In article ,
Dude wrote:
Personally, It seems to me that a speed mod less than $1,000 a knot is
likely a good deal. I presently fly about 142 in a hurry, and 120 when I am
not.

They're probably not worth much of anything until you're talking about
airplanes with stock speeds in the 160kt+ range. That seems to be the
speed aircraft designers can easily get by going to 250-300hp. Getting
beyond that requires smarter aerodynamics.

For example, the price difference between a similar vintage Piper
Cherokee 235 and Comanche 250 is $10-15,000 (based on a quick look
at TAP). If you put $15,000 worth of speed mods (ie all of them) on
a 235 it still doesn't go as fast. The same is probably true of the
Warrior - 235 upgrade.

Once your stock speed is up around 160kt it might cost less to add STCs
than to upgrade to a faster model, but the returns have diminished
significantly. I'm not aware of any combination of mods that take a
160kt stock airplane and give you 180kts (with the possible exception
of an aftermarket turbo, if any still exist). Even that only saves you
20 minutes on a 3 hour trip.

If you're flying long distances and want to cut the total time, the most
cost effective way is to carry enough fuel that you don't have to stop.
If you can cut a 30 minute fuel stop out of a C-172 flightplan it's like
adding 15kts.

--
Ben Jackson

http://www.ben.com/