[hserus]

https://www.topgear.com/car-news/fut...bustion-engine

The engine fires using both compression (like diesels) and spark plug (like petrol mills), not sure just how they managed that.

I wonder just what fuel air mixture and compression ratio adjustment they worked out to manage this and not have the engine catch fire.

What do we have here, an engine that behaves like a diesel if you fill diesel and like a petrol if you fill petrol? One that runs on half petrol half diesel?

[CrAzY dRiVeR]

Originally Posted by hserus

What do we have here, an engine that behaves like a diesel if you fill diesel and like a petrol if you fill petrol? One that runs on half petrol half diesel?

Quite interesting and thanks for sharing.

From what I understand, it's a petrol engine that runs with very high compression ratios as seen in diesel engines. Usually, petrol engines run much lower compression ratios, or need high octane fuel when the compression ratios are increased (But still way short of the diesels) for more performance.

Without the high octane fuel, the fuel will just pre-ignite before reaching the compression stroke and that is bad for the engine.

Now Mazda claims to have developed a system which can monitor and fire the spark plugs and create a pre-ignition (which is now a part of the cycle rather than unintended) before it ignites under the full compression. Benefits include high torque and efficiency typical of high compression diesel engines, but with cleaner petrol emissions.

Sounds complex when it comes to fueling requirements and longevity of the things. My biggest doubt is how they have overcome pre-ignition and made it desirable, so to speak. Hope Mazda cracks it right.

[Sankar]

Originally Posted by hserus

https://www.topgear.com/car-news/fut...bustion-engine

The engine fires using both compression (like diesels) and spark plug (like petrol mills), not sure just how they managed that.

I wonder just what fuel air mixture and compression ratio adjustment they worked out to manage this and not have the engine catch fire.

What do we have here, an engine that behaves like a diesel if you fill diesel and like a petrol if you fill petrol? One that runs on half petrol half diesel?

Mazda is on a high with their Skyactiv Petrol and Skyactiv Diesels. They are thinking outside the box and have tumbled the box upside down so that their Diesels run lower compression and Petrols run higher compression But Skyactiv Diesels have/had a problem of engine oil dilution with Diesel and the oil level in the sump rising. Their solution was to change the dipstick Anyway hope the engines are reliable.

[reignofchaos]

This tech is very similar to what Merc and Ferrari (probably renault? not sure!) are using in F1 - Homogenous Charge Compression Ignition. A pure HCCI engine does not require spark plugs. However the ones being developed right now are still hybrids that use spark plugs. HCCI is used for cruising at low speeds while it shifts to spark plugs when under load such as when accelerating or running at high speeds.

However here they are more optimized for longevity and efficiency than outright power (though both power and efficiency are in a sense interrelated).

The primary advantage over conventional GDI engines is that the fuel burns better and with efficiencies approaching 55% in the ideal case - very similar to the efficiency of a diesel engine.

Many companies are looking at this tech for its potential benefits - VW, GM, Hyundai and now Mazda as it offers better combustion of the fuel with far less NOx emissions. The latter is essential to reach emission targets imposed by governments around the world.

Just like we saw a large scale shift from EFI naturally aspirated engines to GDI turbos in the automotive world in the last few years, the next shift would be to HCCI. Unlike downsizing though, this might offer real benefits.

[Sutripta]

First the Miller cycle, and now HCCI (when others seem to have given up on it).
Working with the Wankel must have really built character at Mazda.

Regards
Sutripta

[shashanka]

Originally Posted by hserus

https://www.topgear.com/car-news/fut...bustion-engine
The engine fires using both compression (like diesels) and spark plug (like petrol mills), not sure just how they managed that.
I wonder just what fuel air mixture and compression ratio adjustment they worked out to manage this and not have the engine catch fire.
What do we have here, an engine that behaves like a diesel if you fill diesel and like a petrol if you fill petrol? One that runs on half petrol half diesel?

Thanks for the update, hserus - the dividing lines between compression ignition / spark ignition is getting increasingly blurred! For one, the compression ratios are getting inverted and so are the performance characteristics - with diesels going up to 5200 rpm (http://www.mazda.com/en/innovation/t...iv/skyactiv-d/), with the gasoline engines giving comparative torque/power outputs & calorific inefficiencies, while their diesel counterparts are claiming particulate emissions comparable to their gasoline stablemates!

The best of all possible worlds indeed. For diesel addicts like me, it is music to the ears that significant engine weight reductions are in the pipeline, due to the lighter scantlings all round, including smaller crank pin/main bearing sizes - the domino effect from that reduced comp. ratio, resulting in reduced stress thresholds!

Well, alright, so there are a few hiccups too - cold start niggles and warm-up misfiring being the ones highlighted in the media releases - but where's the harm in keeping fingers crossed & hoping for the best! In this Utopian world, one can just hope that M&M and TM-JLR try to catch up as best they can!

[sgiitk]

Originally Posted by Sutripta

First the Miller cycle, and now HCCI (when others seem to have given up on it).
Working with the Wankel must have really built character at Mazda.

I still miss the Wankels. Pollution and fuel consumption killed these ultra compact and smooth mills.

[hserus]

Originally Posted by sgiitk

I still miss the Wankels. Pollution and fuel consumption killed these ultra compact and smooth mills.

Lovely article - from a Jalopnik journalist who is a trained automotive engineer - on his trip to the Mazda plant and a preview of the Skyactiv+ engine.

http://jalopnik.com/mazda-s-holy-gra...opnik_facebook

[sumeethaldankar]

Mazda has developed a new gas engine that's far more efficient than existing motors.
The Skyactiv-X engine uses compression rather than spark to ignite the fuel-air mixture.
It can be used quickly and easily in existing Mazda vehicle designs without adding costs.

https://www.yahoo.com/finance/news/w...183036367.html

Mazda has come with a new type of engine which works on compression similar to Diesel engines to improve their fuel efficiency and meet emission regulations. Looks like this might turn out to be a electric car fighter if it manages to get more FE from regular gas engines.

[navin]

Originally Posted by sumeethaldankar

Mazda has come with a new type of engine which works on compression similar to Diesel engines to improve their fuel efficiency and meet emission regulations. Looks like this might turn out to be a electric car fighter if it manages to get more FE from regular gas engines.

Here is a video on HCCI engines and Mazda's twist on it.

https://www.youtube.com/watch?v=9KhzMGbQXmY

In effect there will be a spark plug but it wont be used except when required (too cold/hot).

The same presenter also explains why rotary engines are not as efficient as we thought they are

https://www.youtube.com/watch?v=v3uGJGzUYCI

[extreme_torque]

Originally Posted by navin

Here is a video on HCCI engines and Mazda's twist on it.

I think this one deserves an altogether new thread because this is a problem that none of the big car makers including the Germans could figure out. I have huge respect for Mazda for their combination of performance, reliability, quality and price. Here is a car maker which punches far above its weight when it comes to engineering stuff.

[shashanka]

Originally Posted by extreme_torque

I think this one deserves an altogether new thread because this is a problem that none of the big car makers including the Germans could figure out. I have huge respect for Mazda for their combination of performance, reliability, quality and price. Here is a car maker which punches far above its weight when it comes to engineering stuff.

+1 I'd just add another virtue to the list - tenacity & perseverance. When the rest of the competition had given up on the Wankel rotary, Mazda persevered & came up with some notable cars & came furthest in sorting out the gas sealing problems. One could also add their relatively recent success in the GDI application.

[im_srini]

Originally Posted by reignofchaos

This tech is very similar to what Merc and Ferrari ( probably Renault ? not sure ! ) are using in F1 - Homogenous Charge Compression Ignition.

Cool video about F1 plugs
Who would've thought they moved the pre-combustion chamber into the spark-plug !

https://www.youtube.com/watch?v=rfKN_TwfhnY

Originally Posted by sumeethaldankar

Looks like this might turn out to be a electric car fighter if it manages to get more FE from regular gas engines.

More likely the last gasp of the Otto 4-stroke gasoline engine, the takeover of the electrics is inevitable...

Originally Posted by shashanka

When the rest of the competition had given up on the Wankel rotary, Mazda persevered & came up with some notable cars & came furthest in sorting out the gas sealing problems.

True, the RX-7 & RX-8 still command high prices in the used-car market, but they do come with huge caveats about their thirst for fuel & major reliability issues.
That said, in my book it's their 4-rotor LMP 787s from the early 90's that're really spectacular, even more than their Wankel engined street cars.

On a side note, Suzuki, yes, very same maker of cars for "unsavvy people" made a Wankel-engined bike way back in the early 70's !

https://www.youtube.com/watch?v=ammve9wcIzQ&t=

~

[shashanka]

Originally Posted by im_srini

On a side note, Suzuki, yes, very same maker of cars.... made a Wankel-engined bike way back in the early 70's !

One more feather in the cap for the Maruti owners club!

[Sparky]

As the majority of the automotive industry continues working toward an electrified future, Mazda appears to be making a bold attempt to save the internal combustion engine.

Mazda unveiled an innovative breakthrough dubbed the Skyactiv-X engine that the automaker claims to have the performance of a traditional gasoline engine as well as the torque and fuel-efficiency of a diesel-powered option. Mazda describes it as “the world’s first commercial gasoline engine to use compression ignition.”

Mazda’s new Skyactiv-X engine runs on gasoline yet functions like a diesel engine by using a technology the automaker calls Spark-Controlled Compression Ignition (SCCI). Essentially, the engine uses compression ignition to burn its fuel, while still relying on a spark plug to initiate this combustion. The engine promises up to 30-percent more torque and a 20-percent improvement in fuel economy, figures that can definitely be appreciated in an industry continuing to be influenced by growing fuel emission regulations.

https://www.youtube.com/watch?v=9G1eOU2Eguw

Source: NY Daily News