cooling
I've been breaking in my new engine (IO-360 M1) and have run the engine for 13 hours so far with the mixture full rich to keep the temps cool during break-in.
At what point during the first 50 hours or so of break-in can I begin to lean the mixture so that I'm not burning 12-13 gph all the time?
Hey Don:
The verbiage below assumes your baffling is correct and functional.
Keep in mind: you can cool with fuel, or you can cool with air. Personally, I use the cheaper stuff. Go ahead and pull the red knob back, keep your CHTs under 400F, and you and your engine will be happy. If the CHTs start to creep over 400F, pull that red knob back a bit further.
Eventually (sooner would be best) get those injector orfices set up (Don @ Airflow will be your new best friend) and have at it (LOP operation).
If you have a hot cyl, check the baffling on that cyl.
Engine break-in involves only one part: piston rings. Other parts may 'wear in', but you are only concerned with "breaking in" the rings. Cyl honing pattern determines how fast the cyl will break in -- since yours are new/steel, they're probably right (for a quick break-in). If done correctly, break-in happens in about 20 minutes. It's a hot 20 minutes for sure, but that's all it takes if done correctly, and the engine is built correctly.
BTW using Phillips X-CY during break-in, and for the life of the engine for that matter, is fine. So, change to the better stuff whenever you like.
So, how do you make sure the rings are broken in properly? Cylinder pressure. Lots of it. How do you get the right cylinder pressure? Well, you can run full RPM and MP (kinda spendy), or you can run 'er a bit over square at ~2300-2400RPM (26-27" or so) and get the same results. Lean as you like, but watch the CHTs: keep 'em under 400F unless you have an engine sponsor.
All you guys out there saying you can't lean except under 75% -- you should look at the power settings on a supercharged or turbo'ed engine and where they are leaned at. It would scare ya, till you figured it out. All the leaning info you need is here on the forum -- you just have to squelch out the static and there it is.
You guys with carbs (not FI): you can do the same, just keep a closer eye on those CHTs -- your fuel distribution is not as even as the FI systems provide. A bit of carb heat, and tip the throttle plate a bit (pull back from FT just a bit: stop before the MP starts to drop) and you'll see better results.
Question: if your flight school plane drops a cyl, and it is changed out, do you think the flight school changes to mineral oil for the 'break-in' on that cyl? Of course not. Do you hear this (oil change to mineral) recommended anywhere for a single cyl break-in? Of course not. Why is that? Another OWT bites the dust!
Caveat: if the flight school is running semi-synthetic, then yes the oil should be changed out; it's too slippery. But what flight school has the $$$ for that type of oil?
Carry on!
Mark
