- Joined
- Mar 25, 2013
- Messages
- 1,230
- Reaction score
- 621
High temperatures have been an ongoing issue for me ever since I've had accurate gauges. Back in the good old days when my CHT and EGT always indicated zero I was none the wiser--and happy! A couple of years ago I complained here about my battle with oil temperatures climbing well into the 220's during acro and 190 minimum at cruise. Good ol' Smizo replied with an invite to his compound where he introduced the cowl to a neat little block of wood cut with a notch that he used to bend a lip into bottom of the cowl.
That helped by at least 5 degrees. Later I installed the offending EI CHT gauge and learned that I was suffering from very high CHTs (measured from #3). On a moderate summer day I get 410 in climb, 385 at 2600 RPM cruise and 430+ in acro. You maybe able to see from the (currently sideways) photo that I have a pressure cowl with no exit for the airflow other than a small louver and the opening aft of the louver. That opening is made larger by a rectangular slot cut into the bottom of the fuselage but it is still well short of the 2-1 ratio with the inlet that seems to be accepted for proper airflow.
Newly indoctrinated Biplane Forum wizard Danny Bond recommended two extra louvers or expanding the opening to match the exit area you might get with an open cowl flap. Joe Flood agreed that that could work but before doing all that cutting, he recommended that I extend the lip (or "dam" if you prefer). That's what I have done here using Lexan. It looks like a windscreen for the little Leprechaun who rides along on the belly.
Weather only allowed a non-acro test flight yesterday and it was inconclusive. Max CHT in climb after some aggressive flying was 412. I will post more after I've had a chance to really fly hard.
That helped by at least 5 degrees. Later I installed the offending EI CHT gauge and learned that I was suffering from very high CHTs (measured from #3). On a moderate summer day I get 410 in climb, 385 at 2600 RPM cruise and 430+ in acro. You maybe able to see from the (currently sideways) photo that I have a pressure cowl with no exit for the airflow other than a small louver and the opening aft of the louver. That opening is made larger by a rectangular slot cut into the bottom of the fuselage but it is still well short of the 2-1 ratio with the inlet that seems to be accepted for proper airflow.
Newly indoctrinated Biplane Forum wizard Danny Bond recommended two extra louvers or expanding the opening to match the exit area you might get with an open cowl flap. Joe Flood agreed that that could work but before doing all that cutting, he recommended that I extend the lip (or "dam" if you prefer). That's what I have done here using Lexan. It looks like a windscreen for the little Leprechaun who rides along on the belly.
Weather only allowed a non-acro test flight yesterday and it was inconclusive. Max CHT in climb after some aggressive flying was 412. I will post more after I've had a chance to really fly hard.
