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high EGT on cyl 1 when leaning

glider_rider

Active Member
RV14, IO-390 EXP119 with one mag and one p-mag clocked @20deg, the jumper is in. BA Hartzell prop
In level flight at 6000 feet it would easily exceed 190 knots TAS ...
What puzzles me is that I'm not able to lean beyond 9,5 gal/h when flying 24/2300 at 8000 D alt. Any leaner and the engine would run rough

I'm attaching log from my yesterdays flight. In cruise, 23/2300 at 6000 ft, slightly LOP, CHTs are in the range 311 - 339 deg, EGTs 1360-1374.
As soon as I begun to descent, EGT on cyl 1 went up over 100 deg with respect to other cylinders.
Why would that happen? I've noticed that, when leaning, EGT on cyl 1 is always the highest
 

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Could be a partially blocked injector or 'spider' port.
Do a flow test. [4 small bottles for the lines to squirt into]
Should be information around somewhere ex Airflow Performance website on how to do the test.
 
What puzzles me is that I'm not able to lean beyond 9,5 gal/h when flying 24/2300 at 8000 D alt. Any leaner and the engine would run rough

How far LOP are your cylinders at this point?
Have you tuned your nozzles and if not, do you know what is your spread?

I have also had issues going LOP at higher altitude but that was around 12-13K MSL. I changed all my nozzles to a .27 size and one being .265 and that has given me a bit more leaning capability at higher altitude but still a bit limited at 15K or above. I am considering going one or two size smaller.
 
Could also be an intake gasket leak.. is there a change in EGT spread when going from full throttle to a reduced setting? I’m leaning towards the clogged injector though.
 
How far LOP are your cylinders at this point?

Have you tuned your nozzles and if not, do you know what is your spread?

I have also had issues going LOP at higher altitude but that was around 12-13K MSL. I changed all my nozzles to a .27 size and one being .265 and that has given me a bit more leaning capability at higher altitude but still a bit limited at 15K or above. I am considering going one or two size smaller.

I can lean it to ca. 30 deg, and I'm pretty sure the injector nozzles are clean, checked them twice already

Didn't tune my nozzles, difference between highest and lowest CHT is 28 deg. 14 deg difference for EGTs. That's when leaned ca. 20 deg LOP
 
Could also be an intake gasket leak.. is there a change in EGT spread when going from full throttle to a reduced setting? I’m leaning towards the clogged injector though.

full throttle, EGT on cyl 1 closely matches other EGTs. Skyrockets when going lean

Interesting idea about intake gasket leak. Thank you!
 
Didn't tune my nozzles, difference between highest and lowest CHT is 28 deg. 14 deg difference for EGTs. That's when leaned ca. 20 deg LOP

This is not what balanced injector nozzles mean.

Do a data run. Record total fuel flow when each cylinder reaches peak EGT. The first to peak fuel flow minus the last to peak fuel flow is your GAMI spread. You want this as close to 0.0 gph as possible, but 0.2 or so is fine.

Send your data to Don at Air Flow Performance and he will recommend replacement nozzles (if one or more is needed). They are cheap.

Actual EGT values are not important as there are other variables to the EGT reading, like the position of the probe. Actual EGT reading is good however for huge differences - like a dead cylinder.

Carl
 
What Carl said about tuning injectors.

I don't think there is a debri in the injector nozzle or spider as you would have seen this much more on the ground. Also, the same for leaking intake.

Once you find your spread per Carl's method, I would consider going to a smaller set of nozzles. This really helped with my last plane which had a FM150 but did help me with the FM200 on the new plane but not nearly as much. The size of a nozzle is largely determined based on fuel pressure that you have and GPH at sea level.
 
To be clear - balanced injectors has nothing to do with CHT.
It is EGT... BUT you aren't looking for equal EGT temps... rather that ALL cylinders hit their peak at the same point in leaning. So 1 might peak and 1450 another at 1420, etc. but what is important is that the peaks coincide.

What you clearly have is #1 peaks early (for some reason). You can put a larger nozzle into #1 injector to start to correct that.

What another said about a spider blockage being a bigger factor at idle is true, so I'll drop that theory.

Still a flow test of the lines (all at same time to check equal fuel flow) would be good to confirm no blockage in the line running to #1 that is restricting on high flow conditions.
 
Airflow Performance

I have an older RV6A with a Bendix fuel servo. We replaced the hold Lyc nozzles with Don's tunable ones.

If I had known how inexpensive and easy of an upgrade it would be to work with Don at AFP to tune our injectors I would have done it a LONG time ago.
 
You said the difference spread is close at full throttle, yet skyrockets when reduced throttle.. I’m betting on the intake gasket leaking.. either an intake bolt fell out or the gasket shifted.
 
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