Author Topic: Leaning  (Read 4917 times)

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Offline Hmanvel

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Leaning
« on: February 24, 2007, 09:31:03 AM »
Not to raise an old standby issue, but I would like to hear from others what their S.O.P. is with engine leaning.  My airplane has 0-320's, carbureted.  I would love to run lean of peak, but can't seem to get there without significant engine roughness.  Using the VM1000 monitors, many times I get a really rough engine before the monitor indicates a cylinder peaking.  Really bad fuel distribution apparently.  I have given thought to changing my airbox configuration, etc., to see if I could improve this.  I don't use a ramair type system, I have inlet filters inside the cowls near the firewalls, with scat tubing to the airboxes, typical Rutan plans type induction.  My airboxes came off the Apache that the engines came from, with the flow vanes which divide the 4 quadrants.  Are most of you guys able to go LOP without roughness?
Harry Manvel
Defiant N2HM
PTK / Pontiac, MI

Offline Waiter

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Leaning
« Reply #1 on: February 24, 2007, 12:30:58 PM »
Me too, I start getting rough just about peak or just a tiny bit LOP

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Offline Drew

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Leaning
« Reply #2 on: February 24, 2007, 04:24:07 PM »
I think that it may be pretty difficult to go lean of peak without fuel injection.  And even with fuel injection, I think you have to tune the injecters to get them all to peak at just about the same time...At least that is what I have heard.
Drew Swenson
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Offline Jack

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Re: Leaning
« Reply #3 on: February 26, 2007, 03:22:25 AM »
Quote from: Hmanvel
Not to raise an old standby issue, but I would like to hear from others what their S.O.P. is with engine leaning.  My airplane has 0-320's, carbureted.  I would love to run lean of peak, but can't seem to get there without significant engine roughness.  ?


Geeze my old password and name work.  In big round motors, 2800s we ran LOP.  We had some serious engine gauges to monitor the motors. It was also with a carb and a two speed supercharger.

If it's running rough is the first key.  I generally lean right in the climb. Pull back on the mixture till it's a tad rough and add some rich.  Haven't had a chance to figure out my current motor setup. It has ram induction with a Rose ignition system.  Feels like it might run LOP.

Another trick in the winter, add some carb heat to about 15C or so and then lean.  

Jack

Offline Joe Dubner

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Re: Leaning
« Reply #4 on: February 26, 2007, 09:42:25 AM »
Quote from: Hmanvel
Not to raise an old standby issue, but I would like to hear from others what their S.O.P. is with engine leaning.  My airplane has 0-320's, carbureted.  I would love to run lean of peak, but can't seem to get there without significant engine roughness.  


Harvey, two thoughts: 1) Can we assume you're running wide open throttle?  The Lycoming 4-banger fuel-air mixture is at its most balanced distribution only at WOT (or very nearly so).

2)  Maybe you haven't _really_ experienced rough running :-)  In my O-235 Long-EZ I didn't "get it" until I finally flew with Gary Hertzler in the back seat telling me to keep leaning, keep leaning, keep leaning ... even after I swore the engine was going to quit if I leaned any further!  But he was right, and the RPMs dropped way down and the roughness subsided somewhat.  Bob Eckes also helped: he described it as leaning to a point where the engine felt "weak".  

Of course, this whole exercise must not be attempted above 75% power (and preferable even lower).  For WOT that means at a density altitude above about 8200'.  And smooth air helps; in any kind of turbulence or up/down drafts it's hard to maintain parameters of any sort.

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Joe
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Offline Hmanvel

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Leaning
« Reply #5 on: February 27, 2007, 08:28:48 AM »
Actually I have not tried it at WOT.  My current props (Prince) run up to near 2900 and it gets noisy and vibration is an issue.  I have new Hertzler props coming, which hopefully will allow for WOT operation.  I'll definitely experiment with that.
Harry Manvel
Defiant N2HM
PTK / Pontiac, MI