RV Cold Starts

[David MacRay]

Realistically I think it’s probably time to send the case to a company like DivCo for welding and re-machining of the oil pump cavity but then it’ll be almost too nice for the plane.

No it won’t. If you have the moneys do it.

[Squaretail]

Where do Lycoming and Continental document this critical minimum RPM requirement?

The only time I think I remember seeing something like this was a SB for the horrible lycoming O-320-H2AD which was notorious for eating cams and lifters because it didn’t get enough oil to them at idle, and recommended not being below 1000 rpm for any length of time. Will see if I can dig it up.

[Big Pistons Forever]

From my Continental O 200 Operators Manual (Form X30012, dated FAA approved December 1980)

Page 13 Starting engine

Item 8.4 “throttle retard to 1200 Rpm” ie after engine has started

Page 14

Item 1 Pre Takeoff Check

“Maintain engine speed at approximately 900 to 1000 RPM at least 1 minute in warm weather, and as required during cold weather to prevent cavitation in the oil pump and to ensure adequate lubrication”

[Colonel]

… and that’s exactly how an O-200 should be operated.

I was interested in this

prevent cavitation in the oil pump

As shown above, the Lycoming has no such problem.

I still see no mention of this critical windage.

Windage is driven by both RPM and oil level in the wet sump. I presume everyone is running oil at max all the time to maximize windage with an air-oil separator?

It’s worth mentioning that everyone else tries really hard to minimize the horsepower-robbing windage that is considered beneficial in GA

[Big Pistons Forever]

Lycoming Tech Tips ( an excellent and under-utilized resource IMO) has the following advice in the section titled Extending the Life of Your Engine

“ Avoid rapid acceleration after any cold start-up, and make every effort to maintain a constant speed of about 1000 RPM for several minutes during the initial warm-up period.”

The note specifically references the TIO 540J (ie the Navajo engine) but does say it can be applied to any engine FWIW

[Colonel]

Avoid rapid acceleration after any cold start-up

I wish the RV guys could read that.

about 1000 RPM for several minutes during the initial warm-up period

Exactly! Keep the RPM low after start. This is not rocket science.

Once the engine has a tiny bit of heat it it, you can then switch to "don't foul the plugs and exhaust guide"
mode, and idle at 1100-1200 RPM with the mixture full lean for max RPM.

Do that until all the CHT's are 200F, then you can run it up to 1700 RPM and check the prop and mags.

After that, all you have to worry about is your oil temp, before takeoff. If you are running multi-vis cat piss,
not an issue - it flows just fine at low temps. But if you are running straight grade, you may have to wait
while the oil circulates through the hot head (and the heat conducts from the hot cylinders to the crankcase)
warming the oil to it's minimum temp for takeoff, which increases with viscosity.

[Slick Goodlin]

but then it’ll be almost too nice for the plane.

No it won’t. If you have the moneys do it.

You should meet this plane. It’s… functional.

…mostly.

[Slick Goodlin]

Speaking of oil pressure, I ain’t got none on the Champ.

Fixed it! Sort of.

Checked the regulator, it’s fine. Checked and cleaned the screen too which was okay. Pulled the oil temp bulb out and pumped the cavity full of oil which ran down through the pump and primed it. The first start had the oil pressure rising to normal after about fifteen seconds of sucking air, the second start saw normal pressure almost instantly. It will lose its prime, I have no doubt about that, it’s just a matter of how long it takes.

Good enough for now. There’s a spare 65 kicking around that needs its crank checked (flew into a post at full throttle) but hopefully is otherwise easily rebuildable.

[David MacRay]

It’s good to see you have oil pressure again. That, “Flew into a post at full throttle.” thing sounds like quite a story.

[Colonel]

Your airplane is trying to tell you to fly it more often.

Also stop running that multi-viscosity cat piss.

W100 is the answer. My kid prefers W120 for better RPM control.