Coolness of New Mazda3 Engine Valve Train

Discussion in 'Mazda' started by Jay, Nov 10, 2013.

  1. Jay

    Jay Well-Known Member

    Forgive me if I'm the last person to learn this, but I was looking through the 2014 Mazda3 service manual and came upon the valve train section and was fairly gobsmacked by how ingenious the design is. First, it has roller cam followers, which isn't much of a surprise given that it is a low-friction engine, but the cam follower has a third-class lever arrangement similar to the 14,000rpm BMW S1000RR. At the fulcrum is the showpiece: a hydraulic lash adjuster! I've seen HLAs on OHV engines, of course, and I even had HLAs on my DOHC Suzuki Swift GTi engine many years ago, but those adjusters were part of the un-sprung weight of the valve train. In Mazda's design the HLAs are fixed and don't move--thus they always maintain 0.0mm valve lash under all conditions, never need adjustment, and don't limit rpm by being part of the un-sprung weight. How cool is that?!:cool:

  2. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    That's pretty ingenious. Gotta love Zoom-Zoom engineering voodoo !
  3. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Jay:

    Really good stuff and where did you get this again? Are you a Mazda Service tech?


  4. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    3rd gen prius also has hydraulic adjusters, but not sure if they're fixed position like this. Second gen had shims, a nightmare for DIY.

    The parade of Hondas we've had were all screw and lock nut. Relatively easy DIY . I found after an initial adjustment, any subsequent checks showed much less change in the clearances.
  5. Jay

    Jay Well-Known Member

    Wayne, I found the link on the Mazda 24/7 Forum:

    I love service manuals and this one is an especially good one--particularly the full color (sometimes animated) electrical schematics.

    I see that Mazda uses oil jets to cool the underside of the pistons. Honda also does this on some of their high-performance motorcycle engines and car engines (like the S2000). Mazda also employs variable valve timing on both intake and exhaust cams (instead of just the intake as on my Honda K20A3 engine). Strangely, Mazda's exhaust cam timing is hydraulically activated while the intake is electrically activated.
  6. Jay

    Jay Well-Known Member

    My '86 Honda VFR motorcycle had screw and lock nut adjusters while my '94 Honda VFR had shim-under-bucket adjustment. Both were a bitch to deal with on the VFR because of the V4 engine, but I have a slight preference for the shim-under-bucket design. The cams had to come out to change the shims but that was better than having the clearance always changing when tightening the lock nut on the screw. Also, there was no danger of the lock nut coming loose.

    My Acura has 110,000 mile valve adjustment intervals, but I've done the job once already and no adjustment is much better than few adjustments! Go Mazda! I don't see why Mazda's really smart design couldn't be used to great advantage on motorcycle engines. As I look through this service manual I see a lot of really nice touches everywhere that make the Skyactive engines gems.
  7. RedylC94

    RedylC94 Well-Known Member

    All three cars I've owned (from GM, Subaru, & Mazda) have had screw-&-locknut adjustment. All were easy to adjust, and none ever worked loose.
  8. seftonm

    seftonm Veteran Staff Member

    I thought piston cooling jets were pretty common these days? Or maybe it was moreso a diesel thing.
  9. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Mike:

    It is. Quite a few manufacturers are increasing the CR for better TD by cooling the piston surfaces to reduce Pre detonation. DI helps here too.

  10. tribosessive

    tribosessive Well-Known Member

    It is my understanding that Mazda has done some very innovative things regarding emissions systems. Also they dealt with the common GDI malady of intake valve deposits by increasing combustion chamber temperatures. This burns off the deposits and the engine remains efficient. This is way over my head and sorry if it is repetitious. I would really like to see the boys from Hiroshima lick the problems with North American emission requirements on SkyactivD and bring us der diesel.

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