Oil Sump Rule Change

[smsazzy]

Why should the volume be restricted? What purpose does that have?

Why not say that it simply cannot hang below the car?

[brian]

Volume restriction will reduce attempts to do more with the rule change. Like creating a virtual dry sump. I have no problems with the folks that think they need this rule change, I just don't want to start another have to have upgrade.

[jpetillo]

Brian, how could it create a virtual dry sump.

John

[fvracer]

John,

If the sump is large enough to hold the entire engine oil supply so that no oil is in the case, you have a virtual dry sump.

Doug

[hardingfv32-1]

Yes, the case could be dry when you are standing still, but this has nothing to do with the benefits of a "dry sump" oil system.

No matter what the oil system, when you are in a turn a lot of oil is not going to be returning to the sump. With our engine, at least 1 qt of oil is out of the sump at 5000 rpm. Throw in some some car motion and you have another 1/2 qt in use above the sump. Assuming you use about 4 qts, that leaves 2.5 qts in the sump below the camshaft. IF you have a tight windage tray there should not be any oil sloshing into the camshaft from the sump. There is NO benefit to store the oil one level lower. Having a large sump is not going to SUCK any oil downward.

Brian

[Matt King]

In addition to consistent oil pressure, the main advantage of a multi-stage racing dry sump is creating vaccum in the crankcase that significantly improves ring seal and frees up considerable HP. I don't think that will be an issue with an oversize wet sump!

[jpetillo]

Yes, the case could be dry when you are standing still, but this has nothing to do with the benefits of a "dry sump" oil system.

No matter what the oil system, when you are in a turn a lot of oil is not going to be returning to the sump. With our engine, at least 1 qt of oil is out of the sump at 5000 rpm. Throw in some some car motion and you have another 1/2 qt in use above the sump. Assuming you use about 4 qts, that leaves 2.5 qts in the sump below the camshaft. IF you have a tight windage tray there should not be any oil sloshing into the camshaft from the sump. There is NO benefit to store the oil one level lower. Having a large sump is not going to SUCK any oil downward.

Brian

I agree with Brian, here - and Matt. This is why I asked the question. Just because it's dry doesn't mean you get the vacuum benefit of the dry sump, which seems to be the critical issue.

I have a few questions about real dry sumps that would be applicable to our engines if it were allowed by the rules...
- What volume of oil is stored separately from the engine?
- Where is the oil pickup located?
- Is the vacuum generated because there is no crankcase breather?
- If we used a breather, would that negate the vacuum benefit of a dry sump? - would it negate the full benefit of the dry sump?

John

[SR Racing]

I have a few questions about real dry sumps that would be applicable to our engines if it were allowed by the rules...
- What volume of oil is stored separately from the engine?

4 to 6 quarts is usually required. Assuming proper oil tank design etc. The only issue is oil temp. The more oil in the resevoir the lower your oil temps remain.

- Where is the oil pickup located?

The system used on FST uses the standard pickup in the VW case. (It can be extended and used with a extended sump if you choose.)

- Is the vacuum generated because there is no crankcase breather?

Note that in most fully dry sumped engines. There are 3 to 5 stages. 2 or 3 are used as scavaging pumps and 1 or 2 are used as pressure pumps. The ACVW pump that is used in the FST is a two stage pump. One slightly bigger than the other. The larger pump is the scavage pump and the smaller one is the pressure pump. While the case is scavanged pretty well, a significant vacuum is never acheived. However case pressures are very low. IE. You engine is typically clean enough to eat off of.

- If we used a breather, would that negate the vacuum benefit of a dry sump? - would it negate the full benefit of the dry sump?

In any case, you would always use a breather. On big multistage dry sumps the breather may use a regulator to keep pressures from going too low and sucking in a gasket. On the typical 2-3 stage pump the engine is vented to the oil tank and the oil tank is vented through a filter to the atmosphere (or puke tank which is vented) So you really never develop much in the way of a vaccuum. You simply keep case pressures much lower.

A significant advantage of the dry sump is decreased windage, which is extreme on a Vee due to the higher oil levels you must run. With a dry sump, and at idle on a FST, the dip stick usually shows nothing at all. Lower case pressures do help ring seal as pointed out. Also oil temps drop radically. Most of the oil is always in the tank and no longer sitting in the engine getting heated by blow-by.

[SR Racing]

We have worked on several current race engines that use a dry sump system that uses the production oil pump for pressure and an external 2 stage for scavaging. Hybrid dry sumps systems are becoming very popular now in stock production engines.(the Corvette and some imports.) With all the typical advantages,they can eliminate the oil pan to easily lower the engine or increase ground clearance and lower the center of gravity.

[Dave]

Great write up Jim. I am in favor of dry sumping our motors. I think extending the sump or upping the capacity would be like pissin' in your pants it will give you a nice warm feeling until the smell kicks in. For a one time cost of less than $400 you are done. Jim can correct the prices but about $100 of that for the pump, $50 or so for hose and fittings, and less than $200 for a custom tank. No more mess, No more over filling ,No more blown engines from lack of oil. And no cracked sump from going off track and screwing up my race. That was my recommendation to the CRB.

Dave

[jpetillo]

Jim, thanks. That was very helpful.

A few more questions to the masses...

1) So, if we put a breather from the crankcase to the outside that prevents any vacuum from forming, does that decrease the effectiveness of the dry sump system? If not, then if we want to include dry sumps in the rules for a Vee that won't cause a HP advantage, we make the breather mandatory. The problem would be enforcing it.

2) I don't know where the standard pickup is, but I'm assuming it would be something like a much shorter version of our current sump/pickup. If that's the case, why wouldn't this system be just as prone to oil stacking up the side of the crankcase and not making it to the pickup as what we have now? I can only see that having a larger volume of oil in the system via the external tank allows this system to pump so much oil into the engine that it eventually has to make it back to the pickup. If so, that's fine. I'm not poking holes - just trying to understand.

Anyway, we'd still have windage losses in the corners (maybe more windage losses than now), but perhaps much less in the straights.

Please steer me back on the road where I may have veered off. Thanks for bearing with me.

John

[SR Racing]

So, if we put a breather from the crankcase to the outside that prevents any vacuum from forming, does that decrease the effectiveness of the dry sump system? If not, then if we want to include dry sumps in the rules for a Vee that won't cause a HP advantage, we make the breather mandatory. The problem would be enforcing it.

No. A breather is always used. And since you require a puke tank that also has a breather. (or is vented in some way.) We all use breathers in FST.

I don't know where the standard pickup is, but I'm assuming it would be something like a much shorter version of our current sump/pickup. If that's the case, why wouldn't this system be just as prone to oil stacking up the side of the crankcase and not making it to the pickup as what we have now? I can only see that having a larger volume of oil in the system via the external tank allows this system to pump so much oil into the engine that it eventually has to make it back to the pickup. If so, that's fine. I'm not poking holes - just trying to understand.

The pickup can still be extended or not. You can use an extended sump or not. Remember you have 4+ quarts in a storage tank separate from the engine case. The oil is pumped from there to the journals. The scavage pump removes it from the bottom of the case and sends it back to the storage tank. The pressue pump feeds the bearings. Typically you have 4+ quarts of oil to run the engine on before you have to get oil from the case back to the tank. You don't really need much more oil than you have now, it's just that it's always in the tank ready for use. Even in long extended corners, you will have plenty of oil available for the bearings. In our data acquisition on the FST's, when warm the oil pressure never drops below 30 lbs. Cornering does not affect it at all, only RPM.

Anyway, we'd still have windage losses in the corners (maybe more windage losses than now), but perhaps much less in the straights.

No, you would have decreased windage everywhere. On a vee you have 4+ quarts in the case. Dry sumped there is very little oil in the case. In the corners some oil would not be scavaged and would go to the valve covers etc, but windage is not an issue in the corners. That isn't where you need HP. As soon as the oil goes back to the bottom of the case, it is pulled to the storage tank.

On the straights, the case is totally empty, so windage has no play at all.

[SR Racing]

We did a lot of dyno testing with the 2 stage dry sump on the FST 1600 ACVW engine. There was maybe a 1+HP gain using the dry sump. (base HP in the 85 area).
On track dynamics would predict maybe another 1+ hp gain there since windage issues are more at play. A V8 dry sump system usually provides about 2 to 3% HP. The greatest thing about a dry sump system on a ACVW (2 stage system) is that you have steady oil pressure all the time and as much as 20 degrees lower temps. (and less oil drops on your trailer floor) (checking the oil is nicer also. No dipstick. Just look in the tank and see if it's about right.)

[jpetillo]

Jim,

Answers to questions helped a lot, but just generate more questions. Again, Jim, thanks for spending the time.

With all due respects, that didn't necessarily all add up. Not just the dry sump, but what we're claiming is happening with the Vees supposedly losing oil pressure. Aside from the cooler oil and some relief from windage - mostly in the straights - I don't see how this will solve the Vee oil loss problem if it has the same amount of oil in the reservoir. Let me explain.

If we're saying that our current amount of oil can't make it down the sump hole during cornering, that problem wouldn't change with the dry sump. Is the only difference that at the end of the straight the dry sump will have a full supply in the tank, while the Vee has it in the crankcase? In that case, the dry sump just buys you time, but if enough time goes by it will have the same problem. At 1 quart every 4 seconds, that may not sound like a lot of time - but may be enough.

Also, if there's a breather from the crankcase to the outside, how can there be a vacuum in the crankcase?

I'll hold other questions until we get through these.

Thanks again, John

[SR Racing]

If we're saying that our current amount of oil can't make it down the sump hole during cornering, that problem wouldn't change with the dry sump. Is the only difference that at the end of the straight the dry sump will have a full supply in the tank, while the Vee has it in the crankcase? In that case, the dry sump just buys you time, but if enough time goes by it will have the same problem. At 1 quart every 4 seconds, that may not sound like a lot of time - but may be enough.

Maybe it's tough to explain properly. Let say you have total 5 quart system.

The scavange pump does nothing but take oil from the case and dump it to the separate oil tank. Typically there is little or no oil in the case. It is all in the tank. The pressure pump gets oil from the oil tank and fills the oil journals. So you always have pressure even if there is only .5 quart in the tank and the rest in the case. (Not likely to happen.) The 1 quart per 4 second thing quote here by someone is most certainly open pressure pump flow. We don't have that. I doubt that the pump flows even 1/2 of that when pressureizing.

Also, if there's a breather from the crankcase to the outside, how can there be a vacuum in the crankcase?

Also unlikely with the 2 stage ACVW system. However it does occur on the bigger 3 and 5 stage systems. Even on the 2 stage system, At the end of the straight when you lift on the throttle and downshift the scavage pump is screaming and sucking any oil (and air) oil from the case. The engine is also developing negative pressures due to the throttle being closed. So even with a vent you can lower case pressures dramatically. (On a precision 3 or 5 stage system the certainly can go negative. That is why a filter is installed on any vents. To keep from sucking dirt into the crank case under these conditions. ) On the system we are using, the case pressures are lower all the time and possibly as low as zero, but never negative. (vacuum.)

We have hundreds of hours of track time on many tracks with the FST ACVW and the 2 stage dry sump with data acquisition. Oil pressure is not an issue with a proper dry sump system. (Not to mention cooling.) While we probably never see a vacuum in the case under throttle, case pressures are still much lower.

BTW, on most dry sump tanks you can look in the tank when the engine is running and see the oil flowing into the tank from the scavage pump. It is a foamy broth. (Lots of air in it.) That is air being removed from the case.

On a vee when you go into the corner you have all your oil in the case. On a dry sump, there is no oil in the case.

Hope that helps. Fire away.

[SR Racing]

Great write up Jim. I am in favor of dry sumping our motors. I think extending the sump or upping the capacity would be like pissin' in your pants it will give you a nice warm feeling until the smell kicks in. For a one time cost of less than $400 you are done. Jim can correct the prices but about $100 of that for the pump, $50 or so for hose and fittings, and less than $200 for a custom tank. No more mess, No more over filling ,No more blown engines from lack of oil. And no cracked sump from going off track and screwing up my race. That was my recommendation to the CRB.

Dave thanks,

Clearly a dry sump system would be a great improvement in many ways to the Vee. However, I did not write the CRB on this one. Using your verbage, it would be pissing into the wind. Lots of opposition.

There are some downsides to the dry sump system:

Finding a tank location. We have converted several Vee chassis now and have always made it happen, but it usually takes a custom tank. This is about $300.
Fittings and hose as much as $100
Dry sump pump ~$100
Also some people may not be able or willing to do it themselves. And you would probably have a 6-8 lb weight add.

You are still talking less than a set of tires though. Also, some people have probably spent that much in trying to cool their engines 20 degrees and oil blown out the orifrices.

[brian]

A couple of reality checks:
First, excessive oil leaking is not caused by a wet sump. Assuming the engine has been put together correctly, it is caused by poor ring seating and resulting blowby. A dry sump will reduce the oil leaks but the blowby will continue. If a multi-stage scavanging system is used, ring seal can be improved by pulling vacuum, but the multi-stage approach is not being considered for vees. All vees will incur leakdown soorer or later, it all depends on prep and freshing up the top end must be done at least once a year.

Secondly, oil does not heat itself. If you are having problems with high oil temps chances are you are cooking the heads. There's nothing in a motor like our air cooled heads to heat up the oil. Additional cooling will only mask the hot head issue that is really costing you hp. If I have a hot engine I start with cyl head gauges to see what's happening there. Well over half of the vees I've looked at have poor cooling design.

I kinda like the idea of a dry sump but it will become a have to have since Jim's already proved it's worth a bit of hp.

[Matt King]

If a dry sump is worth 1-2hp, maybe the rules should be you can either have that, OR one of these trick new intake manifolds. Since the dry sump costs half as much, contributes to better engine reliability, and keeps more oil off the racing surface, it seems like a no-brainer. But instead, we have $1200-plus intake manifolds. Woo-hoo. Way to keep the class alive!

[Bill Carroll]

Why not use an accumulator? like accusump, it will maintain positive oil pressure and we don't have to worry about the other guy having another 1 HP. Correctly built engines don't need a dry sump and synthetic oil works fine at the higher temp.

[jpetillo]

Maybe it's tough to explain properly. Let say you have total 5 quart system.

The scavange pump does nothing but take oil from the case and dump it to the separate oil tank. Typically there is little or no oil in the case. It is all in the tank. The pressure pump gets oil from the oil tank and fills the oil journals. So you always have pressure even if there is only .5 quart in the tank and the rest in the case. (Not likely to happen.) The 1 quart per 4 second thing quote here by someone is most certainly open pressure pump flow. We don't have that. I doubt that the pump flows even 1/2 of that when pressurizing.

No, you've explained it quite well several times. I'm the one apparently not explaining myself for you to know what I'm asking about - sorry about that. Anyway, it sounds like your response agrees with what I said. So, we're good here.

Also, if there's a breather from the crankcase to the outside, how can there be a vacuum in the crankcase?

Also unlikely with the 2 stage ACVW system. However it does occur on the bigger 3 and 5 stage systems. Even on the 2 stage system, At the end of the straight when you lift on the throttle and downshift the scavage pump is screaming and sucking any oil (and air) oil from the case. The engine is also developing negative pressures due to the throttle being closed. So even with a vent you can lower case pressures dramatically. (On a precision 3 or 5 stage system the certainly can go negative. That is why a filter is installed on any vents. To keep from sucking dirt into the crank case under these conditions. ) On the system we are using, the case pressures are lower all the time and possibly as low as zero, but never negative. (vacuum.)

We have hundreds of hours of track time on many tracks with the FST ACVW and the 2 stage dry sump with data acquisition. Oil pressure is not an issue with a proper dry sump system. (Not to mention cooling.) While we probably never see a vacuum in the case under throttle, case pressures are still much lower.

Good. So, do you think there is enough of a lower pressure to result in a measurable increase in HP in a Vee's crankcase? Has that been measured?

BTW, on most dry sump tanks you can look in the tank when the engine is running and see the oil flowing into the tank from the scavage pump. It is a foamy broth. (Lots of air in it.) That is air being removed from the case.

Understood. It was just hard to believe that a breather would have so much restriction that a scavenger pump would be able to make a significant change to the pressure in the system.

On a vee when you go into the corner you have all your oil in the case. On a dry sump, there is no oil in the case.

Yes, I think we've agreed on that a few times.

Hope that helps. Fire away.

Thanks again - yes it does help. I have completely understood how the systems work. I just don't have a working experience using them so please excuse my skepticism. It was hard for me to believe that the oil is sucked out so fast that a measurable pressure difference in the case would result even with a breather. How about a better breather?

The point is that if we can state that the dry sump system we would allow for a Vee could cause no significant pressure difference in the crankcase, then there is no performance gain, and then they could be allowed by the rules and used by those who want to anti up.

It would also seem that the Accusump would provide the same improvement as the dry sump in terms of storing oil in an outside tank and keeping it out of the crankcase in the straights. I know that the Accusump capacities tend to be smaller than 4 quarts, but perhaps this is easier to do for the average Vee racer, and then maybe a cheaper alternative if it's a do-it-yourselfer. I know this is allowed right now.

I'm trying to argue for a "sump" rule that let's us do whatever we want by mitigating any potential performance gains. The less restrictions, the better.

John

[Bill Carroll]

An accumulator system only needs a few seconds of oil to protect the engine in the turns, 4 quarts (extra) is way too much.

[SR Racing]

We have 1 qt systems that are adequate for a Vee.

Jim

[SR Racing]

[It would also seem that the Accusump would provide the same improvement as the dry sump in terms of storing oil in an outside tank and keeping it out of the crankcase in the straights. I know that the Accusump capacities tend to be smaller than 4 quarts, but perhaps this is easier to do for the average Vee racer, and then maybe a cheaper alternative if it's a do-it-yourselfer. I know this is allowed right now.

It will protect the engine, but isn't perfect. When a Vee gets warm the oil pressure drops pretty low. The accusump uder this condition will dump all of it's oil into the case. (It typically tries to maintain ~20lbs). So when you lift on the throttle you now have another 1 qt in the case eventually. That is added to the level already there and being thrown into the corners and/or towards the front pulley. The engines I have seen with accusumps did blow more oil, but were probably protected.

I'm trying to argue for a "sump" rule that let's us do whatever we want by mitigating any potential performance gains. The less restrictions, the better.

I understand, but I think you will find that a dry sump system will ALWAYS give better performace. Due to windage and case pressures. Oil is always being removed from the case so windage and case pressures will always be less. I think a limited extended sump rule (more than current) will be about all you will be able to get concensus on.

[jpetillo]

Jim,

Thanks again - I have more questions/comments.

It will protect the engine, but isn't perfect. When a Vee gets warm the oil pressure drops pretty low. The accusump under this condition will dump all of it's oil into the case. (It typically tries to maintain ~20lbs). So when you lift on the throttle you now have another 1 qt in the case eventually. That is added to the level already there and being thrown into the corners and/or towards the front pulley.

Perhaps an Accusump trying to maintain a minimum of 20 PSI will dump all it's oil into the crankcase during off-throttle, eventually. But if this is the case, then so won't a Vee pump at 15 PSI. I don't think that a 5 PSI difference for the short time we're off throttle is really significant with regard to the amount of oil going through the lubrication path. You'll be back on the gas well before anything happens, and pushing more than 20 PSI. Have you see otherwise? I guess I'm saying that I don't think this is a problem or a negative aspect of an Accusump that is significant.

Do we know the flow rate of the oil through the engine (lubrication path) vs. pressure? I'm not talking about what goes through the pump, because some goes through the pressure relief valve and doesn't contribute to engine oiling.

About oil pumps, although the quoted 1qt in 4 seconds might be less under pressure, it's probably not much less. These are positive displacement pumps,right? If so, they pump about the same volume per shaft rotation no matter what. The way these work is that the extra oil that can't be squeezed into the bearings, etc., (the lubrication path) is dumped through a pressure relief valve. So, the oil extra oil not going through the engine is always being dumped into the crankcase, but hopefully not above the windage tray.

I think we need to be careful (I do at least) that we don't confuse windage with baffling. Correct me if I'm wrong. We need to consider what's happening above the windage tray, below the windage tray but above the sump, and then in the sump. The rotating parts are above the windage, and this is where the oil returns to. This is a bad place for losses from rotating parts - is that the strict definition of windage? Then below the windage tray is where the positive displacement pump is throwing all its extra oil, which I believe may be more oil than we're pumping through the engine (I'm assuming that VW didn't put the bypass valve to dump oil above the windage tray - but you can tell me, I don't know). Anyway, the oil is better being down here than above the windage tray. Keeping oil down in this area is done with baffling, right? I'm just trying to tighten up the terminology I'm using. However, in the sump we'd also like baffling to prevent oil from climbing back into the crankcase. Is this correct?

John

[hardingfv32-1]

Off coarse you can set the Accusump at any pressure. I prefer less than 20 psi. It is a compromise, fast dump at an ideal pressure or slow dump at a survival rate.

A windage "tray" could be considered a baffle. To call the simple baffles commonly used below the camshaft in FV engines a windage tray is a stretch.

Windage is not well defined in automotive literature, but it could be considered a disturbance of air around a moving object. That being the case, a true windage tray needs to do something about getting the flying oil out of the crankcase atmosphere. This usually requires the use of a combination of louvers, screens and scrapers. These are not features of the normally found inside a FV engine.

Brian