Splish-Splash

[fitterski]

I just closed the bottom end of a Cummins 5.9 and got me a surprise while measuring some oil stats. The dipstick goes to 4-1/2 inches below the pan gasket line, the FULL mark on it is maybe a good 2 inches above the tip i.e. more or less at 2-1/2 inches below the pan gasket datum. All my life I'd been told that the rod caps spash in this oil and send it flying up all over exposed parts in motion but when I looked at the numbers NOTHING touches the oil unless there is gross overfill!



The image is upside down, the yellow arrow (top edge of ruler) shows the FULL mark. The rod cap shown is pretty well at bottom and makes the situation obvious. Has anyone seen this before? Maybe it's been much longer than I thought since my basic engine classes (1963 ish)

 

[Fallon]

Some performance engines have wipers mounted in the pan to scrape extra oil off the rods to maintain ballance on the rotating mass at high RPMs. With an oil pump there is no benefit to splash lubrication. You get exactly the oil pressure you need on the wear surfaces & minimize the oil spraying around elsewhere.

I know my air compressor is splash lubricated. It actually has some flimsy sheet metal tabs under the rod cap bolts for that purpose. I'd imagine the rod caps barely touch the oil surface if at all & those tabs are all that fling oil around for lubrication. It's been years since I pulled apart a small lawnmower type 4 stroke, but I think those are the same splash lubrication with no oil pump.

 

[90cummins]

Many automotive engines particularly high speed performance engines have windage trays to prevent the oil from contacting the rotating crankshaft assembly.
If the oil comes into contact with the rotating components it creates excessive heat, power loss and can cause the oil to become entrained with air which reduces the ability of the oil to lubricate.
90cummins

 

[CincyFlyer]

Sometimes you can see small cutouts in the top of the big-end of the rod to squirt oil up into the cylinder.

 

[fitterski]

Jeez, I didn't know I was that far behind the times! I kow about skirting onto cyl-walls but didn't know about splash causing overheating or imbalance etc.

 

[1stDeuce]

Pressure lubricated engines don't use splash lube. Haven't ever, as far as I know... Actually, if you overfill an engine enough, the crank will hit the oil, but it usually results in a real mess, or engine damage from foamed oil...

Even engines that are splash lubricated don't dip the crank into the oil, they have a slinger... If you tear apart an older briggs, you'll find a formed steel thingy bolted to the bottom of the connecting rod. This is what makes the "splash", rather than having the rod drop directly into the oil, which would eat up a lot of HP, and probably whip the oil into a real froth, rendering it useless...

My dad told me about his buddy leaving the oil slinger off the rod for more hp on his snowblower. It worked really well, for about 5 minutes...

 

[Spanner]

Consider the engines that are running 'dry-sump' systems. Remote reservoirs, scavenger pumps to collect the oil for recirculation...

Splash-lube is for engines with no oil pump. Most commonly seen on small engines now-days. Also seen on Chev in-line 6 cyl 'dipper' engines mid 1930's prior to the pressure-lubed Blue Flame engine.

Splash can refer to the water-wheel 'slingers' that create a mist of oil when spinning fast. Dippers have the projection from the big-end to dip into the sump contents.

Splashing the big-end into the sump of oil doesn't occur. That is why overfilling is bad. The oil foams and the engine gets less lubrication. Severe overfilling causes 'churning' of the oil like a cake mixer and less splash so no lube again.

Once upon a time all engines were splash/drip lubed.

 

[fitterski]

Consider the engines that are running 'dry-sump' systems. Remote reservoirs, scavenger pumps to collect the oil for recirculation...

Splash-lube is for engines with no oil pump. Most commonly seen on small engines now-days. Also seen on Chev in-line 6 cyl 'dipper' engines mid 1930's prior to the pressure-lubed Blue Flame engine.

Splash can refer to the water-wheel 'slingers' that create a mist of oil when spinning fast. Dippers have the projection from the big-end to dip into the sump contents.

Splashing the big-end into the sump of oil doesn't occur. That is why overfilling is bad. The oil foams and the engine gets less lubrication. Severe overfilling causes 'churning' of the oil like a cake mixer and less splash so no lube again.

Once upon a time all engines were splash/drip lubed.

Lesson learned, I must have fixated on the splash thing way back somewhere and never gave it up as an idea which I never had to really deal with.

The first engine I ever opened was a ford flathead, they had pumps. The first ever book I learned almost everything from was a '59 Lincoln shop manual, the first ever leture on the subject would have been in a '63-ish air-force classroom. I have no idea where this notion came from. Lately I have adopted a policy of believing nothing and validating everything, that's how I got to actually look at the dipstick depth in the pan etc.

 

[Spanner]

Splash is still used today.Usually for single cylinder small HP engines.

Tell us more about your 5.9 - Why is it being rebuilt. What is it going into etc?

 

[fitterski]

I started a snow blower 'revival' project and made the mistake of doing so on 2 or 3 threads almost simultaneously. It became a swamp and I had to steer it all back into a single topic (look it up under snow removal, snow-pump). HOWEVER the are so many sub-topics involved (like this one) that I have found it advisable again to split into several threads, side-bars as they say. But on these, this time, I really don't want to get involved in the mother-thread so to speak. But that's where the engine is headed and it looks like a good find with maybe just a pump issue outstanding.