Toyota targets 45% thermal efficiency for engines in next-gen hybrids

That is just insane. It took 100 years to get to 38%, and they are going to jump 20% from that in a couple of years? Here's hoping.

 

The Atkinson cycle (and the Miller one) are known for almost a century now, just were not used all the time when power and more power was the issue.

Giora.

 

DI and turbo charging were obvious techniques that toyota left off. Both make engines more expensive but I was surprised that they did not use DI. Turbo or super charging are more questionable. For this to be more efficient at these low power levels for the car the engine should shrink, and I'm not sure if toyota has such an engine in their stable.

 

See also the previous PC thread, pointing to a story at Green Car Congress:
Toyota targeting thermal efficiency of more than 45% for next-generation gasoline engines for hybrids

 

Direct Injection is definitely useful in hybrids. Just look at the sonata hybrid versus the camry. The more modern hyundai engine with DI is clearly more efficient than the Toyota in this hybrid scenario.. DI allows better timing and metering of the fuel.. The big problem with Atkinson cycle is lack of low end torque which is solved by adding a electrical motor.

The prius uses Atkinson valve timing. Miller cycle would add a super charger. The prius has no super-charger. Nissan is building a 3-cylinder miller cycle engine. Super charging adds low end torque but turbo charging adds efficiency.

The prius already uses cooled EGR that was mentioned in the blurb. So if gen IV prius gets type one engine they would give it a longer stroke and add DI. They might also add electronic intake valves for more precise control of valve timing like some other engines. Those things should push peak efficiency above 40%.

 

As I said from my post the disadvantage of DI is cost. I don't think that is hard to understand. The article says toyota knows what most of the auto world know - DI has significant advantages. I'm sure toyota is looking beyond their twin injection into the techniques ford, hyundai, bmw, mazda etc are useing on their engines.

Green Car Congress: Toyota targeting thermal efficiency of more than 45% for next-generation gasoline engines for hybrids

The main change from the gen III prius engine and Concept 1 is Direct injection.

 

DI/DFI...is advantageous only if the compression ratio can be raised significantly above the 10:1 level that has otherwise become the standard. For the Prius, HSD system, that would be something in the range of 15:1 base/native which would then be effectively reduced to 12:1 using the Atkinson cycle delayed intake valve closing technique.

And keep in mind that DFI is also only advantageous when/if the cylinders are receiving a FULL charge, WOT operation.

TurboCharging an Atkinson cycle engine...???

Never, NEVER...!

Turbos need/REQUIRE that a significant level of the energy of combustion flow into the exhaust manifold, MORE than what is already required to keep teh catalytic up to operational termperture. That's not exactly desirable for improving thermal efficiency unless you can run on BOOST, no PARTIAL cylinder charging, the clear majority of the time.

Intercooled TurboCharging....REQUIRES even more seriously reduced compression ratios. You want to put as much PRE-COOLED and PRE-COMPRESSED atmosphere into the cylinder as is possible while maintaining some semblance of FE off-boost. 7-8:1 CR is typical for intercooled turbocharging.

The ANSWER:

A) Intercooled SuperCharging via a positive displacement SC driven by a combination of the ICE and a multi-phase AC inverter. NO throttle plate required, the airflow to the intake valves could be controlled independent of engine speed. Even better, drive the SC through a simpler version of the HSD CVT/PSD type "gearbox".

B) SFI + DFI. Throttle body fuel injection "off-boost", idle and cruise, switching to DFI only under "boost". Throttle body fuel injection would help to keep the intake manifold and intake valves free of deposits from EGR and PCV contaminants.

 

Well we should be able to see if toyota buids the beast as di. Ford and Hyundai do have Atkinson dI engines. The idea is to get to wide open throttle, but di helps in multiple phases. When given a partial charge, it can disperse it during the compression stroke and thus deal better with EGR. At higher power levels it can run a higher compression engine without premium fuel or knock. We can think of these valve timing atkinsons as variable compression ratio beasts.

Before you say never you should look at what these engines really are. They are not fixed valve timing atkinson, they are variable. Make those valves electronic and you can switch off between otto and atkinson cycle. The mazda skyactive has electronic intake valves. While supercharging can add to the torque and power of engines it has not been shown to make them more efficient. Turbo can use waste pressure and make an engine more efficient. On this type of engine I would not call it an Atkinson cycle though.

 

We don't know what contributed the most efficiency gain.

Does anyone know the current Gen3 ICE's stroke/bore value? How about the EGR ratio (assuming below 30%)?

What high-energy ignition system? More powerful spark plug?

 

Per [ame="http://en.wikipedia.org/wiki/Toyota_ZR_engine"]Wiki[/ame], the stroke/bore for Gen3 is 1.1 (88.3mm / 80.5mm).

 

Do you have a mouse in your pocket? You may just not understand the technology. The gen III has a high egr ratio around 30%. DI has been added successfully by toyota's competitors, the only draw back of DI is cost. Longer stroke is comparatively easy but does not significantly add to efficiency. by itself. If you understand the engine engineering you would understand DI is the low hanging fruit, and the obvious thing to add to the prius engine to add to its efficiency. When adding DI the valve timing and shape of the piston should also be changed.

More powerfull than what? Is it powerfull enough for the DI system? That is the key. DI allows a leaner charge. The prius engine may already have this high-energy ignition like the egr system.

 

There is an interview with a Toyota engineer that states that DI does not provide much in the way of efficiency to an Atkinson-cycle engine. Probably costs outweigh benefits.

 

If I am reading the RX450h factory repair/shop manual correctly then the Atkinson V6 in that is already switching modes using E/VVT-i.

No delayed intake valve closing until the cylinder charge is beyond simple cruise. The base/native compression ratio 13:1 (15:1 for DI) will not result in knock/ping with only partial cylinder charging. So the intake valve closing delay is not used except in POWER mode.

And insofar as non-premium fuel result in knock/ping that a story of yesteryear. Modern day engines use the crank position sensor and the knock/ping sensor to determine if the knock/ping is due to detonation, dieseling, or spark advance.

Knock/ping prior to spark (regular fuel) will result in enrichment of the A/F mixture via EFI dutycycle change.

"..Ford and Hyundai have Atkinson DI engines.."

News to me...where..?

"..Turbo can use WASTE pressure..."

The point is that there is NO "waste" pressure into the exhaust manifold of an Atkinson cycle engine. If there were then engineering made a mistake. Plus which you cannot gain efficiency via the use of a turbo without sacrificing cruise mode FE.

 

One way to XXXXcharge the Prius is to use an electric supercharger. Then there is no turbolag, and the Prius has a high voltage battery already.