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Discussion Starter #1 (Edited)

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That's a unicorn that everyone has chased to 20+ years. The military had an engine that could run on gas (but was actually a diesel) a LONG time ago (1960s, I think) but it ran like crap on gasoline -- although it WOULD run. It was more of a "if you have nothing else available..." sort of option.

If Mazda has actually solved it, and it appears they're confident they have, then they've truly come up with something special. I have a couple of ideas that might be involved in how they've done it -- we'll see if I'm right or not when it hits the streets. My guess is that their answer involves using variable compression along with very careful combustion-chamber design and flow dynamic modeling of the incoming charge as the entire trick to making HCCI work is having temperatures high enough in the ENTIRE air charge so when injection occurs ignition is even and immediate. It also likely involves a means of sensing the ignition event so as to be able to vary both injection timing and compression ratio to adjust for fuel variation (e.g. octane differences.) This means that at lower RPM and load the compression ratio is materially higher so as to drive way up the charge temperature under those conditions, while at higher load and output it can be lower and still work. Variable-intake timing can (potentially) accomplish that. If you can sense actual ignition delay then you can also time the injection event to account for variations caused by fuel octane (and OAT) differences.

The greatest improvement in efficiency is due to greater volumetric expansion, which extracts more of the heat of combustion. There is likely also a higher combustion temperature component since detonation is not a consideration and thus you do not need to intentionally reduce combustion temperatures to combat it (however, NOx emissions are still at issue, and higher combustion temps produce more NOx....)
 

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BTW if they really have made this work and it shows up there suddenly is an avenue for modding that hasn't existed (really) on the current Skyactiv platform.

See, Skyactiv has a high compression ratio, which is how they get their efficiency. But this means they have to be very "active" in management to avoid detonation, including VVT, ignition timing and similar. That in turn means adding a scroll to get more power is problematic as you quickly run into the limits of pump fuel.

CI engines have no such limit because detonation is not a consideration. As such as long as you can deliver the fuel you can shove more air in there and the penalty for coming up short on the fuel is that you don't make more power -- CI engines by definition run lean all the time except at full output, and that's perfectly ok!

The limit on being able to add more boost and fuel is strength and heat-dissipation related; if you go too far you lift the head (the pressure exceeds what the head gasket and/or bolts can hold), you melt something or something in the driveline (usually the bottom end) fails mechanically and catastrophically. That's wildly different than the world you live under the rules of in the SI world where you are forced into higher and higher octane fuel in order to prevent detonation, and ultimately the area under the curve that results in safe combustion makes further boost ill-advised (unless you want to run straight methanol for fuel or some silliness like that!)

It is entirely possible to get 50% output increases out of most CI engines from "factory" configurations while running straight-up and CHEAP pump fuel with "reasonable" safety, and with some strengthening (e.g. girdles on the bottom end, high-strength studs for the head, etc) a fair number of people have gone quite a bit further without winding up with internal engine parts on the outside of the block. I know a couple of people who have doubled the output of the ALH TDI engines (bigger turbo, crazy-increased flow injectors, higher-range MAP sensor plus the tune to use all that) but you wind up changing a LOT of other parts in the driveline (final drive, clutch, etc) because utterly nothing was originally designed for that and some (the clutch, specifically) will be destroyed immediately if you don't.

This could quite-easily be in our future if those crazy Japanese Mazda dudes have actually made HCCI work.
 

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Discussion Starter #4
It definitely sounds like if the Mazda engineers were able to achieve this technology, they will be ahead of the curve on pretty much all car manufactures. You definitely know your stuff about engines and how HCCI functions.


I know there are other threads about possible changes to the 2018 Mazda 6 (possibly using turbocharging), but I wonder if Mazda has cracked the barrier on this technology if this would be the direction they go?
 

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HCCI sounds promising, but managing the high compression has been the challenge. I think Mazda will be cautious about HCCI until they have some long term real world data. Remember, Mazda was one of the leaders in Wankel rotary engine technology, but outside of the RX7/RX8 it didn't get any traction.
 

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Discussion Starter #6
HCCI sounds promising, but managing the high compression has been the challenge. I think Mazda will be cautious about HCCI until they have some long term real world data. Remember, Mazda was one of the leaders in Wankel rotary engine technology, but outside of the RX7/RX8 it didn't get any traction.


Well, if I'm to believe that article....and autoblog is typically a good website for car info, Mazda is past the testing stage and could be ready to use the HCCI engine in the 2018 Mazda 3.
 

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I only mean that they will offer it in the Mazda 3 in limited numbers until they can get that long term data. I don't see them going gung-ho and offering it across the entire line-up.
 

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I only mean that they will offer it in the Mazda 3 in limited numbers until they can get that long term data. I don't see them going gung-ho and offering it across the entire line-up.


Gotcha, and I agree.
 

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Wankel engine has never panned out for Mazda, I'd be shocked to see them try an unknown technology in the North American market. Car makers used to use the public to test experimental stuff in the 70's and 80's, but they have all but stopped doing that as warranty costs or potential liability when it goes horribly wrong will stop them from anything like that.

It makes a good news soundbite, but the reality is that if they do not have a fully functioning product to show the world in physical driving form then there is little chance we'll see this tech this decade.

I also struggle mightily to believe that this technology would be able to handle extreme temperature changes like we have in Canada and the rust belt in the US. What are they going to use to help a cold engine start? I don't see warmed up gasoline or glow plugs doing the trick.
 

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I wouldn't doubt Mazda's ability or ambition to release new tech. They've done it before. Although people keep pointing back to the rotary as a failure, I see it as nothing but an engineering success. Just because it didn't succeed from a sales point of view doesn't mean that Mazda didn't learn from the experience. The same risk could be said for Skyactiv.


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Toyota hasn't updated the 3.5L engine for 10 years in the Camry and Corolla 1.8L for close to 20 years. The Camry platform hasn't changed much either, I still see the same 109 inch wheelbase from 2007.
That is how Toyota makes billions just like how the old GM made 3 minor changes to the 3800 in what 30 years?

Mazda is making engine changes after introducing the 2.5L within 6 years, expensive for a small car company.
 

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True, but if they actually make HCCI work then they will have something literally nobody else does -- and it will come with VERY sizable efficiency improvements PLUS be easily modified (which means additional "versions" with a LOT higher output will show up, whether through Mazda or third-party bolt-ons.)

Don't underestimate the technology advancement here, assuming they actually make it work. This is not an incremental change by any means -- it's effectively bringing diesel efficiency and power capacity to gasoline engines, which no other manufacturer has (thus far) pulled off.
 

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True, but if they actually make HCCI work then they will have something literally nobody else does -- and it will come with VERY sizable efficiency improvements PLUS be easily modified (which means additional "versions" with a LOT higher output will show up, whether through Mazda or third-party bolt-ons.)

Don't underestimate the technology advancement here, assuming they actually make it work. This is not an incremental change by any means -- it's effectively bringing diesel efficiency and power capacity to gasoline engines, which no other manufacturer has (thus far) pulled off.
Yes!

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I'm down with them trying stuff......as long as they don't stick their necks out so far as to get them chopped off, ie.... go out of business.
JMHO....let the Wankel and diesel die and concentrate on high output/high MPG engines. They should also get cracking on combining Skyactive with Electric motors for a hybrid and use that as a steeping stone to a fully electric car too.
 

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JMHO....let the Wankel and diesel die and concentrate on high output/high MPG engines. They should also get cracking on combining Skyactive with Electric motors for a hybrid and use that as a steeping stone to a fully electric car too.
Disagree on the HCCI.

HCCI, if they can make it work, beats hybrid in a big way -- there's a $3,000 battery (that's heavier than a dead priest as well, and accelerating mass does bad things to your fuel economy) you don't need, nor do you need the electric motors and switchgear. Yet both are going to get into the same efficiency area quite easily. Consider a "6" with an HCCI engine that can get within spitting distance of 50mpg @ 65mph. Impossible you say? Nope -- very possible without any further aero improvements. Hybrid will win in stop-n-go city driving due to regenerative braking, but that's it. That puts the current "6" in Prius territory in terms of fuel economy and yet it's a hell of a lot larger vehicle for materially less money.

Hybrid ultimately loses due to the extra energy conversions. No way around that one, it's physics. On top of that it loses (big) on money simply due to the additional components required. If you amortize acquisition cost + per-mile fuel and maintenance the HCCI engine vehicle wins BIG.

If Mazda has managed to actually make HCCI work they will slaughter anyone making hybrids -- they'll have a vehicle that costs $5,000 less (to make!) at an equivalent trim and quality level, that sells for ~$6-7,000 less, and yet returns equal or better fuel efficiency and performance.

That's fairly simple math, and it explains why they're after it. The other guys all know the math as well which is why they've all been after it to one degree or another.

Mazda can quite-easily go from a "small" car company to a monster with this engine tech if they have actually figured out how to make it work. That's the key "if"..... and it sounds like those crazy Japanese may indeed have figured it out.
 

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Not necessarily. As was mentioned above the majority of car manufacturers are risk averse. Many engines borrowing off 30 year old tech, while those companies who may be more willing to take risks may not have the talent or vision. Also realize that there are stockholders who often cripple a company' ability to invest over years of development. Mazda for better or worse has always been willing to take chances. And that's what makes them an exciting company IMO.

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