• Nov 17th 2007 at 11:10AM
  • 21

While browsing the 2007 Los Angeles Auto Show we discovered Audi's 5.2L V10 FSI engine in all its 450 hp glory. It was perched on a stand in the Audi booth mated to a six-speed Tiptronic automatic transmission, and was strategically displayed amongst the S6 and S8 sedans, which it powers. We remembered reading about this engine in the January 2007 issue of SAE's Automotive Engineering International, so we dug it out to give you a rundown of its specifications. The first thing that must be pointed out is that contrary to popular belief, this engine is entirely different from the V10 used by the Lamborghini Gallardo. The Lambo engine was designed for high RPMs, while the S6/S8 V10 was put together for high torque and fuel economy.

The 5.2L V10 is built for two different outputs between the S6 and the S8 applications. The S6 receives a version that puts down 435 hp at 7000 rpm and churns out 398 ft-lbs of torque, while the S8's creates 450 hp at 6800 rpm and also produces 398 ft-lbs of torque. The varying power numbers are achieved through both its exhaust design and tuning, and the differences in output equate to relatively similar power-to-weight ratios for both cars. Follow the jump for a detailed look at the display engine along with Audi's own renderings.

The key feature that makes Audi's 5.2L V10 engine different than others is the integration of FSI technology. FSI is Audi's name for its direct injection fuel delivery system, and Audi is the first manufacturer to utilize this system in a ten-cylinder engine. In the close-up image of the engine cutaway, the injector can be seen extending into the combustion chamber on its left side. By injecting the fuel directly into the combustion chamber (as opposed to the intake runner) at an extremely high pressure, the fuel exits the injector nozzle as a vapor. This allows for increased fuel-air mixing in the chamber and thus, a more complete burn. The engine can operate at a leaner air-fuel mixture, around stoichiometric, safely without the occurrence of detonation. Fuel economy is increased and the compression ratio can safely be bumped up to 12.5:1 allowing for maximum power output.

On the backside of the engine, the timing chain drive is viewable through clear coverings. Chains are becoming common for coordination of timing as they are more wear-resistant than belts. They also don't stretch or slip which is a critical feature in order to maintain an engine tuned to meet tight emissions and performance standards. Four white cam gears are also noticeable on the engine's rear. They are hydraulically operated to continuously adjust the camshaft phase altering valve timing throughout the engine's rpm range and load conditions. This allows for the optimization of airflow into and out of the combustion chamber.

The engine also incorporates a variable runner intake manifold. Electronically controlled flaps disrupt the airflow at low engine speeds, thus ensuring the flow is turbulent. This increases volumetric efficiency as it sends more air to the combustion chamber. The intake manifold also has multiple stages. An electronically controlled valve switches the intake paths from a longer (26.6 in) to a shorter path (12.1 in). This switchover is dependent on engine speed and load, but is typically somewhere around 4,000 rpm. The longer intake path is intended to emphasis the engine's torque, while the shorter path is used reach maximum power output.

The materials used are as important as the engine design itself, so the 5.2L V10 is not without Audi's impeccable attention to detail in the materials selected for its casings, internal and external components. The crankcase is a die-casted hypereutectic aluminum alloy. Hypereutectic aluminum alloys have lower rates of undesirable thermal expansion. Also to assist in reducing expansion, grey iron bearing bridges are cast into the crankcase. They double as an aid in maintaining critical crankshaft bearing clearances by diminishing deflection under stress. Mated to the crankshaft are forged steel connecting rods and oil cooled aluminum pistons. Other notable material choices are found in the sodium-filled exhaust valves and magnesium intake manifold. The sodium melts in the heat of the combustion chamber and as the valve travels it circulates inside, acting as a heat exchanger between the valve head and the cylinder head. This increases the lifespan of the valves. The use of magnesium in the intake manifold significantly cuts the weight of an otherwise significantly heavy casting. Low weight is important to give the V10 a significant advantage over the W12 configuration.

Audi's 5.2L V10 FSI engine puts together a race-proven package in a roadgoing sedan. It uses many of the most modern and efficient internal combustion engine technologies, and shows the direction where future engine development will be directed -- as long as dino-juice is still around. There are many other design details not even mentioned. Be sure to check out the gallery to get a closer look at the engine internals or click on each image for a better view.

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    • 1 Second Ago
      • 7 Years Ago
      well guenther you might as well be asking what audi did to get 420 hp out of their 4.2L V8 for the RS4 and R8...
      • 7 Years Ago
      I saw a Audi S6 this morning at starbucks..
      When I saw the V10 decal on the side fender I was like WTH? A V10 on a four door sedan does seem like a bit much, but I would love to drive one of those babies.
        • 7 Years Ago
        you're basing that on what?
        • 7 Years Ago
        The 6L LS2 is far smaller, far lighter and far more fuel efficient than this engine. It has a much lower CG too.

        Remember, the 6L is displacement, not a measure of engine size. With the overhead cams and 125% more valves on this car, this engine is far bigger and heavier than a "6L V8".

        I'd love to see this side-by-side with a LS3. There's only 5HP difference between them, but the price and size differential is significant.

        This seems to have the accessory drive belt back at the front end, why the switch from the allroad/RS4 V8 design?
        • 7 Years Ago

        why BMW gets 50hp more from their V10 simple answer.. Audi use the n/a V10 as the second lane engine not the top engine like BMW use the 500hp V10... Audis top of the line is the 5.2l V10 TT with 580hp (underrated) .. the BMW M5 normaly runs only with 400hp and only of you switch into sport mode it offers 500hp.. so the Audi engines has most of the time 50hp more and only if the M5 is set to sport mode it owns the Audi V10
        • 7 Years Ago
        BMW's V10 is bigger than Audi's V10.
        Taller, because of the individual throttles/trumpets
        Wider (if you count the exhaust header)
        Longer: The bore spacing is 98mm for BMW (with 17mm axial offset) vs 90mm for Audi.
        Plus BMW has a dual belt front accessory drive.
        • 7 Years Ago
        As opposed to 6L V8's, right?
        I suppose in this application, "a bit much" is barely enough. What does BMW do so differently to get another 50hp out of their V10 w/o using direct injection?
        • 7 Years Ago
        But is it smaller than BMW's V8, which the LS7 is smaller than? I'm pretty sure the answer is no.
        • 7 Years Ago
        Width of an engine is a non issue. If subaru/porsche can fit boxing engines, then the width of a 90 degree engine isn't a problem for Audi.
        The 90 degree engine reduces height, and audi uses the wider Vee for a dual runner intake manifold (so does MB) Plus new EU pedestrian crash standards require more head/hood space.
        A dry sump could be useful, but audi just loads the engine with something like 9+ quarts of oil (knowing the germans, probably a 40 weight) ,as a hedge.
        The bore spacing is only 90mm here against the 4.4" (about 112mm), so the basic block lengths are basically the same (who has a larger axial offset?)
        So if the total length of the engine is something like 22" versus the 21" of the LS3, big whip.
        Even BMW's inline6s are under 24"
      • 7 Years Ago
      A work of art.
        • 7 Years Ago
        Nah.., where is titanium, they cheapened out.
        LS7 has the upper hand in materials, and is it still wet sump oiled, how outdated. LOL
        • 7 Years Ago
        The don't need titanium to rev to 7000rpm.
        The previous generation A8 W12 had a dry sump.
      • 7 Years Ago
      Am I the only person that thinks it's ridiculous to hang a V10 entirely infront of the front axle?! I'm not saying that the final car won't handle reasonably well, after all Audi just rolled out a spiffy new electronic stability system just to fix this problem. And if electro-nanny wizardry doesn't cure it they could always just add lead ballast over the rear axle like they resorted to doing in the early TTs.

      In my eyes (and admittedly I'm a purist) this is grotesque.
        • 7 Years Ago
        Well Audi did exchange the order of the axle and the torque converter and gained 3" in wheelbase (and 3 inches less overhang), and dropped the weight distribution to 59/41 for the S6
        Now only another 3"
      • 7 Years Ago
      Joshua, the BMW 6 series, has metal quarter panels over the rear wheels. It's used to give the BMW near 50/50 balance. so, it wouldn't surprise me if Audi did something similar.

      • 7 Years Ago
      Holy balls.
      • 7 Years Ago
      What an insane world we live in. When the Easter Islander's looked around after cutting down their last tree, did anyone say, "Oh, that was a bad idea"? So, we are still going to shove insane horsepower cars into the market as we kill off the planet.

      What was the effect of Easter Island changing it's eco-system? 7/8 of the population destroyed. But, we really really Need this V10.

        • 7 Years Ago
        Please get back into your Prius and go away. A few enthusiast cars are not going to destroy the environment.

        Leave us, and our cars alone. You can hug trees in your Prius as much as you want.
        • 7 Years Ago
        especially considering that if you take the whole lifecycle into account (including manufacturing and disposal), most hybrid cars are just as bad, if not worse for the environment and pure petrol/diesel cars.

        Cars aren't the major contributer anyway, it's manufacturing and power plants that are the worst.

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