I can't say this for certain as I'm not a Mazda engineer. However, my educated guess here is that they've changed the crank shaft as the compression ratio is determined by difference between the top most and bottom most travel of the piston. You can change the effective compression ratio by leaving the intake valves open during part of the compression stroke which we know Mazda does. However, if it were simply that I think people would have figured that out already and unlocked higher compression via a tune. I think Mazda is just using that to move between Otto cycle when power is needed and miller for efficiency when under light load. VW is also doing this with their new b cycle 2.0T. Though I think VW is using exhaust not intake but either way it's doing the same thing to the effective compression ratio.
SkyActiv-X Review, glimpse of possibly what to expect in future CX-5s
- Thread starter Xeler8ing
- Start date
I can't say this for certain as I'm not a Mazda engineer. However, my educated guess here is that they've changed the crank shaft as the compression ratio is determined by difference between the top most and bottom most travel of the piston. You can change the effective compression ratio by leaving the intake valves open during part of the compression stroke which we know Mazda does. However, if it were simply that I think people would have figured that out already and unlocked higher compression via a tune. I think Mazda is just using that to move between Otto cycle when power is needed and miller for efficiency when under light load. VW is also doing this with their new b cycle 2.0T. Though I think VW is using exhaust not intake but either way it's doing the same thing to the effective compression ratio.
It's a good thing not to have a minimum fuel requirement of premium.
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- Denver, CO
I thought Chris_Top_Her had tuned his to use premium? Don't recall though.
I think octane numbers in US are derived from ----> (RON + MON)/2
Thing is with exception of the 2.5L turbo, using premium here doesn't alter the power and torque levels
The easiest way to increase compression ration is with a piston that is slightly higher which reduces the volume at top dead center which is likely the way Mazda did it. Someone with part number access could verify that the pistons are different part numbers for the different compression ratio engines. Then you can change the tune to get more power from higher octane gas.
Indeed
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- 2017 CX-5 GT AWD
Skyactive-X review and driving hands on
Good article on what is coming
https://arstechnica.com/cars/2018/0...-the-internal-combustion-engine-has-a-future/
Good article on what is coming
https://arstechnica.com/cars/2018/0...-the-internal-combustion-engine-has-a-future/
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- Plano, Texas, USA
Skyactive-X review and driving hands on
So its no longer spark-plug-less Homogeneous Charge Compression Ignition, HCCI, anymore like originally planned by Mazda, but Spark Controlled Compression Ignition, SPCCI. Nevertheless its a nice break through by Mazda! (cool)
So its no longer spark-plug-less Homogeneous Charge Compression Ignition, HCCI, anymore like originally planned by Mazda, but Spark Controlled Compression Ignition, SPCCI. Nevertheless its a nice break through by Mazda! (cool)
To be fair, they also called SPCCI when it was announced in august/september last year:
https://jalopnik.com/i-drove-mazda-s-holy-grail-of-gasoline-engines-and-it-w-1800874806
It looks very promising
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- 2021 CX-9 Sig
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- 2021 CX-5 GT
This looks good and this caught my attention:
"The end result is a 2.0L, four-cylinder engine, made from aluminum, that runs on 87 octane fuel but has a 30-percent increase in peak torque compared to the company's current Skyactiv-G unit. Because SPCCI releases so much energy in such a short amount of time, it pushes the pistons down with more force at low rpm, which means more torque and therefore more drivability. (You can run the engine on higher octane fuels, and it will adapt to shift the torque peak higher up the rev range.)"
I saw something elsewhere were someone at Mazda mentioned the performance benefits of the new engines and the potential for more sportier cars because of it.
"The end result is a 2.0L, four-cylinder engine, made from aluminum, that runs on 87 octane fuel but has a 30-percent increase in peak torque compared to the company's current Skyactiv-G unit. Because SPCCI releases so much energy in such a short amount of time, it pushes the pistons down with more force at low rpm, which means more torque and therefore more drivability. (You can run the engine on higher octane fuels, and it will adapt to shift the torque peak higher up the rev range.)"
I saw something elsewhere were someone at Mazda mentioned the performance benefits of the new engines and the potential for more sportier cars because of it.
PaulZooms
16.5 GT Sensing
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- Lakewood, CO
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- 2016.5 CX-5 GT
Will the new engine “feature” cylinder deactivation when released?
I doubt it will.
Also SPCCI should give fuel benefits for the whole power band - resulting in better real world mpg numbers.
A 3 with 34 city and 50 highway and a 40 combined is really good.
