The attached is some of the EC3 timing code. I don’t fully understand how the curve is being applied. This is likely only a small part of the code. I had smooth idle when cold at 1600 /561 and 1400 / 491 when warm. But my prop weighted 48#. Cold idle F/A in the 13’s. Once warm it would it was smooth in the 14’s -15’s adjusted with the manual mixture. Bobby From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Monday, October 19, 2020 7:49 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Tuning The racer idles at 2200 RPM. Because the flywheel is just the flex plate and lightened rotors. The engine will shake violently below about 1600 RPM. It will beat the gear box to death with actual reversals. With the steady drag of a prop, idle could be lower but don't let it shake at all. Very bad mojo..... In olden times we ran just 20 degrees of advance. Very safe but a bit less power. Good up to 9,000 RPM. For higher RPM up to 10,000, 24 degrees of advance is fine. Pump gas 87 octane. More advance needs more octane. Once hot, idle advance can be up to 35 degrees with very lean mixture. In a message dated 10/19/2020 9:06:08 AM Atlantic Standard Time, flyrotary@lancaironline.net writes: Hi Matt, when you write 600 or 700 rpm - do you mean engine rpm or prop rpm?? My engine idles at 1700 rpm (engine), because that's where I set it: divided by 2.85 = 596 prop rpm - my engine and the gearbox get rough around 1550 ... so I keep it away from there. Don't know absolute AFR numbers but my engine usually idles richer than 14.7 (stoich) when cold but after it warms up I find it idles better (post-flight taxi back to hangar) a bit on the lean side. Timing - set as per Tracy's manual (25 deg? BTDC) and have never moved it, as EC2 advances timing with rpm ... What AFR and timing are people running for idle, taxi, takeoff, climb, cruise, descent? I seem to have to be around 11afr for it to stay alive. Still trying to get it to idle around 600rpm, maybe bump it up to 700rpm to be smoother without dieing and shaking apart. taxi / takeoff / climb = 13.2afr, 28 timing cruise - not sure aft, 28 timing decent - not sure aft, 32 timing Not sure what the plane likes. I tried 14afr, but the MAP really get's low and engine shakes. Guessing it should be more rich? I attached the timing table and split rotary table (second email). Not sure how to tune timing, I just want safe values for now.
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