Here's a rod side clearance question for the guru's

[Rick360]

The side clearence will not effect pressure which is the same theory that a narrow rod bearing vs a standard rod bearing will not show a loss or gain either in pressure.

Here is the problem. With .030 clearence it is considered excessive and it will throw a significant amount of oil up onto the walls. This is not what you want and it is wrong. .018-.020 is fine.

As far as quantity, it doesn't take rocket science to figure out that rods with .030 side clearence will source more oil onto the cylinder walls than a rod with .020. Thats a 33.3 percent increase

You seem to contradict yourself??? If wider side clearances don't affect oil pressure, why would it throw more oil onto the cylinder walls? Where did this extra oil come from? Do you think it lets more oil past the bearing or not? If it did, why wouldn't that affect oil pressure? You can't have it both ways.

IMO the amount of oil on the cylinder walls would be the same(because the amount of oil past the bearings would be the same), regardless of side clearance, unless the bearing clearance is way to big.

Rick

[Wolfplace]

As far as quantity, it doesn't take rocket science to figure out that rods with .030 side clearence will source more oil onto the cylinder walls than a rod with .020. Thats a 33.3 percent increase

=
Why?
You are not going to get any more oil out of the rod than the journal clearance allows regardless of side clearance

Or in real teknikacal terms,,,
Putting a big leak downstream of a small leak doesn't change what is going to come out of the end,,,

[BLACK BART]

Some quick math on the calculator will show that Mike is correct. What he said has also been stated in other places here.

Assuming a single crank pin of 2.100" and a pair of rods with .003" and .030" clearances for the vertical and side clearances respectively I come up with the following square inch areas for oil to pass through.

2{[π(2.103/2)²]-[π(2.100/2)²]}=.0198
This gives us .0198" for the vertical measurement.

.030×2π(2.100/2)=.1979
This gives us .1979" for the side measurement.

The side measurement is roughly ten times as large as the vertical measurement and couldn't possibly be the larger internal oil leak. Hopefully the numbers are easier to understand and will help the ones that cannot see the concept intuitively. CJ

[Strange Magic]

IMO the amount of oil on the cylinder walls would be the same(because the amount of oil past the bearings would be the same), regardless of side clearance, unless the bearing clearance is way to big

If you had two identical engines, one with .030 side clearence and one with .020 side clearence, the amount projected onto the walls would not be the same. The remainder that would not be thrown onto the walls continues through the oil galleys and up through the top of the engine.

Rod side clearence is one of many key elements in controlling oil on the cylinder walls. Oil pan style/design, crankshaft design and crankcase square inches are also key factors on keeping the cylinders as dry as possible during operation.

Where did this extra oil come from? Do you think it lets more oil past the bearing or not? If it did, why wouldn't that affect oil pressure? You can't have it both ways.

It registers very, very minimal on a pressure gauge but the amount of oil released through that accumulated void or area is quite substaintial.

[robert1]

And all this time I thought rings were the key element for controlling oil. How am I supposed to control the oil in engines that have pin oilers squirting oil on the bottoms of the piston and pins? They spray oil directly at the piston from the bottom side.

[Racerrick]

IMO the amount of oil on the cylinder walls would be the same(because the amount of oil past the bearings would be the same), regardless of side clearance, unless the bearing clearance is way to big

If you had two identical engines, one with .030 side clearence and one with .020 side clearence, the amount projected onto the walls would not be the same. The remainder that would not be thrown onto the walls continues through the oil galleys and up through the top of the engine.

Rod side clearence is one of many key elements in controlling oil on the cylinder walls. Oil pan style/design, crankshaft design and crankcase square inches are also key factors on keeping the cylinders as dry as possible during operation.

Where did this extra oil come from? Do you think it lets more oil past the bearing or not? If it did, why wouldn't that affect oil pressure? You can't have it both ways.

It registers very, very minimal on a pressure gauge but the amount of oil released through that accumulated void or area is quite substaintial.

Okay
In order for the rod side clearence to be the controlling factor in the oil flow out of rod bearing, the ROD side clearence would need to be LESS THAN the bearing clearence. Simply because the rods housing bore is larger in diameter than the crank bearing so it will have more area.

[rooster]

the rod side clearance theorists might want to consider all the cup teams that are running piston guided rods with absolute enormous side clearances. bearing/journal clearance determines oil loss in that area, not side clearance.

[Strange Magic]

Yes, I could understand how we are comparing a 2.200 main with a 1.750 rod, dry sump and crankcase vacuum cup engine to a 572 inch wet sump large main/rod journal engine. It's about as apples to apples comparison as can be.

[RW TECH]

Yes, I could understand how we are comparing a 2.200 main with a 1.750 rod, dry sump and crankcase vacuum cup engine to a 572 inch wet sump large main/rod journal engine. It's about as apples to apples comparison as can be.

Here's an apples to apples comparison:

A 4.750" stroke Callies crank HEMI in an Indy Maxx alum. block that had rods changed from aluminum to steel & gained a gynormous amount of side clearance.

No decrease in oil pressure (would happen if flow increased)
No noticeable oiling issues on spark plugs
No change in power output
Hardly any change in ET (suprising, considering the effect on bobweight)

SIDE CLEARANCE DOES NOT REGULATE OIL FLOW, DIAMERTRICAL CLEARANCE DOES.

[Strange Magic]

SIDE CLEARANCE DOES NOT REGULATE OIL FLOW, DIAMERTRICAL CLEARANCE DOES.

Maybe we are missing the boat here or maybe after 26 years of building and racing, I am missing the boat here.

The question at hand that I am discussing is weather rods in an engine with .030 side clearence disperses out more oil during reciprocating rotation that an engine with rod side clearences of .020.

If I understand you correctly, you are saying that weather the side clearence is .030 or .020 or even greater or less in differential (regardless of the difference in side clearence), it has no effect on how much oil is released from that reciprocating assembly during rotation. Is this what your saying or is this the point your trying to get across?

[k-star]

Lets see if this helps.

If you flow a known diameter say a #90 carb jet, then lay it in a piece of 1/4" hose then flow it again. it still flows the same amount, lay that same jet in a 2" hose and it still flows the same amount. This is looking at the exit flow only, not what changing the input would do to flow.

The amount of oil leaving the rod is determined by the bearing to rod journal clearance not the side clearance.

That is why i asked about your research. I was wondering how you measured the increase of oil on the cylinders walls and what effect it had on the engine...

Keith

[Wolfplace]

Not to be redundant but,,,

Or in real teknikacal terms,,,
Putting a big leak downstream of a small leak doesn't change what is going to come out of the end,,,

[Strange Magic]

The amount of oil leaving the rod is determined by the bearing to rod journal clearance not the side clearance.

The amount of oil leaving the rod is determined by the bearing to rod journal clearence and the connecting rod side clearence.

Hence the words "leaving the rod".

Mathematical area calculations without factoring pressures are not a true indication of what is really going on.

[BLACK BART]

Strange Magic, the SMALLEST leak in the system is what controls how much oil is dispersed on to the cylinder walls.



You have the correct understanding here:

"If I understand you correctly, you are saying that weather the side clearance is .030 or .020 or even greater or less in differential (regardless of the difference in side clearance), it has no effect on how much oil is released from that reciprocating assembly during rotation."



Let's say your vertical clearance allows five gallons per hour leakage and your side clearance allows ten gallons per hour leakage, you can't get any more than five gallons per hour leakage from the rods because the vertical clearance will only allow that much. Since the square inch area of the vertical clearance is roughly one tenth the square inch area of the side clearance, the vertical clearance has to be the limiting factor, not the side clearance. Look at the math I posted earlier and compare the actual areas of the two clearances and it is easy to see the vertical clearance is smaller and also the limiting clearance. Hope this helps. CJ

[Strange Magic]

Look at the math I posted earlier and compare the actual areas of the two clearances and it is easy to see the vertical clearance is smaller and also the limiting clearance. Hope this helps. CJ

Yes, I looked and I didn't see any calculations on the PPH (pounds per hour) of liquid (oil at different viscositys at different operating temps) under pressure.

Pressures have a direct relationship towards volume and the less pressure at the bearing will produce less volume after the rod than an engine with higher pressures. It just makes practical sense. You can not discuss mathematical calculations of area unless you calculate psi on a given set viscosity of fluid.