3M Mintor 170 questions

[Dean Pappas]

Sorry for the incomplete response, before.
Most 2-C setups require a lengthening of the pipe to cure the midrange richness or bog, and to eliminate the power versus throttle position hysteresis that can plague any piped 2-C.
 
The problem was that if you pushed to level from warmed-up WOT vertical and reduce to 1/2 throttle the engine may stay "on the pipe" and you get a different power setting than if you came from idle to the same stick position. Or (and this is a goodie) you may end up with a level flight cruise setting that changes with what thermal/load condition the engine was in a few seconds ago, or a lagged settling time at 1/2 throttle. How about rounding the top of the square loop, pulling the throttle back, getting a good setting, then 1/2 way across the top of the loop, the engine falls completely off the pipe, and gets soft.
 
The long pipes fixed that set of problems, and caused the airspeed dependant mixture problem. O.S. fixed it with a box that looked at RPM versus throttle position, and corrected the mid-range mixture to get rid of the hysteresis. One other way to fix ( or at least help ) this would be controlled spark timing; the other is to make the engine equilibrate thermally much more quickly. As you know, temp is ignition timing in a glow engine. 
 
Dean

-----Original Message-----
From: Woodward James R Civ 412 TW/DRP/ACQ [mailto:James.Woodward2 at edwards.af.mil]
Sent: Monday, May 05, 2003 3:44 PM
To: discussion at nsrca.org
Subject: RE: 3M Mintor 170 questions



Hi Dean,

 

I'm still sort of new.  Does W.O.T. = with out throttle?  On 45 degree downlines of medium length like the reverse Cuban eight from the top (Masters sequence), I'd say the motor just unloads some.  If it were lean, it might cut-out for a second when throttling up.  If it were rich, it might gurgle or give signs of loading up.  The 140 or 170 do neither.  They just increase in rpm as the throttle is increased.  

 

On the 140 setup (15% C.P., 2 OSA5), I needed to lean the low-end screw 1/8 turn during the 2nd tank on the ground.  This setting has held fine since, now with 1.5 gallons through it.  The engines will idle very low, however, I raise it to 2000 for takeoff and flight.  

 

Your technique is the first I've heard of like this.  So, once you get this one flight profile right, you find a prop that gets the torque you want?

 

Jim

 

 

Thanks for the response Jim,

That sounds right, though I just like more prop and more quiet.

When you dive W.O.T at about 15 degrees or so ( simulating using windup for extremely windy conditions) does the engine lean/richen/or just unload ? With the 17-13 on the 140, I shortened 'till the richening was gone. That was just under 1" gap from stock.

Dean

 

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