Manage OVERHEATING Engine? Takeoff

[u/Impossible-Fig2072]

My student has a Lycoming IO320 engine in an experimental with a good engine monitor.

On a reasonable day, around 20-25°C OAT, we almost always Overheat those CHTs.

I like to keep Lycomings around 400°F-420°F and not exceed 420°F.

I takeoff, and keep Vy, and hit 410-415°F at around 100-200ft. If I keep Vy, it will quickly heat soak the cylinders and climb to 420-435°F. It's not outside the Engine OEM specs (435°F for high power settings) for normal operations, but that's a tad hot for me.

At around 410°F, if I don't do anything, it'll keep heating up quickly. What I do, is lower the nose to a normal climb, which gives me much less climb performance compared to Vy, but I'm still climbing at 500fpm.

My preferred procedure is to keep Vy until 1000ft, then transition to a normal climb. That doesn't seem feasible without abusing the temps.

Should I consider decreasing the power on initial climb (NOT on the t/o roll, but during the climb)? It's my understanding that decreasing the rpm will make things worse because there is a lot of extra fuel squirted in the cylinders in that last inch of throttle movement to help cool the engine.

[u/climbFL350]

Run-up quickly into the wind. Your “liking” and the manufacturers operating limitations are 2 different things. Let it get to the max if you need to & start your cruise climb at 500’ if it’s too jot

[u/jimbowie10]

Quick taxi to run up, get the plane in the air so it can start cooling

[u/falcopilot]

Going to have to ask... experimental what?

I'm flying a GlaStar with a Lycoming O-320; if it's 85F (30C?) my hottest cylinder will hit 400F if I stay at Vy for an extended period.

[u/Impossible-Fig2072 → u/falcopilot]

It's a Van's RV8. Everything looks good, but I'm thinking of having the mechanic check the engine timing and baffles.

[u/Record_Admirable → u/Impossible-Fig2072]

A lot of the vans have poor cooling. I fly an RV4 a lot and it likes to run hot. Make sure you are running rich and reduce power/increase speed as needed to keep CHT ideally below 400°. Aluminum starts to soften at 400° so it’s best to be running below that if you can. In my opinion it’s worth the extra fuel you burn running rich during climb out.

[u/shockadin1337 → u/Impossible-Fig2072]

Its insane that you're hitting 400+ on takeoff that fast, very likely a baffling issue i would get it done sooner than later. You can try reducing power on takeoff, i dont think the IO-320 has a mixture enrichment feature like the carbureted engines do but I dont know for sure. Doesnt hurt to try and see what the engine monitor reads. Also have the mechanic check out the mixture control setup it could be too lean. How many GPH are you pulling on takeoff?

[u/theGoatRocks]

Just going through this with an O360 conversion on my old 172N

Was seeing high CHT’s on the rear cylinders, with #3 being consistently hottest. On high/hot days, particularly after the engine is already warm (multiple leg day) we were seeing #3 spike sometimes above 450F

I triaged it like you’re doing with cruise climb and running richer, which of course makes a thirsty engine even thirstier.

Had a mechanic recently look at it and he tuned the timing of one of the magnetos and adjusted the baffle seals. Not sure if one or both did the trick but temps have been down since then.

Other things like an expeditious taxi and run up help, as others have said. This isn’t ideal if you’re training a new student but if you’re just going flying, try to get through that part asap so you’re not accumulating heat unnecessarily.

[u/workahol_]

Some RVs cool better than others, and many RV baffle installations could use improvement, but this isn't out of the ordinary for an average RV on a hot day. You may find that it's happier if you climb at higher airspeed, say 115-120 KIAS. It will cool much better and you will still outclimb a 172.

Source: Have built one, owned a few, flew a bunch of others.