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Four stroke engines

four cylinder FF-320 four stroke engine by www.osengines.com

Four cylinder engines are the most fuel efficient internal combustion engines. They however have  lower vibration and noise levels than the two stroke engines, but have a higher vibration level than a Wankel engine. They also have  a lower power-to-weight ratio than a two stroke engine of comparable power output.

 

 

 

 

 


 

ENYA Engine

ENYA R.155.4C engine from http://www.modelflight.com.au/enya_engines/enya_r155.htm

engine

capacity in cc

weight in kg

power output in kWatts

kW / kg

J/ccfam

120FS

19.93

0.910

1.566 at 11,250 rpm

1.721

0.838

R.155.4C

25.42

0.960

1.86 at 11,250 rpm

1.937

0.780

Notes:

  • All Enya  engines use " glow fuel" : methanol + 5 to 15  % nitromethane + 16% minimum synthetic castor oil lubricant.
  • J/ccfam = energy in Joules per cc of fuel-air mixture
  • J/ccfam = ( power_in_watts x 60 x 2  ) / (capacity_in_cc x rpm ) = measure of energy efficiency

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Kavan

KAVAN 50cc Four Cycle Twin Engine

The Kavan engine: photograph  from www.mecoa.com

  • Engine capacity = 50 cc
  • weight = 2.6 kg for spark ignition version
  • power output at 9,200 rpm =  3.28 kWatts , where the fuel consumption was 25 cc per minute.
  • power-to-weight ratio = 1.261 kW / kg
  • fuel efficiency = 0.856 Joules / cc_fuel_air_mixture

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O.S. Engines

O.S. Engines FS-70 Ultimate high performance, four stroke, engine with a fuel pump.

Photograph from http://www.osengines.com/engines/osmg0875.html

O.S. Engines FT-300 two cylinder engine from www.osengines.com

engine

cylinders

capacity in cc

weight in kg

power output in kWatts

kW / kg

J/ccfam

FS-70 Ultimate

1

11.45

0.502

0.894 at 11,000 rpm

1.781

0.852

FS-91 S II

1

15

0.649

1.193 at 11,000 rpm

1.838

0.868

FS-120S III

1

20

0.921

1.56 at 12,000 rpm

1.694

0.76

FT-160

2

26.5

1.1

1.49 at 10,000 rpm

1.354

0.675

FS-200U

1

32.4

0.83

2.16 at 9,000 rpm

2.605

0.890

FT-300

2

49

1.828

3.0 at 7,000 rpm

1.641

1.050

FF-300 radial

5

49.7

2.673

3.0 at 8,000 rpm

1.122

0.905

FF-320

4

53.2

2.19

3.06 at 8,000 rpm

1.37

0.846

Notes:

  • All O.S.  engines use " glow fuel" : methanol + 5 to 15  % nitromethane + 16% minimum synthetic castor oil lubricant.
  • J/ccfam = energy in Joules per cc of fuel-air mixture
  • J/ccfam = ( power_in_watts x 60 x 2  ) / (capacity_in_cc x rpm ) = measure of energy efficiency

The O.S. Engines FF-300 radial engine from http://www.osengines.com/engines/osmg1300.html

The O.S. Engines FF-320 " flat four" from http://www.osengines.com/engines/osmg1320.html

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RCV Engines

RCV58-CD on left and RCV60-SP on right

RCV engine information from http://rcvengines.com/rcv_modelhome.htm

engine

capacity in cc

weight in kg

power output in kWatts

kW / kg

J/ccfam

RCV58-CD

9.5

0.500

0.640 at 10,800 rpm

1.28

0.748

RCV60-SP

2:1 gear ratio

10

0.570

0.670 at 5,400 rpm

1.175

0.744

RCV91-CD

15

0.715

1.120 at 9,900 rpm

1.566

0.905

RCV90-SP

2:1 gear ratio

15

0.785

1.120 at 5,400 rpm

1.427

0.830

RCV120-SP

2:1  gear ratio

20

1.000

1.340 at 5,400 rpm

1.34

0.744

RCV130-CD

21.3

0.995

1.500 at 9,000 rpm

1.507

0.939

Notes:

  • All RCV  engines use " glow fuel" : methanol + 10 % nitromethane + 15% minimum synthetic castor oil lubricant.
  • J/ccfam = energy in Joules per cc of fuel-air mixture
  • For RCVxx-SP, J/ccfam = ( power_in_watts x 60  ) / (capacity_in_cc x rpm ) = measure of energy efficiency
  • For RCVxx-CD, J/ccfam = ( power_in_watts x 60 x 2  ) / (capacity_in_cc x rpm ) = measure of energy efficiency
  • See the page on RCV engines for more details on this type of engine

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The Rotax 914  by  Bombardier  Rotax

- from http://www.rotax.com/en/

Performance of the four stroke, four cylinder, Rotax 914 F D.C.D.I UAV Engine

power

84.5 kW

@ 5,500 rpm

maximum RPM

5,800

rpm

displacement

1211.2

cc

generator performance

250 Watt DC

@ 5,500 rpm

voltage

13.5

V

fuel usage at 5,400 RPM

20 kg/hr (25 L / hr)

237 g / kWatt / hour

AVGAS 100 LL

engine weight

70

kg

weight of optional extras

6.7

kg

power-to-weight ratio

1.1

kW / kg

engine efficiency

1.55

J / ccfam

This large engine is included to give a data point for a high capacity engine. The Rotax engine has been used in the Predator and other UAVs.

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SAITO

SAITO single cylinder engines

The SAITO 180 engine.

Photograph from http://www.horizonhobby.com/Products/Default.aspx?ProdID=SAIE180

Saito Engine

Capacity

Weight

Power

Power-to-Weight

min rpm

max rpm

fuel efficiency

cc

kg

kWatts

kWatts/kg

 

 

J/ccfam

FA-45S

7.50

0.440

0.522

1.186

2,000

12,000

0.696

FA-50

8.20

0.435

0.634

1.457

2,000

12,000

0.773

FA-56

9.20

0.410

0.671

1.637

2,000

12,000

0.729

FA-56F

9.20

0.410

0.671

1.637

2,000

12,000

0.729

FA-62a

10.24

0.469

0.746

1.590

2,000

12,000

0.728

FA-65

10.60

0.550

0.708

1.288

2,000

12,000

0.668

FA-72

11.80

0.470

0.895

1.904

2,000

12,000

0.758

FA-80

13.10

0.540

0.969

1.795

2,000

12,000

0.740

FA-82a

13.80

0.453

1.119

2.469

2,000

12,000

0.811

FA-91S

15.00

0.555

1.193

2.150

2,000

11,000

0.868

FA-100

17.10

0.551

1.342

2.436

2,000

11,000

0.856

FA-120S

20.00

0.900

1.641

1.823

1,900

10,500

0.937

FA-125a

20.52

0.700

1.641

2.344

1,800

10,500

0.914

FA-150

25.00

0.852

1.864

2.188

2,000

10,500

0.852

FA-180

29.10

0.881

2.088

2.370

2,000

10,000

0.861

FA-220a

36.30

1.100

2.610

2.373

1,900

10,000

0.863

Notes:

  • All Saito  engines use " glow fuel" : methanol + 5 to 15  % nitromethane + 16% minimum synthetic castor oil lubricant.
  • J/ccfam = energy in Joules per cc of fuel-air mixture
  • J/ccfam = ( power_in_watts x 60 x 2  ) / (capacity_in_cc x rpm ) = measure of energy efficiency

SAITO multi-cylinder engines

The Saito FA-300T twin engine

from http://www.horizonhobby.com/Products/Default.aspx?ProdID=SAIE300TTDP

The SAITO FA-170R three cylinder radial engine.

Photograph from http://www.horizonhobby.com/Products/Default.aspx?ProdID=SAIE170R3

Saito Engine

cylinders

Capacity

Weight

Power

Power / Weight

rpm range

fuel efficiency

cc

kg

kWatts

kWatts/kg

k rpm

J/ccfam

FA-60T

2

10

0.75

0.671

0.894

2 - 10

0.895

FA-100T

2

16.4

0.82

1.044

1.273

2.5 - 10

0.848

FA-170R

3

27.8

1.3

1.491

1.147

2 - 9.5

0.753

FA-182TD

2

30.0

1.04

1.864

1.792

2 - 10

0.828

FA-300T

2

50

1.75

3.504

2.002

1.8 - 8

1.168

FA-300TD

2

50

1.85

3.579

1.935

1.6 - 8.4

1.136

FA-325R5

5

53

2.41

2.834

0.971

1.7 - 7.5

0.951

FA-450R3

3

75

2.9

4.101

1.414

1.2 - 8

0.911

The Saito FA-325R5 radial engine, from http://www.horizonhobby.com/Products/Default.aspx?ProdID=SAIE325R5D

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Engine trends  for four stroke engines

Pout scales with engine capacity  as Pout =  0.073 * x + 0.031  for Pout in kWatts, where x is the engine capacity in cc.

The average power-to-weight ratio for the above engines is 1.727 kWatts / kg. The superiority of the Saito engines in respect of power-to-weight ratios is clear.

The average engine efficiency for the above engines is 0.813 J / ccfam. For the Saito engines, we notice the engine efficiency saturates for engines with a capacity of 17 cc and above.

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