Audi reveals new 2.0 TFSI engine
05-07-15, 04:33 PM
#16
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It's only called the Miller cycle when it's supercharged; otherwise it's called the Atkinson cycle, which is first used in a production car by Toyota.
Audi's PR avoided the reference to Toyota by spinning the technology as being "At its core its principle is comparable to the Miller cycle", which is exactly what Atkinson cycle is.
Audi's PR avoided the reference to Toyota by spinning the technology as being "At its core its principle is comparable to the Miller cycle", which is exactly what Atkinson cycle is.
05-07-15, 04:38 PM
#17
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Yes, but is really important ? Atkinson has been around since 1882 and Miller since the 50 ties. It has been used in many applictaions such as ships, locomotives, generators and so on. Its not like Toyota created Atkinson or Mazda the Miller cycle. Just like the turbo or supercharger, they are both over 100 years old in terms of technology.
Last edited by ydooby; 05-07-15 at 04:43 PM.
05-08-15, 10:11 AM
#18
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Technology in detail:
The breakthrough of the 2.0 TFSI lies in a new combustion method. At its core its principle is comparable to the Miller cycle. Audi engineers have further developed that method in crucial ways, however. The increase in efficiency is based on the following factors:
- The intake time has been significantly shortened (140° crank angle (CA) rather than 190 to 200° CA).
- Owing to a higher boost pressure on the inlet side, the engine attains optimal cylinder charges despite the shorter intake time.
- The intake valve also closes earlier – well before the bottom dead center is reached. This lowers the medium pressure, allowing a high, efficiency-boosting compression ratio.
- In the partial load range, an additional injection upstream from the intake valve yields an efficient mixture formation that is already complemented by the direct injection in the intake manifold and in the combustion chamber.
- The Audi Valvelift System (AVS) on the inlet side allows a short intake time at partial load and a longer time at higher loads (full load: 170° CA [as compared to 190 to 200° CA]).
The breakthrough of the 2.0 TFSI lies in a new combustion method. At its core its principle is comparable to the Miller cycle. Audi engineers have further developed that method in crucial ways, however. The increase in efficiency is based on the following factors:
- The intake time has been significantly shortened (140° crank angle (CA) rather than 190 to 200° CA).
- Owing to a higher boost pressure on the inlet side, the engine attains optimal cylinder charges despite the shorter intake time.
- The intake valve also closes earlier – well before the bottom dead center is reached. This lowers the medium pressure, allowing a high, efficiency-boosting compression ratio.
- In the partial load range, an additional injection upstream from the intake valve yields an efficient mixture formation that is already complemented by the direct injection in the intake manifold and in the combustion chamber.
- The Audi Valvelift System (AVS) on the inlet side allows a short intake time at partial load and a longer time at higher loads (full load: 170° CA [as compared to 190 to 200° CA]).
I was just about to say it--Audi copied the exact same techs of Atkinson cycle and D4-S from Toyota, although Audi failed to copy Toyota's automatic switch to Otto cycle during high engine loads, hence the much lower peak horsepower output (but perhaps better efficiency).
"The intake valve also closes earlier – well before the bottom dead center is reached. This lowers the medium pressure, allowing a high, efficiency-boosting compression ratio.", aka. Atkinson cycle.
"In the partial load range, an additional injection upstream from the intake valve yields an efficient mixture formation that is already complemented by the direct injection in the intake manifold and in the combustion chamber.", aka. D4-S.
"The intake valve also closes earlier – well before the bottom dead center is reached. This lowers the medium pressure, allowing a high, efficiency-boosting compression ratio.", aka. Atkinson cycle.
"In the partial load range, an additional injection upstream from the intake valve yields an efficient mixture formation that is already complemented by the direct injection in the intake manifold and in the combustion chamber.", aka. D4-S.
Audi closes the intake valve very early, limiting intake pressure; Toyota closes the valve very late, allowing some pressure to escape, thus lowering intake pressure. Both methods effectively reduce compression ratio (by reducing pressure that has to be compressed) while maintaining expansion ratio.
Toyota's method has become known as the modern Atkinson Cycle. I don't know if Audi could (or wanted to) call their cycle a modern Atkinson Cycle; not calling it an Atkinson Cycle but calling it "comparable to the Miller Cycle" avoids confusion with Toyota's valve-timing system.
Toyota changes over to the normal Otto Cycle at higher loads. Audi does this also but not completely (merely lengthening the intake stroke from 140° crank angle to 170° crank angle when the normal Otto Cycle is 190° to 200° crank angle).
05-08-15, 10:35 AM
#19
Yes, but is really important ? Atkinson has been around since 1882 and Miller since the 50 ties. It has been used in many applictaions such as ships, locomotives, generators and so on. Its not like Toyota created Atkinson or Mazda the Miller cycle. Just like the turbo or supercharger, they are both over 100 years old in terms of technology.
05-08-15, 10:40 AM
#20
Interesting difference in intake valve timing...
Audi closes the intake valve very early, limiting intake pressure; Toyota closes the valve very late, allowing some pressure to escape, thus lowering intake pressure. Both methods effectively reduce compression ratio (by reducing pressure that has to be compressed) while maintaining expansion ratio.
Toyota's method has become known as the modern Atkinson Cycle. I don't know if Audi could (or wanted to) call their cycle a modern Atkinson Cycle; not calling it an Atkinson Cycle but calling it "comparable to the Miller Cycle" avoids confusion with Toyota's valve-timing system.
Toyota changes over to the normal Otto Cycle at higher loads. Audi does this also but not completely (merely lengthening the intake stroke from 140° crank angle to 170° crank angle when the normal Otto Cycle is 190° to 200° crank angle).
Audi closes the intake valve very early, limiting intake pressure; Toyota closes the valve very late, allowing some pressure to escape, thus lowering intake pressure. Both methods effectively reduce compression ratio (by reducing pressure that has to be compressed) while maintaining expansion ratio.
Toyota's method has become known as the modern Atkinson Cycle. I don't know if Audi could (or wanted to) call their cycle a modern Atkinson Cycle; not calling it an Atkinson Cycle but calling it "comparable to the Miller Cycle" avoids confusion with Toyota's valve-timing system.
Toyota changes over to the normal Otto Cycle at higher loads. Audi does this also but not completely (merely lengthening the intake stroke from 140° crank angle to 170° crank angle when the normal Otto Cycle is 190° to 200° crank angle).
05-08-15, 03:21 PM
#21
Lexus Test Driver
Audi's new motor sounds impressive. BMW took a similar approach with their base 3-series engine offering. As long as 0-60 times remain in the magic 7 range, customers should be happy. The added mpg's will likely set a new bar for others to follow.
So I am guessing Audi will have this new motor at the lower end, continue on with the more powerful 2.0T that is standard now, and then once again make the 3.0 supercharged as the top offering (S4). This seems like a better range of choices than what's out now, with the current 2.0 and 3.0 likely getting power boosts during the redesign.
So I am guessing Audi will have this new motor at the lower end, continue on with the more powerful 2.0T that is standard now, and then once again make the 3.0 supercharged as the top offering (S4). This seems like a better range of choices than what's out now, with the current 2.0 and 3.0 likely getting power boosts during the redesign.
05-08-15, 06:36 PM
#22
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Audi most probably uses a hydraulicaly actuated camshaft profile with an offset to achieve Miller cycle, just like the Prius. Hence, the relatively low variable valve timing range of 30 degrees (from 140 to 170 degreees).
NX200t engine has electronically controlled VVT-iW, something the germans have yet to master. W here stands for "wide" and while I have not seen range numbers yet, the normal, non-wide VVT-i has range of about 40 degrees. This is how the NX200t can switch from Otto to Atkinson/Miller cycle.
But anyway, regarding the efficiency of engine, the most important value is the expansion ratio, which Audi does not state.
Honda had integrated manifold on the J30A4 engine from 2003, so it can't be Lotus.
There is a 320i EfficientDynamics edition with 5.4L/100km NEDC result.
Then, there is the tendency of the Germans to overestimate fuel economy by about 30% NEDC vs real world, while Japanese do about 15%.
Therefore, I doubt this new Audi A4 will be more efficient than an IS200t in the real world.
NX200t engine has electronically controlled VVT-iW, something the germans have yet to master. W here stands for "wide" and while I have not seen range numbers yet, the normal, non-wide VVT-i has range of about 40 degrees. This is how the NX200t can switch from Otto to Atkinson/Miller cycle.
But anyway, regarding the efficiency of engine, the most important value is the expansion ratio, which Audi does not state.
4. The fuel economy of the 320i, which uses a detuned engine from the 328i, is rated at 5.9L/100km (combined) in NEDC.
5. Audi's new 2.0 turbo gets better than 5.0L/100km combined in NEDC when it's in the A4, a car in the same class as the 3-series.
6. Therefore Audi's new turbo 2.0 is very likely to be meaningfully more efficient than Lexus's turbo 2.0 too.
5. Audi's new 2.0 turbo gets better than 5.0L/100km combined in NEDC when it's in the A4, a car in the same class as the 3-series.
6. Therefore Audi's new turbo 2.0 is very likely to be meaningfully more efficient than Lexus's turbo 2.0 too.
Then, there is the tendency of the Germans to overestimate fuel economy by about 30% NEDC vs real world, while Japanese do about 15%.
Therefore, I doubt this new Audi A4 will be more efficient than an IS200t in the real world.
05-08-15, 06:41 PM
#23
Lexus Test Driver
So Audi/VW already has a newer 1.8T that can likely put out very similar numbers with some simple boost tweaking. Any thoughts on why that motor was not used as a new base A4 engine? Maybe it's a marketing/psychological thing, where a low number like "1.8" just sounds too cheap for a luxury car. Discuss.
05-08-15, 07:14 PM
#24
Lexus Fanatic
Maybe it's a marketing/psychological thing, where a low number like "1.8" just sounds too cheap for a luxury car. Discuss.
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