Any ideas on drilling out my existing jet ?
That's some good information right there. I was always told that you should have 1 GPH of takeoff fuel flow for every 10 HP but, in retrospect, I think that's too much. I just went back and looked at my last takeoff (yesterday) and my EGTs were between 1320 to 1340 so I guess I'm good. My fuel flow at the time was 11 GPH on my 145 HP engine.A wise man named John Deacon wrote that a properly set up engine should have an EGT of approximately 1300 degrees on takoff and if it runs hotter, add fuel to cool.
A wise man named John Deacon wrote that a properly set up engine should have an EGT of approximately 1300 degrees on takoff and if it runs hotter, add fuel to cool. Again, this is after checking all else........Good Luck
I just went back and looked at my last takeoff (yesterday) and my EGTs were between 1320 to 1340 so I guess I'm good.
I relied on fuel flow alone. I didn't know about the 1,300 degree thing until I read this thread.I don't understand the reliance on absolute EGT values.
I just went back and looked at my last takeoff (yesterday) and my EGTs were between 1320 to 1340 so I guess I'm good. My fuel flow at the time was 11 GPH on my 145 HP engine.
Yes, yes, and yes. Airport elevation was 2165'. Well actually, it was immediately after opening the throttle for takeoff and the data is taken at 6 second intervals. (Hope this embeds OK)Let's look at it. Was that data at WOT, immediately after liftoff, very near airport elevation?
DATE & GMT TIME E1 E2 E3 E4 C1 C2 C3 C4 DIF CLD BAT FF USD
9/28/2017 18:36 1331 1304 1322 1329 363 345 373 363 27 0 14.8 5.5 0.2
9/28/2017 18:37 1320 1293 1322 1329 365 348 376 365 36 0 14.8 11.1 0.2
9/28/2017 18:37 1332 1311 1322 1349 367 351 378 368 38 0 14.8 11.1 0.2
9/28/2017 18:37 1332 1322 1322 1340 369 355 381 371 18 0 14.8 11.3 0.2
9/28/2017 18:37 1332 1322 1331 1340 371 359 383 374 18 0 14.8 11.2 0.4
9/28/2017 18:37 1332 1332 1331 1347 371 362 385 377 16 0 14.1 11.1 0.4
9/28/2017 18:37 1332 1332 1351 1371 373 365 387 379 39 0 14.7 10.8 0.4
9/28/2017 18:37 1332 1325 1351 1371 373 368 387 381 46 0 14.7 10.7 0.4
9/28/2017 18:37 1332 1325 1366 1384 373 370 390 383 59 0 14.7 10.8 0.4
9/28/2017 18:37 1332 1319 1371 1390 375 370 392 385 71 0 14.7 10.7 0.4
9/28/2017 18:37 1332 1311 1385 1390 375 372 392 385 79 0 14.7 10.6 0.4
9/28/2017 18:38 1332 1311 1390 1390 375 372 394 388 79 0 14.7 10.8 0.4
9/28/2017 18:38 1325 1305 1396 1402 375 372 396 388 97 0 14.7 10.6 0.4
9/28/2017 18:38 1319 1305 1402 1412 373 372 396 390 107 0 14.7 10.7 0.4
9/28/2017 18:38 1324 1299 1402 1412 373 372 398 390 113 0 14.7 10.6 0.4
9/28/2017 18:38 1324 1299 1409 1417 373 370 398 390 118 0 14.7 10.8 0.6
9/28/2017 18:38 1319 1299 1409 1417 370 370 400 392 118 -10 14.7 10.7 0.6
9/28/2017 18:38 1319 1299 1414 1409 370 368 400 392 115 -10 14.9 10.8 0.6
9/28/2017 18:38 1327 1299 1424 1409 370 368 403 392 125 0 14.7 10.9 0.6
Actual drilling of the jet is not the recommended procedure. Use jet reamer for the job, inserting from front to exit. Use shank of wire size drill bit at small end, exit, to measure size. They are very hard to find, but I have a set if anybody wants to borrow them. Long time pro in the carburetor rebuilding field.
Regards,
Chris
To help others, I thought I would point out that take off is not the critical area for the FP crowd. On my 320 with FP, I set my fuel flow around 12 GPH on take-off and initial Vy climb. I am well over 200 ROP. As I transition to cruise climb at pattern altitude, the FF goes up to 12.3 or so for 150 ROP. I am slightly under-pitched, so my FF's may not match others.
The CS guys are taking off with a lot more RPM and require more fuel accordingly. Larry
Yes, yes, and yes. Airport elevation was 2165'. Well actually, it was immediately after opening the throttle for takeoff and the data is taken at 6 second intervals. (Hope this embeds OK)
Code:DATE & GMT TIME E1 E2 E3 E4 C1 C2 C3 C4 DIF CLD BAT FF USD 9/28/2017 18:36 1331 1304 1322 1329 363 345 373 363 27 0 14.8 5.5 0.2 9/28/2017 18:37 1320 1293 1322 1329 365 348 376 365 36 0 14.8 11.1 0.2 9/28/2017 18:37 1332 1311 1322 1349 367 351 378 368 38 0 14.8 11.1 0.2 9/28/2017 18:37 1332 1322 1322 1340 369 355 381 371 18 0 14.8 11.3 0.2 9/28/2017 18:37 1332 1322 1331 1340 371 359 383 374 18 0 14.8 11.2 0.4 9/28/2017 18:37 1332 1332 1331 1347 371 362 385 377 16 0 14.1 11.1 0.4 9/28/2017 18:37 1332 1332 1351 1371 373 365 387 379 39 0 14.7 10.8 0.4 9/28/2017 18:37 1332 1325 1351 1371 373 368 387 381 46 0 14.7 10.7 0.4 9/28/2017 18:37 1332 1325 1366 1384 373 370 390 383 59 0 14.7 10.8 0.4 9/28/2017 18:37 1332 1319 1371 1390 375 370 392 385 71 0 14.7 10.7 0.4 9/28/2017 18:37 1332 1311 1385 1390 375 372 392 385 79 0 14.7 10.6 0.4 9/28/2017 18:38 1332 1311 1390 1390 375 372 394 388 79 0 14.7 10.8 0.4 9/28/2017 18:38 1325 1305 1396 1402 375 372 396 388 97 0 14.7 10.6 0.4 9/28/2017 18:38 1319 1305 1402 1412 373 372 396 390 107 0 14.7 10.7 0.4 9/28/2017 18:38 1324 1299 1402 1412 373 372 398 390 113 0 14.7 10.6 0.4 9/28/2017 18:38 1324 1299 1409 1417 373 370 398 390 118 0 14.7 10.8 0.6 9/28/2017 18:38 1319 1299 1409 1417 370 370 400 392 118 -10 14.7 10.7 0.6 9/28/2017 18:38 1319 1299 1414 1409 370 368 400 392 115 -10 14.9 10.8 0.6 9/28/2017 18:38 1327 1299 1424 1409 370 368 403 392 125 0 14.7 10.9 0.6
I just went back and looked at my last takeoff (yesterday) and my EGTs were between 1320 to 1340 so I guess I'm good. My fuel flow at the time was 11 GPH on my 145 HP engine.
More likely from Don George's hindquarters. I don't care about the absolute value of the HP, but it seems like I have plenty. Two days ago on a 10 mile final to KTYS, my IAS was 165Kts and my ground speed was 189 Kts with no tailwind. It really confused Knoxville Approach that a little "experimental" was moving that fast. (video/audio upon request)John, did that number come from a dyno run?
Thanks for the analysis. My EGTs usually peak around 1550, and usually either #3 or #4.
Regarding the CHTs, I have two 2" ducts feeding my oil cooler taken from either side of the rear baffles. That probably explains why #3 & #4 run hotter. Now that fall is here, I'll probably blank off one of them (or both of them half-way).
Good note Larry. RPM is one of multiple variables making fuel flow a rough approximation, at best. Here Larry has considered mixture via reference to peak EGT (a method which does not lie), and found that for his cruise climb condition, an increase in RPM leaned the mixture a wee bit, even though fuel flow went up.
Not a surprise if you think about it. Assume 2200 initial RPM at 1000 MSL, 2450 for cruise climb by 2000 MSL, standard day air density, and 100% VE. The engine is an air pump, so at 2200 it would inhale 908 lbs of air per hour, vs 981 pph at 2450. So, the engine requires 7.5% more fuel flow to maintain the same mixture, despite a 3% decrease in air density (.0721/.0743 lbs/ft^3) during the 1000 ft interval. Without an altitude change, it would need 10% more fuel based on RPM change alone. If the RPM rise brings a speed increase, and we assume a good ram inlet, pressure (thus density) would rise, and it would need even more fuel to maintain correct mixture.
Next time someone insists you need a particular fuel flow for such-and-such engine, ask "At what RPM, what OAT, and what MP?"... and watch for the blank look.
BTW, 150 ROP is good; at or close to best power mixture.
Yes, Initial RPM was 2,400 at 2,130' (indicated) and 180 seconds later it was 2,500 RPM at 3,000'. (I retrieved those figures from my Garmin Virb camera in the cockpit.) I wrote down the OAT, Baro, and DA on my checklist, but all that's at the hangar.Does the 108 seconds include an RPM rise?