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  #11  
Old 03-20-2012, 09:22 PM
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videobobk videobobk is offline
 
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Location: Near Scipio, in Southern Indiana
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I did the two Slicks, one and one, and two P-Mag routine. I went from 650 and close to smooth to 390 and smooth as can be. That is with a three blade Catto. Having variable timing is amazing! I have no idea what the exact firing angle is at low idle, but it is no where near the 25* fixed with a Slick. Maybe 10 or 15*? IMHO it is the closest thing to a CS-style landing you will get with a Catto.

Bob
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  #12  
Old 03-21-2012, 07:05 AM
rv9aviator rv9aviator is offline
 
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Location: Arkansas
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At what RPM does the engine not oil properly?
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  #13  
Old 03-21-2012, 02:00 PM
Pilottonny Pilottonny is offline
 
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Location: Belgium
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Default 850 RPM

Mine is idling at about 850 RPM, anyting lower will make it run rough. There is probably two causes for this: Low weight Whirlwind propeller and the fuel devider that will have troubles in supplying fuel evenly to all four cyilinders at such a low fuel flow (fuel injected). But, due to the CS-prop, "floating" was never a problem. Maybe others can land shorter/stop quicker. I gues I need about 250-300 m (750-900 ft) to touch down and stop comfortably without having to "step on the brakes".

Regards, Tonny.
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  #14  
Old 03-25-2012, 10:59 AM
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Sunriver Ken Sunriver Ken is offline
 
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I'm at 600-650 RPM with O-360 and Lazar electronic and C/S Scimitar prop.
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  #15  
Old 03-25-2012, 04:58 PM
thinkn9a thinkn9a is offline
 
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Location: Mississippi
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Default Vlad, did it "become" 350 suddenly??

If so, you might need to look around and see if something is loose or fouled. Getting too much air,.. not getting spark,... etc.

Unless you know the idle setting moved,...
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  #16  
Old 08-11-2012, 09:02 PM
alpinelakespilot2000 alpinelakespilot2000 is offline
 
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During the first 8 flights, my hot idle (after landing and while taxiing in) is consistently about 700-750 with my Catto prop. Given many admonitions to get the idle speed as low as possible to mitigate the RV-9 float, I should probably begin adjusting it down a bit. Approximately how many turns should I expect to have to turn the idle adjustment spring/screw to get the idle speed down? I was thinking that I'd try to reduce it about 50 rpm at a time but would like to make a good guess at how much of a turn would be required on the screw to get that. Thanks.
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  #17  
Old 08-12-2012, 12:36 AM
PCHunt PCHunt is offline
 
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Location: San Diego, CA
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Default OTOH

Well, here I go sticking my neck out again! I sure do hate disagreeing with Walt, who provides a vast amount of great accurate information on this forum.

BUT....... If you have a fixed pitch prop, I think you should set your idle as low as you possibly can, down into the 450 range.

Here's my rationale: On the ground, taxiing around, you don't have to close the throttle unless you want to. You can idle at 700, or 800 if you wish. But in flight, just because you close the throttle, it doesn't mean you will idle at 450. The forward airspeed will speed the prop up. You will float a lot less with a low idle speed set. Then, at the end of your rollout, you just open the throttle a bit, and idle at your desired RPM.

Perhaps a carbureted engine will idle happily at a lower RPM than an injected one.

YMMV, and I'm sure it will!

Quote:
Originally Posted by Walt View Post
Anything less than around 600 and most engines start to run rough, you also risk the engine quiting at an inopportune time if the RPM gets to low, most folks don't like that.
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  #18  
Old 08-12-2012, 07:48 AM
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ArVeeNiner ArVeeNiner is offline
 
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Quote:
Originally Posted by PCHunt View Post

Here's my rationale: On the ground, taxiing around, you don't have to close the throttle unless you want to. You can idle at 700, or 800 if you wish. But in flight, just because you close the throttle, it doesn't mean you will idle at 450. The forward airspeed will speed the prop up. You will float a lot less with a low idle speed set. Then, at the end of your rollout, you just open the throttle a bit, and idle at your desired RPM.

That has been exactly my experience.
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Last edited by ArVeeNiner : 08-12-2012 at 07:53 AM.
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  #19  
Old 08-12-2012, 07:54 AM
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curtis curtis is offline
 
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Location: Kansas
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Default Lycoming Key Flyer Operations

http://www.lycoming.com/support/tips...Operations.pdf

By the recommendations of Lycoming, see link above, you should not let the engine idle below 1,000 RPM after start. I have heard that this also helps in avoiding premature lifter wear and since I'm running an H2AD engine I have tried to follow this recommendation. I have a wood prop and my actual low idle setting is approx 700 RPM, but I try not to let it idle there very often.

I know that this idle speed may be controversial, it is just what I try to follow based on Lycoming recommendations.

I know a another concern with this practice will be excessive brake wear, but I have close to 200 hours on my plane with the original brake pads, which still have plenty of wear left in them based on my inspection 2 months ago.
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  #20  
Old 08-12-2012, 08:04 AM
tim2542 tim2542 is offline
 
Join Date: Aug 2009
Location: Redding,Ca
Posts: 633
Default

Having variable timing is amazing! I have no idea what the exact firing angle is at low idle, but it is no where near the 25* fixed with a Slick. Maybe 10 or 15*? IMHO it is the closest thing to a CS-style landing you will get with a Catto.

Bob[/quote]

Bob actually at idle you have very low manifold pressure, ergo you get max ign timing (advance). Seems counter intuitive but that's how it works. At high MP it will retard back to base timing, probably 25, then as you climb and or reduce throttle it will beging to advance.
This is one of the (false) reasons why people are so impressed with EI. They are great, but the smooth idle comes primarily from the ign timing, not the more powerful spark. If you were able to set a pair of slicks at 35-40 you probably would not be able to tell the difference at idle.
Tim
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