204 MPH TAS in a 6A??

pierre smith · #1 04-12-2006, 06:22 AM

Hi everybody,
Yesterday I was at 8500 feet from Daytona to Georgia indicating 177 MPH at full throttle and 50 degree OAT. That trued out to 204 MPH in my 6A with the 0-360 turning 2700 RPM with the three-bladed Catto which Craig pitched for max speed. I believe that my airspeed is pretty accurate but does anybody else see that kinda speed in a 6A. She only weighs 1046 lbs and I was solo with full fuel.

Craig told us earlier that with the prop pitched for max speed and we turn it 2700 we should see better than Van's advertized speed. Anybody else also this fast??
Pierre

Mel · #2 04-12-2006, 06:35 AM

I couldn't help notice that your empty weight is less than 1100#. My -6 has an empty weight of 1019#, modified O-320, Catto 3-blade. My TAS at 2725 rpm, WOT, 8000' is 201 mph. And my prop is pitched for CLIMB.
Mel...DAR

Bob Hoffman · #3 04-12-2006, 08:18 AM

Mel,
I have a RV-6A with a O-320 and I'm looking at trying to squeese some extra HP ,trying to see what some of the options might be..Might I ask what some of your mod's might be ??
Thank's for the info
Bob

osxuser · #4 04-12-2006, 08:46 AM

As long as the engines are turning that kinda RPM, your putting out enough power to go that fast. Doesn't matter where it's pitched if at WOT you are turning between 2700-2800. You didn't say if you were at WOT Mel.

BTW that is pretty freakin fast for a -6, one I know of only gets about 160 IAS with a O-320 and a climb catto 3-blade, but he can't get WOT and restricts his RPM to 2700.

Mel · #5 04-12-2006, 08:48 AM

Bob,
My mods include 9.5:1 pistons and roller rocker arms.
To be honest, if I had it to do over again, I wouldn't go with 9.5:1 compression. The engine is not nearly as smooth. (Although the 3-blade prop brought back most of the smoothness). If you want more hp, there is no substitute for cubic inches. Problem with higher compression is you don't get the hp until you get the rpm. With fixed pitch, you don't get the rpm on takeoff where you need it. It helps, but not as much as cubic inches would.
Stephen,
Yes, that is WOT.
Mel...DAR

sprucemoose · #6 04-12-2006, 08:53 AM

Pierre,

What is the pitch of your prop? I have a 3 blade Catto/ RV-6/ O-360 180 HP setup. My prop is slightly underpitched (66 inches IIRC) for climb like Mel. AT 8K and WOT I true 175 kts (201 MPH) but often turn around 2800 RPM due to the under-pitched prop. So your numbers are completely believable. I believe that the Catto is the best fixed pitch prop out there.

Kahuna · #7 04-12-2006, 09:03 AM

204mph tas in a 6a is right on at WOT and ~2700rpm o-360 and 3 blade.
Weight in not a factor for speed unless your a real nit pick.
2 blade and a clean airframe get you to ~210
Best,

rv6ejguy · #8 04-12-2006, 10:09 AM

I've trued 209mph at 15,000 feet with my turbo Subie -6A. I know, that's cheatin'.

sprucemoose · #9 04-12-2006, 12:37 PM

Big time cheatin' for sure. Curious what the fuel burn was at that condition?

pierre smith · #10 04-12-2006, 01:07 PM

Hi Sprucemoose,
Our prop has 76" pitch/66" diameter. I was WOT and leaned and the tach showed 2700 RPM-exactly what Craig said it would. We suffer (I think) on takeoff and climb but still manage almost 2000 ft/min at 135 MPH.
Pierre