Engine question

[duckluv26]

hmmm, i guess it doesn't bother the motor to idle at less than 500. however, i have mine set at 600. it idles smoothly and i "lean it out" to kill it with absolutely no dieseling. to each his own i guess.......

 

[Anonymous]

On my engines..I use a considerably high idle. Higher RPM means better oiling to components. On my stuff I use considerable valvespring pressure and many other things that are much benefited by the increased oil volume. Of course it's basic math that higher RPM will increase cycles to the engine components. In my case...It'scertainly better to run higher RPM. And arguably so in most other apps. But on a A/C engine, it probably doesn't matter as much.

But my main point was that CHOPPING the idle when you shut it down would IMHO be the best way for any application.

Felber

 

[Anonymous]

Duck, I've never seen any value in letting any engine run at a speed where it's less than smooth ...... there are too many other things to consider then like wear and tear on the motor mounts, wear on the engine itself, stress to the engine stand and prop, and lower oil pressure. If the engine is shaking, then so are the magnetos and carburetor. :?

I agree with you and Felber. Set it to a smooth idle and then do what it takes to make it shut down.

feather

 

[cowboy]

Darn Right Duckluv,
To each his own, and I agree that letting hot aircraft engines "run-on" is not a good thing. Not good at all.
Automotive or Aircraft, I can't stand to see an engine dieseling on for however long when the ignition gets killed.

However people do it, they should be afforded a drama free shut down.

I often wondered why aircraft engines were best shut off via interuption of the fuel delivery circuits in the carborators or fuel servos. Shoot, even the original zenith GPU carbs have the same function for shut off.

Perhaps lower than reccomended idle rpm's cause some other less than desireable effects, that the aircraft engine manufacturers wanted to avoid.
Perhaps some of the effects mentioned above. I don't know.

Engines that drive propellers are never fully unloaded, so the throttles are open further at Idle than other applications. Makes perfectly simple sense to me.

I had read prior posts regarding the dashpot method of dealing with throttle plate idle openings for shut down, but never fully understood why this was needed on an airboat application.

Thanks Felber.

We had a boat around here recently that came with the fuel lean to cut-off lever on the carb wired to full rich. (fixed setting)

You could'nt shut it off with out run on, unless you shut of the ignition, and dumped full throttle on it at the same time.

It got a fuel shut of cable installed on it in short order! Problems ended right there, but we always made sure that were running the cable for full rich while running the boat. Just like all the rest of the A/C powered boats we have around here.

Palm Bay, check the adjustment of the cable you have. Make sure it will hit the lever stops for cut-off, and full rich. Especially full rich.


It's all good.