This all sounds like good news!
So Mazda never rolled out the Skyactiv X compression ignition engine (or whatever they call it) in the US. I wish they had.
It sounds like the SkyactivZ will be a similar thing but updated? That's cool. I'd like to see that engine in other models too.
Keith Tanner said:https://www.autoweek.com/news/a64230531/mazda-ev-strategy-2027-suv/
"Including SkyActiv-Z, the number of engine units will be reduced to less than half, and the control software will be consolidated to two-thirds in the future," the automaker noted."
I wonder if the real reason for the 2.5l in the Miata is there will be no appropriate smaller engine in Mazda's lineup. I wonder if this also suggests a Miata specific hot rod engine as in the ND2/3 is off the table.
maschinenbau said:Regarding an electrified Miata, it seems like they are hedging their bets:
UmeE36 M3a says that consideration has been given to a Miata EV, but this is clearly not his favored option.
“If all internal combustion engines were banned, then we would have no choice,” he says, “and of course, our engineering team is studying both ways – battery EV and ICE Miata. But whatever we do, the ICE one is lighter.”
I've read elsewhere that the 2.5 Skyactiv Z will likely be paired to a hybrid powertrain in other applications, probably with an Atkinson cycle. So if they must go hybrid Miata in the near future, they have probably engineered the platform to accommodate. Remember, EV does not necessarily mean EV-only. EV could easily mean battery-ICE mild hybrid, which Mazda has hinted about in the past.
That would make for some really excellent NA parts-bin builds similar to what has been done with Toyota Atkinson motors...
Edit: wait, Ford has an Atkinson MZR motor in a few different hybrids - has anyone made a Frankenstein MZR build using that head?
Snrub said:
I don't really understand lambda 1 from the perspective of higher revs. Are emissions standards that restrictive at 7000rpm?
Yes. Enrichment is being eliminated as much as possible, and for power is one area.
This is exciting news....I've raced every generation of Miata in some form or fashion in the past few years and I seriously love this car.
alfadriver said:Snrub said:
I don't really understand lambda 1 from the perspective of higher revs. Are emissions standards that restrictive at 7000rpm?
Yes. Enrichment is being eliminated as much as possible, and for power is one area.
You can also make more power if you have good atomization. The only real reasons for running rich at max power are for cooling and to ensure that every oxygen molecule gets something to combine with. Direct injection allows for finer atomization to handle point 2.
For point 1... I assume that they are putting some effort into better thermal control and temperature-tolerant materials.
I'll allow that one rotary tuner found best power at .97 Lambda and some IMSA teams were running lean of stoich under race conditions. It's nice to see that piston engines are finally catching up to the way rotaries laugh off high combustion temperatures.
Keith Tanner said:Floating Doc (Forum Supporter) said:If we achieve the goal of smaller, lighter, high efficiency batteries, that might open the door for a hybrid Miata. I don't see it happening if the hybrid system makes the car weight anywhere close to 3,000 pounds. That would make it into a totally different car.
No need for that much battery. A non-plugin Prius battery from 15 years ago is about 85 lbs, and the Miata is already carrying something like 26 lbs of lead acid that may be redundant. The electric motor could replace the flywheel, which is currently 19 lbs.
That's why I specified mild hybrid, it wouldn't have significant electric-only range. The point would be momentary power boosts and regeneration.
So, a rear drive Insight?
I'm down for it!
BTW, many newer hybrids don't even have 12v "batteries" any more. They have a lithium-ion subsection attached to the main battery pack whose job is to supply the 12v bootstrap power. They're about the size of a 20ah USB powerpack.
In reply to Pete. (l33t FS) :
Most enrichment is for temperature control. Generally, you can get through first and second gear, and things are hot enough to need more than LBT to control something. But lots of effort has gone into valves, valve seats, exhaust materials, and sensors to not need to keep the temps down.
Most engines get best output at 12.5:1 or so (for gasoline). Just to make sure as much fuel is burnt as possible. And there are cooling benefits for knock control if the compression is high enough.
But all that generally is academic thanks to temperature problems. Up until recently.
Lots of race engines are developed to run stoich or lean, so they can get better mileage at WOT. But those engines are totally designed around running WOT, where production motors are designed to run 99% all of their lives at part throttle.
In reply to alfadriver :
That was the two big issues with rotaries - they couldn't get much compression without hurting power because of internal airflow issues, and they were only really good at running at or near WOT. Not ideal for a production engine. Most of Mazda's development over the years was in trying to eke out efficiency at low loads where street cars actually drive.
The 10:1 compression RX-8 rotors seem to hurt power in the top end in order to gain more low load efficiency. The highest power race engines used 8.5:1 compression rotors for max internal airflow at high RPM. Sounds a lot like Flathead issues to me...
One engineer on another forum pointed out that even 20 years ago, compression ratios (piston engines) were generally one or two numbers higher than optimal for best power, but low load efficiency was much more important for a street car.
With that in mind, I wonder what Mazda has in store for THIS engine compression wise.
In reply to Pete. (l33t FS) :
My gut tells me close to 12:1.
Had another thought. That engineer's comments were from before VVT and drive by wire could make up for part load drivability and efficiency, so bumping compression up was probably one of the methods they needed for part throttle snappiness...
TravisTheHuman said:Edit: wait, Ford has an Atkinson MZR motor in a few different hybrids - has anyone made a Frankenstein MZR build using that head?
There was a team who was taking hybrid motors from Toyota's, making them non-hybrid, and I believe swapping exhaust cams for intake cams to create some very surprising engines for crap can racing. They had videos on YouTube that were pretty wild to watch. I think they installed a motor in an MR2 and wrote about their experiences and development.
Found it!
Watch Gears And Gasoline Swap A Camry Hybrid Engine Into Their MR-S Race Car
Pete. (l33t FS) said:Had another thought. That engineer's comments were from before VVT and drive by wire could make up for part load drivability and efficiency, so bumping compression up was probably one of the methods they needed for part throttle snappiness...
One thing to add to that, whatever you are doing for throttle response, it has to be pretty quick. ETC has gotten fast enough, but VVT isn't. And it's not really about the speed of the actuators, but it's a problem with going too fast, you transverse areas on the speed-load plane so fast that there are areas that are 1) not mapped, so the running data is wrong, and 2) the actual cam movement causes a huge dip on torque output that can be worsened by ETC.
So ETC can be used to kind of increase the throttle response to make the feel better, but VCT has to be done carefully to not make it worse.
(for those not familiar- ETC = electronic throttle control, aka drive by wire. I'm a lazy typeist, so I'll use the easy initials)
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