I have a new , 30hrs., ECI Titan 0-360- A1AN and experiencing high CHT's. 390* at 75% power, over 400*F at WOT. 75* OAT.
The differential I am seeing, measured with a manometer, top and bottom of the cowling is, @ 145mph indicated, 2500', 8.5" of H2o top., 3.5" of H2o bottom for a 5" of water difference.
There are a few additional parameters you need to know if you wish to compare your cooling performance to a Lycoming cooling air demand chart. First is altitude and temperature, really meaning air density. In bubba terms, thicker air can carry away more heat. Second is mixture state, as the charts assume 0.5 BSFC (fuel lbs per hour/HP). In rough terms, that's a ROP best power mixture. Makes sense; high cooling demand.
I don't have an ECI chart, but here's the Lyc chart:
Assume a standard day temperature (60F at the engine face), and 5000 feet. Power is 75% (135/180) and mixture is 0.5 BSFC. The green line predicts a 435F CHT with a 5" baffle drop. At 2500 ft, a 5" baffle drop nets pretty much the same result.
The unspoken assumption here is typical GA quality baffling, which is pretty awful. Better-than-GA baffle quality is probably why your cooling performance is beating the charts (390F at 75% rather than 435F, at a higher OAT). Chances are good that you can improve further, but a bit more break-in time is in order before direct comparison with known installations.
An excellent indicator of heat transfer efficiency (maximum heat being carried away by the cooling air mass flow) is found by measuring outlet temperature. Since you're actually measuring important parameters (my compliments sir!), you may wish to install a temperature measurement probe or two. You want a probe on the end of a wire which can be re-located anywhere under the cowl as desired.
The output of a National Semiconductor LM34AH-ND (try DigiKey) is read with an ordinary hand-held digital multimeter or a digital voltage display. The voltage corresponds to temperature, 10mV = 1 degree F. Example: Meter says 2.5 volts. 2.5V is 2500mV. 2500/10 = 250F. Whatever the meter says, just move the decimal point two spaces to the right and you have temperature.
Only three connections, aircraft power, ground, and sense. Connecting to the avionics bus so the sensor is “on” with flight instruments is fine. Meter negative and probe ground should both be connected to the aircraft single point ground bus.
You’ll need a way of routing the probe wire through or around your firewall. Some have run it through the heater duct. Installing a screw-type terminal block on the firewall wired to another screw terminal block in the cockpit is a nice, permanent way to make temporary connections in the future.
Solder the LM34 to the ends of the three-conductor tefzel shielded aircraft wire. Insulate each lead connection carefully as you go, the cover the entire end with a short length of ¼” adhesive heat shrink. Leave the cap of the LM34’s can uncovered.
The cockpit end will connect to aircraft power and the aircraft ground bus, with the third wire routed to a convenient location for meter connection. Run a single wire from the ground bus to the same location. The latter two wires are for the voltmeter.
You’ll find a great many temperatures of interest, but the primary in this investigation is cooling air exit temperature. The probe is mounted just inside the cowl exit. It is critical to shield the probe from radiant heating, the primary source being the exhaust pipe(s). Fabricate a radiant heat shield as necessary. Make sure the heat shield itself cannot transmit heat to the probe via conduction.
