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- Plano, Texas, USA
LOL!
But only gets 1 mpg gain on FWD and 0 mpg gain for AWD? Mazda’s programmers need to learn something from VW’s engineers!
CX-5 Cylinder deactivation
- Thread starter sjbraun55
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But only gets 1 mpg gain on FWD and 0 mpg gain for AWD? Mazda’s programmers need to learn something from VW’s engineers!
Mazda engineers are known for taking something really known and common, and tweaking it into much more efficient same. The way they might have decided to go with their design was to keep de-activated cylinders shut for much less cycles at a time then current designs. This is partially to preserve the pressure of the air spring trapped in de-activated cylinder, given low-tension rings. Then run 1 and 4 for a few power cycles to raise the temperature, release accumulated PCV stuff on intake valves, etc, and shut them off again, re-gaining the air spring pressure.
To make it work in the way that the operator wouldn't notice the transition is an art in itself, but doable.
In this case the fuel economy (let's say, theoretical one) wouldn't be that much higher, but that's what we see in the specs. GM V8 engines run in 4-cylinder mode for minutes at a time, and fuel economy improvement is higher, but still negligible.
I'm surprised that they didn't go with something similar to the Dynamic Split Fire system where all cylinders are involved in de-activation, but it is much costlier and heavier proposition.
They might have achieved whatever fuel economy goal they had, however minimal, with tweaked cheapest de-activation system.
To make it work in the way that the operator wouldn't notice the transition is an art in itself, but doable.
In this case the fuel economy (let's say, theoretical one) wouldn't be that much higher, but that's what we see in the specs. GM V8 engines run in 4-cylinder mode for minutes at a time, and fuel economy improvement is higher, but still negligible.
I'm surprised that they didn't go with something similar to the Dynamic Split Fire system where all cylinders are involved in de-activation, but it is much costlier and heavier proposition.
They might have achieved whatever fuel economy goal they had, however minimal, with tweaked cheapest de-activation system.
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- 18 CX-5
From the owner's manuals I noticed that the Automatic Transaxle Fluid capacity has changed between 17 & 18 MY.
2018: 8.0 L (8.5 US qt, 7.0 Imp qt)
2017: 7.8 L (8.2 US qt, 6.9 Imp qt)
Is this change due to CD? If so is it because the cylinders (with CD feature) are actually larger requiring more lubricant? Or is it just a new preventative guideline to refill with more lubricant hopefully to avoid all those potential problems with CD?
2018: 8.0 L (8.5 US qt, 7.0 Imp qt)
2017: 7.8 L (8.2 US qt, 6.9 Imp qt)
Is this change due to CD? If so is it because the cylinders (with CD feature) are actually larger requiring more lubricant? Or is it just a new preventative guideline to refill with more lubricant hopefully to avoid all those potential problems with CD?
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- 2022 2.5GT
By the way, I'm not sure I understand what do you mean by this:
... hydraulic lash adjuster that deactivates the compression in the cylinder.
It shows in the second pdf that the lash adjuster can be shortened by oil pressure so that the valves remain closed. This leaves the piston reciprocating without fuel or ignition. The residual compression and depression balance themselves out and almost eliminates the “pumping losses” that would otherwise work against efficiency.
It seems that it’s as simple as letting cylinders 1 and 4 run light.
The system detects constant (steady) light load demand and then seamlessly shuts down the outer 2 cylinders. If the demand changes, the system immediately brings in the 2 cylinders back in - again, seamlessly. In the above youtube clip, Thomas says he can’t detect it operating in the absence of a light that some vehicles have.
I’m not familiar with other brands but there is only one other 4 cylinder version on a 1.4 Mitsubishi engine which has the reputation of being utterly reliable.
Once you get a bee in your bonnet it seems like no amount of reassurance will convince you and you are not prepared to be open minded. I can tell you that after 5 years of oil consumption issues with 2.2 diesels, this newer version in my 2017 model is completely cured. What has changed? Well they’ve changed the design of the pistons and rings and they’ve changed the mapping of the DPF regeneration to give much shorter periods of post injection. So! After years of dilution problems, they’ve found a solution. In getting up 9000 miles the oil has not budged (unless of course there is an astonishing match of consumption and dilution but unlike the 2016.5 model the oil doesn’t stink of diesel). There are many other manufacturers still suffering with dilution and it appears to me that Mazda have fixed it. I’m not sure what the “many issues” with CD are but with the current success with piston rings is anything to go by, it shouldn’t be associated with that. Add to that newer high tech oils and greater accuracy of engine management systems, why shouldn’t it work? My diesel completely shuts of diesel on over run to conserve fuel so if I was to coast down a several mile descent, those cylinders would be completely starved of fuel. BTW, I’d very interested in the comments from anyone who can compare before and after the 2017 model oil dilution on the 2.5 Skyactive G.
Nope, the system detects constant light load conditions and will work its long as the vehicle is operated. I doubt Mazda would risk any VW shenanigans!
LOL!
But only gets 1 mpg gain on FWD and 0 mpg gain for AWD? Mazda’s programmers need to learn something from VW’s engineers!
This fixation with fuel consumption in the US bewilders me. Its even added to the sales bumf just to keep you happy. Engine development is driven by legislation and the overwhelming driving force is the reduction in harmful emissions. True, there is a modest improvement in fuel consumption but just like a 6 cylinder engine has and exponential improvement in emissions over an 8 cylinder and a 3 cylinder engine has the same improvement over a 4 cylinder engine, a 2 cylinder engine, even if only temporarily, gives a monumental improvement over the same engine running on 4 cylinders - it makes a big difference to the average. When vehicle manufacturers meet with legislators, they have to present plans of how they intend improving emissions to work towards the next mile post. They also have to produce plans for recyclability - the further impact on the environment. Its currently held back by current US policy but even Mr Trump had a softer approach in his recent European meetings. However, the technology and the benefits crossover and CD has been available in Europe for some time, its only new to you. I honestly wish I could get my hands on one but they don’t sell the 2.5G here.
Its a good question and the answer is, probably. In this article on CD there is the only reference I can find to the transmission being equipped to combat potential vibration issues that used to be associated with CD. Again I quote Thomas who says the vehicle is very smooth and very quiet. I have trawled the Mazda tech website and can’t find out what the “fulcrum” consists of but without knowing what it consists of, I might be looking in the wrong place and trust me there are 1000s of pages. Maybe I’m thinking too hard about something that was already there and just serves to dampen vibration.
https://insidemazda.mazdausa.com/the-mazda-way/technology/mazdas-new-cylinder-deactivation/
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Even if the rings and valves sealed perfectly, the pressure in the deactivated cylinder also drops as it cools. Most of that happens during the last power stroke where heat energy is turned into mechanical work. The retained exhaust gas will still be hot initially, but the heat will dissipate into the head, block, and piston, and the pressure will drop accordingly. If you want to keep the cylinder pressure high, you need to keep it hot, which would mean firing the cylinder again relatively frequently. I'm not sure how frequently.
First, cylinder deactivation is not new to the US. It's been around since the early 1980s.
Second, CO2 emissions and fuel economy go hand in hand. A negligible improvement in fuel economy equates to a negligible improvement in CO2 emissions.
Regarding regulatory policy, the US has had stricter controls on things like NOx and particulates while Europe has had stricter controls on CO2. The other difference is that the US has been working the CO2 problem by putting more emphasis on hybrids, EVs, and alternative fuel vehicles, while Europe has lower CO2 limits for regular vehicles. That's why we're filled with hybrids and you're filled with diesels.
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- Plano, Texas, USA
Yeah the capacity change definitely is related to cylinder deactivation which added a fulcrum inside transmission to fight engine vibration. Based on specs from Anchorman, Mazda still uses the same model number on transmissions, FW6A-EL (FWD) and FW6AX-EL (AWD), used by SA-G with or without cylinder deactivation. And transmission with cylinder deactivation has the same capacity as the ones, GW6A-EL (FWD) and GW6AX-EL (AWD), used on diesel. So who knows. (uhm)
BTW, Mazda also dropped rear differential gear lub capacity from 0.48 US qt to 0.37 US qt since 2017 MY for unknown reason.
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- Plano, Texas, USA
We really appreciate all the information you provided to us on Mazdas cylinder deactivation but unfortunately after all the readings Im still not convinced as I dont see anything special by Mazda to fight against inherent issues associated with cylinder deactivation. Im specially concerned on thermodynamic imbalance between 2 always-active inner cylinders and 2 sometime-active outer cylinders. We can only guess Mazda is smart enough to use the system sparsely, but then the question is why bother? And with added complexity on valve train, the longevity of it may suffer even if the system been used only sparsely.
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- 18 CX-5
Could this change in 2017 MY be due to the introduction of "ball bearing rear differential" that was introduced as one of improvements in 2nd gen CX-5? It was mentioned in the All-new CX-5 Press Kit document that boasts about reducing friction & improved efficiency with a ball bearing design
I am far off from this but - will the ball bearing rear differential fit into 2016 as a replacement?
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- Plano, Texas, USA
Actually I remember Mazda had modified the input shaft bearing from sleeve to ball bearing mentioned in one rear differential TSB if my memory serves me correctly. It also mentioned the production change on front differential casing to accommodate new bearing. So most likely you cant just replace the bearing, but the whole rear differential needs to get replaced.
Mazda appear to be going in the other direction to other manufacturers, their cars are dropping weight not adding it on like Mazda.
That's not good for performance or economy.
That's not good for performance or economy.
It's not a surprise their cars are gaining weight. It's because of the move to "premium". Their cars lose weight when they transitioned to the SkyActiv platform, but every new model since then has slowly gained a little weight.
So there's been 8 pages on this thread. What are we really trying to find out in this thread?
2018 Mazda CX-5s are coming with cylinder deactivation whether we like it or not. If you don't like it, vote with your wallet; don't buy the 2018s. I honestly think that's the only way you can convince Mazda to drop cylinder deactivation on their CX-5 engine.
So there's been 8 pages on this thread. What are we really trying to find out in this thread?
2018 Mazda CX-5s are coming with cylinder deactivation whether we like it or not. If you don't like it, vote with your wallet; don't buy the 2018s. I honestly think that's the only way you can convince Mazda to drop cylinder deactivation on their CX-5 engine.
I’ll bet that a lot of the weight gain came when Mazda stiffened their chassis for the 2017 model. The noise deafening added as well. Yet the loss of fuel economy was minor compared to before. Mazda’s bigger vision is to make so called “class above” vehicles that meet their customers desires. I believe they are still on the right track.
Thing is won't be limited to the CX-5, Mazda 6 gets it and my hunch is in the not too distant future so will the Mazda 3
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