The Atkinson cycle was discovered in 1882 by British engineer James Atkinson. It achieves higher efficiency than the Otto cycle by using a longer exhaust and intake stroke compared to the compression and power strokes. The modern Atkinson cycle uses variable valve timing to keep the intake valve open longer during the compression stroke, allowing some of the air-fuel mixture to re-enter the exhaust. It provides benefits like reduced fuel consumption and emissions but with reduced power output. Toyota was an early adopter of the Atkinson cycle, using it in engines like their 1.2-liter turbocharged engine to improve efficiency.

1. Atkinson cycle

2. Introduction
• Discovery of cycle
• Ideal thermodynamic cycle process
• Otto cycle vs. Atkinson cycle
• Types of engines that use this cycle
• Who uses these engines?
• Cost analysis of Gas Engine

3. Discovery of cycle
• Discovered by British engineer James Atkinson in 1882
• Patented on August 2, 1887 under Patent number: US 367496
• Was awarded the John Scott Medal of The Franklin Institute in 1889 for his
invention

4. The true Atkinson cycle and the
modern Atkinson cycle
• A true Atkinson cycle used a complex linkage system in order for the power
and exhaust stroke to be longer than the intake and compression stroke

5. The true Atkinson cycle and the modern
Atkinson cycle
Atkinson cycle achieved through late valve closure
• The modern Atkinson cycle uses a modified Otto
cycle where the complex linkage is replaced by
variable valve timing in which the intake valve is
held open longer to let some of the air fuel mixture
to leave the cylinder

6. Ideal thermodynamic cycle process
Process 1-2: Isentropic compression
Process 2-3: Constant volume heat addition
Process 3-4: Isentropic expansion
Process 4-1: Constant pressure heat rejection

7. Otto cycle vs. Atkinson cycle
Otto Cycle
V.S.
Atkinson Cycle

8. Atkinson Engine
PROS CONS
• Run relatively quietly
• Smooth idling speeds
• Reliable
• Relatively low amounts of
smoke
• Higher overall efficiency
• Complicated
• Heavy in weight
• Costly repairs
• Less power

9. How It All Works
• Uses less fuel
• More efficient
• Less power
• Reduced charge
• Reduced power
• Clean burn

10. Types of engines that use this cycle
• Differential engine
• Gas engine
• Rotary Atkinson-cycle engine
• Hybrid System Engine

11. Who uses these engines?
Figure 1. The 1.2-Liter
Turbo Engine
The first car company uses
the Atkinson cycle engine
is Toyota. Toyota Motor
Cooperation have
developed their 14 high
efficiency engines. One of
them is Toyota Auris 1.2-
liter turbocharged engine
that uses lean burning
Atkinson cycle technology.

12. Figure 2. Lexus IS
200T Engine
The Lexus IS 200T
engine initially runs Otto
cycle, and then it
switches to the Atkinson
cycle. This engine is able
to deliver power of
180KW, and to
accelerate to 62 miles per
hour in a short period of
time of 7 seconds

13. Differential engine

14. • The Atkinson differential engine is designed to provide
efficiency at the expense of the total power produced.
• It comprises of a single crankshaft that is connected non-
linearly by a pin jointed link to two opposed pistons.

15. • In each revolution, one piston provides a compression
stroke and a power stroke, while the other piston
provides an exhaust stroke and a charging stroke.
• the differential engine aims to use all of the energy in the
cylinder by leaving the intake valve open longer, to
create shorter compression strokes.

16. Gas engine
The Atkinson cycle aims to
use all of the energy in the
cylinder. It does this by
leaving the intake valve
open longer, creating a
shorter compression
stroke.

17. Gas engine cost analysis
Atkinson Cost
Full Hybrid
System
$3500
Fuel cost per year $556.68
Total $4056.68
Otto Cost
Full System $3500
Fuel cost per year $1357.93
Total $4857.93
Calculating Fuel Cost:
(13,476
𝑚𝑖
𝑦𝑟
)
1 𝑔𝑎𝑙
68 𝑚𝑖
$2.809
𝑔𝑎𝑙
= $556.68
(13,476
𝑚𝑖
𝑦𝑟
)
1 𝑔𝑎𝑙
28 𝑚𝑖
$2.809
𝑔𝑎𝑙
= $1357.93

18. Questions?