Mazda's SkyActiv X... uses spark-controlled knock! (maybe)

[cRiPpLe_rOoStEr]

Originally Posted by hayden55

Next gen engine after the X is rumored to hit 56% from Mazdas very optimistic mouth so fingers crossed. This is more beneficial to saving energy than electrification if more manufacuters can get their lineups to start utilizing 50%+ efficient engines.

Even though I believe some sort of electrification is unavoidable, such as the mild-hybrids, an enhancement to the thermal efficiency of the ICEs is still desirable. Well, there is a lot of room for improvements which still make more sense than simply trying to outlaw engines.

[hayden55]

Originally Posted by cRiPpLe_rOoStEr

Even though I believe some sort of electrification is unavoidable, such as the mild-hybrids, an enhancement to the thermal efficiency of the ICEs is still desirable. Well, there is a lot of room for improvements which still make more sense than simply trying to outlaw engines.

True I agree with you. People who are trying to outlaw engines don't realize how we get the majority of our fuels to make our "clean" electricity... Sadly for a large majority of the world, it is coal-fired power plants which are extremely inefficient in the 30s on thermal efficiency.
I think a highly efficient engine and a good ERC of some sort is the way to go. Well, ERC meaning energy recovery system aka a hybrid. I think the BEV situation is a large flop when you look at the current picture (extremely complex manufacturing and supply chain, high government subsidies, low range, high weight, expensive etc...).
If you can get one of Mazda's compression ignition engines around 50% thermally efficient running on 87 octane coupled with an ERC system and a fantastic drag coefficient that's pretty much the last nail in the BEV coffin unless you're part of the very small locations in the world that can realistically run solar panels and afford entry.

[Ecky]

Honda has been building ~40% thermally efficient engines for two decades. The engine in my Insight is ~39% efficient over a pretty wide band, and it's not hard to stay in that band. Honda achieved this efficiency in an engine without forced induction, without variable valve timing (thought it still has variable lift), and without resorting to the Miller/Atkinson cycle which robs torque, and these engines will generally run reliably for 3-500k miles before needing any kind of service. The Accord hybrid's engine peaks at over 40%, but I haven't seen any BSFC numbers for it. Which is not to say that Mazda significantly exceeding that isn't an amazing accomplishment, but comparatively speaking the current Skyactiv engines are not that great.

I'm a proponent of PEHV and hybridization. It makes a lot of sense to me to add a small battery and reliable electric motor in return for being able to simplify and downsize gasoline engines. An engine need not be efficient over such a wide power band if by electric assistance, it need only run at its optimal RPM and toggle on and off as needed. This is the arrangement Honda has in the Accord hybrid, and it works. A car need only have a large enough engine for steady-state driving, which for most sedans is a 1.0-1.5L 3 or 4 cylinder, and you can add as much performance and passing power on top of that as you want with the addition of an electrical system.

[hayden55]

Originally Posted by Ecky

Honda has been building ~40% thermally efficient engines for two decades. The engine in my Insight is ~39% efficient over a pretty wide band, and it's not hard to stay in that band. Honda achieved this efficiency in an engine without forced induction, without variable valve timing (thought it still has variable lift), and without resorting to the Miller/Atkinson cycle which robs torque, and these engines will generally run reliably for 3-500k miles before needing any kind of service. The Accord hybrid's engine peaks at over 40%, but I haven't seen any BSFC numbers for it. Which is not to say that Mazda significantly exceeding that isn't an amazing accomplishment, but comparatively speaking the current Skyactiv engines are not that great.

Eh, I love Honda but they are not over 40%. The reason why it may seem like it though is Honda has always been very lightweight with very great aero and low accessory drive losses and were the only ones who could get lean burn to pass emissions until they finally gave up on it. I wanna see some sources lol. Hilariously I have a recent report from a group at Stanford that tested the 1997 LS1 and did a report on it. That damn engine hits 35% thermal efficiency at load at 2000 rpm lol. There are a lot of 35% thermal efficiency engines from the 90s forward though. Makes you wonder if manufacturers stagnated on improvements on purpose to save money and just sell cars until here recently when the regulations went up.

[Ecky]

Originally Posted by hayden55

Eh, I love Honda but they are not over 40%. The reason why it may seem like it though is Honda has always been very lightweight with very great aero and was just were the only ones who could get lean burn to pass emissions until they finally gave up on it. I wanna see some sources lol. Hilariously I have a recent report from a group at Stanford that tested the 1997 LS1 and did a report on it. That damn engine hits 35% thermal efficiency at load at 2000 rpm lol. There are a lot of 35% thermal efficiency engines from the 90s forward though. Makes you wonder if manufacturers stagnated on improvements on purpose to save money and just sell cars until here recently when the regulations went up.

https://www.greencarreports.com/news...shade-of-green

Good news: Honda says that the thermal efficiency of the internal combustion engine is up to 40 percent (compared to 38.9 percent of the last generation). The batteries are also physically smaller this year too, which helps the Accord fit a bigger gas tank between the rear seats and the trunk—14.8 gallons in the normal Accord vs. 12.8 gallons in the hybrid.

They finally dethroned the G1 Insight's motor in 2014.

EDIT: It's also a beltless motor, with no gearbox/transmission to speak of. It connects to the wheels with a single clutched reduction gear. It has heat recovery on the exhaust, and is assisted by a 135kw motor.

[Ecky]

A more direct source:

https://www.hondarandd.jp/point.php?pid=1271&lang=en

A 2.0 L gasoline engine for which the development target was the realization of thermal efficiency of 40% or higher (a first for Honda) has been developed for the new Accord hybrid. As in the case of the previous model, the developed engine employs the Atkinson cycle and the cooled EGR system. In order to further increase theoretical thermal efficiency, knocking has been reduced through the application of mirror finishing to the intake valves and the use of sodium-filled exhaust valves, and the higher compression ratio than the previous model. To reduce heat loss, high-speed combustion has been realized by increasing EGR amount and employing high-tumble-flow ports. Technologies for the reduction of mechanical loss, including low-friction plateau honing and a low-friction balance shaft, have been employed in the other engine framework, helping to enable the realization of a minimum fuel consumption rate of 208.1 g/kWh (thermal efficiency: 40.6%) in the engine unit in isolation.
The verification results of the fuel efficiency performance achieved in an actual vehicle through the use of the newly-developed engine demonstrated a reduction of 1.96 mpg in fuel consumption in the US Combined Mode as an effect of the engine unit in isolation.

For comparison, the 2000 Insight's engine has a zone from ~1500-2500rpm where it can achieve 215g/kwh, or approximately 39.5% thermal efficiency. Most driving occurs in the region of 225g/kwh, or ~37.7% thermally efficient.




If Mazda can break 50%, that will, of course, be revolutionary.

[hayden55]

Ah true. The engineer in me was counting 38.9% as not 40 so I have a problem with being too literal and arguing oops. Using 6.2lb of gasoline and 33557Wh/gal that works out to 38.9% (not 39.5). I guess my point was everyone has stagnated in the 35-39.9 region for the last 20 years until about 2014 when they started hitting 40s in streetcars and bumping crazy percents every year here recently. I thought you meant they have been breaking 40 for the last decades. Honda got lucky because they could do lean burn to get great numbers on most of their small cars from the 80s-00s and could get them to pass emissions before carb basically outlawed lean burn for their atrocious NOx emissions lol. I'm still skeptical on that Accord hybrid number. They are extremely inefficient to be getting 40%+ thermal efficiency.

[Ecky]

The Accord hybrid is a pretty big car to be getting 50mpg...

EDIT: I've been under the impression most others have been in the ~30-35 range, with the exception of maybe Toyota and Mazda with their Skyactiv, but I don't have numbers to back that up. Until rather recently, most American manufacturers had no variable timing or lift on any of their engines.

[hayden55]

Originally Posted by Ecky

The Accord hybrid is a pretty big car to be getting 50mpg...

EDIT: I've been under the impression most others have been in the ~30-35 range, with the exception of maybe Toyota and Mazda with their Skyactiv, but I don't have numbers to back that up. Until rather recently, most American manufacturers had no variable timing or lift on any of their engines.

Ah I see where the confusion is. I thought you were talking about the gen 1 honda accord.