Engines and stuff 1 of 2

Engines are fascinating. Thanks to the internet, most data is available also. So I wanted to see some more characteristics of VW engines and see how they compare against other well known aircraft engines.

The table below shows lots of different engines with some basic characteristics.

EngineMax HPat RPMT (Nm)Weight (kg)CoolingBore (mm)Stroke (mm)Bore/ strokeccCylBMEP (bar)HP/kgXst
AeroVee 2.1803400167.673Air92820.99218049.661.101.134
AeroVee 2.1 T1003400209.480Air92820.992180412.071.251.044
Austro AE3001683880308.3185Water83920.641991419.460.910.474
Centurion 2.01333890243.5134Water83920.641991415.370.990.654
Continental 200AF952750246.091Air103.198.60.86329349.391.041.114
Continental 200DX1002750258.991Air103.198.60.86329349.881.101.114
Continental 2401252800317.9109Air112.898.61.033941410.141.151.134
Continental IO-360ES2102800534.1138Air112.898.61.035912611.351.521.344
D-Motor LF2691.83000217.958Water103.4801.312687410.191.581.554
DB 605180028004577.7756Water1541600.73357631216.092.381.484
Franklin 2351252800317.993Air117.588.91.373856410.361.341.304
Franklin 3502052800521.4135Air117.588.91.375784611.331.521.344
GP 1600553600108.872Air85.5691.21158548.630.760.894
GP 1835653600128.674Air92691.40183548.810.881.004
GP 1915693600136.574Air94691.46191548.950.931.044
GP 2180763400159.275Air92820.99218049.171.011.104
GP 2276803400167.675Air94821.03227649.251.071.154
Grob 2500953400199.095Air100781.292450410.201.000.984
Hirth 3003 E1026500111.751Air72640.99104246.742.002.972
Hirth 3203 E65630073.540Air76690.9562627.371.632.202
Hirth 3701 ES1006000118.754Water76690.9593937.941.852.332
Hirth F23 LW50650054.830Air72640.9952126.601.672.522
HKS 700E60620068.955Air85601.58681212.721.090.864
Hummel 50 HP553600108.873Air85.5691.21158548.630.750.874
Hummel 60 HP653600128.675Air92691.40183548.810.870.984
Hummel 76 HP763400159.276Air92820.99218049.171.001.094
Hummel 85 HP853400178.076Air94860.94238749.371.121.194
Jabiru 2200853300183.463Air97.5741.362210410.431.351.294
Jabiru 33001203300258.983.5Air97.5741.36331569.821.441.464
JPX 4T60653200144.672Air9375.41.19204948.870.901.024
JPX 4TX75823000194.678Air95821.052325410.521.051.004
JPX 4TX90903000213.674Air95880.922495410.761.221.134
Jumo 213E205032504491.7940Water1501650.65349891216.132.181.354
Limbach 1700 E0683600134.573Air88691.281679410.070.930.934
Limbach 2000 E0803400167.674Air9078.41.041995410.551.081.024
Limbach 2000 EB803400167.676.5Air9078.41.041995410.551.050.994
Limbach 2400 DFi1003000237.476Water97821.102424412.311.321.074
Limbach 2400 DT1293000306.286Water97821.102424415.871.500.944
Limbach 2400 DT.X1583000375.086Water97821.102424419.441.840.944
Limbach 2400 EB873200193.682Air97821.102424410.041.061.064
Lycoming 2331152800292.597Air111.198.41.00381649.631.191.234
Lycoming 320A1502700395.6125Air130.298.41.38524049.491.201.264
Lycoming 320B1602700422.0127Air130.298.41.385240410.121.261.254
Lycoming AEIO 3602002700527.5136Air130.2111.11.085917411.201.471.314
Lycoming AEIO 5803152700830.8204Air135111.11.169542610.941.541.414
Lycoming IO-360A2002700527.5150Air130.2111.11.085917411.201.331.194
Lycoming O-360A1802700474.7132Air130.2111.11.085917410.081.361.354
Mikron IIIA652600178.065Air90900.79229049.771.001.024
Mikron IIIB752750194.269Air90960.69244349.991.091.094
Motorav 2.4 R852900208.785Air94880.902443410.741.000.934
Motorav 2.6 R902900221.086Air94940.792609410.641.050.984
Motorav 2.8 R1002900245.584Air98940.852836410.881.191.094
MW B22D953400199.080Water93811.042201411.361.191.054
P&W R-2800 32285027007516.51073Air146.05152.40.72459571820.552.661.294
Revmaster R-2300853200189.177Air94840.982332410.191.101.084
Revmaster R-30001153400240.993Air102.4901.022965410.211.241.214
Rotax 912 ULS98.55800120.970Water84611.491352411.241.411.254
Rotec R28001103600217.6102Air80800.79281579.711.081.114
Rotec R28001503600296.7125Air80800.793619910.301.201.164
RR Griffon 65222027505748.5900Water152.5167.60.65367351219.662.471.254
RR Merlin 61158030003750.3744Water1371520.64268881217.532.121.214
Sauer 1800 UL683200151.363Air92691.401835410.361.081.044
Sauer 1900 UL753200166.964Air94691.461915410.951.171.074
Sauer 2100 ULT1103000261.176Air90.5840.912161415.181.450.954
Sauer 2200 UL853000201.866Air92840.942234411.351.291.134
Sauer 2400 UL Al903000213.675Air94840.982332411.511.201.044
Sauer 2400 UL Mg903000213.668Air94840.982332411.511.321.154
Sauer 2500943000223.177Air97841.052483411.291.221.084
Sauer 2700 UL1053000249.275Air97900.912660411.771.401.194
SMA SR3052272200734.7206AirNANANA5000418.471.100.604
ULPower UL260i973300209.372.3Air105.6741.602592410.151.341.324
ULPower UL260iS1073300230.972.3Air105.6741.602592411.191.481.324
ULPower UL350i1183300254.678.4Air105.61000.88350349.131.511.654
ULPower UL350iS1303300280.578.4Air105.61000.883503410.061.661.654
Vedeneyev M14PF4002900982.2214Air1051300.5110131912.181.871.534
Verner 133MK845500108.864.9Air97900.911330210.271.291.264
Verner 7H1102300340.682Air94850.964129710.361.341.294

Bore - Stroke ratio

I somehow had the impression that the bore/stroke ratio was an important parameter. Engines with longer stroke had more torque, while engines with shorter stroke had less torque and more rpm. This was completely wrong.

An engine with a large bore has more area or space for valves than an engine with small bore. This means that with larger bore/stroke, the engine can have larger valves and therefore will more easily be filled with air. That is basically it, that is the only important factor. The torque of the crank does not change with larger stroke (considering equal displacement). There also are some secondary effects; larger stroke means faster piston speed and more friction, larger bore means more forces on the cylinder and the bearings etc etc. Things that are important for detailed design, but does not really mean anything if the design is done properly.

The bore/stroke ratio is only valid for comparison of engines with equal displacement because the area is proportional to the square of the bore. To compare engines with different displacement some modification is needed. What we are looking for is a ratio of the area (available for valves) over the volume of the cylinder, the displacement. To be able to compare different sized engines, this ratio has to be non dimensional.

The modified bore/stroke = A^3/V^2 = (Pi/4)*bore^2/stroke^2

With this modified bore/stroke ratio, all the engines can be compared on equal basis. This is not a bore stroke ratio anymore, just a representative non dimensional number. This is done in the table below.

EngineMax HPat RPMT (Nm)Weight (kg)CoolingBore (mm)Stroke (mm)Bore/ strokeccCylBMEP (bar)HP/kgXst
Vedeneyev M14PF4002900982.2214Air1051300.5110131912.181.871.534
RR Merlin 61158030003750.3744Water1371520.64268881217.532.121.214
Austro AE3001683880308.3185Water83920.641991419.460.910.474
Centurion 2.01333890243.5134Water83920.641991415.370.990.654
Jumo 213E205032504491.7940Water1501650.65349891216.132.181.354
RR Griffon 65222027505748.5900Water152.5167.60.65367351219.662.471.254
Mikron IIIB752750194.269Air90960.69244349.991.091.094
P&W R-2800 32285027007516.51073Air146.05152.40.72459571820.552.661.294
DB 605180028004577.7756Water1541600.73357631216.092.381.484
Mikron IIIA652600178.065Air90900.79229049.771.001.024
Motorav 2.6 R902900221.086Air94940.792609410.641.050.984
Rotec R28001103600217.6102Air80800.79281579.711.081.114
Rotec R28001503600296.7125Air80800.793619910.301.201.164
Motorav 2.8 R1002900245.584Air98940.852836410.881.191.094
Continental 200AF952750246.091Air103.198.60.86329349.391.041.114
Continental 200DX1002750258.991Air103.198.60.86329349.881.101.114
ULPower UL350i1183300254.678.4Air105.61000.88350349.131.511.654
ULPower UL350iS1303300280.578.4Air105.61000.883503410.061.661.654
Motorav 2.4 R852900208.785Air94880.902443410.741.000.934
Sauer 2100 ULT1103000261.176Air90.5840.912161415.181.450.954
Sauer 2700 UL1053000249.275Air97900.912660411.771.401.194
Verner 133MK845500108.864.9Air97900.911330210.271.291.264
JPX 4TX90903000213.674Air95880.922495410.761.221.134
Hummel 85 HP853400178.076Air94860.94238749.371.121.194
Sauer 2200 UL853000201.866Air92840.942234411.351.291.134
Hirth 3203 E65630073.540Air76690.9562627.371.632.202
Hirth 3701 ES1006000118.754Water76690.9593937.941.852.332
Verner 7H1102300340.682Air94850.964129710.361.341.294
Revmaster R-2300853200189.177Air94840.982332410.191.101.084
Sauer 2400 UL Al903000213.675Air94840.982332411.511.201.044
Sauer 2400 UL Mg903000213.668Air94840.982332411.511.321.154
AeroVee 2.1803400167.673Air92820.99218049.661.101.134
AeroVee 2.1 T1003400209.480Air92820.992180412.071.251.044
GP 2180763400159.275Air92820.99218049.171.011.104
Hummel 76 HP763400159.276Air92820.99218049.171.001.094
Hirth 3003 E1026500111.751Air72640.99104246.742.002.972
Hirth F23 LW50650054.830Air72640.9952126.601.672.522
Lycoming 2331152800292.597Air111.198.41.00381649.631.191.234
Revmaster R-30001153400240.993Air102.4901.022965410.211.241.214
Continental 2401252800317.9109Air112.898.61.033941410.141.151.134
Continental IO-360ES2102800534.1138Air112.898.61.035912611.351.521.344
GP 2276803400167.675Air94821.03227649.251.071.154
Limbach 2000 E0803400167.674Air9078.41.041995410.551.081.024
Limbach 2000 EB803400167.676.5Air9078.41.041995410.551.050.994
MW B22D953400199.080Water93811.042201411.361.191.054
Sauer 2500943000223.177Air97841.052483411.291.221.084
JPX 4TX75823000194.678Air95821.052325410.521.051.004
Lycoming AEIO 3602002700527.5136Air130.2111.11.085917411.201.471.314
Lycoming IO-360A2002700527.5150Air130.2111.11.085917411.201.331.194
Lycoming O-360A1802700474.7132Air130.2111.11.085917410.081.361.354
Limbach 2400 DFi1003000237.476Water97821.102424412.311.321.074
Limbach 2400 DT1293000306.286Water97821.102424415.871.500.944
Limbach 2400 DT.X1583000375.086Water97821.102424419.441.840.944
Limbach 2400 EB873200193.682Air97821.102424410.041.061.064
Lycoming AEIO 5803152700830.8204Air135111.11.169542610.941.541.414
JPX 4T60653200144.672Air9375.41.19204948.870.901.024
GP 1600553600108.872Air85.5691.21158548.630.760.894
Hummel 50 HP553600108.873Air85.5691.21158548.630.750.874
Limbach 1700 E0683600134.573Air88691.281679410.070.930.934
Grob 2500953400199.095Air100781.292450410.201.000.984
D-Motor LF2691.83000217.958Water103.4801.312687410.191.581.554
Jabiru 2200853300183.463Air97.5741.362210410.431.351.294
Jabiru 33001203300258.983.5Air97.5741.36331569.821.441.464
Franklin 2351252800317.993Air117.588.91.373856410.361.341.304
Franklin 3502052800521.4135Air117.588.91.375784611.331.521.344
Lycoming 320A1502700395.6125Air130.298.41.38524049.491.201.264
Lycoming 320B1602700422.0127Air130.298.41.385240410.121.261.254
GP 1835653600128.674Air92691.40183548.810.881.004
Hummel 60 HP653600128.675Air92691.40183548.810.870.984
Sauer 1800 UL683200151.363Air92691.401835410.361.081.044
GP 1915693600136.574Air94691.46191548.950.931.044
Sauer 1900 UL753200166.964Air94691.461915410.951.171.074
Rotax 912 ULS98.55800120.970Water84611.491352411.241.411.254
HKS 700E60620068.955Air85601.58681212.721.090.864
ULPower UL260i973300209.372.3Air105.6741.602592410.151.341.324
ULPower UL260iS1073300230.972.3Air105.6741.602592411.191.481.324
SMA SR3052272200734.7206AirNANANA5000418.471.100.604

The M14PF is the longest stroked engine and the UL260s are the shortest stroked engines. Interestingly the VW engines are all over the place.


BMEP

From what I have gathered of information, the only meaningful parameter representing how well developed and tuned an engine is, is the Break Mean Effective Pressure, or BMEP. The BMEP is the theoretical integrated pressure needed to turn the engine at a certain power at a certain rpm. Max BMEP occurs at max torque, which typically is at a bit lower rpm than max power. BMEP is not the pressure inside the cylinder, but should be proportional to the physical integrated or mean pressure over the power stroke. Higher BMEP means a better engine in terms of engine output. Top fuel dragsters have an insane BMEP for instance. It also means that BMEP is a good number telling how far "pushed" the engine is in terms of tuning. This is not always a good thing, higher tuned engines tends to last shorter than lower tuned engines. More BMEP also means higher power pulses that the shaft, gear and propeller must sustain.

Turbo or supercharger will increase BMEP, which of course is the whole purpose of a turbo. Comparing naturally aspirated engines with boosted engines may not seem "fair". But power is power, how that power is obtained is uninteresting for an aircraft.

BMEP (Pa) = n * P / (D * N)   or when using P = T * N * 2 * Pi
BMEP (Pa) = n * T * 2 * Pi / D
n = revs per power stroke, 2 for 4 stroke and 1 for 2 stroke
P = power in Watt
D = displacement in m^3
N = angular speed in revolutions per second (Hz)
T = torque in Nm

The second relation shows that BMEP is proportional to torque per displacement.

EngineMax HPat RPMT (Nm)Weight (kg)CoolingBore (mm)Stroke (mm)Bore/ strokeccCylBMEP (bar)HP/kgXst
Hirth F23 LW50650054.830Air72640.9952126.601.672.522
Hirth 3003 E1026500111.751Air72640.99104246.742.002.972
Hirth 3203 E65630073.540Air76690.9562627.371.632.202
Hirth 3701 ES1006000118.754Water76690.9593937.941.852.332
GP 1600553600108.872Air85.5691.21158548.630.760.894
Hummel 50 HP553600108.873Air85.5691.21158548.630.750.874
GP 1835653600128.674Air92691.40183548.810.881.004
Hummel 60 HP653600128.675Air92691.40183548.810.870.984
JPX 4T60653200144.672Air9375.41.19204948.870.901.024
GP 1915693600136.574Air94691.46191548.950.931.044
ULPower UL350i1183300254.678.4Air105.61000.88350349.131.511.654
GP 2180763400159.275Air92820.99218049.171.011.104
Hummel 76 HP763400159.276Air92820.99218049.171.001.094
GP 2276803400167.675Air94821.03227649.251.071.154
Hummel 85 HP853400178.076Air94860.94238749.371.121.194
Continental 200AF952750246.091Air103.198.60.86329349.391.041.114
Lycoming 320A1502700395.6125Air130.298.41.38524049.491.201.264
Lycoming 2331152800292.597Air111.198.41.00381649.631.191.234
AeroVee 2.1803400167.673Air92820.99218049.661.101.134
Rotec R28001103600217.6102Air80800.79281579.711.081.114
Mikron IIIA652600178.065Air90900.79229049.771.001.024
Jabiru 33001203300258.983.5Air97.5741.36331569.821.441.464
Continental 200DX1002750258.991Air103.198.60.86329349.881.101.114
Mikron IIIB752750194.269Air90960.69244349.991.091.094
Limbach 2400 EB873200193.682Air97821.102424410.041.061.064
ULPower UL350iS1303300280.578.4Air105.61000.883503410.061.661.654
Limbach 1700 E0683600134.573Air88691.281679410.070.930.934
Lycoming O-360A1802700474.7132Air130.2111.11.085917410.081.361.354
Lycoming 320B1602700422.0127Air130.298.41.385240410.121.261.254
Continental 2401252800317.9109Air112.898.61.033941410.141.151.134
ULPower UL260i973300209.372.3Air105.6741.602592410.151.341.324
D-Motor LF2691.83000217.958Water103.4801.312687410.191.581.554
Revmaster R-2300853200189.177Air94840.982332410.191.101.084
Grob 2500953400199.095Air100781.292450410.201.000.984
Revmaster R-30001153400240.993Air102.4901.022965410.211.241.214
Verner 133MK845500108.864.9Air97900.911330210.271.291.264
Rotec R28001503600296.7125Air80800.793619910.301.201.164
Franklin 2351252800317.993Air117.588.91.373856410.361.341.304
Sauer 1800 UL683200151.363Air92691.401835410.361.081.044
Verner 7H1102300340.682Air94850.964129710.361.341.294
Jabiru 2200853300183.463Air97.5741.362210410.431.351.294
JPX 4TX75823000194.678Air95821.052325410.521.051.004
Limbach 2000 E0803400167.674Air9078.41.041995410.551.081.024
Limbach 2000 EB803400167.676.5Air9078.41.041995410.551.050.994
Motorav 2.6 R902900221.086Air94940.792609410.641.050.984
Motorav 2.4 R852900208.785Air94880.902443410.741.000.934
JPX 4TX90903000213.674Air95880.922495410.761.221.134
Motorav 2.8 R1002900245.584Air98940.852836410.881.191.094
Lycoming AEIO 5803152700830.8204Air135111.11.169542610.941.541.414
Sauer 1900 UL753200166.964Air94691.461915410.951.171.074
ULPower UL260iS1073300230.972.3Air105.6741.602592411.191.481.324
Lycoming AEIO 3602002700527.5136Air130.2111.11.085917411.201.471.314
Lycoming IO-360A2002700527.5150Air130.2111.11.085917411.201.331.194
Rotax 912 ULS98.55800120.970Water84611.491352411.241.411.254
Sauer 2500943000223.177Air97841.052483411.291.221.084
Franklin 3502052800521.4135Air117.588.91.375784611.331.521.344
Sauer 2200 UL853000201.866Air92840.942234411.351.291.134
Continental IO-360ES2102800534.1138Air112.898.61.035912611.351.521.344
MW B22D953400199.080Water93811.042201411.361.191.054
Sauer 2400 UL Al903000213.675Air94840.982332411.511.201.044
Sauer 2400 UL Mg903000213.668Air94840.982332411.511.321.154
Sauer 2700 UL1053000249.275Air97900.912660411.771.401.194
AeroVee 2.1 T1003400209.480Air92820.992180412.071.251.044
Vedeneyev M14PF4002900982.2214Air1051300.5110131912.181.871.534
Limbach 2400 DFi1003000237.476Water97821.102424412.311.321.074
HKS 700E60620068.955Air85601.58681212.721.090.864
Sauer 2100 ULT1103000261.176Air90.5840.912161415.181.450.954
Centurion 2.01333890243.5134Water83920.641991415.370.990.654
Limbach 2400 DT1293000306.286Water97821.102424415.871.500.944
DB 605180028004577.7756Water1541600.73357631216.092.381.484
Jumo 213E205032504491.7940Water1501650.65349891216.132.181.354
RR Merlin 61158030003750.3744Water1371520.64268881217.532.121.214
SMA SR3052272200734.7206AirNANANA5000418.471.100.604
Limbach 2400 DT.X1583000375.086Water97821.102424419.441.840.944
Austro AE3001683880308.3185Water83920.641991419.460.910.474
RR Griffon 65222027505748.5900Water152.5167.60.65367351219.662.471.254
P&W R-2800 32285027007516.51073Air146.05152.40.72459571820.552.661.294

All the two stroke engines have low BMEP. The reason for this is they don't need to have all that much pressure because they have double the power pulses per revs compared with a 4 stroke. At the other end we find the RR Griffon and the P&W R-2800. Also here the VW engines are all over the place, but now there is a clear differentiation between the GP and Hummel engines in the lower end and the Sauer and Limbachs in the higher end. The AeroVee and Revmaster is in the middle somewhere. The AeroVee turbo, rumored to have 100 HP for take off and 80 HP continuous, have less BMEP than a comparable naturally aspirated Limbach 2400 DFi. Suggesting the turbo boost is very low. Also interesting is the ULPower UL350i which sits there at the lower end of the scale along the Hummels and GPs. Sadly the specs for the 2 stroke diesels, the Wilksch WAM and DeltaHawk is nowhere to be found, they would be interesting to see in there.

Engines and stuff part 2

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