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Old 10-10-2017, 05:16 PM
macrafic's Avatar
macrafic macrafic is offline
Join Date: May 2006
Location: Rochester, MN
Posts: 389
Default ICO RPMs

First flight with an RV-7A, 3-blade Catto fixed pitch prop and IO-360-M engine with dual pMags. Getting 730 RPM ICO on the ground and 810 RPM ICO in the air (on landing). Seems a bit high to me, but I am not really that knowledgeable.

Can those of you with a similar setup share your ICO RPMs with me? Am I in the ballpark? High?
Rich and Cindy Macrafic
Rochester, MN
One month to painting and test flying
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Old 10-11-2017, 02:49 PM
penguin penguin is offline
Join Date: Jan 2005
Location: England
Posts: 1,035

Are you mixing up terms? ICO usually means Idle Cut Off and refers to the mixture control pulled fully out.

Do you mean with the throttle closed?

First of all, if you have a new engine the idle speed will change over the first few hours. 650rpm might be desirable at idle, but with a light weight wood prop you may have to accept a slightly higher idle to keep the engine running at all smoothly. Idle when you are just about to land is a factor of the prop and your ground idle speed. Perhaps stick with what you have for the first few hours, always assuming you have a long enough runway to operate from.

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Old 10-11-2017, 02:59 PM
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Raymo Raymo is offline
Join Date: Nov 2014
Location: Richmond Hill, GA (KLHW)
Posts: 1,669

RV-7A, Catto 3 blade with 20 lb crush plate, single P-Mag and one Slick with AFP FI. I see about the same numbers; maybe slightly higher at idle with mixture just rich enough to keep the engine running when taxiing.
RV-7A - Slider - N495KL - First flt 27 Jan 17
O-360-A4M w/ Catto 3 blade NLE, AFP FM-150 FI, 1 PMag, Vetterman Trombone Exh, SkyTech starter,
PlanePower Alt, FlightLines Interior, James cowl & plenum
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Old 10-12-2017, 07:23 AM
Robert Anglin Robert Anglin is offline
Join Date: Mar 2008
Location: houston, texas
Posts: 810
Default Your fine.

As has been said above a light wood prop does need a little more RPM at idle set to be smooth and stay running better. A nice heavy metal prop is kind of like a fly-wheel and can stay smooth with more mass at a lower idle set point.
We run a light 12-13 pound Prince and set our ideal at around 820-850 RPM's.
I even run it a little above that on the ramp to keep the plugs cleaner a little longer. I think you are OK here with this, but it is you that have to be comfortable with you settings. Hope this helps, Yours, R.E.A. III # 80888
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