New cylinder - 75% power. Lean for fuel flow or CHT

k9medic

k9medic

Line Up and Wait
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ATP-H, CMEL, CSEL, CFI/CFII Airplanes and Helicopters
We put a new cylinder on our Cherokee 6 at the last annual and are in the process of breaking it in.

Lycoming says to run it at 75% power during break in with the best altitude for that being below 5k DA.

Normally I operate the plane at 65% cruising between 7-9000k with a fuel flow of 12.5 gallons. CHT and EGT are well within limits.

Any thoughts on how I should do 75%? I have a JPI, CHT and EGT.

Lean to 14.0 fuel flow (75% fuel flow) per the POH?
Lean to max CHT and accept the fuel flow?
Lean until I lose airspeed and then enrich slightly?


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The POH has MP and RPM configurations and also has a corresponding fuel flow of 14 gph at 75%.

If was written in 1967 though.

With the technology that we have today, and all of the discussions of LOP and ROP, I figured somebody might have a better way to run the break-in.


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The break-in procedure hasn’t changed, so do what the manufacturer recommends.
 
I just put a Lycoming factory re-built IO-540. Follow the procedure that the cylinder manufacture gives you for both initial ground run and subsequent break in flight to the letter and you will not go wrong. That means use your POH for the 75% power setting at 5,000' altitude. Trust the POH. My results have been excellent by following the Lycoming written procedure along with my POH.

Good combination. LOP runs will come much later after break in.
 
Stephen Shore said:
I just put a Lycoming factory re-built IO-540. Follow the procedure that the cylinder manufacture gives you for both initial ground run and subsequent break in flight to the letter and you will not go wrong. That means use your POH for the 75% power setting at 5,000' altitude. Trust the POH. My results have been excellent by following the Lycoming written procedure along with my POH.

Good combination. LOP runs will come much later after break in.
Click to expand...

This is what I was looking for.

I’ve followed the break in procedure for the Lycoming service bulletin for the first three hours.

I’m headed on a trip that is going to have two 3 hour legs and didn’t know where to operate it for ensured longevity.


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Run it hard and and rich....with mineral oil...watch for a drop in CHT and then oil change and back to normal...has worked for me.
 
Since this is a cylinder replacement and the original camshaft and lifters are being retained I would NOT run mineral oil. Phillips 20-50 x/c, instead.

Mineral oil combined with high blow by of the new cylinder is very abrasive on the camshaft and lifters. We know these parts are marginal at best, under normal conditions.

Drain the oil after 1.5 hours and again at 5 hours and then at 25. You can keep the same filter on for the first 2drains. What were trying to do here is keep abrasives to a min. I’m not worried about your new cylinder, but I am the camshaft and lifters!


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k9medic said:
I wondered how the mineral oil would work with the other broken in cylinders.
Click to expand...
not a problem,,,Let's not forget that was all we had for years.
 
k9medic said:
I wondered how the mineral oil would work with the other broken in cylinders.
Click to expand...

Mineral oil accelerates wear, with abrasives (blow by combustion products)

I speak from recent experience, along with Ed Collins inventor of cam guard and has intrests in asl remaufacturing parts such as camshafts. He said it’s common to see a spallled camshaft a few hindered hours after a unscheduled cylinder replacement. We’re not sure what the cause is, but high on the list is the accelerated wear on cam and lifters due to mineral oil.

I had a gear up, and found a cam that was spalled. So we replaced the cam with a new lycoming part and bought re-man lifters. We ran mineral oil. 400 hours later and 2 years I had a oil control ring issues and when we pulled the cylinder the new camshaft and lifters was spalled.

Cause? Hot blow by from the culprit cylinder, baking the oil of the cam? (Lycoming) was it the mineral oil at break in? Who knows, all we do know is the pressure exerted between the cam and lifter is to high for a part that only gets splash/mist lubricated.

In my opinion anything we can do to not put additional stress on these parts is a good thing.


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The manufacturing practices have done a lot to alter the break-in process.
we no longer have to wait until the catches on the cylinder fill with carbon to stop oil usage.
the new manufactured cylinders are 99% of the break-in procedure are already done.

the new cylinders will stop using oil and be broken in before you get to pattern altitude.
the last few cylinders were new error cylinders and never use 1/2 qt. of oil in 25 hours.

99% of the reading here is hype of the oil industry.
Unless you have some EP oil, the normal AD is as it needs to be.
 
Lean for best power is what the manufacturer recommends. Simple. And to the oil thing? “Mineral” oil is a reference to non-additized oil. That includes anti corrosives, ashless dispersents, and semi-synthetic blends. There is nothing to fear in your mid time engine by using straight mineral oil for an oil change cycle or two. Some guys use Phillips X/C for break in as it is mineral oil with ashless dispersent. That topic has been discussed many times.
 
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