High barometric pressure

[amillet]

Monday I picked up N1084L from its annual.  On the way home #1 CHT set off the JPI alarm, reading 457 before I noticed.  I flew the rest of the way home with partial cowl flaps to keep the CHT below 400.  I called the shop and found they had put on a new CHT probe under the spark plug.  All the others are under the Tanis heating elements.  Yesterday I flew to KTTD to have it replaced.  On the way home I flew at 6500 ft.  2600 RPMs WOT.  CHT on #1 was 350, similar to the others.  TAS was 167 knots, 4 to 5 knots  higher than I before annual .  Altimeter setting was 30.67, almost an all time record for Seattle.  Would the high pressure make that much difference in TAS or is it the adjustment to gear doors that was done at annual?

[Jeff_S]

You didn't mention what the temp was. Most of the time high pressure is also accompanied by cooler temps, both of which increase the density of air molecules and can lead to higher TAS. But tighter gear doors could also help. Too many variables in your equation to give you an absolute answer.

[amillet]

+4 at 6500

[carusoam]

Speed maxed out for a few reasons...

1) Density altitude. High atmospheric pressure, low temp, and distance above the ground...

2) 6500' is where the power is still good with reduced air resistance for NA planes.

3) engine timing may have been adjusted at annual.  Check CHTs vs prior ones... timing Closer to 25° BTDC will result in more power and higher CHTs.

4) better rigged gear doors is always good. How bad were they before?

5) does the great performance duplicate itself on the next day?