A look inside the Mazda Skyactiv engine

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Originally Posted By: SteveSRT8
Nothing "new" here, just a nice focus on efficiency at many levels.

That piston is not steel, it's aluminium and would be coated in the skirt area for sure. Note that many of these "features" are found on cars back in 05.

Mazda is doing more marketing than anything, at least they consider chassis dynamics. Many FWD platforms don't seem to care about the driving experience, just the infotainment!


However you leave out one thing. The MPG is superior to ANYTHING in 2005. The combination of items is yielding superior MPG.
 
I think somebody just likes dissing Mazda. I don't think anyone is trying to say that "Skyactiv" doesn't sound like a dumb term in the U.S., or that Mazda invented sliced bread. They just did a good job here, plain and simple. You don't make Ward's Ten Best Engines list for nothing. So, just wondering, what's the point of all the negativity? BTW, no one's opinion of my vehicle is taken as an insult.
 
Originally Posted By: DBMaster
I think somebody just likes dissing Mazda. I don't think anyone is trying to say that "Skyactiv" doesn't sound like a dumb term in the U.S., or that Mazda invented sliced bread. They just did a good job here, plain and simple. You don't make Ward's Ten Best Engines list for nothing. So, just wondering, what's the point of all the negativity? BTW, no one's opinion of my vehicle is taken as an insult.


I can break 40 mpg with my 2003 Zx2 - very minor mods and kinda low tech design.
So I don't get the hoopla for this Mazda engine.
Those hydraulic rockers are from a 60s Ford 6.
Those short skirts portend faster wear and rocking, like any other car that uses them. Those hot intake valves are not good for lubrication. And those long plugs are going to be a treat for someone down the line.
 
Originally Posted By: friendly_jacek
Prius engine also has 13:1 compression, but it's obviously an Atkinson cycle.

It's interesting how Mazda avoided knocking by delayed ignition, longer exhaust pipes, and piston cavity.
http://www.mazda.com/mazdaspirit/skyactiv/engine/skyactiv-g.html


It isn't a "true" Atkinson cycle (none of the hybrids are) which requires a special crankshaft design and actually has different stroke lengths for intake/exhaust compression/power.

Modern high efficiency engines labelled "Atkinson" use valve timing to emulate the characteristics of an Atkinson cycle.
 
Originally Posted By: friendly_jacek
Originally Posted By: SteveSRT8
Nothing "new" here, just a nice focus on efficiency at many levels.

That piston is not steel, it's aluminium and would be coated in the skirt area for sure.


Quote:
The SkyActiv program also includes lightening of the reciprocating parts (forged steel pistons, rods, crank)


http://online.wsj.com/article/SB10001424052970204652904577197030609865456.html



The person who wrote that article obviously didn't check their facts.

The last time I saw a steel piston, it was in a gravity oiled tank engine from the early 1900's and had 3ft long connecting rods and spun a max of about 1,000RPM.

These pistons would be forged aluminum if they are forged at all. Hypereutectic (an aluminum/silicon alloy) is more common nowadays because it expands less than a forged aluminum piece and subsequently allows tighter piston-to-wall clearances for reduced blow-by, oil consumption....etc.

Forged rods and crank aren't inherently lighter than castings either. They are just stronger.

I will add that the piston shown earlier is no different in appearance than one from a Modular or LSx engine. Obviously some of you guys haven't seen many engines apart
wink.gif
 
Originally Posted By: friendly_jacek
Originally Posted By: Kiwi_ME
Originally Posted By: NHGUY
...no piston skirts

Clearly there must be minimal skirts on the faces radial to the pins, not shown in the cutaway. It can't work geometrically otherwise.


skyactiv-g_img_03.jpg


Yes, and the skirts look coated. Looks like steel, too!


Aside from the taller dome and the dimple in the top (for the DI), here are some Modular pistons:

Ford_4.6_piston_and_rods.jpg


You'll notice the short, coated skirts and shiny appearance.

Here's an LS1 piston:
cp-bullet-flat-top-pistons-250.jpg
 
^^^Thank you, Overkill.

Mostly a rehash of older tech, they are tweaking it everywhere thus a small gain in efficiency. It's an admirable focus, but much more marketing than ground breaking new technology!

I'm not dissing them at all, I just resent people presenting a high top ring short skirted coated piston design as something "new". As OK said, look at some other engines designs, then comment on how cool it is.

At least Mazda can make something fun to drive.
 
Last edited:
Originally Posted By: OVERK1LL
Originally Posted By: friendly_jacek
Prius engine also has 13:1 compression, but it's obviously an Atkinson cycle.

It's interesting how Mazda avoided knocking by delayed ignition, longer exhaust pipes, and piston cavity.
http://www.mazda.com/mazdaspirit/skyactiv/engine/skyactiv-g.html


It isn't a "true" Atkinson cycle (none of the hybrids are) which requires a special crankshaft design and actually has different stroke lengths for intake/exhaust compression/power.

Modern high efficiency engines labelled "Atkinson" use valve timing to emulate the characteristics of an Atkinson cycle.


yes, I knew that. what is your point again?
 
Originally Posted By: friendly_jacek
Originally Posted By: OVERK1LL
Originally Posted By: friendly_jacek
Prius engine also has 13:1 compression, but it's obviously an Atkinson cycle.

It's interesting how Mazda avoided knocking by delayed ignition, longer exhaust pipes, and piston cavity.
http://www.mazda.com/mazdaspirit/skyactiv/engine/skyactiv-g.html


It isn't a "true" Atkinson cycle (none of the hybrids are) which requires a special crankshaft design and actually has different stroke lengths for intake/exhaust compression/power.

Modern high efficiency engines labelled "Atkinson" use valve timing to emulate the characteristics of an Atkinson cycle.


yes, I knew that. what is your point again?


You said it was an Atkinson cycle. It technically isn't, as it just emulates one. That was my point. Funny that I had to make it again, at your request of course, since I thought it was pretty obvious as to my intentions the first time.....
 
Originally Posted By: friendly_jacek
Originally Posted By: OVERK1LL


The last time I saw a steel piston, it was in a gravity oiled tank engine from the early 1900's and had 3ft long connecting rods and spun a max of about 1,000RPM.



Modern steel pistons do exist, especially for diesel: http://www.federalmogul.com/en/OETechnology/PowertrainEnergy/Pistons/

But, you are right, I never took SkyActiv engine apart, so can't be sure.


Especially for a diesel or *only* for a diesel? I see no mention of steel gasoline engine pistons on Federal Mogul's site, and we are speaking of a gasoline engine in this thread, are we not?

Diesel engines spin much slower and steel pistons are, surprise, much heavier, which require reduced engine RPM. Hence my remark about the tank engine (which was gas BTW) and its RPM ceiling.

I have both a DT466 and a Top fuel NHRA piston at my house if you'd like me to snap pictures and grab weights. The Top Fuel piston I bet weighs less than the pin in the diesel piston. They are THAT different.
 
Originally Posted By: OVERK1LL
Originally Posted By: friendly_jacek
Originally Posted By: OVERK1LL
Originally Posted By: friendly_jacek
Prius engine also has 13:1 compression, but it's obviously an Atkinson cycle.

It's interesting how Mazda avoided knocking by delayed ignition, longer exhaust pipes, and piston cavity.
http://www.mazda.com/mazdaspirit/skyactiv/engine/skyactiv-g.html


It isn't a "true" Atkinson cycle (none of the hybrids are) which requires a special crankshaft design and actually has different stroke lengths for intake/exhaust compression/power.

Modern high efficiency engines labelled "Atkinson" use valve timing to emulate the characteristics of an Atkinson cycle.


yes, I knew that. what is your point again?


You said it was an Atkinson cycle. It technically isn't, as it just emulates one. That was my point. Funny that I had to make it again, at your request of course, since I thought it was pretty obvious as to my intentions the first time.....


I see your point now. You are talking about semantics. Well, 99.99% people talking about Atkinson cycle are not talking literally about that 19 century patent.

Quote:
While Atkinson's original design is no more than a historical curiosity, many modern engines use unconventional valve timing to produce the effect of a shorter compression stroke/longer power stroke, thus realizing the fuel economy improvements the Atkinson cycle can provide
[...]
Recently Atkinson cycle has been used to describe a modified Otto cycle engine in which the intake valve is held open longer than normal to allow a reverse flow of intake air into the intake manifold. The effective compression ratio is reduced (for a time the air is escaping the cylinder freely rather than being compressed) but the expansion ratio is unchanged.


http://en.wikipedia.org/wiki/Atkinson_cycle
 
Originally Posted By: friendly_jacek

I see your point now. You are talking about semantics. Well, 99.99% people talking about Atkinson cycle are not talking literally about that 19 century patent.

Quote:
While Atkinson's original design is no more than a historical curiosity, many modern engines use unconventional valve timing to produce the effect of a shorter compression stroke/longer power stroke, thus realizing the fuel economy improvements the Atkinson cycle can provide
[...]
Recently Atkinson cycle has been used to describe a modified Otto cycle engine in which the intake valve is held open longer than normal to allow a reverse flow of intake air into the intake manifold. The effective compression ratio is reduced (for a time the air is escaping the cylinder freely rather than being compressed) but the expansion ratio is unchanged.


http://en.wikipedia.org/wiki/Atkinson_cycle



Yes, I've seen the wiki on it.

I can't remember who posted it a week or so ago, but somebody put up a video of a Honda demonstration of a single cylinder engine setup in the manner of the original Atkinson cycle, which I thought was very interesting.

Semantics aside, I think there is still an important distinction between an engine with a crankshaft setup to rotate only once over the period of all four strokes and having different intake/exhaust compression/power stroke lengths and an engine that is just an otto-cycle leveraging valve timing to emulate the above.
 
Geesh, there are a lot of people on here that lost their girlfriends to Mazda or something. The thread was just info for those who wanted to see the guts. It didn't need all the pointless "i'm so smart and mazda is so unoriginal" posts that were completely unprovoked.

This site delves into the immature more and more every day.
 
I do not like any of these Green Engines, Bring over a robust Turbo-Diesel mated to a 5-speed manual, then keep it for 15 years.
 
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