Idling the Engine for Warmth

[Guest]

Suggest stopping by an engine shop to look at piston skirts scuffed from lack of proper per heating followed by too quick an application of run up power. Gasoline is cheap, cylinders, pistons and top overhauls not too cheap.

Check out Lycoming S/I 1505 concerning engine pre heating

Clarence

[jetdriven]

Burning 1.8 GPH on the ground is sill a relatively cheap way to warm up your engine on cold days. Why rush?

[jetdriven]

I would let it idle until the oil pressure stabilizes. When you start it when it's very cold it will take a few seconds to show any oil pressure and then usually a rather high oil pressure due to the high viscosity of the oil. Once the pressure stabilizes which my experience is about one minute. Then you are good to go.

 

The Lycoming operators manual for the IO-360 says that the engine has to be warm enough to make full power without stumbling before taking off.

Lycoming engines bang the oil pressure gauge to 90 PSI as soon as it starts. Continental engines sometimes take a full minute to show full oil pressure. The oil systems are basically the same, but the key difference is where the oil pressure sender is located. On a Lycoming, the sender is right near the outlet of the oil pump. It gets pressure immediately. Continental senders are at the end of the cam gallery, the last place to get oil in the system. So even though your Lycoming shows immediate oil pressure it doesn't verify all the engine is pressurized fully and it still may take some time to get oil to everything.

[N601RX]

My oil seems to warm up very quickly.  I just looked back through the JPI data and it seems to warm at a rate of about 12 deg per minute when at 1200 rpm.  After liftoff it rises at about 20 deg per minute until it reaches normal operating temp.

[jlunseth]

I run the TSIO-360-LB .  Idle at 800-1000 is a waste of time with my engine for two reasons.  I am assuming we are talking about cold weather here, say below 40 dF.  First, the mechanically driven alternator will not provide charging to the battery, so operating below 1000 results in a constant drain on the battery.  Second, the last two cylinders on each side are not firing or are barely firing.  The induction system is not tuned, so they are not getting much air.  On my engine monitor (JPI 930) the CHT's on those two cylinders will not register.  In truly cold temps, say 20 dF or below, and if I have for some reason not been able to preheat the engine so the OT is at OAT, then I may idle for a short while at 1000 to get things moving and warm the oil a little.  Other than that, standard idle for me is 1200.  If it is warm and the engine is warm then I can idle at 1000-1100, whatever it takes to stay just above the point where the alternator is charging.

[Shadrach]

I run the TSIO-360-LB .  Idle at 800-1000 is a waste of time with my engine for two reasons.  I am assuming we are talking about cold weather here, say below 40 dF.  First, the mechanically driven alternator will not provide charging to the battery, so operating below 1000 results in a constant drain on the battery.  Second, the last two cylinders on each side are not firing or are barely firing.  The induction system is not tuned, so they are not getting much air.  On my engine monitor (JPI 930) the CHT's on those two cylinders will not register.  In truly cold temps, say 20 dF or below, and if I have for some reason not been able to preheat the engine so the OT is at OAT, then I may idle for a short while at 1000 to get things moving and warm the oil a little.  Other than that, standard idle for me is 1200.  If it is warm and the engine is warm then I can idle at 1000-1100, whatever it takes to stay just above the point where the alternator is charging.

Odd, your alternator seems no more efficient at low RPM than my generator. I need about 1050 RPM to see the system go over battery voltage. Are all of you guys with alternators seeing drain below 1000? I thought the major advantage of an alt besides lower weight was more consistent charging at low RPM...

[jetdriven]

My old prestolite alternator would go negative amps at 950 RPM but the Plane Power won't do that at 650 RPM. His continental may have a different alternator drive ratio than the lycoming belt drive has.

[jlunseth]

The alternator on the 231 is a little odd, and a known issue.  There was an attempt to upgrade the alternators from 70 to 100 amps some years ago, but the 100 amp alternator charged no better than the 70 amp at idle.  It is not the alternator though, it is a mechanically driven alternator and the gearing in the drive mechanism is at fault.  It does not drive an alternator fast enough at low idle.  I flew with one of the Mooney PPP instructors a couple of years ago, who owns a 231.  We all tend to taxi fast because of the charging issue.  When we got in the plane he asked:  "Do you ride the brakes or watch the flashing light?"  I knew immediately what he meant.

[wishboneash]

My old prestolite alternator would go negative amps at 950 RPM but the Plane Power won't do that at 650 RPM. His continental may have a different alternator drive ratio than the lycoming belt drive has.

 

This is interesting. My engine doesn't idle at around 1000 rpm this winter after I switched to the PP alternator (replaced in summer). I have to bump it up to 1200 or so or the engine dies until things warm up. Since the drive ratio changed to drive the alternator faster, the engine is seeing a bigger load now than it did when I had the old Prestolite. One way to ascertain this I guess is to pull the field breaker on the alternator to see the effect on idle. Unless there is something else going on in cold weather operations.

[jetdriven]

It sounds like your mixture link needs adjusting. It should idle smoothly at 800 RPM and I just recently set ours a little lower at 750 RPM to shorten landing distance

[Awqward]

?.....It should idle smoothly at 800 RPM and I just recently set ours a little lower at 750 RPM to shorten landing distance

That's interesting....just how short is your field that this makes a difference?

[jetdriven]

It shortens every landing but I now routinely stop in less than 1000' with a J model and can work hard at it and stop in 800'. I'd say it stops 100' shorter with the less residual thrust working against brakes.

[N201MKTurbo]

The idle speed makes a huge difference in landing distance. I have mine Idling at 500 RPM. If I put my mind to it, I can make the second turnoff without using the brakes. (Less then 1000 feet)