Audi Introduces New 3.0 TFSI Direct Injection Supercharged Engine
27 June 2008
Audi has introduced a new top end to its V6 engine range: the 213 kW (290 hp) 3.0 TFSI with gasoline direct injection and compressor supercharging. The “T” in the Audi engine designation no longer exclusively denotes turbo versions. The new V6 will go into production later this year.
Audi, which has a long tradition of supercharged engines, said that comparative tests showed that the mechanical supercharger was a superior charging solution to a biturbo concept for the 3.0-liter engine. In conjunction with direct injection, the packaging, starting performance and dynamic response of the supercharger were superior.
The compact compressor—a Roots blower—fits inside the 90-degree V of the cylinder banks, in place of the intake manifold. Because it is driven by the engine via poly-V belt, its full thrust is available from idle speed upwards, producing large amounts of pulling power when driving off. The 3.0 TFSI delivers its maximum 420 Nm (310 lb-ft) at only 2,500 rpm and maintains this constantly until 4,850 rpm.
The compressor features two four-vane rotary pistons counter-rotating at a speed of up to 23,000 rpm, with an air gap between them measuring just a few thousandths of a millimeter. The rotors can deliver 1,000 kg (2,205 lb) of air per hour and force it into the combustion chambers at a boost pressure of up to 0.8 bar.
Two water-to-air intercoolers made from aluminum and connected to a separate coolant circuit are integrated into the housing. Here, the compressed and therefore heated intake air is cooled down again in order to boost its oxygen content for the combustion process. A package of measures reduces the level of noise generated by the compressor to a minimum.
The gas paths after the compressor are very short; torque is built up extremely quickly, even more dynamically than on a naturally aspirated engine of the same displacement.
Gasoline direct injection technology enabled the use of the supercharger. Unlike in conventional applications, GDI allows the compressor to be located behind the throttle valve. With the low density of the intake air at loads below supercharging level and when coasting, the compressor rotors are free-running and the amount of power required to drive them is low.
The engine’s high compression ratio of 10.5:1 also contributes to its efficiency. The direct injection intensively swirls the fuel, cooling the combustion chamber and reducing the tendency to knock.
The crankcase has been adapted to the higher prevailing pressures and all components are frictionally optimized. The two intake camshafts can be adjusted through 42 degrees crankshaft angle. In the intake ports, tumble flaps induce movement in the incoming air to promote optimum mixture preparation.
The injection system is a fundamentally new design. A common rail system with six-hole injectors injects the fuel directly into the combustion chambers at a pressure of up to 150 bar. The injectors’ highly dynamic response permits up to three fuel injections per operating cycle across an extensive range of the characteristic map.
The entire engine, including the compressor, weighs 189 kilograms (417 lb). The bore measures 84.5 millimeters (3.33 in) and the stroke 89.0 millimeters (3.5 in), producing a swept volume of 2,995 cm3.
The pulling power of the 3.0 TFSI enables it to extend the transmission ratio, further augmenting its efficiency. The new 3.0 TFSI will achieve an average fuel consumption of “well under” 10 liters per 100 km (23.5 US mpg) in virtually all longitudinally engined Audi models, the concept for which it is envisaged. It is designed to run on either premium or regular gasoline and already complies with the future emission standard Euro 5.
can we have this as a CNG version? Very cheap fuel and low CO2...
Posted by: John Baldwin | 27 June 2008 at 08:33 AM
funny how they say this engine paradigm is "superior". The BMW N54 reaches peak torque at 1400 rpms as opposed to this Audi V6 which reaches peak torque at 2500 rpms. The N54 is a twin turbo fwiw.
Posted by: GreenPlease | 27 June 2008 at 08:52 AM
I was also wondering in what way it is superior. Turbos often have the torque peak very low in the rev range - is this a design decision to try and mask the turbo lag?
The logic of superchargers is simple: it uses the pistons to power the compressor and the car. The advavtage of turbos escapes me: why is a turbine better for powering the compressor (but not the car)?
Posted by: DavidJ | 27 June 2008 at 10:10 AM
A turbine is better to power a centrifugal supercharger (turbo) because the rpm of the turbo is independent of the rpm of the engine. And a centrifugal supercharger is more efficient than a roots blower.
A turbo also doesn't require a more complicated water to air intercooler.
Posted by: globi | 27 June 2008 at 03:39 PM
"The advantage of turbos escapes me: why is a turbine better for powering the compressor (but not the car)?"
thermodynamically, turbocharging is more efficient because it captures (kinetic) energy that would otherwise be lost in the exhaust gas stream; supercharging robs power directly from the crankshaft.
Posted by: eric | 27 June 2008 at 05:18 PM
As eric says superchargers are basically a parasitic device. For the turbo, however, the kinetic capture he mentions is only part of the story. The turbo is in fact a heat engine in its own right with the ability to extract heat from the exhaust flow. Correctly sized the gas flow should be cooled slightly as it passes through the device. This heat loss on exiting represents the work done by the expansion of the gas on the blades of the impeller.
Now about this engine. This 3.0L engine cannot be considered green in any way and should have no place here at GCC. This is precisely the style of engine that is preventing America from reducing its energy needs from OPEC. I notice the Europeans BMW and Mercedes sending their large engines here because we are dumb enough to allow them. There should be a severe tax surcharge on all V6 engines allowed in - like 50%.
T2
Posted by: T2 | 27 June 2008 at 05:50 PM
On gasoline engine turbocharger is also parasitic device: it increases exhaust backpressure and robs engine efficiency on part throttle. The only moment turbocharger is advantageous on gasoline engine (unlike on diesel, when turbocharger is always advantageous) is on full throttle, but how often and for how long you use full throttle?
There are two ways to extract high power from small displacement gasoline engine:
a) have a turbo- or super- charger and loose some efficiency 99.9% of time (smaller displacement do not compensate for reduced compression ratio and increased back pressure of turbocharged engine). With aggressive valve timing on modern engines both disadvantages are diminishing, but not disappearing completely. This is the way European brands prefer.
b) Have an engine with high RPM ability, retain high efficiency on low RPM and loose some efficiency on rare high power-RPM bursts. Japanese manufacturers are good at this.
Current Audi engine is casual performance drivers dream: it is more efficient than turbocharged and offers instant boost of torque from low RPM-closed throttle and exceptional and predictable throttle response. Supercharger is also much cheaper and virtually troubles-free compared to high-temperature gasoline turbocharger.
Posted by: Andrey Levin | 27 June 2008 at 11:27 PM
it increases exhaust backpressure and robs engine efficiency on part throttle.
True, but a turbocharger only increases backpressure when it is actually generating boost. It doesn't rob efficiency at part throttle.
In addition a roots-blower without a clutch always robs some power from the crank at part throttle.
The only moment turbocharger is advantageous on gasoline engine (unlike on diesel, when turbocharger is always advantageous) is on full throttle, but how often and for how long you use full throttle?
Keep in mind, that a smaller engine with a turbocharger is lighter than a larger NA engine. Lighter engines always increase overall vehicle efficiency.
smaller displacement do not compensate for reduced compression ratio
1. A smaller engine is not only lighter it also has less frictional losses than a larger engine. Higher average cylinder pressures generally increase the efficiency of an engine.
2. A smaller engine is driven at higher throttle openings than a larger engine in the same vehicle and thus pumping losses are reduced.
3. The compression ratio does not need to be reduced as long as the compressed charged is properly cooled. The turbo-charged BMW N54 engine has a compression ratio of 10.5.
Posted by: globi | 28 June 2008 at 02:40 AM
Globi;
“…turbocharger only increases backpressure when it is actually generating boost”
Turbocharger always generates boost (dynamic or barymetric), whether it is used or just wasted by throttling or venting.
All your other claims are correct, as are mine. But overall, summing all pluses and minuses, gasoline engine turbocharging does not produce appreciable efficiency gains, if any.
It is great for performance-oriented cars, thought, but it has nothing to do with fuel efficiency of family sedan.
Posted by: Andrey Levin | 28 June 2008 at 05:17 AM
Hmmm considering the PSA/BMW 1.6 turbo 175hp broad power band (actually more like 190hp on rolling roads) this engine in a bluff car gets 40-50 impg and is a massive leap forward over the SC 1.6 chrysler engine before.
IMO this means a real world normal engine for "ordinary cars" can be 1.0 litre triple and still develop 120hp and broad power. This will have great gains through downsizing. IMO TC especially the variable nozzle lag free type is way ahead of SCing and NA.
NA is asthmatic, SCing is parasitic, TCing results in an efficient compact air pump and combined with VVT can achieve a limited variable compression and Atkinson cycle in low load.
But I agree this Audi engine doesnt belong here, esp when their 2.0TFSI just announced is so much better.
Posted by: Ben Collins | 28 June 2008 at 06:47 AM
Turbocharger always generates boost (dynamic or barymetric), whether it is used or just wasted by throttling or venting.
No they do not. And modern turbo-charged engines are not controlled by throttling or venting and therefore wasting valuable boost. They do have waste gates, such that exhaust gases by-pass the turbine. When the turbine is by-passed there's no increased back-pressure. Needless to say that at low rpms the centrifugal compressor of the turbo hardly does any work. And if there's no work done by the compressor, there's no work done by the turbine.
Turbochargers are becoming more popular to improve efficiencies of vehicles:
http://www.greencarcongress.com/2008/05/gm-to-introduce.html
Posted by: globi | 28 June 2008 at 07:15 AM
If a roots blower was just as efficient as a turbo-charger, VW wouldn't have gone through the effort and additional costs and complexity of combining those two superchargers (roots and turbo):
http://www.greencarcongress.com/2005/08/inside_vws_new_.html
Posted by: globi | 28 June 2008 at 09:15 AM
...it is the right engine that gives me the superiority I need and to pull me (320lbs), my wife (330lbs) and my to children (one 270lbs, the other one just 210lbs) from zero to speed of light in just a glimse.
On other terms, is it pssible to aply the law of diminishing marginal utility on the replacement requirement for acceleration?
"zank" you VW/Audi!
Posted by: michel | 05 July 2008 at 12:12 PM
The good thing about the super charger setup is that it is also cheaper then a turbo charger. ( You can use the same exaust manifold that you have already build for the non supercharged engine you don't have to build a new one you don't need to use a blow of valve or divert valve, you don't have to worry about controlling a wast gate for the turbo charger). The bad thing about supercharger is it robs engine hp because it is rotate from the crank shaft , torque curve will be allot worse comparing to a turbocharged engine because there is direct connection between engine rpm and blower rpm. Over all supercharger is a cheap way to build hp . And it is really funny how Audi can misled the customer trying to convince them that supercharger is better then a turbo charger.
Posted by: | 09 August 2008 at 04:52 PM