regs.

For starters, the engine block is made of aluminum – still a rarity for high-compression diesel engines, even after Mercedes-Benz introduced their design some six years ago. Audi also opened up the angle between the cylinder banks to 120 degrees, giving it a lower center of gravity approaching that of a boxer engine, and relocated the exhaust manifolds from port and starboard to a single unit nestled inside the wide V.

The result is a 3.7-liter turbo-diesel V6 that produces over 540 horsepower. The smaller form factor also allowed Audi Sport to optimize the aerodynamics, while its lower weight allowed the engineers to beef up other components. As for a regenerative braking system like its chief rival Peugeot runs (and like those employed in Formula 1), Audi says it is keeping the door open to the idea as development continues, but has yet to implement any such system. Follow the jump to read more about the engine specifically designed for Audi's latest prototype racer in the full press release.



[Source: Audi]
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UNIQUE TDI ENGINE FOR THE AUDI R18 TDI

- Only six weeks to go before the 24 Hours of Le Mans
- Compact V6 TDI power unit with single turbocharger
- Exhaust manifold and VTG sit between cylinder banks

Ingolstadt, April 28, 2011 - The new Audi R18 TDI with which Audi targets its tenth victory in the famous 24 Hours of Le Mans on June 11/12 is ready today with "tomorrow's" technology. During development of the new LMP1 sports car the integration and future electrification of the powertrain and various possible concepts for energy recuperation have been taken into account.

"We are very conscious of such systems," explains Head of Audi Motorsport Dr. Wolfgang Ullrich. "In our opinion, just as soon as this technology proves to be the most efficient we will use it at Le Mans."

Although diesel engines have been repeatedly restricted by the regulations since their victorious introduction in 2006, Audi relies on TDI power once again for its new LMP1. "Audi invented the TDI engine and is convinced that this technology remains one of the most efficient and modern forms to power a car - especially at Le Mans where engines with high specific power, low fuel consumption and low emissions are a necessity."

New regulations devised by the Automobile Club de L'Ouest (ACO) and introduced this year dictate significantly smaller engines. Audi has chosen a particularly compact 3.7 liter V6 TDI engine, which is about 25 per cent lighter than the V10 TDI power plant previously fitted to the older R15 TDI, and which leaves all options open for the technicians with regard to electrification and energy recuperation. "This would not be the case with a V8, for example, which is also permitted by the regulations," explains Ulrich Baretzky, Head of Engine Development at Audi Sport.

However, Audi does not only surprise with its extremely compact engine. The concept is also innovative for an LMP1 sports car. To lower the center of gravity as much as possible and to improve airflow through the car, the exhaust manifolds were migrated from the left and right hand sides of the engine to sit between the two cylinder banks. "Hot side inside" is the name given to this concept by specialists, which was implemented in similar form in Formula 1 in the 1980s. But the V6 TDI engine powering the Audi R18 TDI, which has a cylinder angle of 120 degrees and thus an extremely low center of gravity, is technically generations further along the line and is also a technology-demonstrator for future production engines.

In contrast to previous Audi Le Mans sports cars, which all had twin turbochargers, the R18 TDI is quite logically now only fitted with a single turbocharger that also sits above the engine and draws its air directly through the air scoop mounted on the roof. "In this way we are able to convert the dynamic pressure generated at high speeds with minimal losses into power," explains Dr. Martin Mühlmeier, Head of Technology at Audi Sport.

The mono-turbo concept developed in cooperation with Garrett was only made possible by the variable turbine geometry (VTG) already used victoriously in the R15 TDI. "Otherwise the response characteristics of such a large turbocharger would just be too bad," explains Baretzky.

The concept was continued logically through a single pipe exhaust that exits at the rear of the R18 TDI below the new fin which is stipulated by the regulations. "This also stands for Audi ultra lightweight technology," says Baretzky, "since we save components and weight - for example for a second diesel particle filter."

Audi Sport has worked since July 2009 on the innovative engine concept for which numerous new routes had to be explored. To control the enormous ignition pressures and loads now only distributed between six cylinders, a unique method of cooling the cylinder heads was developed for the aluminum power unit, a concept that could also be interesting in the future for production.

Owing to the compact engine and uncluttered flanks, the airflow from the coolers can now exit practically unobstructed through the rear end. "We could increase the aerodynamic efficiency of the car as a result," says Martin Mühlmeier, Head of Technology at Audi Sport. This aspect is even more important than ever before at Le Mans due to the reduction in engine power - for the Audi R18 TDI more than 397 kW (540 hp).

Another unique aspect of the new Le Mans sports car is its unusual sound. The Audi R18 TDI is probably the quietest race car Audi Sport has ever built. "Noise is unused energy," stresses Dr. Wolfgang Ullrich who is delighted by the whispering murmur of the R18 TDI. "The sound is unique," raves Le Mans record winner Tom Kristensen. "It's hard to describe. You have to hear it yourself. I think it's fantastic."


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    • 1 Second Ago
  • 17 Comments
      QAZZY
      • 4 Years Ago
      Next step: use carbon fiber to lighten up the R8, and drop this diesel in it. Sure it's more expensive, but it could compete with Ferraris (540hp is Ferrari territory, and all that torque is killer, when coupled with AWD). A V6 would hopefully leave more room for a transmission that can handle the torque.
        mathiaswegner
        • 4 Years Ago
        @QAZZY
        That would be hilarious! I can just picture taking an R8 TDI on a road trip and pulling up to the diesel pumps at a truck stop with all the big rigs.
      Jim
      • 4 Years Ago
      IIRC the 120-degree vee angle also lets them have opposing cylinders share a crankpin (like a V8) so the crankshaft should be a lot stronger than one for a 60-degree engine.
      seanleeforever
      • 4 Years Ago
      i simply don't understand if Diesel is that much advanced than Gas, why would Diesel need any assist in Le Mans race? i know audi wins Le Mans like no tomorrow, but i honestly think that's a bunch of bogus. look at Le Mans regulation: gasoline racing engines limited to 3.4 liters normally aspirated gasoline racing engines limited to 2.0 liters turbocharged Diesel racing engines limited to 3.7 liters turbocharged (and allows much higher boost than gas) i mean what? you might as well just say: my turbo charged 7.0 engine beats your stock Honda accord in a straight line. yes, so what? unless they even out the playing field, diesel is forever inferior than gas in my mind. but i understand European's obsession about diesel, since they tend to suck in electronic department, they never openly admit the advantage of Hybrid and keep saying how diesel is superior, even if it means they have to bend the rule. this is just low, LOW.
        Gmoney
        • 4 Years Ago
        @seanleeforever
        As you can see from your own data different engines produce different amount of horsepower per liter. The ACO has decided that a turbo gas engien will be limited to 2 liters while a NA aspirated gas engine will be limited to 3.4 liters because they think that ( with appropriate restrictors) both engines will produce equal amount of horsepowwer. This is how the ACO rules work, hence their decision to provide the diesel the 3.7 liter allowance. The ACO also provides pushrod engines a larger restrictor to have those engines provide the same horsepowewr output as engines with DOHC valvetrain.
        benzaholic
        • 4 Years Ago
        @seanleeforever
        I can only assume that Audi/VW have some significant influence in Le Mans the way Ferrari has in Formula1. It sure does seem like they were able to influence the regulations such that diesels have an advantage. Sure was funny when Peugeot saw the opportunity and jumped into that game. Diesels can't rev as high as gasoline engines (I think it's related to the burn speed difference between the fuels), so that may be a reasonable justification for the odd engine size limits. Different drivetrains have different strengths and weaknesses. Gasoline has the best established distribution infrastructure, and a gas-engined car may not be the best in all areas, but is generally productive in all situations. Diesels tend to have a distinct advantage for highway cruising or for towing. Current hybrids tend to show their advantage in stop-and-go or city driving. It's not just a simple matter of comparing horsepower. One should consider the types of driving they will do in order to make the most appropriate choice of vehicle and drivetrain. Then go buy a slightly used Corvette and be done with it.
        Mark Stearns 
        • 4 Years Ago
        @seanleeforever
        @sean so you really don't like diesel. but you can't deny that it's good for race cars. it's been raced for ages and winning. example Gail Banks ( http://www.bankspower.com/home ) What you call unfair is a change..... but I don't mind it. And the Peugeot team went to diesel to compete with Audi and the racing has been awesome. Speaking of changes, you wanna outlaw the hybrid Porsche? Ease up and enjoy the racing.
        QAZZY
        • 4 Years Ago
        @seanleeforever
        I don't see how electric (hybrid) > diesel. Diesel has the advantage of more torque, and power. Electric aren't great in a racing environment, but they're great in the city.
        Felspawn
        • 4 Years Ago
        @seanleeforever
        Diesel doesnt need assistance...... gas powered competitors do.
        seanleeforever
        • 4 Years Ago
        @seanleeforever
        Felspawn then why don't you look at the Le Mans regulation and then tell me how MUCH advantage is giving to diesel? turbo to turbo, Diesel engine are allowed to be 85% larger than gas counter part (not to mention higher boost) gas power competition need assist? if anything, they just need to play in the even ground. but no, because that will TOTALLY demolish diesel's existence in Le Mans. and since the purpose of Le Mans is to create image of "advanced diesel" to sell cars, this will never happen. diesel simply sucks in any high performance category (with exception of mileage, which is proven to be inferior than gas hybrid). they need a freaking 85% advantage to win, which is implying they are only 40% capable as advanced gas engine.
          LEDfoot
          • 4 Years Ago
          @seanleeforever
          Ok now you're just grasping "facts" out of thin air... gas-hybrids have been _proven_ to have better mileage than TDi? Back it up? The only thing gas-electrics have proven is that the technology can't live up to it's hype. If the tech is that great, then why doesn't Toyota put it's money where it's mouth is and field a factory ges-electric hybrid LMP1 car? Oh yeah, because it would lose to the GT3 cars that's why.
        Johnny-wat
        • 4 Years Ago
        @seanleeforever
        Diesel engines tend to give out better torque. As Carrol Shelby once said, "Horsepower sells cars, torque wins races."
        seanleeforever
        • 4 Years Ago
        @seanleeforever
        sure thing Gmoney, if fair is what you claim. (by the way, those are not my data, those are regulation) so diesel need larger displace to match gas HP. and therefore justified for its 85% larger displace in the Le Mans. how about torque? how much L of NA gas engine required to match the torque a turbo boosted 3.7L diesels produces? OH NOOOO. we cannot possibly give those gas bastard any advantage, so let be selectively blind here. how about weight? oh NOO, let's increase minimum weight to negate ANY advantage gas engine has remaining. if this is what you call fair, you might as well believing it is fair to put a heavy weight boxer and a light weight boxer on the same stage, because, you know, they have the same height.
          Redline
          • 4 Years Ago
          @seanleeforever
          Oh man I'm so with you on this one. People say how well diesel is doing in Le Mans (Peugeot fan here btw) but diesel basically gets the advantage over the petrol cars with the regulations.
        Rotation
        • 4 Years Ago
        @seanleeforever
        The European companies clearly wish to push Diesel, so they lobbied to get advantages for Diesel so it could compete. The only weird part is that the ACO bought into it. Much higher displacement allowed. Much higher turbo boost allowed. Much larger restrictors specified. And the disparity used to be even larger, and Diesel engines were allowed fuel cells with much more energy. Thankfully the differences have been toned down a bit. But still, it is very sad that the ACO thinks it is acceptable to make rules that favor a technology for which there are no openly available engines (only werks engines) and then only from European companies.
        LEDfoot
        • 4 Years Ago
        @seanleeforever
        Have you ever driven a diesel engine? Typically they are much, much heavier than a gasoline engine. They also have a slow rotational speed, and are slow to change rotational speeds (i.e. accelerate). The regulations were made to allow for that and allow diesels to be competitive. If you remember when Audi first brought the R10 everybody was laughing at them bringing a diesel engine to a race. No one was laughing after the race and ever since the regulations for diesels have become more and more restricted in attempts to level the playing field between gas and diesel engines. However as performance gasoline engines seems to have reached a level where huge improvements are no longer to be had through technology, the same has not been true for diesels and you have to admit that there have been huge advances in this technology in the last few years. Just look at this small v6 diesel compared to the v12-lump they brought in the R10, they had to extend the wheelbase and make the car much heavier just to support the size and weight of the engine in the R10, that in itself was a huge penalty compared to gasoline engines. So if your hybrids are that great, why has no one brought one and swept the floor with the rest of the competitors? Truth is hybrids are pointless, on the road and on the racetrack. Batteries just aren't efficient enough and despite all the money and research going into better technology it just doesn't seem to be any big improvements to be had. The KERS system used in F1 has a very small energy storage because anything bigger would just be too heavy. The weight of the system just severely outweighs (pun intended) the minuscule benefits. As far as Europeans not understanding hybrid technology, did you know that the first (probably) hybrid vehicles was built by Ferdinand Porsche in 1899. Did you know that Audi had prototype hybrid vehicles in 1989? However the cost outweighed the benefits and they remained a concept. Not until it was realized that the US EPA fuel efficiency cycle could be totally gamed by hybrid vehicles, severely over inflating their actual performance numbers did these vehicles begin to sell. Though to this day they continue to sell on totally false premises.
      dukeisduke
      • 4 Years Ago
      That Ulrich Baretsky is a genius at engine design.
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