(reposting from p28b.com)
I was wondering how much extra speed I would get if I upgraded my engine to the 260 HP from the Cherokee Six (My understanding it is just new cylinders and exhaust) at the next OH.
I discovered the equation that equates P (power) to v (speed) is
P=A/v + B * v^3
where A and B are constants dependent on airframe and altitude.
A/v represents induced drag, and B * V^3 represents parasitic drag.
I worked out the values for A & B for my Cherokee 235B at sea level and at 9000 feet using the numbers from the POH.
For 9000 feet I got A=3209 and B = 4.2 * 10^-5
For Sea Level I got A = 2189 and B = 5.56 * 10^-5
From there I created a spread sheet (I would love to upload it / how do i do that?) I figured out that the 260 HP would get me only 6 MPH at 9000 feet and 5 MPH at seal level. I suspect more speed higher. I should do the math for 12K feet. But I would imagine it is still be well under 10 mph gain there. I assumed the weight is the same given the increased H/P which is not likely to be the case.
Does anyone have the 260 HP? Do these numbers look right?
(only 350HP required to go 200 MPH!!)
The coumns from left to right:
MPH - this is v
H/P this is the H/P required to go that fast at Sea Level (P)
75 % The max h/p of the engine that outputs that H/P at 75% (P/.75)
H/P this is the H/P required to go that fast at 9000 MSL (density alt.) (P)
75 % The max h/p of the engine that outputs that H/P at 75% (P/.75)
MPH Sea Level 9000 MSL
H/P 75% of H/P 75% of
135 153.01 204.02 127.11 169.47
136 155.96 207.94 129.24 172.33
137 158.95 211.93 131.42 175.23
138 161.99 215.98 133.63 178.18
139 165.07 220.09 135.88 181.18
140 168.20 224.27 138.17 184.23
141 171.39 228.51 140.49 187.33
142 174.62 232.82 142.86 190.48
143 177.90 237.19 145.26 193.68
144 181.22 241.63 147.70 196.93
145 184.60 246.14 150.17 200.23
146 188.03 250.71 152.69 203.59
147 191.51 255.34 155.24 206.99
148 195.04 260.05 157.84 210.45
149 198.62 264.82 160.47 213.96
150 202.25 269.66 163.14 217.52
151 205.93 274.57 165.86 221.14
152 209.66 279.55 168.61 224.81
153 213.44 284.59 171.40 228.53
154 217.28 289.71 174.23 232.31
155 221.17 294.90 177.11 236.14
156 225.11 300.15 180.02 240.03
157 229.11 305.48 182.97 243.97
158 233.16 310.88 185.97 247.96
159 237.26 316.35 189.01 252.01
160 241.42 321.89 192.09 256.12
161 245.63 327.51 195.21 260.28
162 249.90 333.20 198.37 264.50
163 254.22 338.96 201.58 268.77
164 258.60 344.80 204.83 273.10
165 263.03 350.71 208.12 277.49
166 267.52 356.69 211.45 281.94
167 272.06 362.75 214.83 286.44
168 276.67 368.89 218.25 291.00
169 281.33 375.10 221.71 295.62
170 286.04 381.39 225.22 300.30
171 290.81 387.75 228.77 305.03
172 295.65 394.19 232.37 309.83
173 300.54 400.71 236.01 314.68
174 305.48 407.31 239.70 319.60
175 310.49 413.99 243.43 324.57
176 315.56 420.74 247.21 329.61
177 320.68 427.58 251.03 334.71
178 325.87 434.49 254.90 339.86
179 331.12 441.49 258.81 345.08
180 336.42 448.56 262.77 350.36
181 341.79 455.72 266.78 355.70
182 347.22 462.96 270.83 361.11
183 352.71 470.28 274.93 366.58
184 358.26 477.68 279.08 372.11
185 363.87 485.16 283.27 377.70
186 369.55 492.73 287.52 383.36
187 375.29 500.38 291.81 389.08
188 381.09 508.12 296.15 394.86
189 386.95 515.94 300.53 400.71
190 392.88 523.84 304.97 406.62
191 398.88 531.83 309.45 412.60
192 404.93 539.91 313.98 418.65
193 411.06 548.07 318.57 424.76
194 417.24 556.32 323.20 430.93
195 423.49 564.66 327.88 437.17
196 429.81 573.08 332.61 443.48
197 436.20 581.59 337.40 449.86
198 442.65 590.19 342.23 456.30
199 449.16 598.88 347.11 462.81
200 455.75 607.66 352.05 469.39
I was wondering how much extra speed I would get if I upgraded my engine to the 260 HP from the Cherokee Six (My understanding it is just new cylinders and exhaust) at the next OH.
I discovered the equation that equates P (power) to v (speed) is
P=A/v + B * v^3
where A and B are constants dependent on airframe and altitude.
A/v represents induced drag, and B * V^3 represents parasitic drag.
I worked out the values for A & B for my Cherokee 235B at sea level and at 9000 feet using the numbers from the POH.
For 9000 feet I got A=3209 and B = 4.2 * 10^-5
For Sea Level I got A = 2189 and B = 5.56 * 10^-5
From there I created a spread sheet (I would love to upload it / how do i do that?) I figured out that the 260 HP would get me only 6 MPH at 9000 feet and 5 MPH at seal level. I suspect more speed higher. I should do the math for 12K feet. But I would imagine it is still be well under 10 mph gain there. I assumed the weight is the same given the increased H/P which is not likely to be the case.
Does anyone have the 260 HP? Do these numbers look right?
(only 350HP required to go 200 MPH!!)
The coumns from left to right:
MPH - this is v
H/P this is the H/P required to go that fast at Sea Level (P)
75 % The max h/p of the engine that outputs that H/P at 75% (P/.75)
H/P this is the H/P required to go that fast at 9000 MSL (density alt.) (P)
75 % The max h/p of the engine that outputs that H/P at 75% (P/.75)
MPH Sea Level 9000 MSL
H/P 75% of H/P 75% of
135 153.01 204.02 127.11 169.47
136 155.96 207.94 129.24 172.33
137 158.95 211.93 131.42 175.23
138 161.99 215.98 133.63 178.18
139 165.07 220.09 135.88 181.18
140 168.20 224.27 138.17 184.23
141 171.39 228.51 140.49 187.33
142 174.62 232.82 142.86 190.48
143 177.90 237.19 145.26 193.68
144 181.22 241.63 147.70 196.93
145 184.60 246.14 150.17 200.23
146 188.03 250.71 152.69 203.59
147 191.51 255.34 155.24 206.99
148 195.04 260.05 157.84 210.45
149 198.62 264.82 160.47 213.96
150 202.25 269.66 163.14 217.52
151 205.93 274.57 165.86 221.14
152 209.66 279.55 168.61 224.81
153 213.44 284.59 171.40 228.53
154 217.28 289.71 174.23 232.31
155 221.17 294.90 177.11 236.14
156 225.11 300.15 180.02 240.03
157 229.11 305.48 182.97 243.97
158 233.16 310.88 185.97 247.96
159 237.26 316.35 189.01 252.01
160 241.42 321.89 192.09 256.12
161 245.63 327.51 195.21 260.28
162 249.90 333.20 198.37 264.50
163 254.22 338.96 201.58 268.77
164 258.60 344.80 204.83 273.10
165 263.03 350.71 208.12 277.49
166 267.52 356.69 211.45 281.94
167 272.06 362.75 214.83 286.44
168 276.67 368.89 218.25 291.00
169 281.33 375.10 221.71 295.62
170 286.04 381.39 225.22 300.30
171 290.81 387.75 228.77 305.03
172 295.65 394.19 232.37 309.83
173 300.54 400.71 236.01 314.68
174 305.48 407.31 239.70 319.60
175 310.49 413.99 243.43 324.57
176 315.56 420.74 247.21 329.61
177 320.68 427.58 251.03 334.71
178 325.87 434.49 254.90 339.86
179 331.12 441.49 258.81 345.08
180 336.42 448.56 262.77 350.36
181 341.79 455.72 266.78 355.70
182 347.22 462.96 270.83 361.11
183 352.71 470.28 274.93 366.58
184 358.26 477.68 279.08 372.11
185 363.87 485.16 283.27 377.70
186 369.55 492.73 287.52 383.36
187 375.29 500.38 291.81 389.08
188 381.09 508.12 296.15 394.86
189 386.95 515.94 300.53 400.71
190 392.88 523.84 304.97 406.62
191 398.88 531.83 309.45 412.60
192 404.93 539.91 313.98 418.65
193 411.06 548.07 318.57 424.76
194 417.24 556.32 323.20 430.93
195 423.49 564.66 327.88 437.17
196 429.81 573.08 332.61 443.48
197 436.20 581.59 337.40 449.86
198 442.65 590.19 342.23 456.30
199 449.16 598.88 347.11 462.81
200 455.75 607.66 352.05 469.39
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