RV-4 prop pitch

[mh53j]

I have a -4 with a 160 hp 0-320 fixed pitch 72" diameter Sensenich with a pitch of 78". I would like to get a little more speed, has anyone or is anyone running greater pitch than 78"? I'm contemplating going for 81" pitch but not sure of the effects.

Right now I get about 193 mph true at 7000' and 2600 RPM using the 3 and 4 leg gps method.

Any comments are welcomed, Thanks for all the help.


Brett

[tin man]

Brett
Contrary to popular belief increasing pitch usually wont make you go faster, it will however make you faster for a given rpm, but you will lose hp and rpm on the top end so its pretty much a wash. Increasing pitch will have a negative effect on your climb rate and acceleration.
Tom

[osxuser]

It depends if you are WOT at that 2600 RPM. If you still have throttle left, then extra pitch might help, but you will burn more gas.

[Marc DeGirolamo]

[quote=mh53j]I have a -4 with a 160 hp 0-320 fixed pitch 72" diameter Sensenich with a pitch of 78". I would like to get a little more speed, has anyone or is anyone running greater pitch than 78"? I'm contemplating going for 81" pitch but not sure of the effects.

Brett.....FWIW unless you use the same manufacturers prop, changing to a differeent pitch may not achieve what you want. they all measure pitch a little differently or so I'm told. I have a Colin Walker 69 pitch and figure that I need more pitch as well. I bought a 73 pitch Colin Walker (so am comparing apples to apples) but I haven't tried it yet.....!

Marc

[osxuser]

[quote=Marc DeGirolamo]

Originally Posted by mh53j

I have a -4 with a 160 hp 0-320 fixed pitch 72" diameter Sensenich with a pitch of 78". I would like to get a little more speed, has anyone or is anyone running greater pitch than 78"? I'm contemplating going for 81" pitch but not sure of the effects.

Brett.....FWIW unless you use the same manufacturers prop, changing to a differeent pitch may not achieve what you want. they all measure pitch a little differently or so I'm told. I have a Colin Walker 69 pitch and figure that I need more pitch as well. I bought a 73 pitch Colin Walker (so am comparing apples to apples) but I haven't tried it yet.....!

Marc

The metal Sensenich can be re-pitched...

[Marc DeGirolamo]

Originally Posted by osxuser

The metal Sensenich can be re-pitched...

Yes and that would be fine.....I was talking more about the pitch numbers vs: manufacturers and the differences between them.....and I don't want to start another thread here on prop building ...

effects of changing from a 78-81 pitch: (my guestimates)
- lower static RPM
- longer takeoff run
- somewhat higher cruise (assuming same RPM,altitude)
- higher manifold pressure (assuming same RPM,altitude)