Plumbing an oil cooler onto the 4A084

[David]

In general we like them to run at around 160 in all aircraft engines

[brlcla]

David,

Does that mean that the Max. oil temp for the engine should be 180 degrees?

I'll replum the lines tomorrow.

Duane,

How can the water in the oil boil off at 180 degrees? Last I heard, water boils at 212 degrees.

Dave

buster,

the 180F temperature you are reading is usually in the lines coming from the pump (under pressure).... when it exits the lines and hits the bearings it is actually going from a higher pressure to a lower pressure instantaneously and the water flashes off....

[buster]

OK, that is starting to make more sense now. Thanks

Dave

[Papee]

OR!!! you could mount it flat below the engine and let the air blow across it and not through it. That's where I had mine before it met it's clumsy foot demise

[buster]

I had thought about laying it flat. Might be just as well rather that covering it up.

Guess I'll re-plum it first, and take some more readings before I decide.

Thanks,
Dave

[Duane Scarborough]

David,

Does that mean that the Max. oil temp for the engine should be 180 degrees?

I'll replum the lines tomorrow.

Duane,

How can the water in the oil boil off at 180 degrees? Last I heard, water boils at 212 degrees.

Dave

buster,

the 180F temperature you are reading is usually in the lines coming from the pump (under pressure).... when it exits the lines and hits the bearings it is actually going from a higher pressure to a lower pressure instantaneously and the water flashes off....

Buster,

brlcla's explanation was better than I could come up with.

Actually, I kinda' wondered about the water boiling off at 180 degrees thing myself. I just accepted that explanation because I'd seen the same temp quoted from different sources.

My own rationalization of this has to do with a pot of water on the stove. No, water does not "boil" until it reaches 212 degrees, but it starts to give off steam way before it gets that hot. Is that at 160 degrees? Or is it at 180 degrees? I really don't know.

I wish Mr. Wizard was still around. He'd know.

EDIT: I started looking for info on this and the more I learned, the more confused I got. Big surprise.

I'll keep looking. Inquiring minds want to know.

Duane

[buster]

Duane,

I do know, and "Mr. Wizard would confirm it, that water will boil at lower temps if you put in in a vacuum

I'm not sure if that relates to my engine though.

Dave

[brlcla]

actually when you start seeing steam it is boiling.... the bottom of the pot reaches 212... and the gas rises.... it is actually well above 212 when you get a rolling boil (which is large amounts of flashing gas rising quickly).... also you got to realize the bottom of the pot is under a slight amount of pressure due to the water above it so it will boil at maybe 210ish.... i would say the bigger the pot the fast it boils which would hold true if it wasnt for convection... the hot unflashed water rises and cools and so on.... this happens in a small pot but not as noticible as a larger pot is


oh and Duane... it really helps to have a 4 year mechanical engineering degree... which is what backs me up a lot...

[brlcla]

David,

Does that mean that the Max. oil temp for the engine should be 180 degrees?

I'll replum the lines tomorrow.

Duane,

How can the water in the oil boil off at 180 degrees? Last I heard, water boils at 212 degrees.

Dave

buster,

the 180F temperature you are reading is usually in the lines coming from the pump (under pressure).... when it exits the lines and hits the bearings it is actually going from a higher pressure to a lower pressure instantaneously and the water flashes off....

and i have to make a correction on this one... wasnt thinking completely through this.... the 180F is the hot oil... which is cooled... so my theory dont hold up completely... but if you think about it how hot is your bearings... roughly 200-210F... so you pump cool oil across it and the cooler oil gets hot quick and flashes the water off...

[buster]

Hey Duane,

Maybe we got a Mr. Wizard replacement right on our forum already

Dave

[Duane Scarborough]

Buster,

What brlcla said makes more sense than what I've dug up so far.

Yeah, I know about the effect of pressure on the boiling point of water. If it's in a vacuum it boils at a lower temp, and if it's under pressure it boils at a higher temp. I've accepted that most of my life.

I'll cast my Mr. Wizard vote for brlcla right now.

Brlcla,

Don't take this wrong. I DO respect your knowledge on this subject. But, YOU shall be known as Mr. Wizard from now on.

Please change your log on name...

Thanks,

Duane

[buster]

Today I got the oil lines changed around, so now the temp gauge is on the line that comes out of the engine, before it goes to the oil filter, and then the cooler. That should be the hottest oil in the engine.

It is exceptionally warm here today, about 93 degrees, which probably affects my results.

After nearly a half hour, the oil temp was reading almost 180 degrees, and It didn't seem like it was going any higher. The boat was on the trailer, so I hope it won't get that hot when it is in the water and the boat is actually moving.

It has me wondering though, if maybe I need a bigger cooler

Dave

[Duane Scarborough]

Buster,

The more I think that I know, the more confused I get. I'm sure that's a big surprise.

Let's make sure that I understand this correctly. The only thing that YOU changed was the location of the temp sensor. Is that correct?

If so, then I'd guess that your oil cooler is doing a good job. So, the oil coming out of the engine's crankcase is at about 180 degrees, the oil cooler cools it, and then you are returning it to the crankcase at about 125 degrees.

It sure sounds like it is working fine to me.

Duane

[buster]

Duane,

My only concern is that I remember David said that they like them to run around 160 degrees.

I guess that must mean I'm running 20 degrees on the hot side of ideal

Maybe that's not a big deal, I don't know.

Dave

[David]

Hey Buster when it was on the Trailer how was you running it also was it in direct sun light while it was on the trailer

When you are on the water you will probably be fine with the temps

Also if your carb is just a little lean it will make your motor run a little hotter also

[Duane Scarborough]

Duane,

My only concern is that I remember David said that they like them to run around 160 degrees.

I guess that must mean I'm running 20 degrees on the hot side of ideal

Maybe that's not a big deal, I don't know.

Dave

Buster,

I don't "know" either. As you've seen, WHERE you check the oil temp seems to make a BIG difference. Chuck seems to prefer to check the oil temp at the drain plug. (bottom of the oil pan). I do not know where the "correct" place to check oil temp is.

Duane

[buster]

I was running it between 2000, and 3000 rpm most of the time. I don't think It's running lean, I got a 150 main jet in the solex.

Yes, it was in direct sunlight, not so much as a cloud in sight.

It runs smooth except rumbles a little when I let up on the gas.

I guess I'll just wait n see how it goes on the lake.

Thanks, Dave

[David]

Sounds like you have a plan run it

[chuckitt]

Duane, you know the correct place to put the temp sender, i told you.
Chuck

[chuckitt]

buster, i think your temp will be good. When you were running it on the trailer, it was under a stactic load on the engine and that will raise your temp. The engine will be under less load going across the water.
Thanks, Chuck