bonal Posted July 6, 2018 Report Share Posted July 6, 2018 Was looking through some photos of my panel on some different flights and doing the conversations for TAS found the fastest speed to be 156 knots at 6500 feet. I usually don't push Snoopy that hard these days. On a gps three heading run at 8000 ended up with 149 knots. And block fuel is 9 gallons per hour. I'm pretty happy with those numbers not too bad for a converted D with over 6000 hours on it. 1 Quote Link to comment Share on other sites More sharing options...
steingar Posted July 6, 2018 Author Report Share Posted July 6, 2018 I don't get 149 without a stiff tailwind. Mine will do 140 all day. That said I don't flog it, and rarely go past 75% power. Quote Link to comment Share on other sites More sharing options...
FastTex Posted July 7, 2018 Report Share Posted July 7, 2018 (edited) On 7/6/2018 at 9:29 AM, steingar said: I don't get 149 without a stiff tailwind. Mine will do 140 all day. That said I don't flog it, and rarely go past 75% power. Sorry for the silly question...but how do you know you are @75%? Simple math? I'm trying to figure it out on my M20F that's why I ask. Edited July 7, 2018 by FastTex Quote Link to comment Share on other sites More sharing options...
steingar Posted July 7, 2018 Author Report Share Posted July 7, 2018 30 minutes ago, FastTex said: Sorry for the silly question...but how do you know you are @75%? Simple math? I'm trying to figure it out on my M20F that's why I ask. My percentage power is strictly based on the POH. Since the charts therein are brief and don’t deal with that many conditions I admit I could be off a touch. But I really do try not to flog it. Quote Link to comment Share on other sites More sharing options...
carusoam Posted July 7, 2018 Report Share Posted July 7, 2018 On 7/5/2018 at 3:02 PM, MBDiagMan said: Well Paul, what if you put the J windscreen and cowl on an F? See what Bob did to his E... over time.... cowl windscreen paint panel and other engine /prop details... Lots of planning prior to execution... The E makes a great retirement plane. —————————- Same details apply to the F... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted July 7, 2018 Report Share Posted July 7, 2018 4 hours ago, FastTex said: Sorry for the silly question...but how do you know you are @75%? Simple math? I'm trying to figure it out on my M20F that's why I ask. The only way to know while ROP is using a chart, or a simple calculation related to the chart... get a copy of the chart from your POH. Store it on your idevice or preferred electronic device.... When LOP it’s a simple calculation based on Fuel Flow... Using only MP and RPM... one of the best details from the MAPA PPP class.... If concerned about the redbox before going LOP, use altitude to limit the MP... around 8+k’ Best regards, -a- Quote Link to comment Share on other sites More sharing options...
jaylw314 Posted July 7, 2018 Report Share Posted July 7, 2018 5 hours ago, FastTex said: Sorry for the silly question...but how do you know you are @75%? Simple math? I'm trying to figure it out on my M20F that's why I ask. 49 minutes ago, carusoam said: The only way to know while ROP is using a chart, or a simple calculation related to the chart... get a copy of the chart from your POH. Store it on your idevice or preferred electronic device.... When LOP it’s a simple calculation based on Fuel Flow... Using only MP and RPM... one of the best details from the MAPA PPP class.... When you're ROP, your power is determined by airflow in theory. Since 100% power comes at max MAP and RPM, you just take MAP(% of max) x RPM(% of max) to get your actual power, so 24" MAP is 80% of 30", 2430 RPM is 90% of 2700 RPM, so your actual power should be 80% x 90% = 72%. In real life, frictional losses and efficiency losses mean you end up with a few percentage points lower (those numbers give me around 68% in my POH), but lacking a POH, that would be a quick way to guess your power when ROP. It also means changing your MAP by 3" should change your power setting up or down by 10% When LOP, it's just fuel flow off your fuel flow meter. Yes, changing your MAP and RPM will change your power when LOP, but the fuel flow will change correspondingly. 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted July 7, 2018 Report Share Posted July 7, 2018 It would be great to have an air flow meter that was as simple as a FF meter... All the fuel goes through the FF meter... pretty accurate measurement... Expanding on that thought... Max MP on a standard day at SL is near 28” (some loss from 29.92”) Min MP on a standard day is about 11”(?) It would help to have a decimal place on the MP gauge... Technically the air flow IS set by the MP in combination with the set geometry that it is flowing through... Having a JPI That calculates the %hp based on real MP or FF makes a lot of sense! The JPI would need a formula to calculate the airflow based on my engine’s intake geometry and other variables.... Even JPI had difficulty with the %hp calculations for ROP when they first started doing them... interesting discussion... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
FastTex Posted July 8, 2018 Report Share Posted July 8, 2018 4 hours ago, jaylw314 said: When you're ROP, your power is determined by airflow in theory. Since 100% power comes at max MAP and RPM, you just take MAP(% of max) x RPM(% of max) to get your actual power, so 24" MAP is 80% of 30", 2430 RPM is 90% of 2700 RPM, so your actual power should be 80% x 90% = 72%. In real life, frictional losses and efficiency losses mean you end up with a few percentage points lower (those numbers give me around 68% in my POH), but lacking a POH, that would be a quick way to guess your power when ROP. It also means changing your MAP by 3" should change your power setting up or down by 10% When LOP, it's just fuel flow off your fuel flow meter. Yes, changing your MAP and RPM will change your power when LOP, but the fuel flow will change correspondingly. Since we are on this topic...the JPI830 checklist for LOP says to "Pre-lean to 50 degrees below of the estimated peak in any of the cylinders". How do you guys determine the estimated peak? Quote Link to comment Share on other sites More sharing options...
gsxrpilot Posted July 8, 2018 Report Share Posted July 8, 2018 Just pre-lean to where you would normally be cruising ROP. You just don't want to be going from full rich all the way over to LOP. Other wise it's not all that important. Quote Link to comment Share on other sites More sharing options...
jaylw314 Posted July 8, 2018 Report Share Posted July 8, 2018 59 minutes ago, FastTex said: Since we are on this topic...the JPI830 checklist for LOP says to "Pre-lean to 50 degrees below of the estimated peak in any of the cylinders". How do you guys determine the estimated peak? I think JPI wants us to spin the mixture knob to lean somewhere near peak, then spin it back a turn to about 50 deg below peak. Their LOP lean assist algorithm seems to look for a 25 deg increase before watching for peaks so it won't mistakenly think small EGT changes are peaks. There's nothing magical about 50 degrees ROP, they just suggest that to save you time. Alternatively, John Deakin and Mike Busch recommend against using LOP assist programs, since they use algorithms that force you to stay in the danger area for more than a few seconds. They suggest the "big pull" technique, basically leaning to roughness or a known LOP setting, then enriching a small amount. If your EGT's increase with enriching, you are LOP. Quote Link to comment Share on other sites More sharing options...
gsxrpilot Posted July 8, 2018 Report Share Posted July 8, 2018 14 minutes ago, jaylw314 said: Alternatively, John Deakin and Mike Busch recommend against using LOP assist programs, since they use algorithms that force you to stay in the danger area for more than a few seconds. They suggest the "big pull" technique, basically leaning to roughness or a known LOP setting, then enriching a small amount. If your EGT's increase with enriching, you are LOP. As long as you're at 65% power or below, there isn't any danger area to worry about. If you go slowly a few times to learn the fuel flow when LOP at a given MP, then you'll be able to easily use the "big pull" to get there quickly. With my turbo, I don't run LOP at anything by 65% or below Quote Link to comment Share on other sites More sharing options...
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