Technique for leaning an O-320 for takeoff?

Steve Brown · #1 01-09-2014, 07:47 AM

I'm doing a lot of flying around Carson City NV. The city airport is plenty long, but I would like to try some shorter options.
Anyone have a good technique for leaning during run up?
Mine seems to result in fuel starvation once the RPMs climb during takeoff.

David Paule · #2 01-09-2014, 09:24 AM

Caveat, I am flying a Continental O-470. What I do is run up to 1,800 rpm and lean past peak rpm, so that I get a definite rpm drop. Then I enrichen it back to 50-100 rpm past peak rpm on the rich side.

On take-off, I make a quick check for EGT and fuel flow, and tweak as necessary. I'm more likely to lean it slightly than to enrichen it. The mixture is a vernier type, and typically a quarter-turn is a big change.

Although I fly from 5,050 feet, I do this at sea level too.

Dave

AX-O · #3 01-09-2014, 10:21 PM

You should talk to Dayton. He has an rv-4 with a 320 out of Carson City.

SHIPCHIEF · #4 01-09-2014, 11:31 PM

My Wife's RV-4 likes to be leaned at 1700RPM for best power during the run up and mag check. Then the mixture stays amazingly correct for take off and climbs up to 4000-5000 ft.
She leans it to 'best power' where the engine runs strongest for the current throttle setting, always.
Her RV-4 has a 160 HP O-320 with a Sensenich Composite Ground adjustable prop.

sailvi767 · #5 01-10-2014, 12:51 AM

I understand leaning at the higher altitudes for takeoff but are you not reducing your detonation margins substantially at more normal airport altitudes?

George

RV10inOz · #6 01-10-2014, 03:25 AM

The simple method, assuming that your fuel flow is correct at sea level is to use the same target EGT method we talk about in the climb.

The engine does not know it is on the ground, so in a short field, hold the brakes throttle up and reduce the mixture to achieve 1250-1300dF or there about.

No need to sit there for ages, near enough is OK and tweak it in the roll if you need to. This is not a precise setting to the last degree.

If you have a low compression engine, the target EGT will be about 1350-1400dF

pierre smith · #7 01-10-2014, 05:39 AM

....Exactly where my -10's EGT's are during climb from my 328' ASL altitude.

Thanks, Oz,

zav6a · #8 01-10-2014, 08:28 AM

Got a fuel flow meter? A really good investment, not just for leaning but for assessing the stautus of the fuel delivery system.

After a few hours of paying attention to fuel flow and writing things down, it is a quick and straightforward way of managing mixture. Changes with altitude, temp and throttle are very predictable. I have a few key stats on a placard for when memory fails. I end up using EGT and CHT to verify mixture rather than to set it.

Far more time with your eyes out of the cockpit too.

The topic has been discussed at length here so if you are new to the game, take a look around.