Bill,

That sounds a bit optimistic based on my fuel burn.  Tracy has a SWAG that says you'll produce 100 hp for every 10 gph.  At cruise I'm burning about 11.5 - 12.5 gph, so I figure I'm producing around 110- 125 hp at 5100 -5200 rpm.  This results in an IAS of 200 - 210 mph, depending on CG. This is comparable to the IO-540 Lancair ES. 

By comparison, the Lancair Columbia 300, which is based on the same airframe as the Lancair ES, with an IO-550-N2B (6 cyl, 1 turbo, 3-blade c/s prop) cruising at 75% power, shows at 191 kts at 18,000 MSL.  The IO-550-N is rated at 310 hp at 2700 rpm.  If you believe Continental's numbers, 75% of 310 is 232 hp, which is closer to your numbers than to mine. 

From a different approach, if I'm burning 12 gph, at .57 BSFC, that works out to 126 hp, much closer to what we get using Tracy's SWAG method.  One other thing, the Columbia numbers are at 18000 MSL while mine are at 6500 MSL.  

Mark

Sent from my iPad

On Jun 7, 2015, at 5:37 PM, Bill Bradburry <flyrotary@lancaironline.net> wrote:

Mark,

 

Here is a dyno chart where a semi p-port (I don’t know what that means) 20B is making about 190 hp at 5100 rpm.  Do you think that is about what your engine is doing based on your plane’s performance vs ESs with IO-550s in them?

 

Bill

---

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Sunday, June 07, 2015 5:13 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: new operating question

 

Rich,

I've been running a constant speed M/T on my. 3-rotor for years now. I typically adjust prop rpm for a max of 7k rpm for takeoff, WOT.  Once a climb has been established I bring the rpm down to around 6k for the remainder of climb. For cruise, I leave throttle set to WOT, but set rpm via prop setting to give 5100 rpm.  For sightseeing flights, I'll back off the throttle to give around 150 kts. 

 

Mark

Sent from my iPad

On Jun 7, 2015, at 9:33 AM, ARGOLDMAN <flyrotary@lancaironline.net> wrote:

Greetings genlepeople of the rotary pursuasion,

 

For those of you using variable pitch (C/S) props, an operating question that has been bugging me. Perhaps the collective wisdom of this group can set my mind at rest.

 

In piston aircraft engines, the concept of running over squared  MP vs RPM has been heavily questioned to the extent that some suggest running at full throttle all the time and controlling the power output via RPM (within reason). The thought is to, I believe, eliminate the induction restriction of the butterfly valve increasing the efficiency.

 

Now we have a rotor spinning, a gear box gearing and a propeller propelling. Does this concept hold true for the rotaries. What are people doing in terms of setting power after take off (full throttle max RPM).

 

My enquiring and rotating mind wants to know. 

 

(Unturbocharged Renesis with RD1-c Box)

 

Thanks

 

Rich