Engines and stuff 2 of 2

HP per kg

For an aircraft weight is very important. An engine with higher power per kg is therefore better. The next table is sorted according to HP per kg.

Engine	Max HP	at RPM	T (Nm)	Weight (kg)	Cooling	Bore (mm)	Stroke (mm)	Bore/ stroke	cc	Cyl	BMEP (bar)	HP/kg	X	st
Hummel 50 HP	55	3600	108.8	73	Air	85.5	69	1.21	1585	4	8.63	0.75	0.87	4
GP 1600	55	3600	108.8	72	Air	85.5	69	1.21	1585	4	8.63	0.76	0.89	4
Hummel 60 HP	65	3600	128.6	75	Air	92	69	1.40	1835	4	8.81	0.87	0.98	4
GP 1835	65	3600	128.6	74	Air	92	69	1.40	1835	4	8.81	0.88	1.00	4
JPX 4T60	65	3200	144.6	72	Air	93	75.4	1.19	2049	4	8.87	0.90	1.02	4
Austro AE300	168	3880	308.3	185	Water	83	92	0.64	1991	4	19.46	0.91	0.47	4
Limbach 1700 E0	68	3600	134.5	73	Air	88	69	1.28	1679	4	10.07	0.93	0.93	4
GP 1915	69	3600	136.5	74	Air	94	69	1.46	1915	4	8.95	0.93	1.04	4
Centurion 2.0	133	3890	243.5	134	Water	83	92	0.64	1991	4	15.37	0.99	0.65	4
Hummel 76 HP	76	3400	159.2	76	Air	92	82	0.99	2180	4	9.17	1.00	1.09	4
Mikron IIIA	65	2600	178.0	65	Air	90	90	0.79	2290	4	9.77	1.00	1.02	4
Grob 2500	95	3400	199.0	95	Air	100	78	1.29	2450	4	10.20	1.00	0.98	4
Motorav 2.4 R	85	2900	208.7	85	Air	94	88	0.90	2443	4	10.74	1.00	0.93	4
GP 2180	76	3400	159.2	75	Air	92	82	0.99	2180	4	9.17	1.01	1.10	4
Continental 200AF	95	2750	246.0	91	Air	103.1	98.6	0.86	3293	4	9.39	1.04	1.11	4
Limbach 2000 EB	80	3400	167.6	76.5	Air	90	78.4	1.04	1995	4	10.55	1.05	0.99	4
Motorav 2.6 R	90	2900	221.0	86	Air	94	94	0.79	2609	4	10.64	1.05	0.98	4
JPX 4TX75	82	3000	194.6	78	Air	95	82	1.05	2325	4	10.52	1.05	1.00	4
Limbach 2400 EB	87	3200	193.6	82	Air	97	82	1.10	2424	4	10.04	1.06	1.06	4
GP 2276	80	3400	167.6	75	Air	94	82	1.03	2276	4	9.25	1.07	1.15	4
Rotec R2800	110	3600	217.6	102	Air	80	80	0.79	2815	7	9.71	1.08	1.11	4
Sauer 1800 UL	68	3200	151.3	63	Air	92	69	1.40	1835	4	10.36	1.08	1.04	4
Limbach 2000 E0	80	3400	167.6	74	Air	90	78.4	1.04	1995	4	10.55	1.08	1.02	4
Mikron IIIB	75	2750	194.2	69	Air	90	96	0.69	2443	4	9.99	1.09	1.09	4
HKS 700E	60	6200	68.9	55	Air	85	60	1.58	681	2	12.72	1.09	0.86	4
AeroVee 2.1	80	3400	167.6	73	Air	92	82	0.99	2180	4	9.66	1.10	1.13	4
Continental 200DX	100	2750	258.9	91	Air	103.1	98.6	0.86	3293	4	9.88	1.10	1.11	4
SMA SR305	227	2200	734.7	206	Air	NA	NA	NA	5000	4	18.47	1.10	0.60	4
Revmaster R-2300	85	3200	189.1	77	Air	94	84	0.98	2332	4	10.19	1.10	1.08	4
Hummel 85 HP	85	3400	178.0	76	Air	94	86	0.94	2387	4	9.37	1.12	1.19	4
Continental 240	125	2800	317.9	109	Air	112.8	98.6	1.03	3941	4	10.14	1.15	1.13	4
Sauer 1900 UL	75	3200	166.9	64	Air	94	69	1.46	1915	4	10.95	1.17	1.07	4
Lycoming 233	115	2800	292.5	97	Air	111.1	98.4	1.00	3816	4	9.63	1.19	1.23	4
MW B22D	95	3400	199.0	80	Water	93	81	1.04	2201	4	11.36	1.19	1.05	4
Motorav 2.8 R	100	2900	245.5	84	Air	98	94	0.85	2836	4	10.88	1.19	1.09	4
Lycoming 320A	150	2700	395.6	125	Air	130.2	98.4	1.38	5240	4	9.49	1.20	1.26	4
Rotec R2800	150	3600	296.7	125	Air	80	80	0.79	3619	9	10.30	1.20	1.16	4
Sauer 2400 UL Al	90	3000	213.6	75	Air	94	84	0.98	2332	4	11.51	1.20	1.04	4
JPX 4TX90	90	3000	213.6	74	Air	95	88	0.92	2495	4	10.76	1.22	1.13	4
Sauer 2500	94	3000	223.1	77	Air	97	84	1.05	2483	4	11.29	1.22	1.08	4
Revmaster R-3000	115	3400	240.9	93	Air	102.4	90	1.02	2965	4	10.21	1.24	1.21	4
AeroVee 2.1 T	100	3400	209.4	80	Air	92	82	0.99	2180	4	12.07	1.25	1.04	4
Lycoming 320B	160	2700	422.0	127	Air	130.2	98.4	1.38	5240	4	10.12	1.26	1.25	4
Sauer 2200 UL	85	3000	201.8	66	Air	92	84	0.94	2234	4	11.35	1.29	1.13	4
Verner 133MK	84	5500	108.8	64.9	Air	97	90	0.91	1330	2	10.27	1.29	1.26	4
Limbach 2400 DFi	100	3000	237.4	76	Water	97	82	1.10	2424	4	12.31	1.32	1.07	4
Sauer 2400 UL Mg	90	3000	213.6	68	Air	94	84	0.98	2332	4	11.51	1.32	1.15	4
Lycoming IO-360A	200	2700	527.5	150	Air	130.2	111.1	1.08	5917	4	11.20	1.33	1.19	4
Verner 7H	110	2300	340.6	82	Air	94	85	0.96	4129	7	10.36	1.34	1.29	4
ULPower UL260i	97	3300	209.3	72.3	Air	105.6	74	1.60	2592	4	10.15	1.34	1.32	4
Franklin 235	125	2800	317.9	93	Air	117.5	88.9	1.37	3856	4	10.36	1.34	1.30	4
Jabiru 2200	85	3300	183.4	63	Air	97.5	74	1.36	2210	4	10.43	1.35	1.29	4
Lycoming O-360A	180	2700	474.7	132	Air	130.2	111.1	1.08	5917	4	10.08	1.36	1.35	4
Sauer 2700 UL	105	3000	249.2	75	Air	97	90	0.91	2660	4	11.77	1.40	1.19	4
Rotax 912 ULS	98.5	5800	120.9	70	Water	84	61	1.49	1352	4	11.24	1.41	1.25	4
Jabiru 3300	120	3300	258.9	83.5	Air	97.5	74	1.36	3315	6	9.82	1.44	1.46	4
Sauer 2100 ULT	110	3000	261.1	76	Air	90.5	84	0.91	2161	4	15.18	1.45	0.95	4
Lycoming AEIO 360	200	2700	527.5	136	Air	130.2	111.1	1.08	5917	4	11.20	1.47	1.31	4
ULPower UL260iS	107	3300	230.9	72.3	Air	105.6	74	1.60	2592	4	11.19	1.48	1.32	4
Limbach 2400 DT	129	3000	306.2	86	Water	97	82	1.10	2424	4	15.87	1.50	0.94	4
ULPower UL350i	118	3300	254.6	78.4	Air	105.6	100	0.88	3503	4	9.13	1.51	1.65	4
Franklin 350	205	2800	521.4	135	Air	117.5	88.9	1.37	5784	6	11.33	1.52	1.34	4
Continental IO-360ES	210	2800	534.1	138	Air	112.8	98.6	1.03	5912	6	11.35	1.52	1.34	4
Lycoming AEIO 580	315	2700	830.8	204	Air	135	111.1	1.16	9542	6	10.94	1.54	1.41	4
D-Motor LF26	91.8	3000	217.9	58	Water	103.4	80	1.31	2687	4	10.19	1.58	1.55	4
Hirth 3203 E	65	6300	73.5	40	Air	76	69	0.95	626	2	7.37	1.63	2.20	2
ULPower UL350iS	130	3300	280.5	78.4	Air	105.6	100	0.88	3503	4	10.06	1.66	1.65	4
Hirth F23 LW	50	6500	54.8	30	Air	72	64	0.99	521	2	6.60	1.67	2.52	2
Limbach 2400 DT.X	158	3000	375.0	86	Water	97	82	1.10	2424	4	19.44	1.84	0.94	4
Hirth 3701 ES	100	6000	118.7	54	Water	76	69	0.95	939	3	7.94	1.85	2.33	2
Vedeneyev M14PF	400	2900	982.2	214	Air	105	130	0.51	10131	9	12.18	1.87	1.53	4
Hirth 3003 E	102	6500	111.7	51	Air	72	64	0.99	1042	4	6.74	2.00	2.97	2
RR Merlin 61	1580	3000	3750.3	744	Water	137	152	0.64	26888	12	17.53	2.12	1.21	4
Jumo 213E	2050	3250	4491.7	940	Water	150	165	0.65	34989	12	16.13	2.18	1.35	4
DB 605	1800	2800	4577.7	756	Water	154	160	0.73	35763	12	16.09	2.38	1.48	4
RR Griffon 65	2220	2750	5748.5	900	Water	152.5	167.6	0.65	36735	12	19.66	2.47	1.25	4
P&W R-2800 32	2850	2700	7516.5	1073	Air	146.05	152.4	0.72	45957	18	20.55	2.66	1.29	4

Also here the VW engines are all over the place, although most of them are at the lower end of the scale. At the top end are the huge monsters from WW2, better than all the 2 stroke engines.

The best engines

The column marked with an "x" is a simple calculation of what is a good aircraft engine. It may very well be pure nonsense, but the reasoning is like this: A good aircraft engine is the engine with a high power to weight ratio with a low BMEP. High power to weight ratio is obvious. A low BMEP is not obvious, and may not be desirable, but when two engines have the same power to weight ratio, the one with the lowest BMEP will, at least theoretically, last longer and potentially be more reliable because there are less forces involved.

So the "x" is simply the hp/kg divided by the BMEP and multiplied by 10 to get the number around 1. There is of course a whole lot of other things to consider regarding the reliability of an engine other than BMEP, but the reasoning is sound. So at least this number shows a potential for the relative difference between engines, even though it may be far from the truth. One thing is for certain, higher BMEP while retaining high reliability cost money, lots of it. Engines with high BMEP therefore are more expensive on average than more "moderate" engines.

There are no conclusions to be drawn from this questionable theoretical maneuver, but this doesn't mean some insight can't be found.

Engine	Max HP	at RPM	T (Nm)	Weight (kg)	Cooling	Bore (mm)	Stroke (mm)	Bore/ stroke	cc	Cyl	BMEP (bar)	HP/kg	X	st
Austro AE300	168	3880	308.3	185	Water	83	92	0.64	1991	4	19.46	0.91	0.47	4
SMA SR305	227	2200	734.7	206	Air	NA	NA	NA	5000	4	18.47	1.10	0.60	4
Centurion 2.0	133	3890	243.5	134	Water	83	92	0.64	1991	4	15.37	0.99	0.65	4
HKS 700E	60	6200	68.9	55	Air	85	60	1.58	681	2	12.72	1.09	0.86	4
Hummel 50 HP	55	3600	108.8	73	Air	85.5	69	1.21	1585	4	8.63	0.75	0.87	4
GP 1600	55	3600	108.8	72	Air	85.5	69	1.21	1585	4	8.63	0.76	0.89	4
Limbach 1700 E0	68	3600	134.5	73	Air	88	69	1.28	1679	4	10.07	0.93	0.93	4
Motorav 2.4 R	85	2900	208.7	85	Air	94	88	0.90	2443	4	10.74	1.00	0.93	4
Limbach 2400 DT	129	3000	306.2	86	Water	97	82	1.10	2424	4	15.87	1.50	0.94	4
Limbach 2400 DT.X	158	3000	375.0	86	Water	97	82	1.10	2424	4	19.44	1.84	0.94	4
Sauer 2100 ULT	110	3000	261.1	76	Air	90.5	84	0.91	2161	4	15.18	1.45	0.95	4
Grob 2500	95	3400	199.0	95	Air	100	78	1.29	2450	4	10.20	1.00	0.98	4
Motorav 2.6 R	90	2900	221.0	86	Air	94	94	0.79	2609	4	10.64	1.05	0.98	4
Hummel 60 HP	65	3600	128.6	75	Air	92	69	1.40	1835	4	8.81	0.87	0.98	4
Limbach 2000 EB	80	3400	167.6	76.5	Air	90	78.4	1.04	1995	4	10.55	1.05	0.99	4
GP 1835	65	3600	128.6	74	Air	92	69	1.40	1835	4	8.81	0.88	1.00	4
JPX 4TX75	82	3000	194.6	78	Air	95	82	1.05	2325	4	10.52	1.05	1.00	4
JPX 4T60	65	3200	144.6	72	Air	93	75.4	1.19	2049	4	8.87	0.90	1.02	4
Mikron IIIA	65	2600	178.0	65	Air	90	90	0.79	2290	4	9.77	1.00	1.02	4
Limbach 2000 E0	80	3400	167.6	74	Air	90	78.4	1.04	1995	4	10.55	1.08	1.02	4
AeroVee 2.1 T	100	3400	209.4	80	Air	92	82	0.99	2180	4	12.07	1.25	1.04	4
GP 1915	69	3600	136.5	74	Air	94	69	1.46	1915	4	8.95	0.93	1.04	4
Sauer 1800 UL	68	3200	151.3	63	Air	92	69	1.40	1835	4	10.36	1.08	1.04	4
Sauer 2400 UL Al	90	3000	213.6	75	Air	94	84	0.98	2332	4	11.51	1.20	1.04	4
MW B22D	95	3400	199.0	80	Water	93	81	1.04	2201	4	11.36	1.19	1.05	4
Limbach 2400 EB	87	3200	193.6	82	Air	97	82	1.10	2424	4	10.04	1.06	1.06	4
Limbach 2400 DFi	100	3000	237.4	76	Water	97	82	1.10	2424	4	12.31	1.32	1.07	4
Sauer 1900 UL	75	3200	166.9	64	Air	94	69	1.46	1915	4	10.95	1.17	1.07	4
Sauer 2500	94	3000	223.1	77	Air	97	84	1.05	2483	4	11.29	1.22	1.08	4
Revmaster R-2300	85	3200	189.1	77	Air	94	84	0.98	2332	4	10.19	1.10	1.08	4
Mikron IIIB	75	2750	194.2	69	Air	90	96	0.69	2443	4	9.99	1.09	1.09	4
Hummel 76 HP	76	3400	159.2	76	Air	92	82	0.99	2180	4	9.17	1.00	1.09	4
Motorav 2.8 R	100	2900	245.5	84	Air	98	94	0.85	2836	4	10.88	1.19	1.09	4
GP 2180	76	3400	159.2	75	Air	92	82	0.99	2180	4	9.17	1.01	1.10	4
Rotec R2800	110	3600	217.6	102	Air	80	80	0.79	2815	7	9.71	1.08	1.11	4
Continental 200AF	95	2750	246.0	91	Air	103.1	98.6	0.86	3293	4	9.39	1.04	1.11	4
Continental 200DX	100	2750	258.9	91	Air	103.1	98.6	0.86	3293	4	9.88	1.10	1.11	4
JPX 4TX90	90	3000	213.6	74	Air	95	88	0.92	2495	4	10.76	1.22	1.13	4
Continental 240	125	2800	317.9	109	Air	112.8	98.6	1.03	3941	4	10.14	1.15	1.13	4
Sauer 2200 UL	85	3000	201.8	66	Air	92	84	0.94	2234	4	11.35	1.29	1.13	4
AeroVee 2.1	80	3400	167.6	73	Air	92	82	0.99	2180	4	9.66	1.10	1.13	4
Sauer 2400 UL Mg	90	3000	213.6	68	Air	94	84	0.98	2332	4	11.51	1.32	1.15	4
GP 2276	80	3400	167.6	75	Air	94	82	1.03	2276	4	9.25	1.07	1.15	4
Rotec R2800	150	3600	296.7	125	Air	80	80	0.79	3619	9	10.30	1.20	1.16	4
Sauer 2700 UL	105	3000	249.2	75	Air	97	90	0.91	2660	4	11.77	1.40	1.19	4
Lycoming IO-360A	200	2700	527.5	150	Air	130.2	111.1	1.08	5917	4	11.20	1.33	1.19	4
Hummel 85 HP	85	3400	178.0	76	Air	94	86	0.94	2387	4	9.37	1.12	1.19	4
Revmaster R-3000	115	3400	240.9	93	Air	102.4	90	1.02	2965	4	10.21	1.24	1.21	4
RR Merlin 61	1580	3000	3750.3	744	Water	137	152	0.64	26888	12	17.53	2.12	1.21	4
Lycoming 233	115	2800	292.5	97	Air	111.1	98.4	1.00	3816	4	9.63	1.19	1.23	4
Lycoming 320B	160	2700	422.0	127	Air	130.2	98.4	1.38	5240	4	10.12	1.26	1.25	4
Rotax 912 ULS	98.5	5800	120.9	70	Water	84	61	1.49	1352	4	11.24	1.41	1.25	4
RR Griffon 65	2220	2750	5748.5	900	Water	152.5	167.6	0.65	36735	12	19.66	2.47	1.25	4
Verner 133MK	84	5500	108.8	64.9	Air	97	90	0.91	1330	2	10.27	1.29	1.26	4
Lycoming 320A	150	2700	395.6	125	Air	130.2	98.4	1.38	5240	4	9.49	1.20	1.26	4
P&W R-2800 32	2850	2700	7516.5	1073	Air	146.05	152.4	0.72	45957	18	20.55	2.66	1.29	4
Jabiru 2200	85	3300	183.4	63	Air	97.5	74	1.36	2210	4	10.43	1.35	1.29	4
Verner 7H	110	2300	340.6	82	Air	94	85	0.96	4129	7	10.36	1.34	1.29	4
Franklin 235	125	2800	317.9	93	Air	117.5	88.9	1.37	3856	4	10.36	1.34	1.30	4
Lycoming AEIO 360	200	2700	527.5	136	Air	130.2	111.1	1.08	5917	4	11.20	1.47	1.31	4
ULPower UL260iS	107	3300	230.9	72.3	Air	105.6	74	1.60	2592	4	11.19	1.48	1.32	4
ULPower UL260i	97	3300	209.3	72.3	Air	105.6	74	1.60	2592	4	10.15	1.34	1.32	4
Continental IO-360ES	210	2800	534.1	138	Air	112.8	98.6	1.03	5912	6	11.35	1.52	1.34	4
Franklin 350	205	2800	521.4	135	Air	117.5	88.9	1.37	5784	6	11.33	1.52	1.34	4
Jumo 213E	2050	3250	4491.7	940	Water	150	165	0.65	34989	12	16.13	2.18	1.35	4
Lycoming O-360A	180	2700	474.7	132	Air	130.2	111.1	1.08	5917	4	10.08	1.36	1.35	4
Lycoming AEIO 580	315	2700	830.8	204	Air	135	111.1	1.16	9542	6	10.94	1.54	1.41	4
Jabiru 3300	120	3300	258.9	83.5	Air	97.5	74	1.36	3315	6	9.82	1.44	1.46	4
DB 605	1800	2800	4577.7	756	Water	154	160	0.73	35763	12	16.09	2.38	1.48	4
Vedeneyev M14PF	400	2900	982.2	214	Air	105	130	0.51	10131	9	12.18	1.87	1.53	4
D-Motor LF26	91.8	3000	217.9	58	Water	103.4	80	1.31	2687	4	10.19	1.58	1.55	4
ULPower UL350i	118	3300	254.6	78.4	Air	105.6	100	0.88	3503	4	9.13	1.51	1.65	4
ULPower UL350iS	130	3300	280.5	78.4	Air	105.6	100	0.88	3503	4	10.06	1.66	1.65	4
Hirth 3203 E	65	6300	73.5	40	Air	76	69	0.95	626	2	7.37	1.63	2.20	2
Hirth 3701 ES	100	6000	118.7	54	Water	76	69	0.95	939	3	7.94	1.85	2.33	2
Hirth F23 LW	50	6500	54.8	30	Air	72	64	0.99	521	2	6.60	1.67	2.52	2
Hirth 3003 E	102	6500	111.7	51	Air	72	64	0.99	1042	4	6.74	2.00	2.97	2

Now all the VW engines comes in the lower half of the scale. They either have high BMEP or they have low power to weight ratio.

All the two stroke engines from Hirth comes out on top. This is due to high power to weight ratio combined with the low BMEP for 2 stroke engines.

At the very low end of the scale is all the 4 stroke diesels. This means a 4 stroke diesel aircraft engine is bound to be heavy and expensive. Being more speculative, one could also say they will be troublesome.

At the very high end is the two ULPower 350s followed by the D-motor and the M14PF. The D-Motor is too new to have any real world experience, but the UL350 and the MP14 in particular are excellent engines. Also interesting is the "vanilla" Lycoming O-360 with a very good score, but then again the Franklin 350 with similar score has become obsolete.

The VW engines ends up very similar, the larger displacement being "better" because they have higher power to weight ratio.

I wrote that no conclusions could be drawn from this, but I think some things are so obvious in any case so I will make a few after all.

• 4 stroke diesel as aircraft engines ? 
• ULPower and possibly D-motor could OK. The Jabiru 3300 is also interesting.
• The Lycoming O-360 is far from heavy and low powered.
• A larger VW engine is better than a smaller VW engine due to better power to weight ratio, but proper cooling is probably a limiting factor?
• 2 stroke engines are "under-rated", probably due to things like reliability and fuel consumption. However, the "2 stroke logic" is a very good one, as can be read here.
• No 2 stroke diesel engines are here due to lack of data, which is a pity.