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2 cylinders overheating with a aerocarb setup
- Thread starter NickZ
- Start date
I'm not familiar with the Aero carb, but carburated engines (4 or 6 cyl) can have quite a bit of variation in fuel distribution between fwd and aft cylinders depending on the throttle position (throttle plate acts like a flow control deflector) and the performance of a particular carburetor.
In cruise flight I can tweek the EGT's on my carbed four cyl to have a very tight spread by moving the throttle small amounts.
Assuming all of the baffling is installed and performing correctly, the issue is probably related to fuel distribution.
It is hard to comment further without more details (flight conditions it occurs, throttle and mixture setting, etc.).
During cruise there is definitely a fuel issue I'm thinking. I can barely run 20 map without seeing temps between 420s and 450s. Had the baffles professionally replaced.
Can’t comment on the AeroCarb, but I can’t imagine putting much faith into “professionally replaced” baffles. If you had them done by an A&P, that mechanic might never have actually done baffles before - and every baffle installation is pretty much custom. If you had them replaced by a multi-time RV builder (A&P or not), then you might have a little more confidence in them. And even then….I have built many sets of baffles, and have to tweak them a big once the airplane gets flying…every time….
Pics might help of the front cylinder air dams, baffles and other holes (oil cooler, heat muffs, blast tubes, leaks) created in the baffle area that reduce pressure.
What CHTs are the other cylinders experiencing when #1 & 2 are approaching 450F in cruise? Are the CHTs any different during the climb? Are all of the CHT probes the same type (J or K)? Is this a new problem or has it done this all along?
And yes, let's see some pics of the baffles, especially around the inlet area and all of the inter-cylinder baffles. A pic of the transition piece at the top of the cowl would be helpful as well. Yours may be just fine, but we've solved more than a couple of issues here with people's baffling that were "checked by others".
And yes, let's see some pics of the baffles, especially around the inlet area and all of the inter-cylinder baffles. A pic of the transition piece at the top of the cowl would be helpful as well. Yours may be just fine, but we've solved more than a couple of issues here with people's baffling that were "checked by others".
After seeing Michael's post, I looked up the manual for AeroCarb. It lists a Lycoming 0-320 as the biggest engine it can go on. And the OP is mounted on a Lycoming O-540? What? Did we miss something? Was the term "aero carb" not intended to mean a specific brand of carburetor?
What makes you think 450* chts is due to a fuel issue? At 20” of map, no mixture from extreme lean to extreme rich is going to cause 450*, with all other things normal. Top suspects are excessive ignition advance and blockage or obstruction of cooling air. Detonation highly unlikely at 20”
