2018 - [Mazda] 3 IV

Auto Actualité a écrit:En deux mots, les moteurs essence Mazda vont carburer sur le même fonctionnement des moteurs diesel, par haute compression du mélange air essence. Si cela devait se concrétiser, Mazda deviendrait le premier constructeur à produire ce type de moteur en série.
L’auto-allumage par haute compression (allumage par compression) apportera plusieurs avantages; meilleur rendement du couple moteur à bas régime, consommation réduite de 30%, émissions réduites. Les mêmes avantages que le moteur diesel, sans les problèmes d’émissions qui, on l’a appris ces derniers mois, donnent bien du mal aux constructeurs qui s’évertuent à respecter les normes antipollution sur les NOx et les particules. Mais ce type de moteur ne réduit en rien les émissions de CO2.

L’auto-allumage par haute compression (allumage par compression) apportera plusieurs avantages; meilleur rendement du couple moteur à bas régime, consommation réduite de 30%, émissions réduites. Les mêmes avantages que le moteur diesel, sans les problèmes d’émissions qui, on l’a appris ces derniers mois, donnent bien du mal aux constructeurs qui s’évertuent à respecter les normes antipollution sur les NOx et les particules. Mais ce type de moteur ne réduit en rien les émissions de CO2.

Motoring.com.au a écrit:Mazda will introduce a pioneering new engine next year that’s claimed to return 30 per cent better fuel consumption by combusting petrol without a spark plug, using ultra-high compression.

According to Japanese news site Nikkei.com, the new technology will be a world first when it’s introduced towards the end of 2018 — most likely in the next-generation Mazda3.


The new tech, called Homogeneous Charge Compression Ignition (HCCI), sees the fuel-air mix subjected to pressures well beyond current petrol engine technology.

Mazda’s SKYACTIV-G petrol engine already has a high — for a petrol engine — 14:1 compression ratio but the new range of engines are thought to come with a stratospheric 18:1 ratio.

The pressures involved during combustion are so high in the HCCI engine that spark plugs are not needed to trigger a combustion.

In the past other car-makers have experimented with HCCI but have struggled with issues of premature combustion and controlling the burn of petrol to ensure there is no ‘spike’ in emissions.

Managing heat and the rate of combustion at high revs has also proven huge problems in the past.

It’s not known how Mazda’s new engine manages the combustion over an entire engine range while complying with emission regulations, but the claim that it has achieved a 30 per cent boost in efficiency while reducing exhaust emissions could prove yet another blow for the diesel engine.

As well as the new HCCI engine, Nikkei reports that the Japanese car-maker has developed a new pure-electric vehicle that it plans to begin mass-producing in 2019.

Following the new pure-EV, Mazda will also launch its next-generation plug-in hybrid technology in 2021.

It’s not yet known how this will differ from existing tech used by other car-makers.

Mazda is expected to continue offering conventionally powered vehicles until at least 2030.

Disadvantages
-Achieving cold start capability.
- High heat release and pressure rise rates contribute to engine wear.
- Autoignition is difficult to control, unlike the ignition event in SI and diesel engines, which are controlled by spark plugs and in-cylinder fuel injectors, respectively.[6]
- HCCI engines have a small power range, constrained at low loads by lean flammability limits and high loads by in-cylinder pressure restrictions.[7]
- Carbon monoxide (CO) and hydrocarbon (HC) pre-catalyst emissions are higher than a typical spark ignition engine, caused by incomplete oxidation (due to the rapid combustion event and low in-cylinder temperatures) and trapped crevice gases, respectively.[8]

Advantages
- Since HCCI engines are fuel-lean, they can operate at diesel-like compression ratios (>15), thus achieving 30% higher efficiencies than conventional SI gasoline engines.[2]
- Homogeneous mixing of fuel and air leads to cleaner combustion and lower emissions. Because peak temperatures are significantly lower than in typical SI engines, NOx levels are almost negligible. Additionally, the technique does not produce soot.[3]
- HCCI engines can operate on gasoline, diesel fuel, and most alternative fuels.[4]
- HCCI avoids throttle losses, which further improves efficiency.[5]

Minh Nhut a écrit:Présentation de la technologie au salon de Francfort + concept de la 3 au salon de Tokyo selon Motoring
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Hence, again as per the ‘half new’ MkII CX-5, the successor for the MkIII Mazda3 (launched in January 2014, facelifted in July 2016 and pictured here in a design sketch) will be known internally as a ‘6.5-generation’ model.