5 MPH loss in 70F vs 30F (common)?

[LSaupe 123]

I am seeing about 5-7 MPH slower cruise (for a given RPM) than during cold weather (70F vs 30F).  I have 2 IAS and 1 GPS instruments and the are all trending the same way.

Is this common/typical/anticipated?  I anticipated a bit of change due to density altitude, but only envisioned a TAS vs IAS change (which hasn't really changed much).

I took a 4 month break so went from one extreme to the other.

 

 

Edited 3 Jul 2016 by LSaupe

[akflyer 1427]

How are your RPMS looking WOT.  With thicker air in the winter I normally run a little flatter pitch than in the summer.  There is a pretty substantial performance difference between the 30 deg. temps and 70+ temps though.  I am reminded of this every summer when I start playing on sand and gravel bars.

 

[C5Engineer 1170]

What kind of static system you running? I lose close to 5mph indicate when I open the 3" vents in both doors due to the pressure change. 

[LSaupe 123]

Max RPM is about the same (6,600 Tiny Tach and 6,800 reg tach).

This is 200 RPM higher than in the winter. Using a GSC 3 blade, probably not the most efficient beater to have out there.   My static system is just open behind the dash (no vents to open in my cowling - yet), however, my IAS cross check is my completely external (Hall Bros.) airspeed indicator.  All follow the same trend (including GPS ground speed). Even gave her a bath today just in case is was the dust that had accumulated (no change, but she sure did look better).  Still flies great, hands off with predictable performance.

I also have not yet installed the lift strut fairings or prop nose cone.  Assume that will help a bit, but envisioned the delta to be the same (winter to summer).

 

[akflyer 1427]

If your running more RPM now I would reset the prop.  I use 61-6200 static and that normally gives me 64-6500 on take off.  Max HP is at 6500.  Use the tiny tach readings as the analog tach is never right.  That should help keeping your EGTS under control and give you better take off and cruise.

 

[LSaupe 123]

AKFLYER:

I added 1 degree pitch today and that made a world of difference.  Got my 5 MPH back and dropped the  EGT's about 75 degrees.  Thanks for the suggestion.  4 good hours this weekend.