Matthew Law writes: > IIRC, running lean at high power settings increases CHT. Running > rich decreases it since there is more fuel to help dissipate heat.
That's an OIT (Old Instructor's Tale) as far as I can tell, though I'm sure that a little heat gets carried off that way. What actually seems to control the CHT is the efficiency of combustion. The hottest CHT's come at about 50 degF rich of peak EGT (ROP), and the greatest power comes at 100 degF ROP. At peak EGT, CHT's will be already be getting cooler, and they start to drop significantly as you go lean of peak EGT (LOP). By 50 degF LOP, CHTs will have dropped nearly 20 degC -- you need to run almost 250 degF ROP to get the same result. In other worlds, 50 degF ROP is the hottest the engine will run -- either leaning or enriching the mixture from that point will make the engine run much cooler, but you have to lean only a little, while you have to enrich quite a bit to get the same effect (bringing on the joy of fouled plugs, stuck values, high fuel consumption, and lots of carbon monoxide in your exhaust). You can find a little chart in any Lycoming (or, presumably, Continental) engine manual showing how all this works -- I bought my O-320 manual on eBay for almost nothing. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
