PT20J

Sea level IO-360 takeoff fuel flow

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I'm interested in what others are seeing for takeoff fuel flow at sea level in an M20J. I can't find a specification for this from Lycoming. The Operator's manual shows  94 pph (15.7 gph) at 100% power, best power mixture (not full rich). For the HIO-360 it shows a suggested high limit of 105 pph (17.5 gph) for 100% power. The test stand data that came with my rebuilt IO-360-A3B6 shows 92.83 pph at an airflow of 1000 pph. Max power generated an airflow of 1118.5 pph but fuel flow was not recorded at this condition. Assuming linearity and extrapolating, this would be 103.8 pph (17.3 gph) at 100% power. So, my guess is that the fuel flow should be between 17 and 17.5 gph. 

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Mine was 18.5 GPH. And at 6000 feet it was 14.5 GPH to get the same target EGT.

 

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 It varies based upon the springs and diaphragms and stuff and your particular Bendix fuel injection servo. I think the result little bit of production tolerance in there. However for full Rich mixture has to be something like 10 to 20% above best power mixture fuel flow. So I think around 17 gallons an hour is right. Just the other day I took off here near Sea level of warm day it was about 16.8 gph. 
The Bendix RSA fuel servo fuel flow is not adjustable. Idle mixture is however but that’s it

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I see 19.2 to 19.4 gph at 2700 RPM @ sea level.

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Thank you for this topic. I also have been looking into this for temp issues during the climb. So 16.9 FF at sea level and 2700 RPM. M20J.

Brian

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My IO360A1A peaked at 17.7 Thursday on takeoff from 6B6 elevation 268'.

It peaked at 17.8 Tuesday departing MRN elevation 1270'. Don't recall BARO  

And... I took off from KGCN elevation 6609' on 8/4. Fuel flow 14.5 with red knob partially closed. MAP 24". 

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I get around 17.0-17.2 gph on standard days.  We get a lot of standard days here in the PNW :)

Nowadays it's more like 16.8-17.0 gph

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Dividing horsepower by 11.48 will give the target fuel flow in gallons per hour for standard day conditions in a normally aspirated engine.

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1 hour ago, philiplane said:

Dividing horsepower by 11.48 will give the target fuel flow in gallons per hour for standard day conditions in a normally aspirated engine.

Seems to give a reasonable number in this case, but I’m curious about the derivation. 

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All of you on Savvy can run a report card on your aircraft and see how your FF compares to the entire cohort of M20J/F's that we have data on, which is over a couple hundred aircraft. You'll find the median value is just under 18 GPH, with 75% of them ranging from 17-18.5 GPH. 

If you have lower than median max FF, and you are familiar with the Target EGT method for leaning at any altitude in flight, you can make up for this it climb by targeting for a richer EGT than what you see at sea level takeoff. For example if your max FF is on the lean side, you'll be seeing max EGTs of 1350 or higher; rather than in the 1200's with a max just under or close to 1300F. So rather than lean to your higher sea level for rich EGTs in climb, keep it rich till you see your max EGTs drop to 1300F, which is going to be really close to what the 18+ GPH max FF will look like taking off from sea level. You should be there within a few thousand feet. If its really low, a RSA or fuel specialist repair station can adjust it up for you.

I don't see many PowerFlow's on J's but if you do have one, you likely really do need higher than normal FF to keep it cool.  

Edited by kortopates
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31 minutes ago, kortopates said:

All of you on Savvy can run a report card on your aircraft and see how your FF compares to the entire cohort of M20J/F's that we have data on, which is over a couple hundred aircraft. You'll find the median value is just under 18 GPH, with 75% of them ranging from 17-18.5 GPH. 

 

Paul, unfortunately, and in spite of the title, Savvy still lumps the IO360, 200 hp Es with the O360, 180 hp models. I'm not sure why the Fs are with the Js but the Es are with the Cs? Does that make sense to someone? 

My cohort:

N943RW · M20 (A/B/C/D/E/G) · IO-360 · EDM-930

Includes 62 flights between Aug 10, 2018 and Aug 10, 2019, compared with 1423 flights by a cohort of 46 M20 (A/B/C/D/E/G) aircraft.

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13 minutes ago, Bob_Belville said:

Paul, unfortunately, and in spite of the title, Savvy still lumps the IO360, 200 hp Es with the O360, 180 hp models. I'm not sure why the Fs are with the Js but the Es are with the Cs? Does that make sense to someone? 

My cohort:

N943RW · M20 (A/B/C/D/E/G) · IO-360 · EDM-930

Includes 62 flights between Aug 10, 2018 and Aug 10, 2019, compared with 1423 flights by a cohort of 46 M20 (A/B/C/D/E/G) aircraft.

I agree the E should be its own cohort. The F made sense to include with the J because of the same airframe. Although the E has the same engine as the F/J the airframe and cowling differences do alter some of the airframe related values.

I have spoken to Chris about breaking out the E's before, including adding them to the F/J cohort. I think his main concern was the relatively small number of E's - we currently have 42 of them, which is still low. I'll remind him of this situation though and see what he says.

Edited by kortopates
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1 minute ago, kortopates said:

I agree the E should be its own cohort. The F made sense to include with the J because of the same airframe. Although the E has the same engine as the F/J the airframe and cowling differences do alter some of the airframe related values.

I have spoken to Chris about breaking out the E's before, including adding them to the F/J cohort.I think is main concern was the relatively small number of E's - we currently have 42 of them, which is still low. I'll remind him of this situation though and see what he says.

Many (most?) Es, and Fs(for that matter?) have modified cowls mimicking Js to one extent or another so ISTM the fuel injected, slant valve, 200 hp ram air features outweigh the 5" longer snout. 

IMG_20190107_153600437_HDR.jpg

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3 minutes ago, Bob_Belville said:

Many (most?) Es, and Fs(for that matter?) have modified cowls mimicking Js to one extent or another so ISTM the fuel injected, slant valve, 200 hp ram air features outweigh the 5" longer snout. 

 

Good point Bob, I just added your update with your Pic to my request to Chris. 

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15 hours ago, jetdriven said:

 It varies based upon the springs and diaphragms and stuff and your particular Bendix fuel injection servo. I think the result little bit of production tolerance in there. However for full Rich mixture has to be something like 10 to 20% above best power mixture fuel flow. So I think around 17 gallons an hour is right. Just the other day I took off here near Sea level of warm day it was about 16.8 gph. 
The Bendix RSA fuel servo fuel flow is not adjustable. Idle mixture is however but that’s it

While it is not field adjustable. I am pretty sure it is indeed adjustable by the overhauler. This means the posiblity of fuel flows other than optimal.

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When the overhauler gets it, they tear it down and overhaul it. Then you get the FF it delivers then.  When they get it in for a fuel flow adjustment, they tear it down and overhaul it. :(
it’s almost like these repair stations never saw an accessory that didn’t need an overhaul. 

Edited by jetdriven

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1 hour ago, jetdriven said:

When the overhauled gets it, they tear it down and overhaul it. Then you get the FF it delivers then.  When they get it in for a fuel flow adjustment, they tear it down and overhaul it. :(

When I sent mine in for overhaul (local fuel system specialist), I noted that I wanted it set as rich as spec would allow. I received no information on the ticket about where it was set but since the install all of my take off EGTs are in the mid 1100s. They used to be closer to 1300. I have no cooling issues with my 25° engine, even on the hottest days.

Edited by Shadrach
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I’m at 17.5-17.8 depending on alt temp and baro.  EGTs on takeoff are in the mid 1200s and I lean during climb to achieve this target (ends up being about 200-250 ROP) prior to the big pull. 

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