Announcement

Collapse
No announcement yet.

Mazda's New Engines: SkyActiv-G and D

Collapse
This is a sticky topic.
X
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    #16
    thank god ford's influence is gone........... thats all i have to say
    ---Has ClubProtege helped you in someway? show your support by Contributing--- Click Here---

    1992- project FE3..... 313 WHP @ 9.3psi




    I pet my dash when I get into the car..."good car"
    he actually has a mazda tree, parts grow on it

    Comment


      #17
      I was talking with a Lexus trainer the other day and we where discussing the unreal CRs that todays engines use (my mother-in-laws GMC is 13:1!). The trainer made a good point: that compression ratio is the calculated comresssion ratio, your actual CR my vary. What is really going on is with Variable valve timing, the PCM can delay the closing point of the intake valve and drop actual comression ratio down to a point that a gas engine car really run. So most of these new engines are really running a varation of the Atkins cycle.

      Comment


        #18
        Originally posted by Rivet View Post
        I was talking with a Lexus trainer the other day and we where discussing the unreal CRs that todays engines use (my mother-in-laws GMC is 13:1!). The trainer made a good point: that compression ratio is the calculated comresssion ratio, your actual CR my vary. What is really going on is with Variable valve timing, the PCM can delay the closing point of the intake valve and drop actual comression ratio down to a point that a gas engine car really run. So most of these new engines are really running a varation of the Atkins cycle.
        The CR of a given engine never varies regardless of valve timing (overlap, etc.), or any other factor, as it's a fixed mechanical property. There is no such thing as an actual vs. a calculated CR. The SkyActiv-G engine does not work, and avoid detonation, because its actual CR is dropped down through VVT; the CR is mechanically set, and remains, at either 14 or 13:1 throughout all driving cycles. To reiterate, it works for two principal reasons: the combustion temperature is reduced through the use of an ultra-long exhaust header that prevents hot exhaust gases from mixing with the intake charge in the next firing cylinder, and by configuring the combustion chamber and piston shape to ensure a shorter combustion time to aid in preventing knock.

        The Dresser Industries Waukesha engine used to measure the octane rating of gasoline does in fact utilize a true variable CR but to achieve this the entire cylinder must be moved up and down with respect to the piston while the engine is running, changing the actual mechanical CR during operation. For more information, go to:


        Happy Motoring!
        Last edited by goldstar; 08-22-2011, 06:59 AM.
        02 DX Millenium Red - The Penultimate Driving Machine
        MP3 Strut Tower Bar kit; Cusco Front Lower Arm Tie Bar
        MSP Springs, Struts, Stabilizer Bars, Trailing Links, #3 Engine Mount
        Kartboy Stabilizer Bar Bushings; Nyloil Shifter Bushings; Red Line MT-90 Gear Oil
        MP3 Shifter, Knob and Aluminum Pedal Set
        Suvlights HD Wiring Harness; Osram Night Breaker H4 Bulbs; Exide Edge AGM Battery
        Summer: 5Zigen FN01R-C 16 x 7" Wheels; Yoko S.drive 205/45-16s
        Winter: Enkei OR52 16 x 7" Wheels; Falken Ziex ZE-912 205/45-16s
        Modified OEM Air Intake; Racing Beat Exhaust System; Techna-Fit SS Clutch Line
        Denso SKJ16CR-L11 Extended Tip Spark Plugs; Magnecor Wires
        Power Slot Front Brake Rotors; Techna-Fit SS Brake Lines; Hawk HPS Pads
        Red Line Synthetic Engine Oil; C/S Aluminum Oil Cap
        Cyberdyne Digital Gauges: Tach; Ambient Air Temp; Voltmeter

        Comment


          #19
          Homogeneous Charge Compression Ignition Engine

          Originally posted by irishkev90 View Post
          Interesting tid-bit from Car and Driver: The Sky-D's exhaust manifold is integrated into the block.

          They also mentioned something about HCCI (Homogeneous Charge Compression Ignition) in a gas engine. Imagine driving a gasoline engine without spark plugs. Hmm.....

          Sent from my HTC Incredible using Tapatalk.
          Thanks for bringing up the HCCI engine. This is a fascinating, relatively new concept and since Mazda is currently working with this design, I figure many of us would want to know more about it. Again, this represents a very brief overview.

          As is well known, the ideal or stoichiometric A/F ratio for most gasoline-type hydrocarbon fuels is very close to 15:1, with combustion still possible for values in the range 6 to 25. A/F less than 6 is too rich to sustain combustion and A/F greater than 25 is too lean. Spark ignition (SI) lean-burn engines can have A/F as high as 25 to 40 but need special intake and mixing arrangements for successful ignition.

          Compression ignition (CI) engines typically have A/F ratios in the range of 18 to 70 which appears to be outside the limits within which combustion is possible. Combustion occurs because the cylinder of a CI engine, unlike an SI engine, has a very non-homogeneous A/F mixture, with reaction occurring only in those areas in which a combustible (nearer to stoich) mixture exists, other regions being either too rich or too lean.

          Consequently, combustion in a CI engine is very different from that in an SI engine. Whereas SI combustion involves essentially a flame front moving through a locally homogeneous A/F mixture, combustion in a CI engine is an unsteady process occurring simultaneously at many different spots in a very non-homogeneous A/F mixture at a rate controlled by the fuel injection parameters. Thus, the flame front in a CI engine is highly non-uniform.

          In the combustion zone where the A/F mixture is rich, and just marginally combustible, and there is not enough O2 to form stoichiometric CO2, large amounts of unburned C (soot) are generated. To keep exhaust smoke, soot, within acceptable limits, CI engines are operated with an overall lean A/F mixture. If these engines were to operate with an overall stoich A/F mixture, the amount of black exhaust smoke would be unacceptable nor would power increase appreciably. Because of this lean-burn condition, the power output of CI engines is always below that of SI engines of equal displacement.

          Enter the HCCI engine. This engine uses a combustion principle new to CI engines. Using added intake port injectors, some fuel is added to the intake air in much the same way as occurs in an SI engine. This results in an almost homogeneous A/F mixture filling the combustion chamber before combustion actually occurs. Ignition occurs from normal CI injection but the resulting combustion is a combination of normal diesel diffusion flame combustion along with homogeneous mixture combustion. Thus, compared with a normal CI engine more of the A/F mixture is stoich leading to greater power output and cleaner operation (less soot production). Additionally, the engine can operate on dual fuel, with the homogeneous charge of fuel filling the combustion chamber (such as natural gas or ethanol) and diesel fuel supplying ignition. It's good to know that Mazda is involved with such cutting edge research.
          Reference:
          Engineering Fundamentals of the Internal Combustion Engine, Second Edition by Willard W. Pulkrabek; Chapter 2: Section 2.6 Air-Fuel Ratio and Fuel-Air Ratio, pages 62-64; Chapter 7: Section 7.5 Combustion in CI Engines, pages 297-304.

          Happy Motoring!
          02 DX Millenium Red - The Penultimate Driving Machine
          MP3 Strut Tower Bar kit; Cusco Front Lower Arm Tie Bar
          MSP Springs, Struts, Stabilizer Bars, Trailing Links, #3 Engine Mount
          Kartboy Stabilizer Bar Bushings; Nyloil Shifter Bushings; Red Line MT-90 Gear Oil
          MP3 Shifter, Knob and Aluminum Pedal Set
          Suvlights HD Wiring Harness; Osram Night Breaker H4 Bulbs; Exide Edge AGM Battery
          Summer: 5Zigen FN01R-C 16 x 7" Wheels; Yoko S.drive 205/45-16s
          Winter: Enkei OR52 16 x 7" Wheels; Falken Ziex ZE-912 205/45-16s
          Modified OEM Air Intake; Racing Beat Exhaust System; Techna-Fit SS Clutch Line
          Denso SKJ16CR-L11 Extended Tip Spark Plugs; Magnecor Wires
          Power Slot Front Brake Rotors; Techna-Fit SS Brake Lines; Hawk HPS Pads
          Red Line Synthetic Engine Oil; C/S Aluminum Oil Cap
          Cyberdyne Digital Gauges: Tach; Ambient Air Temp; Voltmeter

          Comment


            #20
            ^ good read!
            ---Has ClubProtege helped you in someway? show your support by Contributing--- Click Here---

            1992- project FE3..... 313 WHP @ 9.3psi




            I pet my dash when I get into the car..."good car"
            he actually has a mazda tree, parts grow on it

            Comment


              #21
              Goldstar, you are correct, CR is fixed value; I should have said cylinder pressure. Two very differnt things. CR used to give you an idea of what cylinder pressure would be. As we all know, in the olden days of a few years back, you could not run pump gas in an engine with CR of 13 to 1. Cylinder pressure would be too high and you would experince abnormal combustion.

              Comment


                #22
                Now your Lexus trainer is making more sense. I can see how hanging a valve is gonna reduce cylinder pressures when you want it to if you have control over valve timing. Clever, that.
                '90 AWD Protege, full GTR drivetrain swap, ~320 whp daily driver, RIP, and
                '90 AWD Protege, yet another GTR swap, Open class rallycar with a Toyota GT4 gearbox swap, thus crossing the line between hobby and mental illness. And a Brabus E55 K8, removing all doubt.
                http://www.wihandyman.com/forum/vbpi...?do=view&g=110
                http://www.cardomain.com/ride/2599486

                Comment


                  #23
                  Skyactive first drive impressions

                  More info on the upcoming lineup, courtesy of windingroad. Man that diesel is sounding better and better. I'd rally that bad boy in a heartbeat.
                  '90 AWD Protege, full GTR drivetrain swap, ~320 whp daily driver, RIP, and
                  '90 AWD Protege, yet another GTR swap, Open class rallycar with a Toyota GT4 gearbox swap, thus crossing the line between hobby and mental illness. And a Brabus E55 K8, removing all doubt.
                  http://www.wihandyman.com/forum/vbpi...?do=view&g=110
                  http://www.cardomain.com/ride/2599486

                  Comment


                    #24
                    I can't remember where I read this (it was posted on Twitter and led me to a website), but I guess someone test driving the diesel CX-5 (Autoweek, Autoguide, something of the sort) was able to eek out 63 mpg. They compared it to the Honda Insight's highest of 61mpg. Now if only we could convince Mazda to keep the two together for the U.S. market, preferably with the 6-speed manual and AWD, I would be all over it like white on a polar bear eating marshmallows in a blizzard.

                    Comment


                      #25
                      Here are seven pages worth reading if you're intrested in a more in-depth view of how the SkyActiv-G engine works. Very detailed, including photos of specific engine components. Enjoy, I know I did

                      Comment


                        #26
                        That exhaust manifold is prolly the trickest factory one I've ever seen.
                        (reads more) Holy f@cking crap. They are claiming a BSFC of 0.28. That's well into the efficiency range of diesels...
                        Last edited by jay; 09-27-2011, 11:08 AM.
                        '90 AWD Protege, full GTR drivetrain swap, ~320 whp daily driver, RIP, and
                        '90 AWD Protege, yet another GTR swap, Open class rallycar with a Toyota GT4 gearbox swap, thus crossing the line between hobby and mental illness. And a Brabus E55 K8, removing all doubt.
                        http://www.wihandyman.com/forum/vbpi...?do=view&g=110
                        http://www.cardomain.com/ride/2599486

                        Comment


                          #27
                          Also, I don't think this has anything to do with Mazda's SkyActiv technologies, but imagine the gasoline or diesel engines with Mazda's i-Stop technology. Here's the video I watched about it. In fact, all these "The Mazda Story" videos are quite interesting. I love how Mazda takes an unprecedented, innovative approach to all challenges. Which is exactly where the SkyActiv program came from. Mazda could have gone the route of all other manufacturers by downsizing their engines and turbocharging them or licensing hybrid technology. Instead, they decided to optimize the combustion process through compression, direct injection, piston shape, etc.

                          Same goes for this i-Stop technology. As stated in the video, manufacturers program the engine to shut off when the vehicle is stopped and restarts the engine with the starter motor, just like normally starting the car. Mazda programs the engine to stop with the pistons in the middle of their strokes. It uses the alternator and throttle body to position the pistons. When the engine need to start again, fuel is injected directly into the cylinder and ignited. This combustion along with the aid of the starter motor, allows for quicker, seamless restarts.



                          Keep up the great work Mazda

                          Comment


                            #28
                            I don't think this was posted yet. There's a few typo's here and there, but it's a good read with some decent illustrations and a video explaining everything at the top of the pages.

                            Comment


                              #29
                              The SKYACTIV-G engine has now become available in the MY 2012 3 so its production line power output specifications are now defined. For more information, go to:


                              Happy Motoring!
                              02 DX Millenium Red - The Penultimate Driving Machine
                              MP3 Strut Tower Bar kit; Cusco Front Lower Arm Tie Bar
                              MSP Springs, Struts, Stabilizer Bars, Trailing Links, #3 Engine Mount
                              Kartboy Stabilizer Bar Bushings; Nyloil Shifter Bushings; Red Line MT-90 Gear Oil
                              MP3 Shifter, Knob and Aluminum Pedal Set
                              Suvlights HD Wiring Harness; Osram Night Breaker H4 Bulbs; Exide Edge AGM Battery
                              Summer: 5Zigen FN01R-C 16 x 7" Wheels; Yoko S.drive 205/45-16s
                              Winter: Enkei OR52 16 x 7" Wheels; Falken Ziex ZE-912 205/45-16s
                              Modified OEM Air Intake; Racing Beat Exhaust System; Techna-Fit SS Clutch Line
                              Denso SKJ16CR-L11 Extended Tip Spark Plugs; Magnecor Wires
                              Power Slot Front Brake Rotors; Techna-Fit SS Brake Lines; Hawk HPS Pads
                              Red Line Synthetic Engine Oil; C/S Aluminum Oil Cap
                              Cyberdyne Digital Gauges: Tach; Ambient Air Temp; Voltmeter

                              Comment


                                #30
                                I thought the compression ratio of the SkyActiv-G for the US market was supposed to be 13:1, with 14:1 being used outside the US. Did they make the change to 12:1 and I didn't catch it, or were the first reports of 13:1 just a bunch of misinformation?

                                Sent from my HTC Incredible using Tapatalk.

                                Comment

                                Working...
                                X