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Solving the Ground Cooling Problem 7 – Test Data

Blog, Cooling
Date:  01-18-2025
Number of Hours:  0
Manual Reference:  no ref

This is the data collected from 11 engine runs in different cooling configurations. Cowls on and off, 4 cooling fans behind the radiators, installed and removed with two bottom cowl flap openings and finally with all four openings and the flaps temporarily installed fully opened.

NOTE: My engine is liquid cooled. My interest is in the coolant temperature, similar to the numbers that you might have in your car. Oil temperatures are also important.  CHT’s have no relevance of course in a liquid cooled set up.

Results
With the four large flaps open and no cooling fans I can stay in the hold for 40 minutes with engine temperatures low enough to safety take off.  (Coolant 192F, Oil 205F)

I can now start the flap modification on my permanent cowls now these ‘test dummy ones’ have given me a proof of concept.

Summary Data Chart

You can see with the cowl flaps open and no fans I am below 200F after 40 minutes at idle RPM and the oil is 205F as well. Safe engine temperatures for a take off. I hope I’ll never have to wait 40 minutes in the hold but now I know the plane can handle it.

You can see with no flaps I would be good for less than 10 minutes, a bit like my old Long-EZ with the air cooled engine. This graph also shows that the addition of fans was a very minor improvement and is certainly not worth the trouble.

The Raw Data
I have a lot more data than this. My G3X record numbers every second! I took notes every 2 minutes in the cockpit. That is plenty. What follows are copies from my excel sheet and may be easier to read in this format. Feel free to get in touch if anything is unclear. Temperatures are in F° time is in minutes.

Time Test Duration Coolant F Temp Post Pre Rad Temp1 Pre Rad Temp2 OIL Temp Oil PSI Aux Pump ON Coolant PSI Engine RPM Volts Amps COMMENTS
Taxi Cooling tests Auto Temp set to 170F, Non fan radiator areas gaffer taped on rear side 3 X 5.2″ Spal Puller Fans
28/11/2024   BOTH COWLS OFF
12.51 0 48 Startup
12.56 5 162 169
12.59 8 171 177
13.02 10 174 179
13.04 12 176 179
13.09 17 177 180
13.16 24 181 185 ON 7 12.7 38
13.18 26 182 188
13.19 27 184 189
13.22 30 185 187
13.23 31 184 186 8
13.24 32 183 185
13.26 34 183
13.31 39 Shut Down
28/11/2024   BOTTOM COWL ON TOP COWL OFF
15.22 0 105 104 106 7
15.27 5 175 176 177 159 ON
15.31 9 182 185 185 177 50
15.35 13 190 193 192 196 49 9
15.38 16 195 197 198 206 47 10
15.41 19 199 201 201 211 47 10
15.44 22 203 205 205 216 47 11
15.47 24 208 210 210 219 47 12
15.50 27 209 211 210 222 47 12
15.52 29 209 212 211 223 47 12 870
15.56 33 Shut Down
2/12/2024   BOTTOM COWL OFF TOP COWL ON   OAT 24C
9.45 0 109 130 115 1
9.49 4 141 160 155
9.52 7 171 176 176 ON 6
9.56 11 177 181 181 178 7
10.00 15 185 189 189 186 48 7 870
10.04 19 192 196 196 198 47 8 870
10.07 22 196 200 200 204 47 9
10.10 25 196 199 200 208 46 9 12.5
10.13 28 198 201 202 211 46 9 40/4
10.15 30 200 203 203 212 9
10.18 33 202 206 206 215 10
10.21 36 204 208 208 217 10 12.4
10.24 39 203 207 207 219 45 10 12.2 38/4
10.25 40 Shut Down
2/12/2024   BOTTOM COWL ON TOP COWL ON   OAT 31C 3 Fans flush with areas in-between blocked off
13.54 0 94 104 111 109 0 860 14.1/13.0 30
13.57 3 143 162 154 135 1.2
13.59 5 173 177 177 153 ON 7 860
14.02 8 189 193 194 180 9 850
14.05 11 198 202 203 194 11
14.08 14 209 213 214 209 12 900
14.12 18 219 223 224 225 14 830
14.14 20 222 226 227 231 15 brief taxi @ higher rpm
14.16 22 226 230 231 236 16 820
14.19 25 227 231 231 244 16 12.7 34
14.20 26 228 232 252 245 16 17psi = 1.2BAR
14.22 28 226 230 241 241 19 Shut Down 20psi = 1.4BAR (max pressure)
24/12/2024   BOTH COWLS ON 3D Prototpe1 Rear Shrouds 4 fans two large two small  BAD DATA (Melt down)
15.56 0 77 87 77 0 NOTE Fans melted, shrouds melted BAD DATA
16.01 5 167 171 172 147 5
16.05 9 175 182 182 177 6
16.08 12 189 196 196 190 6
16.11 15 199 206 206 203 6 900 13.4 37
16.14 17 209 216 217 216 9
16.17 20 217 224 224 227 10 Rear shrouds shifted out of position
16.22 25 233 226 233 243 12
16.26 27 239 232 240 247 13
16.28 29 236 243 243 251 14
16.30 31 238 245 245 254 14 Coolant boiled
27/12/2024 BOTH COWLS ON No fans or Shrouds – BASE LINE NUMBERS  Both pumps on after 110F OAT 23
13.59 0
14.01 2 124 128 128 103 3 880 13.9 47/1
14.04 5 149 152 152 127 6 910 13.7 46/2
14.06 7 167 171 172 152 8 920 13.5 43/2
14.08 9 177 180 181 165 9 870 42/2
14.10 11 187 186 190 177 11 900 13 39/2
14.12 13 194 198 199 190 12 910 12.8 38/2
14.14 15 202 206 207 201 14 910 13 37/3
14.16 17 209 213 213 210 15 930 12.9 36/3
14.18 19 214 219 220 220 17 890
14.19 21 STOP
29/12/24 BOTH COWLS ON 4 Fans (two large 2 small) Good new shrouds OAT 28 Pump on at 104F
15.32 0 85 100 98 85 1010 39/0
15.36 4 139 143 143 122 860 46/0 aux pump on
15.38 6 155 159 160 140 910 44/1 (no change)
15.40 8 167 172 172 156 910 43/3
15.42 10 176 180 181 172 910 41/4
15.44 12 184 188 189 184 9 920 40/5
15.46 14 192 197 197 195 10 920 38/6
15.48 16 199 204 204 205 12 920 37/6
15.50 18 206 211 216 214 13 930 36/7
15.52 20 211 216 221 222 14 940 35/7
15.54 22 214 212 226 229 15 950 12.7 34/7
15.56 24 218 227 232 233 15 850 34/3
15.58 26 224 232 231 245 16 35/3
15.60 28 226 239 239 242 21 36/3
Pump on at 104F
31/12/24 TOP COWL ON BOTTOM DUMMY COWL WITH COWL FLAP HOLES 4 Fans (2 large,2 small) SLIGHTLY MELTED new shrouds OAT 27C
15.55 0 89 103 98 60 14.1 28/1
15.59 4 137 103 142 123 4 44/1
16.01 6 153 157 157 143 5 50/1
16.03 8 161 167 167 159 AUX OFF 6 43/0
16.05 10 169 175 175 169 6 850 43/0
15.07 12 176 182 182 178 7 42/0
16.09 14 180 187 187 186 8 41/1
16.11 16 186 192 192 193 8 40/1
16.13 18 189 196 196 200 9 40/1
16.15 20 193 199 199 205 10 13.3 40/1
16.17 22 194 200 201 209 10 13.4 39/1
16.19 24 197 204 203 213 10 13.3 38/1
16.21 26 200 206 206 217 11 38/1
16.23 28 202 209 209 219 11 13.1 37/1
16.25 30 205 212 212 222 12 37/1
16.27 32 208 214 214 225 13 37/1
16.30 35 211 215 215 230 13 12.8 34/2
1/1/25 TOP COWL ON BOTTOM DUMMY COWL WITH COWL FLAP HOLES NO FANS OAT 23C Pump on at 104F
14.50 0 75 74 75 71
14.53 3 124 128 127 101 2 14.1 30/1
14.57 7 147 152 151 123 4 14.1 29/1
15.59 9 163 169 168 142 5 14.1 28/1
15.01 11 177 181 181 159 6 14.1 28/1
15.03 13 189 193 193 172 8 14.1 28/1
15.05 15 200 205 204 185 9 14.1 28/1
15.07 17 208 213 212 196 11 14.1 27/0
15.09 19 213 217 217 209 12 14.1 27/0
15.10 20 221 224 224 213 14 14.0 0/0
SHUT DOWN  temps too high
17/1/25 BOTH DUMMY COWLS, TOP & BOTTOM FLAPS, 4 FANS OAT 21 Pump on at 104F
9.11 0 77 84 85 67 AUX ON
9.14 3 113 115 115 81 3 800 45
9.16 5 132 138 137 108 4 820 44
9.18 7 140 143 142 121 4 830 43/2
9.20 9 147 150 150 132 5 830 42/2
9.22 11 152 155 156 145 5 840 42/2
9.24 13 156 159 159 154 6 840 41/3
9.26 15 160 160 164 164 7 850 12.7 41/3
9.28 17 165 169 169 169 7 850 12.7 40/3
9.30 19 168 173 172 175 7 860 12.7 40/3
9.32 21 170 174 174 180 8 860 12.6 40/3
9.34 23 174 178 178 184 8 860 12.6 40/3
9.36 25 181 185 185 189 9 860 12.6 39/3
9.38 27 184 189 187 193 9 860 12.6 39/3
9.40 29 187 191 190 197 9 860 12.6 39/3
9.42 31 187 191 191 200 9 860 12.6 39/3
9.44 33 189 193 192 202 9 860 12.5 38/4
9.46 35 189 193 193 204 10 850 12.5 38/4
9.48 37 192 195 195 206 10 850 12.5 38/4
9.50 39 191 196 195 207 10 850 12.5 38/3
9.52 41 192 196 196 209 10 860 12.5 38/3
9.55 44 189 193 193 210 9 860 12.4 37/3
18/1/25 BOTH DUMMY COWLS, TOP & BOTTOM FLAPS, NO FANS (removed) OAT 24C Pump on at 104F
10.09 0 77 78 79 66 AUX ON 0 820 13.8 34
10.12 3 119 118 118 89 2 820 13.9 38
10.14 5 128 130 130 101 2 820 13.9 38/1
10.16 7 144 146 146 120 4 860 13.9 38
10.18 9 154 156 156 124 5 860 13.8 38/1
10.20 11 162 164 164 148 6 860 13.8 38
10.22 13 168 171 171 158 7 860 13.8 38/1
10.24 15 172 175 176 167 7 820 13.8 38
10.26 17 175 177 178 174 8 820 13.7 39
10.28 19 178 180 180 179 8 820 13.7 39
10.30 21 179 182 182 183 8 830 13.7 39
10.32 23 180 183 183 187 8 840 13.7 39
10.34 25 182 185 185 190 9 840 13.7 39
10.36 27 189 191 191 193 10 830 13.7 39
10.38 29 191 193 194 197 10 850 13.7 39
10.40 31 190 192 192 199 10 830 13.7 39
10.42 33 192 195 195 201 11 840 13.7 39
10.44 35 190 193 193 202 11 830 13.7 39
10.46 37 193 196 196 204 11 840 13.7 39
10.48 39 192 195 195 205 11 840 13.7 39

 

This last graph shows that the addition of fans was a very minor improvement and is certainly not worth the trouble.
They will block air in flight and use too many amps for the alternator to keep up at low RPM.
The result with the huge cowl flaps is not far off both bottom and top cowls removed, a good result.
The cowl flaps may also be useful in flight for prolonged climbs or just after take off in hot conditions.

All this testing work has put me in a position to confidently cut up my good white cowls.  Let me know if you need a very expensive but now useless set of two ply Long-EZ cowls! Despite the carbon they are really flimsy.

 

 

 

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Solving the Ground Cooling Problem 6 Dummy Cowl Flaps

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