Toyota's approach to improving ICE efficiency
 

Toyota

"Dynamic Force" tech gets them to 40% thermal efficiency?!? :eek:

Very nice! :thumbup:

Toyota's strategy is quite interesting, even though at a first sight that engine could be initially pointed out as "outdated" due to the absence of a turbo. But it's still surprising how far the ICE can be improved before resorting to the expenses of forced induction (even though I actually like the altitude compensation provided by a turbo).

It works more effectively with direct injection for the matter of handling different grades of suitable fuel, but that Toyota engine has a dual-injection setup so it might eventually be capable to do so too.

There must be more to it. Do other hemis have 40% efficiency?

Nissan are about to release the MR20DDT Variable compression engine soon:

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

You're correct. All modern turbo engines use computer controlled wastegates rather than vacuum controlled wastegates to manage boost. It gives small engines more torque at low speeds because they close the wastegate and go to boost when taking off. Rather than waiting for vacuum to finish before closing the wastegate. That's most of the secret to the modern turbo engine.

Toyota are also following along with their C-HR having a 1.2T.

40% is a fantastic peak efficiency. What will the average efficiency end up being?

What is the average efficiency of a typical engine?

Indeed. But anyway, direct injection does increase the ability of an engine to avoid knocking while using lower-octane fuel with higher compression.

Direct injection is still expensive but is a huge step forward when paired with turbos since there is no fuel in the combustion chamber to pre ignite. And it is even possible to utilize multiple injections per firing cycle to get the exact stratified mixture and pressure profile all throughout the piston excursion. But it is expensive, complex, and noisy. Mercedes is achieving 181 hp/ Liter with maximum pulse boost pressures of 1.8 bar/ 26 psi. With flat torque of 450nm/ 332 ftlb from 2250-5000. In a family car.
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Mercedes A 45 AMG: The most powerful 4-cylinder turbo engine in the world
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I'm pretty sure most of these gains come from cooled EGR. The electric water pump would only help a little, and the rest of the engine is unremarkable compared to the 2AR predecessor. Direct injection and high compression only adds a small bit.

It really just goes to show that older engines were just really held back for cost reasons.

What is really interesting is that Toyota is sticking with relatively large displacement NA when Honda is committing to small turbo engines.

Considering that so many international markets apply some displacement-based taxes, it makes sense that Honda would focus on the downsizing. When it comes to Toyota, it seems like they're looking forward into benefits for hybrids regardless of displacement.

OK, that's probably impressive, but what MPG can it achieve under low loads considering an 8:1 compression ratio?

My 16 year old motorcycle puts out 200 hp/liter with no turbo. I'm getting 47 MPG with all that power to weight.

I don't get the appeal of powerful sedans. It's pointless in that a sedan is a practical vehicle, made uselessly fast and expensive. I'm getting older, and perhaps riding motorcycles has ruined my expectations for affordable fun.

8:1 is an error. 9.8:1 is reported. And, that is only at idle. variable vane turbos crank up pressure quickly at low rpm's.
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https://www.edmunds.com/mercedes-ben...st-specs1.html
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At least in a sedan you could carry more "witnesses" than in a 2-seater roadster :D

To my knowledge, Honda hit approximately 40% thermal efficiency (give or take) with the G1 Insight's engine back in 1999, without the Atkinson cycle, and slightly surpassed it with the 2L i4 in the 2nd gen Accord Hybrid. Honda cited many of the same technologies back in 1999. Makes me wonder why it has taken so long to make it into more mainstream engines.

Customers warm up slowly, and maybe manufacturers did not see a need to implement the technology, saving costs.

I've done turbos and I've done NA. At the moment my heart -- and money -- is in the NA camp. The Toyota technology sounds promising. I drive two of their v6 engines currently; one is the seriously understressed 4.0 in my Tacoma pickup, the other is a more highly refined 3.5L that makes impressive power and torque when required, and surprisingly decent gas mileage the rest of the time. I'm eager to see this new tech in a Toyota v6.

Even though I don't believe NA to have become obsolete at all, mostly due to the cost too, I've been more favorable to forced induction.

Different application. Aircraft engines are almost steady state. Although with the way traffic levels are growing...

The majority of the piston engines for aircraft in use nowadays are quite outdated, and mostly NA. Just recently with the introduction of modern turbodiesels to light aircraft that turbocharging is catching up again. In this case, the cost of certification and liability is what has driven the general aviation market to retain some rather outdated tech.

I would argue that modern base-engine sedans *are* powerful as well as affordable. 0-60 in under 8 seconds used be considered quick. Fact, its just as quick as it ever was, its just that people are power drunk these days.

Absolutely. Personally, I prefer a lower-power, lower-revving engine with some greater low-end torque than a high-power, high-revving one with such a low torque. I see it comparing some 1.0L engines fitted to small cars in my country due to fiscal benefits, while a 1.2L or 1.4L with a similar power rating and more torque could do better.

I saw this article the other day about Mazda's new engine... Mazda

Example: Ford Tempo. Intended to be mated to old-school 3-speed no lock-up no OD a/ts, it's 2.4 was tuned for low and mid-range torque vs high rpm horsepower. The result? It was a sales leader for many years in spite of nearly universal disparaging publicity in the motoring press about it's "tractor engine". :rolleyes:

It's been my impression that greater volume in the cylinder = less cylinder wall per unit of volume through which to lose heat. When Deere was still using two cylinder engines, one of their biggest tractors at the time set a record for fuel efficiency that wasn't broken for over 25 years. Each cylinder displaced about three quarts - seriously, each cylinder displaced more than my truck's entire engine.

Turn up the compression, keep the cylinders big, employ Atkinson cycle because that works, laugh all the way past the gas station on your way to the bank.

Makes sense.


Match the bigger cylinder displacement with a fewer amount of cylinders, and it ends up decreasing the overall amount of internal friction spots.

Bob Lutz once said...
 

"Americans buy horsepower but drive torque."

Torque output of the HSC engine available in the old Tempo/Topaz twins was modest but decent at about 125-130 ft-lbs.

Decades ago SAAB or Volvo figured that 36 lbs per horsepower was ideal. I rarely get my engine (Dodge 3.3L) above 3600 rpm and cruise at 2500 rpm.

The late Carroll Shelby would say "horsepower sells cars, torque wins races". Soichiro Honda would strongly disagree with that :p

Probably best to look at torque after the transmission. Two 200HP motors, one with twice the torque at the crank and the other with twice the RPM, both have the same output after gearing.

Sure. And that explains why some older and apparently oversized engines may eventually get better mileage and more reliability than some downsized high-revving ones.

Except that the modern engines use new techniques for efficieny such as Atkinson and high egr. Or ulta high effective compression ratio with turbos and direct injection along with minimized surface area to lose less heat energy via smaller displacement.

Who says it's impossible to add such tech to a lower-revving high-displacement engine in order to further increase both efficiency and long-term reliability?

Larger displacement makes for more surface area in the combustion chamber to pick up heat which is wasted energy.

It depends. The larger-displacement engine could eventually have a more undersquare profile, eventually with the same bore of the smaller engine.

Agreed. Undersquare is a key to heat efficiency in piston engines.

X2

Cars were plenty "fast" in the 1960s before weight and emissions ruined a good pairing. Good relative highway fuel mileage as well.

Load the sedan to maximum capacity.

Or hook up a trailer that represents the same.

In each case 0-60 in 20-seconds has always been considered good. 30" is just at acceptable.

Steady state economy should factor. Along with running air-conditioning, power accessories and the rest. What only a really big cubic inch engine in a luxury car could do.

More than this is kinda stupid.

Everyone likes to cruise effortlessly. And great mpg with a great ride.