Four stroke engines using methanol

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 4 stroke engine

ENYA R.155.4C engine from http://www.modelflight.com

engine capacity in cc power output in kWatts J/ccfam
120FS 19.93 1.566 at 11,250 rpm 0.838
R.155.4C 25.42 1.86 at 11,250 rpm 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
  • For RCVxx-CD, J/ccfam = ( power_in_watts x 60 x 2 ) / (capacity_in_cc x rpm ) = measure of energy efficiency

O.S. Engines

O.S. Engines FS-70 Ultimate high performance

O.S. Engines FS-70 Ultimate high performance, four stroke, engine with a fuel pump. Photograph from www.osengines.com

O.S. Engines FT-300 two cylinder engine

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
  • For RCVxx-CD, J/ccfam = ( power_in_watts x 60 x 2 ) / (capacity_in_cc x rpm ) = measure of energy efficiency
O.S. Engines FF-300 radial engine The O.S. Engines FF-300 radial engine from http://www.towerhobbies.com/products/os_engines/osmg1160m.html O.S. Engines FF-320 flat four

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

SAITO single cylinder engines

SAITO 180 engine

The SAITO 180 engine. Photograph from http://www.horizonhobby.com.

Saito Engine capacity in cc weight in kg power output in kWatts Power-to-Weight in kWatts/kg min rpm max rpm fuel efficiency in 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

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
  • For RCVxx-CD, J/ccfam = ( power_in_watts x 60 x 2 ) / (capacity_in_cc x rpm ) = measure of energy efficiency

SAITO multi-cylinder engines

Images from http://www.horizonhobby.com

The vibration-free SAITO FA-182TD

The "vibration-free" SAITO FA-182TD.

The Saito FA-300T twin engine

The Saito FA-300T twin engine.

The SAITO FA-170R three cylinder radial engine.

The SAITO FA-170R three cylinder radial engine.

The Saito FA-325R5 radial engine

The Saito FA-325R5 radial engine.

Engine trends for four stroke engines

power output vs 4 stroke engine capacity

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

power to weight ratio vs engine capacity for 4 stroke engines

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.

engine efficiency vs engine capacity for 4 stroke engines

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.