Homogeneous Charge Compression Ignition From Mazda

[stevorocket]

http://www.roadandtrack.com/new-car...asoline-engine-compression-ignition-skyactiv/



BY COLLIN WOODARD Road and Track
JAN 17, 2017
6.0k
If you want a car that's enjoyable to drive, you owe it to yourself to swing by the Mazda dealership. Every vehicle the company builds gets an added dose of sporty driving character. But Mazda has also quietly turned itself into an MPG leader over the past several years with its thrifty SkyActiv family of engines. Now, the automaker is doing something particularly revolutionary to boost the economy of its gasoline engines: Removing the spark plugs entirely.

According to a report from the Nikkei Asian Review, next-generation SkyActiv engines won't use spark plugs at all. Instead, they'll borrow a page out of the diesel engine's book and use compression ignition.

Called Homogeneous Charge Compression Ignition, it's a technology that promises diesel-like fuel economy out of gasoline engines. HCCI isn't a new concept—numerous major automakers have built experimental concepts powered by HCCI engines—though Mazda stands to be the first automaker to use it in production vehicles. Reportedly, it will improve gas mileage by 30 percent, while also reducing emissions.

The 2018 Mazda3 is the first car expected to use the new engine design, with the rest of the lineup getting it over the next few years.

via Autoblog

 

[Stuart]

Although it may increase economy, does it have the same NOx issues that diesel has?

 

[stevorocket]

More here

http://www.nissan-global.com/EN/TECHNOLOGY/OVERVIEW/hcci.html

 

[Moobs]

It's so new the first papers were written about it in the 1930s. The first motorcycle to use HCCI in anger was the Honda ARC250 (Active Radical Combustion) around about 30 years ago, Nissan, Toyota and Ford have all had vehicles in the market that have operated a form of HCCI over part of their map, although these 3 have all been diesel engines. GM were "months away" from launching a gasoline HCCI car about 7 years ago, as were hyundai.

Low NOx is the main reason for HCCI, the efficiency benefits are over-hyped and largely an artifact of inappropriate testing. Mazda need to do something as they're really going to struggle to hit their CO2 targets in the future.

Anyone who remembers "run-on" will have personally experienced HCCI combustion.

J

 

[Stuart]

If other manufacturers have dabbled with it, what's the reason for them not using it?
Or is it just that there is insufficient reason to change.

 

[Moobs]

If other manufacturers have dabbled with it, what's the reason for them not using it?
Or is it just that there is insufficient reason to change.

HCCI is fine at steady-state (fixed speed and load) but doesn't cope with transients very well and also only operates a restricted speed and load. As it approaches idealistic constant-volume combustion (otto-cycle) it should be reasonably efficient, however due to the limited speed-load window, it can't really take advantage of this - hence why you never see generators operating in an HCCI mode.

The other manufacturers just know that the only way they can hit their future CO2 targets (now that the diesel market will disappear in the 2020s) is through wide-scale electrification.