Any experience in main cap dividers to oil pan?

[Jeff Lee]

Are these segment barriers intended to manage air flow or oil flow?

In terms of air flow, in a four cylinder engine, one wants to either seal the bays completely or make them completely open. Small breathing holes are worst, because they neither allow the air to work as air spring nor allow for relatively constant pressure in the bay.

For a cross-plane V8 engine, managing the air flow is harder because per cylinder displacement is usually even larger and because there is no way to seal off the pistons on the same crank pin. Because of this, theory says that pulling a vacuum in the crankcase is especially beneficial in a big V8.

So what’s the theory why one would want to hose bay to bay dividers in a big wet-sump V8 without crankcase vacuum?

As mentioned above, I THINK this could reduce the amount of oil roping around. Isn’t that an avenue to pursue? Your obviously more versed in this than I so I appreciate your input.
NHRA does not allow for any vacuum pumps in my class and am limited to a pan-e-vac or creative use of PCV valves and such. Used the creative PCV with a low speed / high speed system in Stock Eliminator. It would pull some impressive numbers on the dyno but when I removed the system from the car to see how it performed, I saw no change in performance. I believe a pan-e-vac will do a better job.

[Kevin Johnson]

Radius the ends of the caps. I believe you are running 4-bolt mains -- if they are not radiused already then you should do this. It is not an accident that OEM caps are often radiused. Numerous examples. It allows better bay to bay breathing -- lower pumping losses. Just don't extend your dividers past the top bolt pad (center two main bolts of four).

Yes, I have Pro-Gram Engineering 4-bolt caps on the center and their 2-bot caps front and rear. I am not aware of rounded main caps. Interesting idea and I’ll definitely look at that this weekend and consider incorporating that idea. Thank you.
What OEM has this feature?

The AMC V8 second main cap is rounded but the others less so. I suspect that the patterns for the others were damaged or worn and a decision was made for the foundry to adjust the molds rather than spend the money for new ones.

Packard, Studebaker, Chevy, Oldsmobile, Buick, Mercedes, Nissan, Toyota ...

After-market caps are generally squared off. After-market pickups are generally square boxes. Square shapes are easier to design and manufacture.

There are MANY more but I don't have the time to go through and find pictures of dozens of different engines. I think you get the gist.

[ptuomov]

Are these segment barriers intended to manage air flow or oil flow?

In terms of air flow, in a four cylinder engine, one wants to either seal the bays completely or make them completely open. Small breathing holes are worst, because they neither allow the air to work as air spring nor allow for relatively constant pressure in the bay.

For a cross-plane V8 engine, managing the air flow is harder because per cylinder displacement is usually even larger and because there is no way to seal off the pistons on the same crank pin. Because of this, theory says that pulling a vacuum in the crankcase is especially beneficial in a big V8.

So what’s the theory why one would want to hose bay to bay dividers in a big wet-sump V8 without crankcase vacuum?

As mentioned above, I THINK this could reduce the amount of oil roping around. Isn’t that an avenue to pursue? Your obviously more versed in this than I so I appreciate your input.
NHRA does not allow for any vacuum pumps in my class and am limited to a pan-e-vac or creative use of PCV valves and such. Used the creative PCV with a low speed / high speed system in Stock Eliminator. It would pull some impressive numbers on the dyno but when I removed the system from the car to see how it performed, I saw no change in performance. I believe a pan-e-vac will do a better job.

I don't have much experience on this, but I have thought about it some. Mostly I'm just asking people what is the logic why they do what they do.

Generally, I believe that there is a conflict between managing air flow and managing oil flow in a wet-sump crankcase operating at atmospheric pressure. The air flow and oil flow interact, too, so I personally view solving the air flow problem a priority. In a big V8, the air flow is almost entirely caused by the piston pumping pulses and the air flow caused by the crankshaft rotating is relatively unimportant. To manage the piston pumping pulses, in my opinion one must leave generous enough breathing areas between the bays if the pan is small and between the bay and the pan if the pan is large. What this means to me based on my logic is that the windage tray can only have those bay-to-bay dividers if it has huge breathing holes into a big pan.

Furthermore, I don't really understand what is the intended benefit of those bay dividers in the windage tray on a wet-sump engine with atmospheric crankcase, is it to manage oil flow or air flow or what?

[Kevin Johnson]

If the rotating airflow was unimportant then the windage cloud would not draw in oil droplets at higher rpms because of the pressure differential. Einstein's Tea Leaf Paradox explains the counter-intuitive effect.

Large displacement engines with wet sumps that do not have proper shielding of the oil sump reservoir or a deep physically separated reservoir level will experience the oil being pushed to one side of the pan and this invites vortexing of air through the oil to the pickup because the surface of the oil on one side of the sump is markedly lower. In that respect, the air displaced by larger diameter pistons and/or increased stroke is very important.

When Porsche developed their V8 to replace the Mercedes M10x V8 mule engine used in chassis development, they initially shielded the sump with woven screening (and they experimented with mesh sizes) as well as using a special pickup head/body. In the later engines they went with a less expensive sheet metal shield and borrowed the less expensive pickup design from the 944. The original bedplate design in the Porsche V8 had much more attention to windage airflow. Unfortunately that design failed during extended durability testing and a design was created that was stronger but was an absolute disaster with respect to airflow. People nowadays forget that Porsche did not have deep pockets at that time for product development that would require clean sheet redesigns.

[ptuomov]

If the rotating airflow was unimportant then the windage cloud would not draw in oil droplets at higher rpms because of the pressure differential. Einstein's Tea Leaf Paradox explains the counter-intuitive effect.

I'm not saying that a small effect doesn't exist. I'm simply saying that the effect of rotating crankshaft is totally trivial compared to piston pumping pulses in a big cross-plane V8. This is an application specific comment, for a motorcycle inline four, the rotating crankshaft may be significant and solutions may be different.

[Kevin Johnson]

That was an idea floating around when I first started making scrapers sixteen years ago. Another version is the opposite, i.e., that it is important for big v8 engines but not small engines (v, boxer, inline, etc.). It really is not controversial at this point.

[ptuomov]

That was an idea floating around when I first started making scrapers sixteen years ago. Another version is the opposite, i.e., that it is important for big v8 engines but not small engines (v, inline, etc.). It really is not controversial at this point.

Once I saw the details of the Chrysler crankcase air-flow simulations, it become not controversial personally to me. I think science is settled on this one, with a typical 6L V8, the piston pumping pulses are the elephant and the crankshaft rotation is the mouse.

[Kevin Johnson]

Ok, Tuomo,

I have pasted in a picture of the current oil pan gasket for the monster V8 in the current crop of Hemis.

The windows are a type of scraper technology. They are used in the old Miata B6 and BP trays (~30 year old design). They were used in the Studebaker Type R trays from over 50 years ago. They were used in the Northstar V8.

You can choose to focus simply on the pumping losses -- that is fine with me. The addition of a dedicated scraper will still reduce losses over and above this. The smooth interior of the trays will still initiate early oil entrainment issues.

[ptuomov]

Ok, Tuomo,

I have pasted in a picture of the current oil pan gasket for the monster V8 in the current crop of Hemis.

The windows are a type of scraper technology. They are used in the old Miata B6 and BP trays (~30 year old design). They were used in the Studebaker Type R trays from over 50 years ago. They were used in the Northstar V8.

You can choose to focus simply on the pumping losses -- that is fine with me. The addition of a dedicated scraper will still reduce losses over and above this. The smooth interior of the trays will still initiate early oil entrainment issues.

I agree that preventing the oil that is sprayed from the bearings from rebounding back into the crankshaft is beneficial. Also as you say, meeting that goal is often in conflict with the goals of air flow management. Semantics aside, the windage tray or scraper or whatever that has a large breathing area but nevertheless prevents the oil droplets from rebounding back to the crankshaft should work well. Given the direction of oil spray, breathing area in the main webs and under the main caps is especially beneficial as it doesn’t conflict too much with oil flow management. That’s why I’m wondering about the motivation for those bay to bay dividers in the windage trays shown earlier in this thread.