Primarily for general aviation discussion, but other aviation topics are also welcome.
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By marioair
#1712150
I'm trying to equate what I am seeing in the aircraft POH (PA32), engine POH io540 3 blade, the wisdom of various blogs e.g. Pelican Perch etc and what I've seen in a couple of test flights!



The question is relating to a cruise climb to 10,000ft plus. From the various sources above I have ascertained:



  • The POHs suggests mixture full rich until 5000 feet at max power (no limitation on max continuous power due 3 blade prop).
  • The POH states 65% cruise power at 10,000 feet should give me 53 litres/hour fuel flow

    So far so good. But then:

  • The aircraft POH then goes on to state that leaning can take place below 65% or above 5000. However this is in the cruise section. Nothing is mentioned in the climb section
  • The engine POH states that leaning can be performed by the method of peak EGT or by fuel flow or the "run it till rough and then enrich" method. However, per aircraft POH, it doesnt approve of in climb leaning;

    On engines with manual mixture control, maintain mixture control in “Full Rich” position for rated takeoff, climb and maximum cruise powers (above approximately 75%)


  • The John Deakin/Pelican Perch method, basically agrees with the "peak EGT" in the engine POH with a couple of deviations. (a) It encourages doing so in the climb. (b) No mention of 5000 feet limitation. (c) It suggests noting the EGT(and eventually CHT) at about 1000 feet and using that. (d) It also mentions, how above a certain altitude, enriching rather than leaning will maintain target EGT/CHT.

So my basic understanding of physics suggest that leaning in the climb HAS to happen to achieve best power and the POH's are covering their as* to avoid cooking the engine.

I did try the approach on a test flight.

  1. I noted 1500deg EGT, kept leaning to 10000ft, full throttle, 2400 RPM.
  2. Once I leveled out i noticed i only had 1300deg EGT. I assumed this was due to increased cooling due to airpseed however I noticed that i only had about 40 litres/hour
  3. so i think I'd hit the peak EGT sooner than anticipated as the POH said I should have about 53 litres/hour for 65% (23 squared)

Interested in your thoughts/wisdom in (a) should I ignore the POH and (b) what did i do wrong in the test flight.
User avatar
By Flyin'Dutch'
#1712157
If your engine has a 6 channel engine monitor and accurate fuel flow method use John Deakin's method.

If your engine is equipped with the monitoring equipment as per the factory go by the POH.
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User avatar
By marioair
#1712167
I have the EDM700 6 channel. I’m confused why continuing to lean gives me 1300deg EGT and 40l/min when POH states I should be 53l/min.
User avatar
By Awful Charlie
#1712169
My preferred for normally aspirated if the "Target EGT" climb which works well for the first few thousand feet, but for protracted climbs you will eventually reach the point where the engine doesn't have the air to burn enough fuel, so the EGT can only drop
User avatar
By Paul_Sengupta
#1712178
marioair wrote:I have the EDM700 6 channel. I’m confused why continuing to lean gives me 1300deg EGT and 40l/min when POH states I should be 53l/min.


You're probably running lean of peak EGT.

The EGT won't change much with airspeed, it's all about the gases burning in the engine. CHT will go down as speed goes up, but as altitude increases cooling is less, so watch out for that.

I agree that the POH seems like a bit CYA, it only says to lean where you can't hurt the engine whatever you do. Careful leaning, as you have been, will save fuel and pollute less, but you have to watch your EGTs and particularly it's your CHTs you need to keep an eye on, while using the EGT to set the mixture.
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By marioair
#1712187
Yeah sounds like at some point in the climb I’m inadvertently going from ROP to LOP and then continuing leaning whereas I should actually be enriching. Will have a look at he logs from the EDM and keep an eye out next flight
By johnm
#1712190
marioair wrote:Yeah sounds like at some point in the climb I’m inadvertently going from ROP to LOP and then continuing leaning whereas I should actually be enriching. Will have a look at he logs from the EDM and keep an eye out next flight


If the CHT. are OK and performance good and engine running smoothly why would lean be other than good?
User avatar
By Flyin'Dutch'
#1712194
GAMI injectors are no different from the normal injectors - their 'product' is that they balance the fuel flow between the cylinders and by doing that they will all run at similar temperatures and that makes leaning a more precise exercise. They just mix stock injectors to get to the desired result.

If your spread is good then there is nothing stopping you from leaning to LOP and save a lot of fuel for a very small speed penalty.
User avatar
By flybymike
#1712195
They just mix stock injectors to get to the desired result.

Gami claim that each individual injector is an individually calibrated and hand crafted work of art, not standard stock.
Each GAMIjector® fuel injector is carefully calibrated to much tighter tolerances than standard fuel injectors available for your engine. Our award winning GAMIjector® fuel injectors alter the fuel/air ratio in each cylinder so that each cylinder operates with a much more nearly uniform fuel/air ratio than occurs with any standard factory set of injectors. You will see the difference on your engine monitor with the very first flight!

https://gami.com/gamijectors/gamijectors.php
User avatar
By Awful Charlie
#1712268
The GAMI injectors are not the same at the Lycoming ones (the construction is markedly different, the latter would seem to have an easier method for adjustment!), and they get tailored to each individual engine so that all cylinders peak at the same time. Each injector is marked from A to at least J, where an A would be small/lean and J would be large/rich. I did a factory exchange engine last year - the injectors on the previous engine were G-G-C-D-E-E and well balanced, the new engine is currently E-G-C-E-D-G and close, but we still have a little fine tuning to do (#5 probably to a C I guess)

It often takes more than one attempt to get the injectors spot on (you send GAMI your engine data, and they propose/send you the injectors to install), but depending on your starting point, the difference can be well worth having.
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By Trent772
#1712323
Airborne

Reduce to 24/24 for an econ climb, speed around 100 - 110kts

After power reduction - mixture back to top of green.

Climb to cruise, cruise at whatever you want but 23/23 or 24/24 works. Lean to peak and decide whether you want to run rich or lean of peak - makes little difference at those settings.

We operated a Cherokee 6 with O-540 and a PA-32 Lance with an IO-540 for 2,000 hours parachute flying - ran slightly harder than that in the climb but leaned after take off. Both engines went onto condition. Cherokee 6 had 3200 hours on when I stopped !