Mazda's engine development
 

Sounds weird to me...kind of a gas engine, but semi diesel design?

https://www.caranddriver.com/reviews/2019-mazda-3-with-skyactiv-x-compression-ignition-gas-engine-prototype-drive-review

Engineering explained always does a good job braking down new car tech. "lean burning" gasoline engines has been one of those techs that have been pursued forever. It seems mazda has commercialized it for at least part of the engines operating conditions

https://www.youtube.com/watch?v=yNSxow3W7ek

Not a new concept, but Mazda seems to be able to make it work commercially.

A friend of mine had one of those in high school. Darned thing would ping like crazy every time he pushed on the gas.
Took 30 seconds to shut down after he turned off the key too!

Mazda goes mmmmmmmmmmm

They have been calling their variable cam timing SkyActive for some time now.
My general description is it's load based variable cam timing with mixture and ignition to match.

Friend as a year old Mazda 3. It does pretty well. Seems to have plenty of power when needed and gets great gas mileage cruising.

Ford is doing an Achates opposed Piston engine. The plan is to make a 2.7l engine with 42-45% thermal efficiency. This will mean mileage in the 40+ mpg range with a Ford F150, on gasoline.

A lot of the articles refrain from speculating on gas mileage, I think I read to expect Prius type of gas mileage, like 50+ MPG with 60 MPG not out of the question.

If they hit that mark it will be a game changer.

30% improvement would be pretty substantial. Mazda is such a cool company, the smallest of the Japanese manufacturers but possibly the most innovative.

Variable compression, right?

45% thermal efficiency?

http://forums.pelicanparts.com/suppo...ys/explode.gif

Almost like a common rail.

I like

Ooo? What’s the timeline on that. I’ve been saying I want an f150 sometime in the next 5 years....

Carnot Cycle! About the only thing I remember from my ME classes.

The article did not mention variable mechanical compression.

However it using an explosion of richer fuel/air near the spark plug to further compress the leaner fuel/air that was taken in during the intake stroke.

so I read the first few paragraphs and I'm not clear on what's new here?

mazda wanted to use compression only to ignite an ultra lean fuel/air mixture but it wouldn't work so they brilliantly introduced spark to the mixture and boom, skyactiv x!

I think Infiniti has come out with a variable compression engine, also a cool idea.

It's both a compression and spark ignition engine, and goes between the two modes depending on load. Best of both worlds between a diesel and gas engine, but using gas and at a cost comparable to a standard gas engine.

Think of it like a thermonuclear bomb.

A fission bomb creates the environment for a fusion bomb to go off.

The combustion chamber has a fuel/air ratio for compression ignition.

A precise second direct injection fuel pulse creates a small area near the spark plug that fires off like a conventional gasoline engine, this explosion raises the compression of the remaining leaner fuel/air in the cylinder and allows it to combust from compression rather than ignition spark.

Did that make sense?

yes. we had fuel and air in the cylinder as it compressed but it wasn't going to ignite under just the pressure so we injected more fuel and added a spark.

it this really a variable compression engine now?

That is like asking if a thermonuclear bomb does not have a fusion reaction.

It is a dynamic variable compression in that the compression required to light off the majority of the chamber is higher than the fixed compression ratio of the piston motion.

Reaction one is used to create the conditions for reaction two.

One more attempt in case that doesn't stick.

In the conventional engine the spark creates a higher temperature as the source of ignition, heat radiation is how the reaction spreads through the combustion chamber.

In this Mazda engine a small reaction in the combustion chamber creates an increase in pressure, and compression is how the remaining fuel/air mixture burns.

So in the conventional engine it is heat radiation for ignition at a given compression.

In this Mazda engine it is heat radiation with a small part of the chamber in fuel air mixture ratio 1 that is ignited. This combustion expansion changes the compression ratio for fuel air ratio 2 that fills the remaining area of the chamber. This change in compression ignites fuel air ratio 2.

So the part of the chamber at fuel air 1 ignites by heat at compression level A, the part of the chamber at fuel air 2 ignites by increased compression to compression level B.

The compression ratio for ignition of fuel air 2 is higher than that of fuel air 1.

Fuel air mixture 1's combustion is used to control the compression of fuel air mixture 2.

If you spray food coloring into water, there is time for it to dissipate to median levels.
The second injection of fuel does not have time to mix with the remaining part of the chamber.
This results in two different fuel/air ratios in the chamber at the same time, one of which is used to raise the compression of the other.

CVCC. And with a carburetor!!

CVCC used a rich mixture on one side of a perforated barrier (which had its own valve) and a lean mixture on the other side. The rich mixture is used to ignite the lean mixture.

Mazda is using a small rich mixture just in front of the spark plug to compress the remaining lean mixture without a barrier.

I need pictures:

<iframe width="914" height="514" src="https://www.youtube.com/embed/PT2Mt-tkJ_4" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

Mazda's SPCCI compression engine: Here's how it works

https://www.mazdausa.com/why-mazda/skyactiv

<iframe width="560" height="315" src="https://www.youtube.com/embed/UF5j1DvC954" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

I find myself more confused by animations than I do by reading about it.

I would think that any gains that an opposed piston engine would be able to muster from more efficiently capturing combustion energy would be lost from more complicated mechanicals (two crankshafts, for example).

I am exactly the opposite.

The first time I went through training on the SH-60 was in 1984...very rudimentary slides but lots of words to describe systems, which we were tested on.

I of course memorized how everything worked but really didn't understand the more esoteric systems, like the fuel control system.

Going back through a shortened syllabus in 1994, they had computer animations of all the systems and it was the first time I really understood the complex interactions.

I get what Mazda is doing and now understand the concept.

I was involved in some testing of a horizontally opposed 8 cylinder diesel aircraft engine that had a single crankshaft. The cylinders were staggered slightly and shared a crank journal if I remember correctly. Very cool product that is slowly making its way towards certification.

Extra crankshaft but no valvetrain.

Matt, do you have a diagram? I can't picture how you can have horizontally opposed cylinders with only one crankshaft.

Infiniti has been selling cars with it's variable compression engine for a year now.
http://forums.pelicanparts.com/off-topic-discussions/944574-variable-compression-engines.html

Sadly no, it's been at least 5 years and there's not much online in terms of public information. Like I said, I think they were slightly offset such that the opposed cylinders shared a crank journal but it's been a while.

Mazda is doing interesting work here combining the spark ignition and diesel ICE techs ... compress the fuel to almost the point of self ignition, inject a tad more into the vortex and ignite the center, creating a compression wave which ignites the rest of the fuel ... more power, more torque at lower rpm, improved efficiency.

https://spectrum.ieee.org/transportation/efficiency/mazdas-new-skyactivx-engine-gives-new-life-to-internal-combustion

I friend of mine has and drives his 1999 Honda Insight as his commuter vehicle.

<iframe width="1054" height="593" src="https://www.youtube.com/embed/EzG2bQK2Ygs" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

He get 60 MPH even today. The battery pack is dead. He has to pull the fuse to the system to get it to start and run, and withing a few minutes the error lights come back on, so he is running on just gasoline. He plans to maybe pull the battery pack and guys on the internet have figured out how to test each cell of the pack, and replace the bad cells. He said it is a slow and tedious process. He said people ask him more questions about it than any of his Porsches. Many people ask if he built the car himself, as they have never seen one like it.

The really fun thing about a fuel efficient car, is you can "race" your best MPG efficiency without the risk of blue lights from say, racing MPH.

There are very competitive males I know that track these things, and are all out to beat eachother. The end result is they pay attention to their driving, look ahead, and do their best to maintain momentum without giving it up.

Wasn’t Porsche the first to market a variable compression spark ignition gasoline fueled car? Sometime in 1975???

Anything with a turbo is variable compression...

Having owned a rotary, I'm biased toward Mazda but this Infinity take on variable compression looks like a mechanical engineering exercise gone wild. :eek:

Turbo Corvairs showed up in 1962.

repost: selectable squish

http://forums.pelicanparts.com/uploa...1574962080.jpg
Raising an engine’s compression ratio improves fuel efficiency during low-load operation, but it can also lead to catastrophic detonation when maximum power is requested. Engineers have long sought to navigate this challenge with a variable-compression-ratio engine, and Infiniti promises to implement its solution in early 2018 with a complex system of links in the crankcase.

There’s more than one way to skin this cat, though. German powertrain engineering company FEV proposes a piston wrist pin that passes through an eccentric bushing at the top of the connecting rod. As the bushing rotates, the piston moves vertically relative to the rod, in turn adjusting the compression ratio. The position of the bushing is determined passively by a pair of miniature pistons inside the connecting rod that rotate the cam in reaction to combustion and inertia forces. FEV’s 1.7-liter turbocharged inline-four demonstrator can adjust its compression ratio from 8.8:1 to 12.0:1 in 0.2 to 0.6 second.

I bet that puppy ain't cheap.