Low fuel flow, full rich, wide open throttle

Nancy, Welcome to the forum and here's you very own thread

Earlier, you replied.....

The WOT fuel flow is with the boost pump on. The boost pump does not affect the WOT fuel flow at all. Don explained to me that in order to get 18 GPH I need a corresponding volume of air. I tried opening the alternate air but that had no effect. The reason I ponder the low flow is:

1. Does this mean my engine is not developing full HP on takeoff?
2. On hot days (85F) I can see my CHTs approach 400F by the time I get to pattern altitude.

I read that the WOT fuel flow cools the engine. In cruise flight I run LOP and the CHTs will drop below 330F.

Be that as it may, my engine runs so much better after getting overhauled by AFP.

Bubblehead, I look forward to hearing how things go when you get the FI back.

Nancy

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1) maybe, 2) not uncommon, but unrelated unless not very ROP.

Don has a nice closed loop flow bench that measures both fuel and air, so if he says it's ready to do 18 gph on a IO360 (not an IO390), I'd not wonder to much about that until exhausting other possibilities.

The first thing I'd check is calibration of your flow meter. Does your fuel burn on the meter agree with the certified avgas sales meter?

If that is a positive, then confirm the mixture linkage allows going to the rich stop on the controller.
Another check on the controller is how far you are rich of peak, when the mixture knob is forward (should be 200 deg or more ROP).

So, if all those are good, then probably should talk about cam lobes, but I wouldn't go looking for that until the above is answered.

best

Hi Stan,

The Shadin Econoflow usually agrees within two gallons of total fuel consumed with a fillup of 20 gallons; accurate within about 10%. I will research my fuel logs to see if there is a consistent error. I may need to tweak the transducer K factor.

I rebuilt the engine in the Fall of 2010. The cam was replaced at that time, so I don't think the cam is worn.

I have verified that the mixture and throttle cables operate from stop to stop.

I noticed on takeoff my engine RPM is 2675, measured with an optical tachometer. I will need to research the Woodward prop governor to see if I can tweak the maximum RPM.

The next time I fly I will do a full rich to LOP test to see how the EGTs vary.

Nancy

hoyden said:

Hi Stan,

The Shadin Econoflow usually agrees within two gallons of total fuel consumed with a fillup of 20 gallons; accurate within about 10%. I will research my fuel logs to see if there is a consistent error. I may need to tweak the transducer K factor.

I rebuilt the engine in the Fall of 2010. The cam was replaced at that time, so I don't think the cam is worn.

I have verified that the mixture and throttle cables operate from stop to stop.

I noticed on takeoff my engine RPM is 2675, measured with an optical tachometer. I will need to research the Woodward prop governor to see if I can tweak the maximum RPM.

The next time I fly I will do a full rich to LOP test to see how the EGTs vary.

Nancy

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Good plan Nancy. 2 gal off on 20 is quite a bit, with K factor tweaks, I'll bet you can get that under a half gallon.

And, it will be instructive to find how many degrees ROP the engine is. If it is only 100 ROP, instead of 250 or so, that could account for the low fuel flow.

best

Nancy

When you verify that your cables go stop to stop, that is only done when the engine is not not moving on its mounts.

Please check that when you are full rich that you can wiggle the mixture cable without the mixture coming back off the stop. What can happen and has for us, is the engine thrust pulled the cable which was too short/tight and the cable mounting bracket would flex, pulling the mixture back.

The next time I fly I will do a full rich to LOP test to see how the EGTs vary.

Click to expand...

When you do a LOP test...or GAMI Lean test, you are not concerned so much with the actual EGT numbers compared to each other, this means very little, it is the fuel flow at the time the first one peaks compared to the fuel flow at the point the last one peaks. Less than 0.5 GPH is a good spread.

Cheers

DB