Mercedes Benz were sure their DiesOtto concept was the future and that was nearly 20 years ago!
Asking motorists what they want brings to mind Henry Ford's comment that 'When you ask what they want they say 'a faster horse''. In the UK it is going to be hard to prize the driver from their diesel. Big fat car with all the gadgets that would be unaffordable to fuel if the fuel was petrol, they're not going to give them up easily.
But the EV situation is one of a lack of charging infrastructure and in cities where EV's are most relevant, that problem becomes more acute.
Mazda may have faith in the ICE but diesel is just too expensive to build with the exhaust aftertreatments required. 4T petrol is heading in the same direction - unsolvable NOx output. Will Mazda succeed with HCCI where Mercedes Benz failed? Time will tell I guess, but HCCI is still fundamentally flawed in two crucial respects in my mind and successfully surmounting them will mean a high build cost - on a par with diesel.
And still, with the exception of Renault, no one is even considering 2T. If I can reduce idling UBHC from 9700ppm to 1600ppm, surely the OEMs could get the same improvement (and better) across the entire operating range faster that I will.
Quote from http://media.daimler.com/marsMediaSite/en/instance/ko/Engine-technology-Supercharger-diesel-engine-direct-gasoline-injection-DIESOTTO.xhtml?oid=9274497
"The DIESOTTO engine (2007)
The Mercedes-Benz F 700 research car outlines new approaches to mobility which uses resources sparingly. The key element is a novel propulsion system which combines the advantages of the low-emission gasoline engine with the fuel economy of the diesel engine.
The decisive steps in the development of the diesel engine to its present-day standard – combining dynamic performance with low fuel consumption – were made possible by turbocharging and common rail direct injection, both pioneering inventions of Mercedes-Benz. The DIESOTTO engine even takes this development a couple of important steps further in that systematic downsizing, achieved through the reduction in displacement and the number of cylinders, improves the degree of efficiency. Over and above this, a hybrid module supports the internal combustion engine especially in stop-and-go operation. With controlled homogeneous charge compression ignition, the diesel principle of controlled compression ignition is incorporated in a gasoline engine for the first time.
During start-off and under full load, the gasoline/air mixture is ignited by a spark plug as in a conventional gasoline engine. At part-load, i.e. at low and medium engine speeds, the DIESOTTO automatically switches to controlled charge compression ignition (homogeneous combustion) within one power stroke.
This minimizes nitrogen oxide emissions thanks to homogeneous combustion at reduced reaction temperatures. Additional emission control in the DIESOTTO engine is performed by a standard three-way catalytic converter. And finally, a highly efficient engine control system was incorporated to network the individual sub-systems into a unified propulsion concept.
The F 700 is powered by a compact four-cylinder engine with a displacement of 1.8 liters, which nevertheless affords the superior performance of a luxury-class sedan. A two-stage turbocharger is responsible for the engine’s excellent responsiveness and high-torque accelerating power. In addition, the internal combustion engine is supported by the electric motor of the hybrid module for starting off. Maximum output is 175 kW (238 hp); the electric motor develops another 15 kW (20 hp), and the system’s maximum torque is as high as 400 Newton meters. Acceleration from standstill to 100 km/h in 7.5 seconds testifies to the dynamism of the F 700 whose top speed is limited to 200 km/h. Despite this outstanding performance, the F 700 has a fuel consumption in the European Driving Cycle of just 5.3 liters (44.3 mpg), which corresponds to carbon dioxide emissions of 127 grams – an extremely low level for a car of this size."
End of Quote
The above are from the official site of Daimler.
The "downsizing" was in fashion in 2007.
Later, the heavily supercharged direct injection gasoline engines (good at the lab emission tests) proved not really good in the real world (consumption, emissions, etc).
Mercedes/Daimler failed because Mercedes had no control over the HCCI combustion.
The HCCI starts when the conditions pass over the threshold for auto-ignition.
A little more humidity in the air, a little leaner the air-fuel mixture, a little different the revs etc, etc, and the combustion starts from way earlier to way later than the ideal (what is the ideal? Just a few degrees after the TDC).
The only Mercedes could do was to use the HCCI combustion into a quite limited range of revs and loads.
According the previous,
the failure of the DiesOtto project of the Daimler/Mercedes is justified technically.
They had good reasons for not putting it in mass production.
In comparison to Mercedes uncontrolled HCCI, here is how Mazda solves the same problem.
MAZDA's SkyActiv-X solution
The Mazda SkyActiv-X HCCI (SP-CCI) is a different strory.
ISSUES ASSOCIATED WITH HOMOGENOUS CHARGE COMPRESSION IGNITION
One concept underpinning compression ignition in gasoline engines is homogenous charge compression ignition (HCCI). When a spark plug is used for ignition, the combustion has to spread out from the initial spark, resulting in a slower combustion speed. If, in addition to this, a leaner air-fuel mixture with more air is used, the flames created by the spark plug will fail to spread throughout the combustion chamber. With compression ignition, however, all fuel in the combustion chamber combusts simultaneously, resulting in a far higher combustion speed which, in turn, means that a leaner air-fuel mixture can be burned.
However, HCCI has not yet reached the point where it can be used in commercial applications because it is only used at low revolutions per minute and engine load ranges, and even these ranges are apt to change depending on driving conditions. Furthermore, the very limited range across which HCCI can take place makes it difficult to achieve stable switching between spark ignition and compression ignition.
Until now, overcoming these issues had required a major increase in the compression ratio, a more complex structure and the addition of high-precision controls.
. . .
Mazda has the control over the HCCI combustion:
it is an expanding fire ball into a united combustion chamber,
and this control allows Mazda to use the HCCI combustion (and its advantages) in a far wider range of revs and loads (only at the highest revs of the engine the SkyActiv-X turns to conventional gasoline with progressive combustion:
Do see the analysis of a Mazda SkyActiv-X expert in the following youtube video:
Go directly in the 21':35'' to 21':55'':
From the above video / lecture of Mazda:
"The ideal case is to keep this compression ignition event right after top dead center, so you get the maximum power output of that stroke.
Well, there is a problem:
In the lab this is great.
When you are outside, temperature, pressure, humidity all these things change.
And when these things change it might take a longer time for you to get actually to
this compression ignition threshold.
That way we don't get compression ignition happening when we need it to; we get less power out of each stroke.
The obvious solution is that we need to change our ignition timing relative to our ambient conditions.
So this is we do:
In SP-CCI,
inside the engine we actually place cylinder pressure sensors in each and every cylinder.
We're constantly looking at the pressure rise profile in each cylinder and we are adjusting the spark timing.
We have an ideal case where this is the rise rate, so that we could keep the peak pressure right after top dead center; and when we see something that's contrary to that, we adjust at the next combustion event, at the next cycle.
This way the cylinder pressure sensors not only let us monitor and control SP-CCI, but it also acts as a way to predict knock, predict at normal combustion as well as detecting knocking itself; hopefully it never knocks and it never pre ignites because we are already seeing trends and we can back off or change the spark timing to compensate for that.
So, these solutions along with a lot of other more much more complicated ones kind of led to this breakthrough that we call SP-CCI.
It's what makes the compression-ignition possible in our SkyActiv-X engine because we are running the spark plug all the time in both compression ignition mode and spark ignition mode.
We can actually drastically expand the range of compression ignition throughout most engine RPMs and engine loads; only at the very high engine speeds do we switch back to a spark ignition mode.
And not only that; because we're using this spark continuously, we could kind of phase in and out of the two modes very seamlessly, so we can avoid the problems of what other OEMs have run into.
When you guys drive these vehicles you actually know it's like I don't feel any difference it drives just like a regular gas car which is really the amazing part if you are not noticing anything that's a good sign.
So this is what SkyActiv-X and SP-CCI looks like. . ."
End of “Quote” from the above video.
PatBam HCCI Solution
According Mazda:
"The ideal case is to keep this compression ignition event right after top dead center, so you get the maximum power output of that stroke.”
Isn’t this exactly what the PatBam HCCI is doing?
Isn’t the PatBam solution a by far simpler solution than the SkyActiv-X of Mazda?
In the PatBam HCCI (divided combustion chamber, two-stage ignition) there are two cooperating combustion chambers: a small auxiliary and a big main.
A high compression ratio is used in the auxiliary combustion chamber.
A moderate compression ratio is used in the main combustion chamber wherein a homogeneous air-fuel mixture is compressed / heated near, yet below, the auto-ignition threshold.
The high compression ratio in the auxiliary combustion chamber causes the auto-ignition of the homogeneous lean air-fuel mixture therein (no spark plug required); the burnt gas bursts - through some "transfer ports", just before the TDC - into the main combustion chamber triggering its auto-ignition.
were made possible by turbocharging and common rail direct injection,
Wow! MB claim they invented turbocharging and common rail direct injection - when the rest of the world credit Buchi and Fiat (respectively). Corporate MB bullshit!
Until the world sees a functioning HCCI engine that can be controlled over the entire load/speed range and isn't excessively oversized to compensate for the lack of air utilisation then it is just so much words. Proof is what is required. And that Manolis is true of your concept also. I'm not taking a pop at you, but HCCI has existed as a possibility for so long now only a functioning example to prove its worth is plausible. Anything else is merely bolstering share price.
"It’s . . . Alive!"
. . .
In its current state of tune, the prototype engine is functional. That’s noteworthy only because the SPCCI tech is so unique that its working didn’t seem like a given until we had keyed the ignition for ourselves. Mazda’s engineers are operating on a more ambitious plane, however, and are adamant that they didn’t want the X’s efficiency to come with any compromises that would threaten the brand’s zoom-zoom image. They’re on the right track, because the X is plenty responsive and feels about as powerful as the current Mazda 3’s larger 2.5-liter four.
. . .
So far, the switchover from spark ignition to compression ignition is the only issue needing attention outside of final, production-ready engine calibration. The process is seamless, with zero vibrational cues that the X has chosen an ignition type and fully committed to it. However, it is audible, thanks to copious knock (detonation) that hangs around any time the engine isn’t fully in a single ignition setting. During clean transitions from spark to compression ignition or back, the X emits its stuttered knocking soundtrack for about a second or two. However, whenever the computers move close to one ignition state from the other, the knocking drags on. This condition, in which fuel mixtures aren’t quite set for the desired state of ignition, occurred whenever the engine was spinning at low rpm—a CI-favorable condition—but loads were moderate, favoring spark ignition. "
"But before you wonder why it's so much less powerful than the new turbocharged Skyactiv-G 2.5T that'll be out soon in the Mazda6, remember this: The Skyactiv-X engine is really intended to beat the weakling 2.0's fuel economy numbers (28 city, 38 highway) by as much as 30 percent, while seriously exceeding its power output of 155 hp and 150 lb-ft. In short, it aims to crush the 2.0 liter's economy with 2.5-liter power.
And it does so with a pleasing torque curve, which couldn't be more different from the peaky downsized turbo gas engines competitors use. Now, it's not as steep a torque curve as a modern turbodiesel, but it also doesn't run out of breath as early. There's unusual grunt all the way to redline, indicated at just shy of 6,000 rpm (where the true redline will be isn't clear at this point). While there will be a small electric motor to enable start-stop functionality on the production version of this engine, it's disabled in these prototypes, so all we're actually feeling is the extra churn enabled by the compression-ignition scheme.
That extra torque also lets Mazda get away with a shorter drive ratio and six-speed transmissions (both manual and automatic were available to test) without sacrificing economy, since the efficient operating range of the engine is so broad. That means less gears to run through when downchanging, less hunting in the automatic, and less complexity. The engine will turn about 1,000 more revs at 60 mph than a comparable Skyactiv-G, which also offers better response.
Really hammer on it at full load and it'll switch to spark ignition, seamlessly. It's only a tablet running on the dashboard that gives away which combustion type is happening, and in normal driving it's almost always in SPCCI mode. Snap off the throttle or back onto it quickly, and there's loud and obvious clatter, the most obvious sign that something's unusual.
That clatter is not supposed to be there. The Mazda engineer riding along tells us that these abrupt throttle position changes are very hard to tune for, that some preignition happens in these situations where the engine can't react quickly enough to the changed circumstances, and also that the company intends to tune these interludes out completely for production. That's going to be essential from an NVH (noise, vibration and harshness) standpoint, in our opinion, because the clatter is loud and jarring — it could certainly hinder broad acceptance."
You can find several similar reviews / drive tests in the Internet for the pre-production Mazda SkyActiv-X.
According the auto journalists / testers it is alive and it is working fine, As Mazda promises.
If the consumption is also as low as Mazda claims (20% lower than their current high-tech SkyActiv-G ), then it has the required qualifications / characteristics to become a great success.
You write:
"Until the world sees a functioning HCCI engine that can be controlled over the entire load/speed range and isn't excessively oversized to compensate for the lack of air utilisation then it is just so much words. Proof is what is required."
Aren't the previous reviews / drive tests the proof you are looking for?
You write:
"Until the world sees a functioning HCCI engine that can be controlled over the entire load/speed range and isn't excessively oversized to compensate for the lack of air utilisation then it is just so much words. Proof is what is required."
Aren't the previous reviews / drive tests the proof you are looking for?
Nope! Hyundai had its HCCI to the same stage but yet it didn't make production.
And.....
That clatter is not supposed to be there. The Mazda engineer riding along tells us that these abrupt throttle position changes are very hard to tune for, that some preignition happens in these situations where the engine can't react quickly enough to the changed circumstances, and also that the company intends to tune these interludes out completely for production. That's going to be essential from an NVH (noise, vibration and harshness) standpoint, in our opinion, because the clatter is loud and jarring — it could certainly hinder broad acceptance."
.....and given the above, unless that noise is silenced, Mazda's may not make production either. In its defence though, I'd say that it would be a shame if that prevented it being produced. Diesels make such a disgusting noise (nearly all of the time they are running) that a bit of clatter from the Mazda unit shouldn't deny it a future. With regard to production and the 'control' difficulties (inherent with HCCI) Mazda will have to be confident of the unit's ability to cope out in the field after thousands of miles of use. Hats off to Mazda if they succeed, but this is not going to be a cheap engine to build and onerous maintenance costs won't be welcome with end users.
Those who deal with engines, transmissions, fuel consumption optimization and the similar, may like to read the following “quote” from Mazda’s video / lecture at https://youtu.be/a82Wt53gu78 (the video in post #2358).
How is SkyActiv-X better?
Well, contrary to our intuition, in other words are trying to save the environment, we’re burning less gas, SkyActiv-X actually lets us have a better performance. The reason why it does that, is because of again compression ignition.
We’re plant work we’re anticipating on seeing about a 30% gain in torque over our current generation 2-liter SkyActiv-G engines.
The reason why, is because compression ignition happens so fast, that all the pressure released at the same time pushes the piston down in a harder fashion; that force of the piston moving down literally translates to torque.
So, like a Diesel engine, using compression ignition we get a lot more torque gains especially at low rpm. Low rpm torque, especially on the street, is what increases drivability.
Everybody likes a big American V8, because it is very very drivable. Why? Because it has torque right off the bat, so this is the main benefit, performance benefit, of SkyActiv-X.
Is intently I do want to point out the car does is tuned for 87 octane, but it will run a whole gamut of fuels, all the way to 92 – 93 octane, just because of the SP CCI process and similar to our SkyActiv turbo engines the torque peak will move with the change in octane of gas and that just results in slightly different performance feel, but there’s no diminishing, there’s no reduction of torque.
Of course we expect to have great fuel economy as well.
In this graph
we see fuel economy for your engine geeks this is BSFC and then engine load. When you compare our old generation shared platform MZR engines to our current SkyActiv-G engines to the new 2-liter SkyActiv-G engines, you’ll see on average about a 20% gain in fuel economy.
That’s again of course to do the benefits of compression lean compression ignition.
More importantly if you at the profile of this graph it’s really broad and flat over this wide range of engine loads.
It doesn’t have just one little sweet spot that actually affects how real-world fuel economy gets better and that’s really important to us as a brand at Mazda.
Of course this just shows 2,000rpm.
If you want to get a bigger picture of how the car does over a wide range of operating conditions, we would have to put slices of different engine speeds on top of that and build out a 3D map.
So another way to look at that is let’s assign a color to each range of fuel efficiency, black up here, being really thirsty orange. Not so orange is actually very efficient, and we stack all the different slices for all the different engine speeds on top of that, and then we come up with this 3D map, rotate it on its side; here imagine this orange area as being the topmost layer of a very efficient; think of it as a cake each color represents it’s a layer stack them on top of each other, and you have a fuel economy cake for lack of a better term you have cakes of different shapes; the SkyActiv-G cake is a little shorter, a little peak here the SkyActiv-X is taller and broader.
Now the reason why this matters is that most engines design right now target this concept of downsized turbo charging right we use us less displacement which means less fuel while you’re just what were you’re just humming along but instant that you need torque or to accelerate; you have this very thirsty turbocharger that kicks in and then it uses a lot of fuel.
An engine like that it actually has a very peaky the fuel economy cake while it’s running on just as three cylinder there’s loes displacement it’s o its high peak, but the instant the turbo kicks in you fall off the cliffs on the side. That’s why most of these engines have to be coupled with a CVT transmission because it needs to be kept in the sweet pot right on its peak but as we know driving these things usually doesn’t result in a lot of driving pleasure for us.
So, SkyActiv-X allows us to not only make a taller cake but a broader cake. The yellow region now expands all the way out here; well the reason why I have to explain this strange concept of a fuel economy cake because I can’t call it an efficiency island which is more complicated to understand is at least to the next point and this is what you guys will really feel when you get into the cars and drive it right off the bat. OK.
Most transmissions are designed with fuel economy in mind.
We have to save gas by staying at a low rpm at highway speeds, right?.
So many factors just add a lot more gears onto it, so that at eighth gear, or ninth gear on the highway you’re just sipping gas but the instant that you need to accelerate nothing happens because you need to downshift because there’s no torque available in that gear.
SkyActiv-G also suffers from this problem not nearly as much but we had to set the final drive ratio so that it stayed on a higher level of the fuel economy cake/
Then let’s say, at 3,000rpm so our final drive ratio was set so that let’s say at 60mph we’re running at 2,000rpm instead of 3,000rpm which uses a lot more gas.
Now you might already figure this out on a SkyActiv cake we’re running at the same layer 2,000rpm at 3,000rpm suddenly we don’t have to compromise or this constrain to run low rpm as you guys all know our tpm typically means more power, better response.
So now we can gear SkyActiv-X car with the shorter final drive ratio so that we can run out 3,000rpm on the highway all day long with no fuel penalties, that means you have better drivability, you have the same great fuel economy. There’s no trade-off what\s that noise? Yeah um actually if you guys look at the cars there’s another entire realm of NVH packaging that we tool these cars to, in order to control the noise of both, compression ignition combustion and the higher rpm and all that if you guys have noticed driving some of out six generation as they’ve progressed they’ve gotten a lot quieter. We’ve taken NVH very seriously and we’ve also applied that and leaps and bounds above and beyond in the cementation cars and they will talk about that a lot more too.
So, that’s actually a great segue now we have a great, we have a fun driving car, you don’t have to match on the gas all the time so you actually become very smooth and controlled with your inputs. It’s very direct, fun.
End of “Quote”
The HCCI can be considered as a substantially more "constant volume combustion".
The combustion is "instantaneous"; it completes into a few crankshaft degrees (4-5 degrees at lower revs, 12-15 degree at higher revs).
All the fuel is burnt at high expansion ratios.
In comparison, the progressive combustion in the conventional spark ignition and compression ignition (Diesel) engines
ends up with a big percentage of the fuel being burnt at lower expansion ratios (in a spark ignition engine having 13:1 compression ratio, a good part of the fuel is burnt at a, say, 8:1, or even lower, expansion ratio (lower expansion ratio means lower BTE). The nominal compression ratio is not saying the whole truth. The "average expansion ratio" says a lot more for the efficiency of the engine.
In the above video the one series of playing cards represent the progressive combustion wherein there is a flame front (the falling playing card) separating the burnt gas (the already fallen playing cards) from the not yet burnt air-fuel mixture (the still standing playing cards).
The other series of playing cards represents the instantaneous HCCI combustion: when the pressure / temperature pass the threshold, all the air-fuel mixture burns simultaneously (all the playing cards fall simultaneously).
The HCCI fits with lean and extra lean air fuel mixtures.
The leaner the mixture, the lower the peak temperature in the cylinder (they call it: low temperature combustion) and the less the thermal loss to the cylinder walls.
Mazda's SkyActiv-X has to switch to conventional (progressive combustion) spark ignition at high revs because they cannot further delay the spark to successfully create the fire ball that triggers the HCCI combustion.
In comparison, the PatBam HCCI architecture (two-stage combustion, divided combustion chamber, no spark plug at all), is expected to run on "constant volume combustion" all the way: from the lower revs to the red line revs.
I really hope you are making a demo engine with PatBam HCCI.
I expect there may be some burning issues on the edges of the auxiliary chamber but that can be overcome.
I watched the entire Mazda video. I really liked the simple clear explanation of how it works, how & why they came to the design & the advantages it gives. Thanks for the link.
Ok, back on 2T topic, Motocross Action magazine (as a matter of technical interest) recently dyno-tested a Euro-4
Husky ( KTM near-clone) TPI 250cc enduro bike & sawed-out a bit over 47 RWHP - even in its 'soft-tune' form..
A potential light-lithe, 2T 750 triple, emissions legal roadbike using that cylinder basic set-up would make a farce of the new Moto 2 Triumph 4T, as a showcase of G.P. racing progress..
But of course, the possible advent of a return of such a 2T, could well be seen.. as too much of a threat..
.. to the increasingly 'formulaic' Moto G.P. 'show', as the 'main event'...
"Well, we knocked the bastard off!"
Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).
Ok, back on 2T topic, Motocross Action magazine (as a matter of technical interest) recently dyno-tested a Euro-4
Husky ( KTM near-clone) TPI 250cc enduro bike & sawed-out a bit over 47 RWHP - even in its 'soft-tune' form..
A potential light-lithe, 2T 750 triple, emissions legal roadbike using that cylinder basic set-up would make a farce of the new Moto 2 Triumph 4T, as a showcase of G.P. racing progress..
But of course, the possible advent of a return of such a 2T, could well be seen.. as too much of a threat..
.. to the increasingly 'formulaic' Moto G.P. 'show', as the 'main event'...
Mach 3 or a Waterbottle in maybe a bit better chassis?
Or Team Kawasaki Australia KR 750, such as Croz punted around Mt Panorama, Bathurst - in a tidy.. (even now), 2min:13 odd.. nearly 40 years ago.. maybe Johnny, but by an 'order of magnitude' or 3.. more advanced..
"Well, we knocked the bastard off!"
Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).
Team Kawasaki Australia KR 750, such as Croz punted around Mt Panorama, Bathurst in 2min:13sec odd, nearly
40 years ago.. maybe Johnny, but by an 'order of magnitude' or 3.. more advanced..
Yes, the Neville Doyle days, remember them well. And that other kiwi Ginger Molloy on the Kawasaki H1R triple.
Friends had a bored kwaka triple in a jetski that cut out on me and couldnt be started and a plurry shark swam under me. Taught me to make sure the jetting was right from then on.
Johnny, while on the subject of marine 2T's & also a matter of technical interest,
Manolis has previously posted some interesting data on BRP/Evinrude E-TEC DFI - BSFC capabilities..
& those engines have long since operated on a dual 'stratified charge'/S.I. best fuel econ/emissions set-up..
"Well, we knocked the bastard off!"
Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).
Johnny, while on the subject of marine 2T's & also a matter of technical interest,
Manolis has previously posted some interesting data on BRP/Evinrude E-TEC DFI - BSFC capabilities..
& those engines have long since operated on a dual 'stratified charge'/S.I. best fuel econ/emissions set-up..
Righto, thank you. Am working on a two stroke design at the moment.
