Cobra4B

iTrader: (9)

Trying to understand exactly what happens when you run a high volume and/or a high pressure pump. I've run the high volume LS4 pump on two LS6s now w/o any issues. I'm building a LS1 for my father's Panoz that doesn't have the batwing pan so I'm taking a 2nd look at which oil pump to use; LS6 or LS4 with 42 psi relief.

I read all this conjecture about "sucking the pan dry" and putting too much oil in the top end of the motor.

1. Have there been any truly documented cases of sucking the pan dry? Or, is it internet hearsay?

2. Can you actually pump more oil to the top end of the motor?

My thinking is this... the maximum amount of flow through the engine is determined by the clearances right? So a high volume pump would just let the oil pressure come up faster and the bump would reach bypass sooner. If the stock bypass pressure is 32psi and you had a high volume pump with the same relief spring, then you'd just get to bypass sooner right? You wouldn't pump any more oil to the top of the engine?

Now how about pressure? Pressure is created from resistance to volume and/or increasing the bypass spring pressure in the pump. If you put a 52 psi relief spring in the stock pump then it'd keep on building pressure longer. If you had a high volume pump with a 52psi spring then you'd build that pressure more quickly at and at a lower rpm right? Would the increased pressure actually put more oil in the top end of the motor? Wouldn't the existing engine clearances limit actual oil flow?

Just trying to better understand what's going on. And how you could actually suck an oil pan dry.

427

iTrader: (3)

The oil pan does not end up dry normally, the engine fails before that happens. High volume pumps will pump more oil for some of the reasons you listed. Another thing is you are thinking the spring is like a regulator, it is not. A 42 pound spring will make two different oil pressures, more as pump volume is increased. The LS pump is running at crank speed, this causes volume losses as rpm increases. This loss results in pressure falling off when consumption is higher than delivery, the high volume pump holds this off to a higher rpm causing more flow when the problem is most likely to hurt you.

Kurt

Cobra4B

iTrader: (9)

I'm not quite following you.

Can you elaborate on this? I don't follow the whole 'two different oil pressures" I thought the bypass opens at a specific pressure to bleed off excess oil? I know the resultant pressure is higher than 42 psi, but doesn't that relief function as a regulator?

What is 'the problem' and how is it going to hurt the engine?

Drokkers

iTrader: (2)

sorry i cant help you, i was just reading the post.

thought this was super funny!!! ---> -My memory's not as sharp as it used to be.
Also, my memory's not as sharp as it used to be.

427

iTrader: (3)

A relief valve is a piston in a bore controlled by a short spring. The pressure of the spring is not constant, it rises as you move it farther by pushing the piston. The piston needs to move back further when more volume needs to be dumped.
A 42 pound spring might make 60 psi on a standard volume pump because the piston is say .500 up the bore to bleed off excess volume. That .500 up the bore raised the spring from 42pounds to 60 (just a guess)
On the high volume pump it may go .750 up the bore to bleed the amount of unused oil which is greater now. That extra .250 of spring compression causes the spring pressure to increase to 80 (another guess!) making the oil pressure 80 with the same base 42 spring.

The "problem" is the one you asked about, commonly called sucking the pan dry. When the oil falls back into the pan it passes by the rods/crank spinning, as they spin faster the oil returns slower as the windage in the engine is getting greater from speed. The higher oil pressure/volume is sending it up, the higher rpm is not letting it back. The problem also has a little help from piston ring leakage in the bottom crankcase area that is trying to get into the valvecovers so it can go out the breather, making oil drainback harder/slower. The problem will start as oil pressure that drops 15-20 psi at higher rpm or oil pressure readings bouncing on a mechanical gauge. The bouncing means you have a mix of oil and air. How fast the engine gets damaged depends on power levels, although no hard fast rule exists. When the oil problem happens it will normally hurt rod bearings first causing a broken rod if you don't get lucky and catch it.

Kurt

Sales@Tick

iTrader: (3)

Kurt we were assembling a LT1 motor today at the shop and Jonathan was telling me how much better the LS1 would of been in this regard if it had used the cam gear to drive the oil pump like the LT1 does than the crank like it does because of exactly what you stated about the volume losses as rpm's rise.

One of the few things the LT1 has going for it lol.

Cobra4B

iTrader: (9)

So for the road race LS1 I'm putting in this Panoz (using stock 241 heads and the stock cam with a max rpm of 6500) should I go with another LS4 pump as I have in all my Corvettes?

Is there any need for a high volume pump in a road race application where the oil temps will be in the 250-260 range and the car will see high rpm use for 30-60 minutes at a time?

And no I'm not going dry sump... been racing Z06s for years w/o an oil related failure. The LS6s just work.... why I'm not 100% sure.

Since this LS1 won't have the "batwing" pan it had me thinking about oiling issues and if I should stick with a stock LS6 pump or mildly shimmed one?

Thoughts?

Darkman

iTrader: (2)

Are you going to run an oil cooler and/or Accusump?

S10xGN

iTrader: (11)

Kurt,

Respectfully, I've got to disagree to an extent. After 35 years working in the oil industry on refinery units with many relief valves, I can tell you, the spring is a regulator up until the point where the valve is either fully open or fully closed. On a cold start when the oil is thick, the valve will be open more than usual, but will still maintain 42# until it becomes fully open. At that point, oil pressure will rise as there is nowhere else for it to go. Once hot and the oil is thin, the pressure will be maintained at 42# until the oil is so thin that the valve is fully closed. At that point the oil pressure will begin to drop. The "trick" is balancing the bearing clearances, oil viscosity, pump capacity, and bypass spring pressure. Fortunately, GM has a pretty good handle on these parameters and seldom is any "adjustment" necessary.

427

iTrader: (3)

I would use the stock pump for what you do, and I normally use .040 shim. What pan are you using now?

Kurt

427

iTrader: (3)

I have never worked at a refinery, my experience is all with car engine oil pumps. A regulator will maintain a constant pressure, like the ones used on some fuel systems with returns. The oil system uses a by-pass type system, that's why the volume increase pushes the pressure up as the valving is not sized to maintain.
GM has a very good handle on pump size although some fudge factor exists. The high volume pump is for DOD and cam phase engines, that is the reason they started using them.

Kurt

Cobra4B

iTrader: (9)

Oil cooler is already on the car. It's a larger Setrab unit. Accusump is under consideration. I've never needed one on my Z06 racecar. On the Z06 I simply have a Setrab 625 cooler and the later LS4 pump with the 42 psi relief. I run Amsoil 10w40 and a K&N filter FWIW.

This is exactly what I see with my cars with the LS4 pumps. Cold start I see 70-80 PSI. Once the car is up to temp during a race (250-260) The car stays 45-50. In some high G high RPM sections it'll get in the lower 40s, but it never drops below 40 no matter what.

On my Z06 it's stock. For this Panoz build I've ordered the Kevko LS F-body 6.5" deep road race pan with 4-way gaiting.




My goal is to set up this car right. I'm re-building it for my father since he's broken two SBFs. I know LSXs and I want to give him something that is trouble free. I know LS4 pumps work well with 10w40 oil in LS6s. However, this car won't have the batwing pan which I hear is part of the "magic" to making the LS6 heartier than LS2/3/7 when raced.

My current thinking is as follows:

* LS4 pump w/ 42psi relief
* Restricted pushrods
* Kevko gaited pan
* Vented valve covers to allow air flow for drainback

Curious of the success of the LS6 is due to the pan and whether or not I'd be better off w/ the standard LS6 pump that came on this crate motor. That said, the oil pressures I see on track in my LS6 at speed and hot are what I want to see 45-50. I really wouldn't want less on track at temp.

So I've been researching oil flow and trying to understand if a high volume pump actually pumps more oil up into the heads or if the oil is limited by the engine clearances and I'm just pumping more through the bypass (hence this discussion).

/rambling

Darkman

iTrader: (2)

A high volume oil pump is a pressure regulated device and will pump the same amount of oil at any given pressure as the standard pump. The high-volume pump will deliver higher flows at various rpm levels up to the rpm at which the maximum (regulated) pressure is obtained.

Assuming both devices are operated at the same maximum pressure the high-volume is no more likely to suck the pan dry than standard pump. If the pan does get sucked dry when operated with high-volume pump it would have been sucked dry using a standard pump under the same circumstances. If the oil is not returning to the pan quickly enough the oil return system is the problem, not the oil pump selection.

The purpose of the high-volume pump is to handle larger bearing clearances, high-temperature oil viscosity decline, and to increase oil cooling at low and mid-range rpm operation. The high-volume pump can also be used to increase capacity requirments from external devices such as Accusumps and oil coolers.

The disadvantge of a high-volume oil pump is parasitic horsepower loss.

Finally, the oil system and flow within the LS6 block is improved over the LS1.

Che70velle

iTrader: (6)

You stated you want to set this car up right. Why not go dry sump? They are expensive, yes, but also give you trouble free oiling.

Cobra4B

iTrader: (9)

Can you explain this in layman's terms? I've been googleing "pump volume vs rpm" etc. etc. and can't find anything that illustrates volume falling off.

http://www.engineeringtoolbox.com/af...aws-d_408.html

This shows flow, pressure, and power all increasing with rpm. Are you saying the rate of volume increase is diminishing as rpm increases?

Another poster mentioned that the LT, with a cam gear driven oil pump, didn't suffer this. How does that work? Last I checked the cam gear speeds up along with the crankshaft.

What am I not getting?

Cobra4B

iTrader: (9)

Expense and the fact that they have their own issues. I don't want a $4000 dry sump on a $2900 crate engine. Also, if that belt breaks or a screw backs out you can loose oil pressure.

If the old GTS-R Vipers can run ALMS with a wet sump I know it can be made to work well enough for my intended application. Yes I know they have fancy swinging pick-ups and such.

Cobra4B

iTrader: (9)

Flow creates pressure right? So it makes sense that it'd be the same. But the high volume pump will flow more with each revolution so it'll flow more at any given rpm vs. the standard pump thus resulting in higher pressure right? So the pump would reach bypass pressure earlier.

That said, it seems like the above discussion shows that the bypass can't handle the entire oil volume until the oil is very hot. So the high volume pump will create more flow and high pressure even when the bypass if fully open right?

But wouldn't the high volume pump create a higher maximum pressure over the standard pump for the reasons listed above? It would only equalize when the oil is very hot and the bypass can handle 100% of the flow to truly keep the pressure at the relief pressure?

Well high temp viscosity decline and capacity increases both apply in my situation. How does oil system capacity increasing cause a need for a higher volume pump? I thought if I use -10 lines for the oil cooler and accusump then the pressure drops would be minimal. Do I need more capacity just because the oil path is now bigger? If so, why?

Don't car about a little parasitic loss. FWIW the 2001+ LS1 and LS6 are the exact same thing other than the head casting and cam profile. The crate motor I have is a 2004 GTO crate motor.

Che70velle

iTrader: (6)

I built my own cars and raced NASCAR late models for quite a few years. We utilized $30k dry sump engines, and I never had a $4k dry sump system. You can find seriously sweet deals on used equipment, if necessary. Ive also never had any issues with belts or fasteners, nor ever knew anybody else who did.
I'd have to say that the bat wing pan must have helped with oil control, in your previous road racing. I'd also have to say that in the high g force areas of the track, you were risking it with your wet sump set up. It's in those areas, as you well know, that looking at pressure gauges is impossible. This is where a dry sump set up is appreciated. It's oil control at its finest. $2900 in a road race engine? Very impressive!

Darkman

iTrader: (2)

Yes, all else equal, the high-volume pump will hit maximum pressure earlier in the rpm range.

[/QUOTE]That said, it seems like the above discussion shows that the bypass can't handle the entire oil volume until the oil is very hot. So the high volume pump will create more flow and high pressure even when the bypass if fully open right?[/QUOTE]

No. That suggests that the manufacturer selected the wrong spring to achieve the desired pressure limitation. If that were the case, you would simply correct the spring rate.

[/QUOTE]But wouldn't the high volume pump create a higher maximum pressure over the standard pump for the reasons listed above? It would only equalize when the oil is very hot and the bypass can handle 100% of the flow to truly keep the pressure at the relief pressure?[/QUOTE]

The high volume will not exceed the maximum pressure.

[/QUOTE]Well high temp viscosity decline and capacity increases both apply in my situation. How does oil system capacity increasing cause a need for a higher volume pump? I thought if I use -10 lines for the oil cooler and accusump then the pressure drops would be minimal. Do I need more capacity just because the oil path is now bigger? If so, why?[/QUOTE]

The length of the path is a factor since pressure declines with distance as well as line size. For example, if you locate an oil cooler 10 feet away from the engine, it will create more of a pressure drop than the same cooler located 3 feet away from the engine assuming you use the same size lines. (This is simply because "pressure" in this context equates to energy, and energy is consumed by the movement of liquid from one point to another.) The obvious work around is to use larger lines (e.g. -12 AN) to cover greater distances to minimize the pressure drop. An oil cooler, in and off itself, may not create the need for a larger-volume oil pump depending on how much of a pressure drop it has created.[/QUOTE]

427

iTrader: (3)

The LT engine pump is running at cam speed, that is half crank speed which is better for pumping oil.
Hi volume pumps move more oil up top on both ends of the curve from increased pressure, some is based on ability to run at higher pressure. Top rpm is based on less drop off as speed diminishes volume.
The pressure you describe in your car is classic air/oil mix, you will sometimes hear slightly louder clattering of the valve gear when you come off track that quiets back down after running a few minutes. I had some that would run as low as 30 psi in the early years of Motorola cup.
The LS pump runs faster than it can properly fill at higher rpm, so when you see a flow graph the gallons per minute is like a hill, it climbs smoothly,levels, then starts dropping off. If you can imagine a turnstile type door leading into a building that had a power drive you could speed up. Run the turnstile slow with a group of people out side telling two to get in each section. They can fit and you just keep loading two at a time. If you keep speeding up the turnstile the time the people can get in gets to short and suddenly only one can get in as the opening goes by, this is volume decreasing with speed. In the oil pump the speed increases vacuum at the opening and actually starts cavitation in the pump. The higher volume pump maintains pressure longer as it can pull more vacuum, but that causes just as many problems as it cures. The engine is pretty constant in its needs, at 250F it will consume about 4.5-5 gallons per minute. As the pump runs faster it will not be able to keep up with this demand and flow/pressure drops. The standard volume pump can keep up with your needs at 6500 and that pan looks much better than the batwing (the batwing is not great),it reminds me of the road race Moroso. I would shim the pump for your dads car and limit the pushrods with the standard volume pump, that is something that should be much better than your car with the batwing pan combo.

Kurt