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Looking back at my data, I stayed full rich up to about 1500', at full rich I gulp down nearly 17 GPH. I had my servo checked out as I thought it was too rich but they returned it to me saying it was operating correctly and within specs. Can you tell me what your fuel flow is at full rich? I then leaned it down to 13 GPH for most of the remainder of the climb up to 4500, with some deviation as I was experimenting with the mixture and watching CHTs. Once established at 4500' I initially pulled it back to LOP with 8.5 GPH but wanted to get my speed back so after a bit I went back to 11.6 GPH which is pretty close to best power, 100F ROP, but the CHTs were climbing so I settled in on 13.3 GPH to keep my speed with CHTs staying in the low 390F range. (My TAS was 168 knots) It would be quite interesting to compare my data charting from Savvy Analysis with another similar installation in similar flight conditions. Do you have a flight that you could share here in the same way? Any one else? This seems like a great way to learn more about operating these engines and trouble shoot installations via comparison with others. "Try leaning in the climb so the EGT stays the same as the full power sea level EGT." OK so to do this I would start out full rich as usual, but note the EGTs, and as they drop in temperature due to climbing up into thinner air, gradually lean to keep them at the same temperature as they were at full power and full rich at take off down low? OK so writing that question clarifies it for me. It is just not a technique I have tried before but will now that you have pointed it out. I think I have been reluctant to keep it running at what seems like excessive rich. I will give this a try but I do wonder if my fuel flow should be up at 17 GPH to start with... I have always felt the fuel flow was excessive, especially when I go full rich as I pull onto the runway and hear the engine kind of groan at what seems like excess fuel flow. Before I do much more experimenting I do plan to get a timing light and verify where my timing is set without making any changes. Always more to learn:) Randall |
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Fuel Flow on Takeoff
Randy,
In my aircraft the fuel flow during takeoff at sea level is around 17 gph so yours seems reasonable. At 5,000' leaned to my target EGT I still see around 14 gph. Cheers Nige |
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I recently replaced two bendix mags with Pmags on my 9.0:1 compression engine and have since been struggling with high cht's during climbs. All cylinders are 25-30 degrees hotter than before. I'm going to clean up the baffling before I adjust the timing.
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Target EGT Climb
Randy,
Here is the link from a flight I did yesterday, of interest to you is the climb from time 10:00 to 25:00, https://www.savvyanalysis.com/flight...b-92812fb3312e My home airport is at 4001' so you would expect higher fuel flow at sea level. I takeoff with WOT, Prop 2700 RPM and mixture full rich and boost pump on. If you plot the fuel flow against EGT on the top graph and PALT against the CHT on the bottom graph you will see the following: The first reduction in fuel flow is the prop coming back to 2500 RPM from 2700 RPM with the throttle still wide open. The second reduction is the boost pump coming off. After that you will see little step reductions in fuel flow as I lean to about 1150 - 1200F EGT every couple of thousand feet, in-between you see a gradual reception in fuel flow which is the normal action of the fuel servo (for a great explanation of mechanical fuel injection see Dan H's article earlier this year in Kit Planes). You will see that the CHT's stay around 375F. If they get a little hotter I just delay the next leaning until they have cooled a little bit. If they are a nice and cool I lean a little more. You can see that I pretty high fuel flow all the way to 17,500'. Target EGT leaning is a technique not a law so if the CHT's are higher than you want, richen slightly, if they are cool lean a little more. If you can't climb like this with CHT's less than 400F the problem is probably not the ignition timing. In my engine with 0 deg advance shift and a max advance of 35 degrees I see the full 35 degrees by the time I am at 5,000' PA with WOT and 2,500 RPM. Cheers Nige |
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Yet one more reason people should be giving more consideration to open and flexible systems, like Ross' CPI system. Larry |
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