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IO-360-M1B Fuel Flow question? Need help Please

RV7ForMe

Well Known Member
Hello engine people... I need your help.

So we are getting ready to fly this thing (RV7-A, IO-360-M1B, CS all STOCK from VANS) GARMIN G3X Touch with Red Cube FF and everything else that comes with the Garmin Engine Monitor Kit for the lyc.

We did some engine ground runs and have a few problems that may be related.

So far we did a static run up to 2570 RPM / 23,8 MAP just to see if the governor and all that worked. Engine sounds and runs smooth.
However
CHT were very hot. Spread is very close except for #1 running about 35F hotter)
EGT at about 1400-1440 across all 4.
Fuel flow was at about 11 G/H (indicated). According to the Lyc Manual the engine needs about 14G/H at this RPM

I may need an explanation on how a fuel servo works in the injector engine or where I can read about it.

How can I test the fuel flow and adjust it without running the engine? I do not want to run the engine under these bad cooling conditions for any more time than it needs to. This engine needs to fly!

Adding the boost pump did nothing for the fuel flow.

Also I am not sure if the reading from the Red Cube are accurate (located at the right before the spider on the engine). Since the fuel servo wont let a lot of fuel through without the engine running and sucking air.

Please help us: What is the procedure for setting this up correctly with the Horizontal Induction fuel servo IO360 from VANS? The thing is I do not know if I can trust any of the readings because it is all new.

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You would definitely need more fuel than that for full power - but if you were at 2600 rpm with partial throttle that might be about right. How much manifold pressure were you showing at 2600 rpm?

My same engine will show about 16.5 gph at takeoff power (2700 MSL at home) with a constant speed prop.
 
2570 RPM / 23,8 MAP I added it to the above text....
I think 11G is just about right for 23" of manifold and 2600 RPM for that engine. Your EGT shows that you are a bit on the lean side.

You can always test your fuel flow rate thru your plumbing and pump by disconnecting the fuel line from the servo and run your pump for X number of minutes and see how many gallon you get. A simple calculation will show how many G/H your pump will push fuel and will remove any doubts of inaccuracy of reports by your engine instruments.
 
Your EGT shows that you are a bit on the lean side.

Not necessarily. The absolute values alone tell nothing. Full rich EGT value compared to peak EGT value tells the tale.

You can always test your fuel flow rate thru your plumbing and pump by disconnecting the fuel line from the servo and run your pump for X number of minutes and see how many gallon you get. A simple calculation will show how many G/H your pump will push fuel and will remove any doubts of inaccuracy of reports by your engine instruments.

Good idea...a check for the accuracy of the red cube.
 
Thanks but ?

I think 11G is just about right for 23" of manifold and 2600 RPM for that engine. Your EGT shows that you are a bit on the lean side.

You can always test your fuel flow rate thru your plumbing and pump by disconnecting the fuel line from the servo and run your pump for X number of minutes and see how many gallon you get. A simple calculation will show how many G/H your pump will push fuel and will remove any doubts of inaccuracy of reports by your engine instruments.

Glad you brought this up because it is what is confusing to me in terms of how the fuel servo works.

We did multiple test even in simulated take off attitude during final assembly about a month ago. (BTW we have the AFP pump Vans sells)

1. Test:
"free flow" plumbing disconnected right before the fuel servo:
We actually let the pump empty a full tank and timed it in 2 minutes intervals.
We got an average of 46.5 G/H. No Air found!

2. Test:
plumbing disconnected right before spider (after fuel servo) with engine off obviously.
We got an average of 3.6 G/H

This led me to believe I do not fully understand the works of the fuel servo. I understand it mixes air and fuel. Thus it only takes what it needs. When the engine is off even with the pump trying to pump 46 G/H it only lets 3.6 G/H pass?

Is the ram air pressure needed for the fuel servo to work properly? In other words will it set the fuel flow to right number when on the ground and not flying?

Forgive my ignorance but I have tried to google this and I can't find the answer.
 
Good call

Good idea...a check for the accuracy of the red cube.

OK this test is one I have not done. I could disconnect the line at the spider and let the pump do its job with the red cube still connected. If the G3X matches the 3.x G/H I can measure with a bucket and see if its the same?

Are these red cubes accurate over the entire spread? I want it to be accurate at about 14 gal but I cant test that with the engine off? correct? In other words are we sure if it is accurate between 3-4 G/H it will be at 14-16?
 
fuel flow

I have the same engine & prop all from Van's and just started Phase 1. I've got about 10 hours on it. I'm also using Red Cube. Here is what I'm seeing.

1. I did two engine idle tests but didn't allow CHTs to get over 250F per advice from Lycoming. Only full power test was run up before first flight.
2. Did several fuel flow tests by running boost pump. But this doesn't really test the spider or injection nozzles. Did find slight plug in a vent line.
2a. Dedicated first flight to break-in for engine. Cruised around at 24.5x24.5 for about an hour, with some fluctuations. I'm hoping this was at least 75%.
3. I do see 16GPH climbing at 29.6MP and 2710 RPM which is full power climb at 1500 msl and 117kts.
3a. I'm seeing 12 GPH cruising around at 25x25,
3b. I see about 10GPH or less when below 23x23 cruising around.
4. Had one CHT that was hot. Turned out to be #3 and it needed a dent on the forward side of the aft baffle where the fins go flush. 1/8" dent lets some air flow around aft side of cylinder.
5. Had one high EGT turned out to be partial plugged nozzle. Plug was just a small hair, that was barely visible. Quick cleaning fixed it.

I hope that helps. I'm still concerned I'm not getting full rich. And a little concerned about CHTs which do get up to 400. More flying and testing to do.
 
Glad you brought this up because it is what is confusing to me in terms of how the fuel servo works.

We did multiple test even in simulated take off attitude during final assembly about a month ago. (BTW we have the AFP pump Vans sells)

1. Test:
"free flow" plumbing disconnected right before the fuel servo:
We actually let the pump empty a full tank and timed it in 2 minutes intervals.
We got an average of 46.5 G/H. No Air found!

2. Test:
plumbing disconnected right before spider (after fuel servo) with engine off obviously.
We got an average of 3.6 G/H

This led me to believe I do not fully understand the works of the fuel servo. I understand it mixes air and fuel. Thus it only takes what it needs. When the engine is off even with the pump trying to pump 46 G/H it only lets 3.6 G/H pass?

Is the ram air pressure needed for the fuel servo to work properly? In other words will it set the fuel flow to right number when on the ground and not flying?

Forgive my ignorance but I have tried to google this and I can't find the answer.

The fuel servo does not mix air and fuel - it meters the correct amount of fuel for the amount of air passing through the servo, and sends that metered fuel to the flow divider. The mixture knob can tweak the metered flow rich or lean of the target, and can be used to provide a positive cut-off of fuel to kill the engine. If the mixture is NOT in ICO position, and the engine is stopped (no air flow through the servo) there is a minimum amount of fuel that continues to pass through for priming and start. That amount is usually in the ~3gph range, yes.

In my airplane for instance, to start I have throttle and mixture full in, turn on my fuel pump, wait for 1 second (warm weather) or 2 seconds (cold weather) then pull the throttle closed and hit the starter. That one or two second period allows fuel to trickle through the injectors and prime the engine for start prior to cranking, and allows enough fuel to allow the engine to start and come up to RPM, where the air flow through the servo then becomes the controller to how much fuel is passed.
 
Thanks guys

I have the same engine & prop all from Van's and just started Phase 1. I've got about 10 hours on it. I'm also using Red Cube. Here is what I'm seeing.

Thank you for your numbers Steve. How did you adjust and check the engine gets 16G/H at full power before first flight?

The fuel servo does not mix air and fuel - it meters the correct amount of fuel for the amount of air passing through the servo...

Thanks Greg for explaining that to me.

---

Ok so I will check the red cube as suggested above.

But what is the "proper" process in adjusting and testing the engine gets what it needs before first flight?
 
My red cube was under reading quite significantly when using the default calibration values, so much so that the fuel flow was registering as below the lower limit for the engine on takeoff (red cube between the servo and spider). It wasn't until a couple of flights that I was able to re-calibrate the red cube in the G3X, and sure enough the fuel flow is now smack bang in the middle of published range.
I wouldn't spend too much time beating it up on the ground glazing cylinders and risking stone chips. Just get it ready, ensure your baffles are as good as they possibly can be (go to town on the Permatex Ultra in any gap you can find between the AL baffles and the engine), go fly and keep that nose down on climbout (130kts) to ensure good cooling during the break in. I did my first oil change at 5hrs, a second at 25hrs then switched from break-in oil to W100+ at 50hrs and saw a 25degF drop in CHT (although unfortunately no speed gain). I did the first few hard running break-in flights using 100LL Avgas, then switched to BP 98RON mogas since.
Good luck.
Tom.
RV-7
IO-360M1B with dual PMAG
 
Thank you for your numbers Steve. How did you adjust and check the engine gets 16G/H at full power before first flight?

RV74ME
I didn't check for 16GPH before first flight other than running the AUX Pump and measuring fuel at the hose going into the "Integrator / servo" which showed 40 gph. I figured with this kinda of test the only thing left that could have starved the engine of fuel was plugged nozzles. So the only thing I did was run full throttle for about 20 seconds on the runway prior to take off. It held full power fine. The brakes could hardly hold it. So I took off because of the need to break-in the engine before glazing the cylinder walls. I took a photo of the panel during climb out and that's how I know what the numbers are. Here is link to that photo.

20190412_111933.jpg



But I know how you are "thinking" or "feeling" about this first flight and fuel flow. My runway ends at the Pacific Ocean so was my RV going to get me to 500 feet and out over the ocean and then stop running? It was possible. PS, the ocean is 40F in Puget Sound. I did wear a life preserver. I did have ground crew. I did not have Coast Guard, but probably should have.

I did communicate with Lycoming and they reminded me that the NEW engine had been run and tested at their factory and that it is ready to run for 10 hours before any oil change. They reminded me this is not like a field rebuilt engine that needs more testing. They assured me that if I got fuel to the Integrator or servo the rest of the engine would run. So . . . I'm glad that first flight is complete.
 
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I could disconnect the line at the spider and let the pump do its job with the red cube still connected. If the G3X matches the 3.x G/H I can measure with a bucket and see if its the same?

That would check the accuracy of the red cube.

Are these red cubes accurate over the entire spread? I want it to be accurate at about 14 gal but I cant test that with the engine off? correct? In other words are we sure if it is accurate between 3-4 G/H it will be at 14-16?

Correct.

This led me to believe I do not fully understand the works of the fuel servo. I understand it mixes air and fuel.

No fuel-air mixing in the servo. The servo meters fuel to the flow divider (the spider), which delivers it to a nozzle at each intake port.

When the engine is off even with the pump trying to pump 46 G/H it only lets 3.6 G/H pass?

Correct

Is the ram air pressure needed for the fuel servo to work properly?

Ram and pressure drop from a venturi. Some info here:

https://www.danhorton.net/Articles/Bendix-and-Beyond (1).pdf

But what is the "proper" process in adjusting and testing the engine gets what it needs before first flight?

You've already checked fuel delivery to the servo. Check for full travel of the throttle and mixture arms. Adjustments are generally limited to idle mixture and idle RPM. Full rich mixture is set on a test lab bench, not in the field.
 
Something I picked up was that my mixture knob was dead against the panel on full rich. Which meant that every time I took off at full throttle the carb would "auto-lean" due to the engine pulling slightly forward on the mountings, thereby pulling against the mixture cable. So, make 100% sure your red knob is set at about 1/8th of an inch away from the panel on full rich. That brought my temps down by about 25 degrees. ;)
 
Thanks

go fly and keep that nose down on climbout (130kts) to ensure good cooling during the break in. I did my first oil change at 5hrs, a second at 25hrs then switched from break-in oil to W100+ at 50hrs and saw a 25degF drop in CHT

Alright Thanks for the Info Tom!

I didn't check for 16GPH before first flight other than running the AUX Pump and measuring fuel at the hose going into the "Integrator / servo" which showed 40 gph. I figured with this kinda of test the only thing left that could have starved the engine of fuel was plugged nozzles.

Ok. understood.

But I know how you are "thinking" or "feeling" about this first flight and fuel flow.

I did communicate with Lycoming and they reminded me that the NEW engine had been run and tested at their factory and that it is ready to run for 10 hours before any oil change. They reminded me this is not like a field rebuilt engine that needs more testing. They assured me that if I got fuel to the Integrator or servo the rest of the engine would run. So . . . I'm glad that first flight is complete.

Ok this does make me feel a little better. I just didn't want it to run lean on first flight

That would check the accuracy of the red cube.

OK this I will do next.

No fuel-air mixing in the servo. The servo meters fuel to the flow divider (the spider), which delivers it to a nozzle at each intake port.

Thanks.

Ram and pressure drop from a venturi. Some info here:

https://www.danhorton.net/Articles/Bendix-and-Beyond (1).pdf
OK This is great!!!

You've already checked fuel delivery to the servo. Check for full travel of the throttle and mixture arms. Adjustments are generally limited to idle mixture and idle RPM. Full rich mixture is set on a test lab bench, not in the field.

To the best of my abilities I have done this correctly. If I can actually not adjust the full mixture I am guessing this is the reason I did not find much info on how to do it! Thanks for making it clear Dan.
 
WOW!

Something I picked up was that my mixture knob was dead against the panel on full rich. Which meant that every time I took off at full throttle the carb would "auto-lean" due to the engine pulling slightly forward on the mountings, thereby pulling against the mixture cable. So, make 100% sure your red knob is set at about 1/8th of an inch away from the panel on full rich. That brought my temps down by about 25 degrees. ;)

I never thought about this! thank you.
 
Why are you only getting 23.8 inches at full throttle. Are you getting full travel on the throttle linkage? Are you at a high elevation?
 
Why are you only getting 23.8 inches at full throttle. Are you getting full travel on the throttle linkage? Are you at a high elevation?

This is not full throttle it was at 2570 RPM. Full throttle should be around 2700 RPM and no we are at 400feet :) it was about all the brakes will hold
 
If any thing, in addition to these recommendation, I recommend to check the timing of you ignition. That is something that is well worth checking and could have an effect on the CHT temp.
 
If any thing, in addition to these recommendation, I recommend to check the timing of you ignition. That is something that is well worth checking and could have an effect on the CHT temp.

I believe that one is correct but I will put it on the list and recheck again. Thank you
 
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