CX-9 Skyactiv 2.5L turbo engine

[NelsonLewis]

He never lost any credibility here. Seems rather knowledgeable on all the matters presented, and most importantly, on the Skyactiv engine, which has caught my interest being in the game and all now. Hopefully we can all learn together, with an occasional Google hiccup here and there...

 

[Lbear]

Here is the FORGED SkyActiv crankshaft (2.0L):

SKyActiv 2.0L piston on the right:

The Skyactiv piston (right) is smaller and lighter. It also has a racing piston style slipper skirt which reduces weight and friction. You can see how much smaller the surface area is. Note the anti friction coating on both pistons. The silver dots on the skirts are nothing super duper or high tech, they are simply where the piston is indexed in the tooling. The Skyactiv piston is a strutted slipper skirt design, just like a racing piston, and has many of the same design features as current racing pistons such as butresses between the ring land area and the piston strut. The reduced skirts are lighter and have less friction.

 

[NelsonLewis]

Nice! Thanks for posting.

 

[NelsonLewis]

Let's talk about those intake ports. Are they in need of some port work, length okay, or where do they seem inferior?

 

[Chris_Top_Her]

Yes I know what they are referring to. I built my engine to handle more power, but it never "blew up" it did get torn down and rebuilt though (that is not the same). That engine is still running to this day.

If you don't think they won't make stuff up out of thin air, I highly recommend join MSF and see for yourself. Do this, just this:
Join MSF, make a thread saying " I'm going to turbo my CX5".

and just wait. they will swarm your ass like bees.

I'm going to do this, after I'm all set up.. just to be like what now lol

 

[vroom]

The closer the part is to the limit under stock power the higher chance there is for failures. Why would any manufacture risk that to shave a few grams off some rotating parts? You have to understand the casting, forging process is not perfect. Not even part that comes out will be identical or have the same tensile strength and fatigue limits as one another. If they add only 10% additional strength to a part vs what it can handle stock, there is a lot more chance for failure from the parts.

OK, so Mazda built in a nice fat safety margin into their engine that makes them (and me!) happy. So by tuning the engine you are eating into these margins a bit, so you increase the risks. It's a matter of deciding if the added HP are worth it. For me is not, but for some I see how it might. Kind of reminds me of the days I was over clocking my Pentium 2 CPU in the 90s because l craved the additional few MHz, even though I knew I had a small chance of frying it.

Are you aware of Skyactive engine parts that are overspeced and could be shaved down? I mean I get that shaving a fraction of a mm of the wall thickness of the connection rod wouldn't put a dent in MPG, but do it for enough components and it might add up to something significant.

Obviously it wouldn't be good for you as a tuner, but I'm curious.

 

[Kinghardcor]

I'd also like to hear about the intake ports.

 

[MikeM.]

He never lost any credibility here.

You can speak for yourself because when I'm accused of ripping off articles and presenting them as my own, well, I'm offended. Because I do not respect plagiarists. And to be clear, do you even know which "articles" he's speaking of? That I presented as my own?

He just made it up out of thin air.

 

[NelsonLewis]

You can speak for yourself because when I'm accused of ripping off articles and presenting them as my own, well, I'm offended. Because I do not respect plagiarists. And to be clear, do you even know which "articles" he's speaking of? That I presented as my own?

He just made it up out of thin air.

Thanks, I did just that, spoke for myself. I couldn't careless about which articles he's speaking of. I'm interested in the Skyactiv engine, how it's made, and it's tuning parameters. I can form my own opinion on what's been presented and/or discussed, and that is tuning, and based on my own experience and real world results, I can attest that the gains are manageable based on the criteria involved. Hell, you can pull 20 on the octane boost, leaning out, and timing alone. I've done so on an engine that's 55% smaller, and in stock trim...

Who's to say Mazda's next step up in power for this engine in NA form isn't doing something very similar to what's being discussed, or attempted to be anyways...

 

[MikeM.]

Hell, you can pull 20 on the octane boost, leaning out, and timing alone.

Yes, but the claimed gains on a stock engine is 25-35 HP.

Who's to say Mazda's next step up in power for this engine in NA form isn't doing something very similar to what's being discussed, or attempted to be anyways...

You mean introducing a naturally aspirated premium fuel performance version here in North America? That may very well be. But you can bet it will probably have upgraded hardware, not just tuning if it's a 2.5L Skyactiv rated at 209-219 hp.

 

[Unobtanium]

Let's talk about those intake ports. Are they in need of some port work, length okay, or where do they seem inferior?

Who knows? I asked MikeM for flowbench data on the heads, and intake, and TB, etc., since he seems to know what they are/are not capable of supporting, and he has yet to respond. I do know that 5.0L mustang heads from the late 80's supported 180whp or so, on a stock 302ci V8 just fine, and they flowed for crap. Same for the 4.6L non-PI heads that came after them.

 

[Unobtanium]

I have a complete 2.0L engine that I have torn down, and have seen what is inside. They shaved weight sure, but they designed the rods different than the MZR engine and you can clearly see by looking at them they will be able to take more abuse because of the design.

If you think weight and size is the factor that determines strength, that's incorrect. A billet H-beam connecting rod is almost always lighter than a factory rod, yet due to it's design and material (billet) they will handle enormous amounts of power vs a stock one.

The DESIGN of the connecting rod is the key, NOT the weight or size. If the design didn't matter than lightweight H-beams or Aluminum rods would suck! but they dont.

Look at the difference, the DESIGN of the rod is the important factor, they shaved weight were it isn't as important and does not take as much stress, like the rod cap for example, the rod bolts, etc:

I think billet is over-hyped, personally. Billet is just cheaper than forged, whether that be shape, or hand.

 

[Tbot101]

Who knows? I asked MikeM for flowbench data on the heads, and intake, and TB, etc., since he seems to know what they are/are not capable of supporting, and he has yet to respond. I do know that 5.0L mustang heads from the late 80's supported 180whp or so, on a stock 302ci V8 just fine, and they flowed for crap. Same for the 4.6L non-PI heads that came after them.

So there isn't anything wrong with the ports, just the design of them, and the cams. LoL at asking MikeM to find you something that isn't easily found on google

The intake port flow sucks (and yes we have flow bench data on it)
The cam profiles for both the intake and exhaust cams also aren't good for power.

Now don't get me wrong they are designed for a purpose, but mazda *could* of made just a few tiny changes that would make a lot more power with these.

Mazda has a "premium fuel version" (the MX5 miata). But even then the problem is still there, intake port sizes and cam profile

 

[Unobtanium]

So there isn't anything wrong with the ports, just the design of them, and the cams. LoL at asking MikeM to find you something that isn't easily found on google

The intake port flow sucks (and yes we have flow bench data on it)
The cam profiles for both the intake and exhaust cams also aren't good for power.

Now don't get me wrong they are designed for a purpose, but mazda *could* of made just a few tiny changes that would make a lot more power with these.

Mazda has a "premium fuel version" (the MX5 miata). But even then the problem is still there, intake port sizes and cam profile

Mazda built the thing from the ground up. It wasn't a bunch of parts stolen from another project. I am very leery of wanting to change something of that nature when more power is "easily available" with just a few tweaks, without understanding why Mazda knowingly left it on the table.

 

[Tbot101]

Mazda built the thing from the ground up. It wasn't a bunch of parts stolen from another project. I am very leery of wanting to change something of that nature when more power is "easily available" with just a few tweaks, without understanding why Mazda knowingly left it on the table.

Well we have a few friends who know Dave Coleman, and Mazdas intentions were to build the engine for enhance low end torque, not so much top end performance

 

[Unobtanium]

Well we have a few friends who know Dave Coleman, and Mazdas intentions were to build the engine for enhance low end torque, not so much top end performance

So modifying the design would have cost low-end torque?

 

[Tbot101]

So modifying the design would have cost low-end torque?

Not necessarily, we are testing that right now, but we have seen so far that modifying the cam timing quite a bit in the low end increases the torque and keeps it from falling off

 

[MikeM.]

So modifying the design would have cost low-end torque?

Mazda did design the engine around having a meaty mid-range (which is the same design philosophy with the new CX-9). If you want the intake optimized for all rpm's you will need variable length intake tracts which Mazda has actually developed and implemented on race engines (they were controlled by high speed electric servo motors). Kinda like a bunch of electrically operated trombones that were synchronized with the engine rpm's. Actually, there are also a number of ways to optimize the intake geometry so the intake flow is optimized for the flow rate and that have been implemented by a number of manufacturers over the years but they tend to add a lot of cost and complexity. And yes, the fixed CX-5 intakes are optimized for midrange are not going to flow optimally at high rpm. This is what I was referring to a few days ago when you asked me for flow bench data. I don't need flow bench data to know this but if you want a bunch of tables of numbers, it sounds like you could get them from Tbot101. I don't know why you want them though!

 

[Tbot101]

Mazda did design the engine around having a meaty mid-range (which is the same design philosophy with the new CX-9). If you want the intake optimized for all rpm's you will need variable length intake tracts which Mazda has actually developed and implemented on race engines (they were controlled by high speed electric servo motors). Kinda like a bunch of electrically operated trombones that were synchronized with the engine rpm's. Actually, there are also a number of ways to optimize the intake geometry so the intake flow is optimized for the flow rate and that have been implemented by a number of manufacturers over the years but they tend to add a lot of cost and complexity. And yes, the fixed CX-5 intakes are optimized for midrange are not going to flow optimally at high rpm. This is what I was referring to a few days ago when you asked me for flow bench data. I don't need flow bench data to know this but if you want a bunch of tables of numbers, it sounds like you could get them from Tbot101. I don't know why you want them though!

Please tell us how you came to the conclusion on how the intake, ports, and such are made for a "meaty mid range" ??


You don't know why people want scientifically backed evidence rather than forum speculation by a so called "expert" ??

 

[Unobtanium]

Mazda did design the engine around having a meaty mid-range (which is the same design philosophy with the new CX-9). If you want the intake optimized for all rpm's you will need variable length intake tracts which Mazda has actually developed and implemented on race engines (they were controlled by high speed electric servo motors). Kinda like a bunch of electrically operated trombones that were synchronized with the engine rpm's. Actually, there are also a number of ways to optimize the intake geometry so the intake flow is optimized for the flow rate and that have been implemented by a number of manufacturers over the years but they tend to add a lot of cost and complexity. And yes, the fixed CX-5 intakes are optimized for midrange are not going to flow optimally at high rpm. This is what I was referring to a few days ago when you asked me for flow bench data. I don't need flow bench data to know this but if you want a bunch of tables of numbers, it sounds like you could get them from Tbot101. I don't know why you want them though!

I dunno about that. Here is a dyno from a VQ37 like in my 370Z. It does not have variable intake runners. It is a lot more complex motor than the SkyActiv, though, with a lot more processing going on, IMO