Fuel Flow at Full Power

[Guitarmaster]

On 7/29/2018 at 11:32 PM, MikeOH said:

Well, I make full rpm at take-off.

FF is likely pretty close as I have the K-factor dialed in to 1% error or less based on full top-off fuel fills.

The idea that something is blocking flow is worth checking! Thanks.

Do you have a digital tach, or are you relying on the mechanical one?  The reason I ask, when I installed the EDM-900, I found I was only making 2550 RPM on takeoff even though the mechanical was indicating 2700.  
If not using a digital instrument, try using an optical tach to make sure you are achieving max RPM.
As others have mentioned, how is your k-factor?  Mine was a bit off from factory and had to be fine tuned considerably.
I see about 18.3 GPH on takeoff in my 75"F"

Edited August 5, 2018 by Guitarmaster

[carusoam]

Important point, Matt!

There is an easy way to check the accuracy of the tach... using a smartphone app and the sound of the engine/prop....

Find an app for your phone.  Low cost, quick solution...

If the engine is only turning 2500 rpm when showing 2700 on the tach... the FF and power will be nearly 10% reduced from full power and full FF @2700 rpm...

Effects of rpm on T/O run... my plane using 2500 rpm uses 1200’, Using 2700 rpm uses 800’... a 400’ difference

If you are expecting an 800’ roll and you get a 1200’ roll... There is probably 10% power missing...

Notes... my plane is a 310hp O... 280hp @2500 rpm... 310hp @2700rpm... the T/O run data is from the POH, and STC, and measured using CloudAhoy with a SkyRadar WAAS source...

PP thoughts only...

Best regards,

-a-

[Skates97]

15 minutes ago, Guitarmaster said:

Do you have a digital tach, or are you relying on the mechanical one?  The reason I ask, when I installed the EDM-900, I found I was only making 2550 RPM on takeoff even though the mechanical was indicating 2700.  
If not using a digital instrument, try using an optical tach to make sure you are achieving max RPM.
As others have mentioned, how is your k-factor?  Mine was a bit off from factory and had to be fine tuned considerably.
I see about 18.3 GPH on takeoff in my 75"F"

I saw the same thing when I had the EDM-830 put in, my original mechanical tach reads about 125-150 higher than the EDM at full power. At lower RPM's it reads closer to the EDM but is still off some on the high side. 

[MikeOH]

6 hours ago, Guitarmaster said:

Do you have a digital tach, or are you relying on the mechanical one?  The reason I ask, when I installed the EDM-900, I found I was only making 2550 RPM on takeoff even though the mechanical was indicating 2700.  
If not using a digital instrument, try using an optical tach to make sure you are achieving max RPM.
As others have mentioned, how is your k-factor?  Mine was a bit off from factory and had to be fine tuned considerably.
I see about 18.3 GPH on takeoff in my 75"F"

Horizon digital tach and G3 insight... both agree with each other within a few rpm.

Yes, I have checked my K-factor; it is within 1%.

Thanks for the input as those items are definitely worth checking!

[Guest]

7 hours ago, Guitarmaster said:

Do you have a digital tach, or are you relying on the mechanical one?  The reason I ask, when I installed the EDM-900, I found I was only making 2550 RPM on takeoff even though the mechanical was indicating 2700.  
If not using a digital instrument, try using an optical tach to make sure you are achieving max RPM.
As others have mentioned, how is your k-factor?  Mine was a bit off from factory and had to be fine tuned considerably.
I see about 18.3 GPH on takeoff in my 75"F"

Depending on your propeller model, that much tachometer inaccuracy could put your engine a prop in a bad RPM range.

Clarence

[MyNameIsNobody]

On 7/30/2018 at 10:11 AM, teejayevans said:

Do you need the extra cooling? My J stays below 375° with similar numbers, closer to 17 gph.

I flow 18+GPH in 200HP IO-360 and I NEVER see over 360 on cylinders in 120mph cruise climb EVER regardless of outside temps.  Fuel flow definitely cools cylinders.

[Prior owner]

FWIW, while inspecting my metal fuel lines, I discovered that the right tank line was pinched in two places- one right after it passes in front of the Johnson bar.. It is going to be replaced, and appears to have been damaged during installation at the factory...it is the original, very aged line, and was kinked right where it should have been smoothly bent at a corner. Might be worth checking the next time you have the panel off. It is very difficult to see the line behind the linkages .  I think the lines were formed by hand during installation, based upon my observations- they are a very tight fit in there.

Edited August 7, 2018 by PilotCoyote

[0TreeLemur]

3 hours ago, PilotCoyote said:

FWIW, while inspecting my metal fuel lines, I discovered that the right tank line was pinched in two places- one right after it passes in front of the Johnson bar.. It is going to be replaced, and appears to have been damaged during installation at the factory...it is the original, very aged line, and was kinked right where it should have been smoothly bent at a corner. Might be worth checking the next time you have the panel off. It very difficult to see.  I think the lines were formed by hand during installation, based upon my observations- they are a very tight fit in there.

Hi @PilotCoyote.  Thanks for posting this.  We'd all benefit from a picture if you can post one.   I've never had that part of my a/c torn apart.  Thanks!

[Prior owner]

I’ll get a pic the next time I’m at the hangar.