Who knows
cytoxin said:
if using one cht, and egt, which cylinder usually runs the hottest on your rv W/lycoming 360?
The Gent's above are right and agree, but there's no 100% telling. It's based on your unique engine, cowl and baffle. It varies w/ throttle position and climb/cruise attitude as these Guy's show. For example #1 is often the coolest, but in climb it can get higher because of the airflow into the cowl, which tends to favor the left side in climb (P-factor, corkscrew airflow), which is not as prevalent in cruise. I would not vote for #1 but that shows you how the baffle and individual plane can be critical.
CHT has to do with air flow thru and around the cylinder so the back ones are more likely to get hot. However after #3 (right rear) strangely the #2 (left front) is often 2nd hottest (but not always). Why? It's the baffle and fin gaps. I made up a sketch:
In general the #3 is hottest due to being in the right rear and the baffle choking air flow. Also is climb there is more air going into the right cowl inlet (cyl #2 and #4).
When you have 4 CHT probes you can balance the cyl temps by playing with the baffle to fin gaps, especially on #2 and #3. However with one CHT
you can't be 100% sure that the #3 is the hottest, but it's a good bet.
EGT has to do more with fuel distribution within the intake runners or injectors if you are FI. This also effects CHT as well. Bottom line who knows but it tends to be #1 or #3. Typically most will put both the CHT/EGT on the #3.
The throttle position is a big player since with a partially closed throttle, the throttle plate (butterfly) is deflecting forward more, which makes the fuel/air mixture richer forward. At full or wide open throttle this effect is minimized, which is typical at takeoff and cruise at higher altitudes where full throttle is typically used.
You can move your CHT probe after flying for while, record the data for #3 than move the probe to another jug. Fly under similar flight conditions, recorded data, move again, record again, verify the #3 is hottest CHT under all conditions or not. May be as important as finding the hottest cylinder, make sure that say the #1 cylinder is not running TOO cool in cruise, which is sometimes the case. Often you have to block the whole front of #1 to get the temp up to near the other cylinders. The idea is balance all CHT's. Also by bypassing some air on the #1, you get more air to the #3, which definitely needs it. However until you measure it you don't know for sure.
Since the EGT requires a hole in the pipes it is not easy to move a single EGT probe around. You may consider three more probes and a rotary switch, but the single is fine. Just be aware unless you know for sure that your EGT probe is on the first cylinder to peak, you really can't rely on it to lean by, but it's guide.
Just remember CHT's over 400F mean possible maintenance issues. Just make sure you use a the "WELL" type probe and it is calibrated. The spark plug CHT ring type are terrible. All Lyc data is on the well type.
