Extended sump question

[brian]

Thanks Mad Dog for pointing out a pet peeve of mine. You are complelety right. No more puking because the engine builder can't figure out the windage.

[SR Racing]

I wouldn't shoot from the hip and say, yes you can run lower oil levels until I did some data acquisition on real track sessions. But I think with proper windage you could lower oil levels using a larger sump. Most of the mess from a Vee is oil that is forced out the front pulley from case pressures and braking. A larger sump would keep much of the oil from getting into the front of the case.

[hardingfv32-1]

1) I'm not sure the crankcase oil has a good enough flow path to the cam gear chamber to the cause the front pulley oil leakage issue. I think it is a blow-by phenomena. Also, there is a lip in the crankcase for removing the oil from the cam gear that would keep the chamber pretty dry. I run serious engine slope, about 10 degs, and do not have an issue with oil out the front pulley hole. I can fit only a 1" deep sump and must use an Accusump.

2) Remember, only 1/2 the sump capacity is ever available before the pick up is exposed while in a turn. I'm not sure you are going to get far with any effort to lower the oil level using the 1 qt sump.

Brian

[jpetillo]

2) Remember, only 1/2 the sump capacity is ever available before the pick up is exposed while in a turn. I'm not sure you are going to get far with any effort to lower the oil level using the 1 qt sump. Brian

Brian, you said the above and asked earlier "If we use a wide 2 qt sump, the pick up tube lowered to the floor of the sump, and assume it is full when we enter the turn ... then we should have access to 1 qt before the pickup is starved for oil. Is my thinking correct?"

Yes, you're thinking is correct on both accounts, but it's slightly more complicated which is why others are adding in the "I thinks". I'm not sure of the right solution yet, either. Let me throw out a few things and see if you folks agree. (Before I get flamed too badly, let me mention that numbers I'll state below are approximate, although it would be easy to come up with more precise numbers - always fun.)

Assuming a 1G corner or 1G braking to make it simple. In this case the oil will move to a position where the surface has a roughly 45 degree slope. If we start off with the same oil height as before, the larger sump will force more oil up into the crankcase as it takes on this angle (I'm assuming air pockets can get into the sump). In the picture I drew for myself that has some arbitrary depth, for whatever size winged rectangular sump that's sized the same as the bottom of the crankcase, you will not have 1/2 of the sump capacity available anymore for pickup - more like a bit over 1/4 of the capacity - still good. But, 1/4 of the capacity has been sloshed up into the crankcase, and that might be too high. (These are hand waving numbers based on the pictures I drew.)

If I now get that picture and made the sump twice as deep, then what was 1/4 capacity available becomes 3/8 capacity of double the volume, so 3 times more oil available - much nicer. However, I've still only sloshed about the same volume of oil into the crankcase as before - still nice. But, you can minimize sloshing back up by making the width of the sump smaller or shaping it differently on top. You can also lower the oil level by this sloshing amount and forget it. I'd choose the former, because it's dangerous to guess sloshing amounts.

To minimize sloshing of oil back into the crankcase, the top of the sump should be angled down at the angle for maximum G's. But, you still want the full width side to side for whatever direction the G force is in to give the maximum amount of oil available. There's always a tradeoff.

I apologize for the free streaming thoughts. I know I didn't write enough detail to fully explain what I was thinking - I hope it was tolerable. Please let me know what you think and also correct me where I'm wrong or straying from reality.

If anyone can send me crankcase dimensions so I can get a better idea of the height of the oil we typically run in the crankcase and then also what the opening hole size down into the sump is that would be helpful. What sustained cornering and braking G's can we assume?

John

[SR Racing]

John,

I think we can assume that "sustained" (a couple secs) lateral G's will never be more than 1.7 or so. Braking appears to be about 1G. Forward acceleration G's .. under .3. This is from a data log sent to me by Stephen Saslow (thanks) that I happen to have on this computer. (Portland). I am sure most all tracks will be at or under these.

The hole in the bottom of the case is ~3.3" in diameter. The depth of the oil at the bottom of the case when idling is about 1.3+ inch. (Assuming a flat mounted engine and typical oil levels)

I think if you were to use the large slimline type sump you would do some different windage design. Actually a tube around the hole at the standard sump pickup with a hole at the back of the tube could optimize keeping most of the oil in the lower center section. (In corners and under braking.) A little hard to describe.

[SR Racing]

1) I'm not sure the crankcase oil has a good enough flow path to the cam gear chamber to the cause the front pulley oil leakage issue. I think it is a blow-by phenomena. Also, there is a lip in the crankcase for removing the oil from the cam gear that would keep the chamber pretty dry. I run serious engine slope, about 10 degs, and do not have an issue with oil out the front pulley hole.

You are correct in that the hole feeding the cam gear area is small. (Pencil size on most cases.) Then there is a "scaper" hole of sorts at the top of the cam gear fro putting it back into the main case. I am sure that this works well in the BUG application. However with blowby I suspect that the thin hot oil is forced through that oil pretty well and the pressure also keeps the "scraper" from even working. You see lots of vee's come in with oil all over the fire wall and top of the engine. This always seemed to me to be oil forced through the front pulley and flung all over the place. It will vary across engines.

[jpetillo]

Jim, thanks for the information. Yes I think I know what you're talking about with the tube. I agree. it probably wouldn't be hard to keep most of the oil in the bottom.
John

[Matt King]

I think if you were to use the large slimline type sump you would do some different windage design. Actually a tube around the hole at the standard sump pickup with a hole at the back of the tube could optimize keeping most of the oil in the lower center section. (In corners and under braking.) A little hard to describe.

Same principle as the surge tank in most factory EFI fuel tanks that keeps the fuel from sloshing away from the pump pickup when the level is low. Alternatively, if there is enough space in the sump to work with, you could install swinging trap doors like some of the road race V-8 oil pans use.

[jpetillo]

Same principle as the surge tank in most factory EFI fuel tanks that keeps the fuel from sloshing away from the pump pickup when the level is low. Alternatively, if there is enough space in the sump to work with, you could install swinging trap doors like some of the road race V-8 oil pans use.

MAtt, Do you have a link to something that uses the swinging trap doors?

[SR Racing]

Here are some pictures of oil control doors on a V8 pan.

http://www.autocomponenti.com/performan ... il_pan.htm
http://www.circletrack.com/nls/76818/photo_03.html

Due to the design of the split case ACVW and sump size,it might be a bit of a chore to make decent performing oil control doors on one. Active oil control works much better then static, but I don't think I have ever seen any used on an ACVW.

[jpetillo]

Jim, thanks. Those helped me understand the trap door concept much better. It seems like the idea is to keep the oil that wants to flow up due to cornering near the pickup, so that it doesn't flow away from the pickup on it way up. In some sense, our reduced 3.3" diameter hole sort of does that to a large extent. Of course the 3.3" hole is also the reason for the starvation because it cuts off oil from flowing down during hard cornering and the sump empties - but we can't do anything about the hole size.
If I understood what you described earlier about adding a downward tube, again because of the 3.3" hole, I think that would do almost as much as we can to keep the oil near the pickup, like the trap doors concept does. We need to make sure that the tube doesn't trap air down the bottom as we return to the 0.3 G acceleration.
I need to still think about it more, but does that make sense? John

[Mad Dog Racing]

"Thanks Mad Dog for pointing out a pet peeve of mine. You are complelety right. No more puking because the engine builder can't figure out the windage."

Brian, I'm always in enough trouble with engine builders, I didn't make the comment to criticize any of them. I said I run as much oil as I can without putting much to the catch tank. That's my choice. In the old days, I ran a quart over the stock mark because that's what everybody said to do and my catch tank was mostly dry. Now with better tires and suspensions and more revs, I'm running a lower oil level , I'd just worry a lot less with more oil around the pickup and less up in the case.

On the capacity in the sump under cornering, it seems like the small top opening area would have more influence on the displacement of oil than the larger sump area. It seems to me the "lost oil" in the larger sump would not be significantly more than the "lost oil" in the smaller sump. If it's half of the .25 qt in the small sump, I would expect it to be closer to the same amount lost, not the same percent, in the 1 qt sump in the same period of time. I realize that what I'm doing is not carrying things to steady state, but if it takes longer to get to steady state, I'd hope not to get there as often. The trick is, do you reach steady state in .01 sec, .1 sec or 1 sec? Don't know. To me it looks like when you lose 50% of the oil in the current sump, you will likely still have 6 or 7 times as much oil in the big sump and when the big sump reaches 50%, you will still have twice as much oil as the little sump had before you even started the corner.

Recognizing that the above is nowhere exact because the pump is pumping out oil all the time and there is oil running into the sump all the time, even during cornering. It still looks good to have the big sump.

[hardingfv32-1]

So has anyone made a formal request to the CRB?

Shall I send this:

Formula Category
9.1.1.C.5.D.29

Any oil sump may be fitted with a max exterior dimension of 10.0" wide and 11.0" long and max capacity of 2.0 quarts. The oil pickup pipe may be modified. Accumulators (Accusump) may be fitted.

Brian Harding

[Matt King]

Send it and I'll send it too, after I figure out the protocol for emailing the CRB!

[jpetillo]

So has anyone made a formal request to the CRB?
Shall I send this:
Formula Category
9.1.1.C.5.D.29
Any oil sump may be fitted with a max exterior dimension of 10.0" wide and 11.0" long and max capacity of 2.0 quarts. The oil pickup pipe may be modified. Accumulators (Accusump) may be fitted.
Brian Harding

Brian, no don't send it yet. I like what you wrote - nice and simple - but we may want more freedom. Although the bigger sump is clearly a great improvement, it doesn't necessarily solve the problem completely. Like Mad Dog says, it's all about rates, and the steady state situation. I've been going through some mental and paper and pencil models, and there may be some simple mods that will help a lot more. Just don't want to forever live in shame by saying something stupid before I've convinced myself. After I've convinced myself, then I don't mind saying something stupid! John