Zoom Zoom or Putt Putt

[deepfriedsushi]

Thanks Paris.

I'd like to point out that this "bogging" or "straining" is actually not very noticeable. You'd have to be paying attention quite a bit. It comes across as a low frequency hum with a very slight increase in low frequency vibration. MUCH MUCH less dramatic than how my Miata strains when I apply more throttle in too high of a gear.

All cars would bog or strain in the same manner if under the same situation. However, on a flat road, the 2.5L actually has enough torque at that low rpm to accelerate while it's bogging/straining. But on a hill, I think all it really takes is a slightly larger increase to the throttle to get it to downshift.

CX-SV - the talk about a graph makes me want to dyno the CX5. There are always some going on with the car clubs in the bay area. Would be neat to see what the output curves are like with the 2.5L. I love that the maximum torque output is at a low 3250rpm, but it'd be cool to see how flat that torque curve is through out the rev band.

 

[CX-SV]

CX-SV - the talk about a graph makes me want to dyno the CX5. There are always some going on with the car clubs in the bay area. Would be neat to see what the output curves are like with the 2.5L. I love that the maximum torque output is at a low 3250rpm, but it'd be cool to see how flat that torque curve is through out the rev band.

Yes, that would be nice to see that graph via dyno, hope somebody does this. I would expect torque curves of both engines to be quite flat.

Torque stats showing nice step up with the 2.5L:

2.0L 150 lb-ft @4000
2.5L 185 lb-ft @3250

I still have same question as above, are any other automakers using Atkinson Cycle on a non-hybrid engine? I suspect its use has noticeable impact on low rpm feel.

 

[MikeM.]

I still have same question as above, are any other automakers using Atkinson Cycle on a non-hybrid engine? I suspect its use has noticeable impact on low rpm feel.

My unscientific observation has been the biggest difference in efficiency between the Skyactiv 2.0L engine and traditional (non-Atkinson) engines is related more to power demand than RPM. To clarify, Atkinson cycle is of greatest use when the engine is being asked to produce less power than it is capable of at a given rpm. At very low rpm the power demand is often almost equal to max power at that rpm so Atkinson not of much benefit. Exceptions to this would include very light throttle applications at low rpm (such as when descending a slight grade or very gradually coasting to a lower speed). Also, idling. The 2.0L Atkinson engine appears to be very miserly with fuel when it is fully warmed up and is merely idling.

Under heavier loads an Atkinson cycle engine behaves as a non-Atkinson cycle engine.

 

[CX-SV]

My unscientific observation has been the biggest difference in efficiency between the Skyactiv 2.0L engine and traditional (non-Atkinson) engines is related more to power demand than RPM. To clarify, Atkinson cycle is of greatest use when the engine is being asked to produce less power than it is capable of at a given rpm. At very low rpm the power demand is often almost equal to max power at that rpm so Atkinson not of much benefit. Exceptions to this would include very light throttle applications at low rpm (such as when descending a slight grade or very gradually coasting to a lower speed). Also, idling. The 2.0L Atkinson engine appears to be very miserly with fuel when it is fully warmed up and is merely idling.

Under heavier loads an Atkinson cycle engine behaves as a non-Atkinson cycle engine.

Thanks, sounds reasonable, I think the feel might be noticeable under light loads at moderate revs, when more power is demanded. I know of no other automaker producing Atkinson cycle engines in non-hybrid applications.

 

[paris1]

Yes, that would be nice to see that graph via dyno, hope somebody does this. I would expect torque curves of both engines to be quite flat.

Torque stats showing nice step up with the 2.5L:

2.0L 150 lb-ft @4000
2.5L 185 lb-ft @3250

I still have same question as above, are any other automakers using Atkinson Cycle on a non-hybrid engine? I suspect its use has noticeable impact on low rpm feel.

What would really be interesting is to see how much torque is produced below those peaks and how flat the resultant curve is.

 

[MikeM.]

Thanks, sounds reasonable, I think the feel might be noticeable under light loads at moderate revs, when more power is demanded. I know of no other automaker producing Atkinson cycle engines in non-hybrid applications.

Keep in mind, the modern "Atkinson" engines, such as Skyactiv, are not true Atkinson cycle engines but modified Otto cycle engines because they use standard Otto cycle crankshafts and linkages. It is due to the way the variable valve timing is used that they are called "Atkinson" engines.

One major disadvantage of a true Atkinson cycle engine is lower power output at all rpm's and especially at lower rpm's. Since the Skyactive engines appear to produce competitive hp and torque, I'm thinking the variable valve timing changes from Atkinson to Otto when more power is demanded at any given rpm. Thus, the variable valve timing can be used to increase power above what an engine without variable valve timing could achieve (at the expense of efficiency). This could be the difference in "the feel" you refer to when more power is demanded (variable valve timing after it switches from Atkinson mode to Otto power mode).

By watching the instantaneous MPG figures under many different conditions I have come to the conclusion the engine is sometimes more efficient climbing a hill at higher rpm's (lower gear) than "lugging" up the hill at rpm's so low that no acceleration is possible without switching down a gear. But this kind of observation is very difficult to make because, switching to a lower gear often causes the car to accelerate (difficult to maintain steady speed) and thus the instantaneous MPG's may appear lower in the lower gear. To achieve maximum MPG, I encourage the transmission to shift to a lower gear (generally just by depressing the accelerator quickly just enough to affect a one (or sometimes two) gear downshift. I then gently accelerate UP the hill in the lower gear until I can ease off the throttle and let the transmission shift into the higher gear as I ease over the top of the hill gradually bleeding the extra speed I had built up while climbing the hill. It can also be done in manual shift mode but the auto mode works fine once you learn how the transmission responds to different inputs. This is now second nature to me but of course it's only useful when I am not in traffic tight enough to make gradual variations in speed problematic to other drivers.

I should add that, the reason I think this technique works to increase MPG is that it keeps the engine in Atkinson cycle mode longer. Even though it takes more power to slowly accelerate up the hill, it allows the engine to stay in Atkinson mode due to the higher rpms. And then, the benefit of building a little speed comes into play as you are able to hold a higher gear with very light throttle input as you roll over the top of the hill, also a condition in which the engine can remain in Atkinson cycle mode. My best guess why Mazda didn't design this shift behavior into the transmission is because there is no way for the tranny to know how long a given condition (in this case a hill climb) is going to last. That will not happen until they mate the transmission shift logic to a GPS that knows the grade of every road. So the shift behavior is, as all things are, a compromise. In this case it is holding the higher gear to avoid constant gear changes (called "hunting").

 

[CX-SV]

Keep in mind, the modern "Atkinson" engines, such as Skyactiv, are not true Atkinson cycle engines but modified Otto cycle engines because they use standard Otto cycle crankshafts and linkages. It is due to the way the variable valve timing is used that they are called "Atkinson" engines.

One major disadvantage of a true Atkinson cycle engine is lower power output at all rpm's and especially at lower rpm's. Since the Skyactive engines appear to produce competitive hp and torque, I'm thinking the variable valve timing changes from Atkinson to Otto when more power is demanded at any given rpm. Thus, the variable valve timing can be used to increase power above what an engine without variable valve timing could achieve (at the expense of efficiency). This could be the difference in "the feel" you refer to when more power is demanded (variable valve timing after it switches from Atkinson mode to Otto power mode).

.

Yes, I was aware of Atkinson cycle being achieved via the variable value timing for Mazda Skyactiv gas engines (essentially simulated Atkinsons), same holds true for the hybrids using Atkinson cycle too. Agreed, this could account for the boggy "feel" many are noticing under certain lower rpm conditions.

 

[gk26]

Got a graph of the 2.0L here
http://wardsauto.com/vehicles-amp-technology/how-mazdas-skyactiv-fuel-efficiency-technology-works

 

[MikeM.]

Got a graph of the 2.0L here
http://wardsauto.com/vehicles-amp-technology/how-mazdas-skyactiv-fuel-efficiency-technology-works

Good find!

That's a really informative article and the torque curve graph is impressive (very flat from 2000 rpm all the way to redline). Of course I already knew this from driving one almost daily but it's nice to see a graphical representation of what I've been experiencing.

I'm not a Mazda fanboy (the CX-5 is my first Mazda) but it's pretty obvious, Mazda has hit a home run with this engine and tranny.

It's too bad because all internal combustion engines are eventually dated technology.

 

[piotrek91]

Got a graph of the 2.0L here
http://wardsauto.com/vehicles-amp-technology/how-mazdas-skyactiv-fuel-efficiency-technology-works

That graph is for the 2012-2013 mazda 3.
The CX-5 has 13:1 compression and the 4-2-1 exhaust header, and has a nicer torque curve:

(image found by googling for CX-5 torque curve.. not sure exactly where it came from, but it looks like a legit mazda graph)

 

[CX-SV]

Good catch piotrek91 on the 2.0L Skyactiv (Mazda 3) chart, I was wondering why the torque rating was 148 lb-ft. at 4100 rpm.

 

[NinjaNoises]

I thought this thread was a bash on the transmission. OP said the engine was fine.

Solution: get the manual transmission

 

[CX-SV]

Solution: Use the very good manual mode of Skyactiv auto transmission, it's a more cost effective solution than trading/selling and buying another CX-5.

 

[piotrek91]

Solution: Use the very good manual mode of Skyactiv auto transmission, it's a more cost effective solution than trading/selling and buying another CX-5.

I fully agree with this statement.
The manual mode on the auto CX-5 I test drove was excellent.

 

[Chris_Top_Her]

Putt Putt in the butt..

 

[Nikoman]

The transmission in the 2.5 is actually very GOOD. It shifts faster and smoother than my Audi A4 tiptronic. The uphill issue is simply laughable.

 

[CodyZoom]

I agree with most posts on here, I came from a WRX then a Turbocharged Saab - the CX-5 is definitely pokey compared to the turbos, but you get used to it. Once you learn how to anticipate the tranny, it's really smooth and trouble free. Loving the MPGs and 87 octane prices!

 

[29134]

Thanks for all of the feedback guys. Sorry I wasn't able to respond sooner. Thanks especially to Nick3434, TreyP, deepfriedsushi, and ALafya for confirming my observations. And I laugh at those who were of the opinion that it's the driver that's defective.

A few of you described the problem as "bogging down" or "straining". Thank you. That's a much better description of the problem, rather than "shuddering". I agree that for the most part, the transmission is very smooth. I'm just disappointed that the transmission isn't smarter when it comes to downshifting. Why would the programmers program the transmission to stay in a gear that causes the engine to bog down or strain?

The car that I traded in was a CX-9, which obviously was a V6 and a had a lot more horsepower, but I also used to own an Automatic Miata (I know, what was I thinking), and I don't recall having any issues with that transmission.

I guess I'll just have to get used to being more aggressive with the throttle, or gets used to shifting into manual mode.

 

[CX-SV]

A few of you described the problem as "bogging down" or "straining". Thank you. That's a much better description of the problem, rather than "shuddering". I agree that for the most part, the transmission is very smooth. I'm just disappointed that the transmission isn't smarter when it comes to downshifting. Why would the programmers program the transmission to stay in a gear that causes the engine to bog down or strain?
The car that I traded in was a CX-9, which obviously was a V6 and a had a lot more horsepower, but I also used to own an Automatic Miata (I know, what was I thinking), and I don't recall having any issues with that transmission.

.

Gas mileage/fuel efficiency is the short answer. Look at the large difference in gas mileage between CX-5 and CX-9, versus the smaller difference in performance.

 

[paris1]

The car that I traded in was a CX-9, which obviously was a V6 and a had a lot more horsepower, but I also used to own an Automatic Miata (I know, what was I thinking), and I don't recall having any issues with that transmission. I guess I'll just have to get used to being more aggressive with the throttle, or gets used to shifting into manual mode.

I assume you know that the CX-9 and MX-5 autoboxes are traditional torque converter designs with an entirely different set of priorities than the CX-5 gearbox. Think of it this way, the earlier automatics were designed with the following priorities in mind: 1)automated operation 2)minimizing performance losses compared to a manual gearbox and 3)minimizing fuel economy loss while maintaining advatages of torque converter. The SkyActiv automatic reorders its prioities thusly: 1) automated operation similar to, but not the same as, a traditional torque converter box, 2) maximizing fuel economy and 3)performance more or less equal to an manual. Your job, as you indicated in your last sentence, is to learn to play those priorities in a manner that suits you. It's a brave new world with everyone chasing our exalted leader's 54.5 mpg 2025 CAFE bogey. It can only get worse from here (unless a sudden epidemic of sanity breaks out in DC), so be glad you got in early when technology is still able to stay one step ahead of the madness.