garytex

Help Please What is IO 360 Wide Open Minimum Fuel Flow

Recommended Posts

I think my WOT takeoff fuel flow is too lean at 15 GPH, std. conditions.  Seems like it should be around 18 GPH.  Sent the RSA injector body for adjustment, came back same, "set to spec on the bench" at Navajo in San Antonio.  I'm seeing 1200 egt at WOT 1500 at peak.  

I have looked for the WOT fuel flow, haven't found anything concrete.  Anybody in proud possession of the straight skinny?

 

Thanks Gary

Share this post


Link to post
Share on other sites

*Members that donate $10 or more do not see advertisements*

I'm seeing a little over 19 at near sea level conditions.

From a flight Sunday afternoon at takeoff.

FF=19.1

RPM=2706

FP=24.2

EGT=1200

MP=28.9

OAT=66

 

Perhaps your fuel flow is reading low at high flow?

Share this post


Link to post
Share on other sites

The totalizer is usually within 3-5% of correct, however I guess that the instantaneous flow could be lying.  I see your egt is about the same as mine. Couriouser and couriouser.

Share this post


Link to post
Share on other sites

I am also seeing a little distress on the tops of the pistons, never run at more than 65%, and wonder if the cause could be low WOT fuel flow.  CHTs stay reasonable if I keep speed up to 130 MPH.

Share this post


Link to post
Share on other sites

Your seeing egt's about 300 below peak which is consistent with being very rich.  At 15gpm and full power I don't think you would be anywhere near 300 deg less than peak.  Lycoming specs best power at a little over 16gpm.

Share this post


Link to post
Share on other sites

Just went though this, TWICE. Got a overhaul done and my fuel flow was at 15.8gph to 16 at sea level, full throttle generating a egt of 1340 instead of 1250-1270 at the normal 17.8-18.5gph. I had the same fuel flow transducer before the overhaul, so I suspected the fuel servo from the start.

The other problem I had was the engine kept killing on the runway after landing and the cause was something was hanging up in the fuel servo and fuel would actually increase to 5gph when throttle was brought back to idle after flight. It didn't do this at start up. Sent the fuel servo back to Michigan to the overhaul shop reinstalled, same issue. Removed again and they gave me a different unit and it worked correctly.

On mine it was a issue with the auto lean needle diaphram hanging up. It wouldn't do it when bench testing and even fuel flow was higher on bench, but when installed on aircraft (with vibration) and it wouldn't work.

Share this post


Link to post
Share on other sites

So what is the correct answer for an IO-360 A1A? My fuel flow at 400' MSL at take-off is consistently around 16 GPH. Bad? Good?

FP with boost off is 24.6, EGTs are below 1300 and cylinder temps on a 50 degree day are in the 360 range.

Share this post


Link to post
Share on other sites

Have you considered that the fuel flow indicator might be off?

 

On our J, at SL, we usually get about 18 GPH with the highest EGT of about 1300 or so.  Our peak is a little over 1500 at cruise (don't know what the peak would be at SL).

 

With you getting 1200 at full rich and 1500 peak, I'd say your fuel flow is OK.  I'd check the fuel flow indicator.

 

Bob

Share this post


Link to post
Share on other sites

You want 1250 EGT at sea level take off. I live at sea level and for me to get that 1250 it was 19.2 GPH +/- due to FF transducer error. If you live at a higher altitude airport and take off with a density altitude above sea level it will get you 1250 EGT with less FF. You should be adjusted to Sea level.

Edit: forgot to mention this was in my J not my S which requires 31 GPH to get 1280 EGT at sea level:)

Share this post


Link to post
Share on other sites

So what is the correct answer for an IO-360 A1A? My fuel flow at 400' MSL at take-off is consistently around 16 GPH. Bad? Good?

FP with boost off is 24.6, EGTs are below 1300 and cylinder temps on a 50 degree day are in the 360 range.

My A1A pulled 17.9 GPH @ a 600AGL field on my last flight (a sea level take off from KSSI was 17.7) fuel pressure drops from 26 to 23.5 when I went BTTW = 96% HP. EGTs were momentarily @ 1320-1338 which is only about 175 below peak. When I pulled back to 80% power EGTs dropped to 1250 all at full rich.

 

EGT absolute value is pretty installation sensitive. As I recall mine are 1/4"-1/2" further from the flange than recommended. The delta across the 4 cyls is very tight. I have a PowerFlow Exhaust.

Share this post


Link to post
Share on other sites

Diagnostic never Neverland where you have multiple places for there to be a problem and one has to figure out which indication is wrong. Is the fuel for servo set up wrong or is the fuel flow gauge lying to me? I'm showing around 1200 EGT wide-open throttle sea level which agrees with the guys who are getting the 18-19 gallon flows.The posts indicating that a 300° drop from Peak is about the right number we're also very helpful, thank you

Aaron 25k, your post was very helpful thank you.

Your post showing 15 gallons and 1350 EGT tends to make me think that my fuel flow indicator is underreporting at high flow values.The red herring is that it totalizes very well and I think is accurate in the 7 to 9 gallon an hour range where I normally fly the airplane.

I guess if I want to know the answer to this conundrum I'm going to have to lay my hands on another flow transducer someplace.

Does anybody see any errors in this logic or things that I have missed in my thinking?

Thanks Gary

Also what actually is the wide-open fuel flow supposed to be?

Share this post


Link to post
Share on other sites

Sounds like the transducer and/or wiring has something funny going on.  Your takeoff EGT ought to be in the 1250 +/- range, and fuel flow should be ~18 GPH +/- depending on temperature because that affects density and thus fuel flow commanded by the injection system.  Colder/higher density air will require more fuel and vice versa.

 

A good estimate I learned from APS is your standard, sea level takeoff fuel flow should be in the neighborhood of 9% of your rated HP.  ie 200 HP * 0.09 = 18 GPH.

Share this post


Link to post
Share on other sites

The Lycoming operators manual for the IO360 doesn't list a takeoff fuel flow, but does give a best power fuel flow of about 16.5gph for 200hp.  Full rich would have to be something higher than this.  Also which fuel flow do you have?  I've saw some pictures posted on here where the installer ignored everything the STC said about the mounting parameters of the transducer.

Share this post


Link to post
Share on other sites

And the lycoming take off fuel flow is not adjustable. My limited knowledge from trouble shooting my system does indicate that the auto lean does have some control on total fuel flow.

I'd think your thinking is correct and you have a fuel flow transducer not accurate, at least on take off.

Share this post


Link to post
Share on other sites

aaronk25

There are 3 different  adjustments for low, medium and high power ranges in the RSA according to the tech at Navajo.  He says that adjusting high and medium is a PITA.  Idle mixture is via a turnbuckle like hex rod on the side of the servo.  it has a symbol that tells which way to turn the hex for richer idle

Share this post


Link to post
Share on other sites

aaronk25

There are 3 different adjustments for low, medium and high power ranges in the RSA according to the tech at Navajo. He says that adjusting high and medium is a PITA. Idle mixture is via a turnbuckle like hex rod on the side of the servo. it has a symbol that tells which way to turn the hex for richer idle

Interesting Ross at DG supply said there was no adjustment for wide open fuel flow and its factory set, which lead me to believe it was a fixed size orfice and maybe the needle that slid back and forth wasn't retracting all the way.

Share this post


Link to post
Share on other sites

Ah,dueling mechanic opinions.

The guy at Navajo said you had to tear the servo apart and there was some small little tiddlywinker that you could adjust with some tiny little special tool. I think he was talking about the needle looking thing that's attached to a round metal plate that's on the diaphragm inside the servo. I didn't pay a whole hell of a lot of attention to exactly what the process was cause I knew I was never taking my servo body a part to play with it.

I wonder which guy is right.

It makes sense to me that the fuel flows would be adjustable.

But I could easily be wrong about that, frequently am.

Anybody got the straight skinny?

  • Like 1

Share this post


Link to post
Share on other sites

On our IO-360 A3B6 it was 18+ gph with the hottest EGT around 1225 at full rich. When leaned to the 1250 EGT method for climb it was mid-17s.

I guess turbos like the lucky number of 13% FF to generate 210 HP.

Share this post


Link to post
Share on other sites

Note: a restriction in the injectors will reduce fuel flow. However, a restriction will also increase system working pressure. So, if you use the pressure method to double check fuel flow, make absolutely sure the injectors are the correct ones, not worn out (yes, they erode) and not dirty/clogged. Also, it's not unusual to have a floating piece of debris in the injector lines. Causing intermittent problems.  

 

With that in mind, a quick way to check fuel flow is to hook up a pressure gauge on the spider. You should see about 10 PSI at full power, sea level, cool day. 

 

Don't forget to check your fuel flow with the boost pump on and off. 

 

There is no simple adjustment for fuel flow at full power. The internals consist of a metered orifice that is fully open (unrestricted) at full rich mixture, full power. 

Share this post


Link to post
Share on other sites

Aaron, I believe I may be having the same issue with my Beechcraft Sierra, Lycoming i.o. 360 We have been troubleshooting for weeks on this thing. Can you please give me a call so I can understand better your issue, if its the same as mine, and what you did to correct it? 318-787-9337    Gary V.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.