Atkinson Cycle Animation

Atkinson Cycle Animation

[sszhao]

Basically at low load situations. Reduce the compression. Losing power definitely, but it's only when you don't need the power from full compression.

[andali]

These comments tell a lot about Toyotas Atkinson engines, they missed the mark. But Mazda got it right, my Mazda 3 gets 40mpg and the transition between Otto and Atkinson is seamless

[richardschofield]

This video did a poor job explaining why the Atkinson cycle is more efficient.

Basically to idle you need less than when under load. Less air means less fuel.
With the Otto cycle this reduced air is only achieved using the throttle valve.
The problem with the throttle valve is it creates huge pumping losses on the engine.
Imaging you have a water pump and you block the inlet, the pump has to work hard and struggles.
This is one of the reasons why big engine typically get less miles per gallon even if they are more efficient at peak torque. Because they need more throttling.
Throttling = low efficiency.
The Atkinson cycle needs less throttling as it purges some of the air back through the intake valve.
Therefore more efficient.

[timjohnson]

Just think, the Atkinson cycle was patented back in the 1880's. Just getting to it now.

[markparent]

I have a 21 Taco. I can't wait to sell it.

[bowensmith]

Too bad they missed the mark with this motor. The 2grfe was a fantastic engine. Not for a truck but great usable power and long life from a complex engine.

[djambush]

The best way is to get rid of the camshafts like it's done with the 'FreeValve' technology.

[colindewolfe]

VW should do this. They can send the extra fuel back into the intake of their direct injection engines to clean the valves.

[Logovanni]

IIRC the original Atkinson engine had a mechanism that made the intake and compression strokes shorter than the power and exhaust strokes. So on a normal engine you can just simulate that process by holding the intake valve open a bit into the compression stroke? And that’s it? Same effect?

[brucewiemer]

This is nice, but prefer Buick Turbo swirl compression on straight 8's from 38 to 52. Good power and decent milage for pushing around 3 tons of detroit iron back in the day.

[JoeUrbanYYC]

So is a Miller cycle dealing with increased power demands via a supercharger instead of switching to an Otto cycle? Eg this: low power=Atkinson, high power=Otto vs low power=Atkinson, high power=Atkinson+supercharger?

[rjk]

I wonder what the compression ratio would be if this animation were correct, the piston comes mighty close to the top of the cylinder.

[toomanyhobbies]

That was one of the prettiest and most worthless explanations I've ever seen. I guess they spent all their effort on the way this looks, which is amazing, instead of coming up with adequate instruction.

[jeronimomurruni]

Compression ratio and cylinder pressure are not the same thing, this system reduces cylinder pressure, not the compression ratio which remains constant.

[nomebear]

I owned a Geo Prizm hatchback in the early 90's that would get 47 mpg if driven at a constant speed on flat roads (think Texas). I own a 1998 Mercedes C230 naturally aspirated that will do up to 29 mpg on the highway. My 2019 Subaru Legacy naturally aspirated gets mid to high teens in town, low 20's on the highway, and it's a boring car to drive.

[MidnightMechanic]

If it's running in Atkinson cycle, it's not adding fuel to the air, right? Seems to me this would be great tech for a Diesel, since the intake air is fuel sterile.

[salovila]

SInce 2001-2002 when variable valves: position and timing were introduced nothing much has been done to improve fuel economy. Sure they made everything they could electric, from oil pumps to steering to take load of the engine, but nothing new mechanically.
My point: 1980 Mercedes sedan cruising at 80 mph will probably be doing 12-16 MPG
2002 Mercedes sedan cruising at 80 mph will do around 18-24 MPG
2022 Mercedes sedan cruising at 80 mph will do around 19-25 MPG

We are driving cars from the early 2000s with gizmos and screens.

The evolution of cars suddenly stopped in the early 2000s. Why?

[Gnerko]

The point is not that it becomes easier for the piston to move up due to the open intake valve; that work is canceled out when the piston moves doen again.

The point is that in an otto cycle the gas isn’t done expanding at BDC, thereby wasting energy. The atkinson cycle fixes that by effectively allowing the gas to expand more, thereby wastig less energy in the exhaust.

[MatthewBerginGarage]

The reversion in the intake and the reduced compression will make the engine less efficient not more.

[jakezgab]

Another words “ Variable Compression Ratio” that simple