The SkyActiv-G, in its 2.0 L form, is a gasoline-powered, direct injection engine scheduled to launch in the 2012 MY in the 3 and/or the 6. In the future, additional versions from 1.3 to 2.5 L displacement are planned. There is also a diesel powered version of the engine, the SkyActiv-D, that will not be discussed by me in this thread, since as yet I have little information about its specs.
SkyActiv-G 2.0 L Engine
The new JDM engine will have a CR of 14:1, compared with the current MZR 2.0 L engine's 11:1 and will require premium grade (91 oct) gasoline. The USDM engine will have a CR of 13:1 compared with the current 3's 10:1, thus permitting the use of regular grade fuel. This substantial increase in thermal efficiency leads to increased power output and decreased fuel consumption. However, the increased heat build-up from this high CR would normally result in pre-ignition and destructive detonation. In order to reduce the combustion temperature to a manageable level, Mazda utilizes an extremely long 4-into-2-into-1 exhaust header designed to prevent the hot exhaust gases from getting pulled back into the combustion chamber during the next cylinder's intake stroke.
While reducing the combustion temperature to eliminate detonation, at the same time engine heat loss is minimized by using a smaller bore and a much more complex piston shape compared with the current 2.0 L engine to increase overall efficiency. To aid in this effort, a cavity is placed directly in the piston's center just under the hot area where the spark plug fires. This has the effect of ensuring a shorter combustion time and suppresses the impact on power and torque from engine knocking. Additionally, multi-hole injectors are employed to improve fuel spray characteristics.
Friction has also been reduced in the pistons, rods and crankshaft which is now forged steel instead of cast iron. To further reduce friction, roller finger followers are used in the valvetrain along with 0W-20 engine oil.
The Sky is also fitted with dual sequential, variable valve timing, reducing pumping losses and electronically controlled on the intake side so that rapid adjustments can be made even during cold starts.
With respect to the current 2.0 L engine, overall weight has been reduced by about 15 lbs, including 10 saved by thinning out the block where additional strength wasn't needed.
How does the Sky engine compare with the current Mazda3 MZR type? The figures are tabulated below and, as is my usual custom, I calculated the BMEPs at max BHP and max torque for the two engines since from an engineering standpoint this provides the most thorough, comprehensive and meaningful measure of comparative engine performance. For more information, go to:
________________ 2011 Mazda3 2.0 L ________ 2012 SkyActiv 2.0 L
BHP _____________ 148 @ 6,500 rpm* __________ 155 @ 6,000 rpm
Torque ___________ 135 @4,500 rpm* __________ 148 @ 4,100 rpm
Hwy MPG ____________ 30 mpg __________________ 39-40 mpg
BMEP (Max BHP) ______ 148 psi ___________________ 168 psi
BMEP (Max Torque) ___ 166 psi ___________________ 184 psi
* Non-PZEV (Partial Zero Emission Vehicle) engines. For an explanation, go to:
Note the substantial increase in BMEPs between the two engines undoubtedly primarily due to the increased CR in the SkyActiv engine. This is even more significant since the BMEPs of the MZR 2.0 L and 2.5 L engines used in the 2011 3 are essentially the same.
Remarks
Some of these details, specs and figures may be subject to change in respect to the actual production models. The new engine will be available as an option in the 2012 3 as the current MZR 2.0 L engine will still be available. Additionally, although previously only available with the MZR 2.5 L engine, the 2012 3 five-door hatchback will now also be offered with the SkyActiv-G 2.0 L engine, although weight and aerodynamic differences will yield slightly higher fuel consumption (~ 38 mpg). As yet, I don't have a firm grasp of all the technical details of the new engine so excuse my rather sketchy description. Those of you who have more information please add to the material here and/or correct any details I may have gotten wrong. I want to apologize in advance for any incorrect info I may inadvertantly disseminate.
The good news for we performance oriented drivers is that the new engine will be available with a 6-speed M/T as well as a 6-speed ATX. The ATX is said to incorporate the features of a continuously variable transmission (CVT) and a dual clutch as well as a torque converter with a lock-up clutch to ensure a minimal decrease in fuel economy and to provide a more direct driving feel.
The MTX is based on the current 6-speed now only available with the MZR 2.5 L or the MZR 2.3 L DISI turbo engine. To create a more responsive and sporty feel, the shift lever stroke was shortened by ~ 10 % and a number of internal modifications were made including locating 2nd and 3rd gear on a common shaft. Due to the reconfiguration enabling fewer components, the weight was reduced by ~ 4.4 lbs.
For more information, and photos, go to:
http://www.mazda.com/mazdaspirit/sky...kyactiv-g.html.
Happy Motoring!
SkyActiv-G 2.0 L Engine
The new JDM engine will have a CR of 14:1, compared with the current MZR 2.0 L engine's 11:1 and will require premium grade (91 oct) gasoline. The USDM engine will have a CR of 13:1 compared with the current 3's 10:1, thus permitting the use of regular grade fuel. This substantial increase in thermal efficiency leads to increased power output and decreased fuel consumption. However, the increased heat build-up from this high CR would normally result in pre-ignition and destructive detonation. In order to reduce the combustion temperature to a manageable level, Mazda utilizes an extremely long 4-into-2-into-1 exhaust header designed to prevent the hot exhaust gases from getting pulled back into the combustion chamber during the next cylinder's intake stroke.
While reducing the combustion temperature to eliminate detonation, at the same time engine heat loss is minimized by using a smaller bore and a much more complex piston shape compared with the current 2.0 L engine to increase overall efficiency. To aid in this effort, a cavity is placed directly in the piston's center just under the hot area where the spark plug fires. This has the effect of ensuring a shorter combustion time and suppresses the impact on power and torque from engine knocking. Additionally, multi-hole injectors are employed to improve fuel spray characteristics.
Friction has also been reduced in the pistons, rods and crankshaft which is now forged steel instead of cast iron. To further reduce friction, roller finger followers are used in the valvetrain along with 0W-20 engine oil.
The Sky is also fitted with dual sequential, variable valve timing, reducing pumping losses and electronically controlled on the intake side so that rapid adjustments can be made even during cold starts.
With respect to the current 2.0 L engine, overall weight has been reduced by about 15 lbs, including 10 saved by thinning out the block where additional strength wasn't needed.
How does the Sky engine compare with the current Mazda3 MZR type? The figures are tabulated below and, as is my usual custom, I calculated the BMEPs at max BHP and max torque for the two engines since from an engineering standpoint this provides the most thorough, comprehensive and meaningful measure of comparative engine performance. For more information, go to:
________________ 2011 Mazda3 2.0 L ________ 2012 SkyActiv 2.0 L
BHP _____________ 148 @ 6,500 rpm* __________ 155 @ 6,000 rpm
Torque ___________ 135 @4,500 rpm* __________ 148 @ 4,100 rpm
Hwy MPG ____________ 30 mpg __________________ 39-40 mpg
BMEP (Max BHP) ______ 148 psi ___________________ 168 psi
BMEP (Max Torque) ___ 166 psi ___________________ 184 psi
* Non-PZEV (Partial Zero Emission Vehicle) engines. For an explanation, go to:
Note the substantial increase in BMEPs between the two engines undoubtedly primarily due to the increased CR in the SkyActiv engine. This is even more significant since the BMEPs of the MZR 2.0 L and 2.5 L engines used in the 2011 3 are essentially the same.
Remarks
Some of these details, specs and figures may be subject to change in respect to the actual production models. The new engine will be available as an option in the 2012 3 as the current MZR 2.0 L engine will still be available. Additionally, although previously only available with the MZR 2.5 L engine, the 2012 3 five-door hatchback will now also be offered with the SkyActiv-G 2.0 L engine, although weight and aerodynamic differences will yield slightly higher fuel consumption (~ 38 mpg). As yet, I don't have a firm grasp of all the technical details of the new engine so excuse my rather sketchy description. Those of you who have more information please add to the material here and/or correct any details I may have gotten wrong. I want to apologize in advance for any incorrect info I may inadvertantly disseminate.
The good news for we performance oriented drivers is that the new engine will be available with a 6-speed M/T as well as a 6-speed ATX. The ATX is said to incorporate the features of a continuously variable transmission (CVT) and a dual clutch as well as a torque converter with a lock-up clutch to ensure a minimal decrease in fuel economy and to provide a more direct driving feel.
The MTX is based on the current 6-speed now only available with the MZR 2.5 L or the MZR 2.3 L DISI turbo engine. To create a more responsive and sporty feel, the shift lever stroke was shortened by ~ 10 % and a number of internal modifications were made including locating 2nd and 3rd gear on a common shaft. Due to the reconfiguration enabling fewer components, the weight was reduced by ~ 4.4 lbs.
For more information, and photos, go to:
http://www.mazda.com/mazdaspirit/sky...kyactiv-g.html.
Happy Motoring!
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