Will be breaking in six new cylinders on a C206 soon.
I have done this a number of times with fixed prop according to Lycoming’s service letter, which calls for extended periods of WOT (but at altitude, so 75-80% power I guess).
The new cylinders are Millenniums and Superior’s instructions are here:
http://www.superiorairparts.com/downloads/serviceletters/L96-08.pdf
Any advice on MP and Prop settings? Better to run at low rpm and high MP when breaking in? (Still according to one of the “approved” settings in POH.)
G
For the benefit of those amongst us who hate acronyms please explain “WOT”
thanks
Wide open throttle
GaryStorm wrote:
on a C206
Lycoming or Continental ? Assuming NA ? (Normally Asprirated vs Turbo for those that don’t like ancronyms)
At any rate both Lycoming and Conti give detailed instructions for the first N hours following a major or cylinder change.
It is a Conti but the instructions says 75% for one hour, 65 to 75% for the next hour varying every 15 mins. No details about cruise RPM/MP.
75%: Assuming 4000ft pressure altitude I can do 24"/2550 rpm, or slightly higher MP and slightly lower RPM, e.g. 25"/2450. Which is better?
It is naturally aspirated.
G
GaryStorm wrote:
No details about cruise RPM/MP.75%: Assuming 4000ft pressure altitude I can do 24"/2550 rpm, or slightly higher MP and slightly lower RPM, e.g. 25"/2450. Which is better?
Honestly, there is no significant difference between those setting to make a difference.
Do you have an engine monitor ?
Ifso, I would run it hard, even 80% power, but not over 400° CHT .
If done correctly and with an engine monitor, you will actually see the exact moment when each cylinder “seats” the rings since the CHT will drop about 2 bars (50°) on one cylinder after another usually within just a couple of minutes of each other. This usually occurs from about 5 hours to up to about 15 hours running time.
The main issue is to avoid at all costs low prolonged low poser setting before the rings seat.
Can the break-in be done on a test stand?
Rwy20 wrote:
Can the break-in be done on a test stand?
In theory, yes but in practice, very rare.
A fully instrumented engine test “stand” with cooling and exhaust extraction is rather expensive to set-up and run, hence most engine builders perform only initial , short tests.
Barrett Precision do 1hr.
The biggest issue is the huge airflow required for an engine at high power.
But also nobody wants to pay for the avgas 
The main issue is to avoid at all costs low prolonged low poser setting before the rings seat.
Sometimes spellcheck can be quite poetic.
I don’t think these engines were designed to be babied – I run my new cylinders at 80% until the first 50 hours.
