Vacuum Pumps

[BluemeanieTSi]

i noticed it said it dropped oil presure by 10 or so psi...not a bad side effect either when you figure we run way-too-high pressures to begin with. although i can't see the pressure graph they're talking about so i dont' know where/rpm it did that at, anyone know?

 

[MNGSX]

It will be interesting to see. On some engines with strong pumps and tight clearances I think the actuall drop will be alot less as compared to no pump due to the bypass valve being engaged.

 

[Defiant]

i noticed it said it dropped oil presure by 10 or so psi...not a bad side effect either when you figure we run way-too-high pressures to begin with.

Do we? Or is that just a matter of reading it at the output nozzle of the oil pump. What's the pressure at the fitting on the head?

 

[BluemeanieTSi]

Do we? Or is that just a matter of reading it at the output nozzle of the oil pump. What's the pressure at the fitting on the head?

based on the calcuation that an engine needs 10psi per 1000 rpms, several testamonies (i know leon mentioned something about it in the high pressure oil pump thread) and i read somewhere about some hole not bleeding off pressure fast enough and that's what causes oil pressure to go from like 30psi at 2k to 80psi at 4k

 

[Tallen]

I will be using an exhaust venturi type crankcase evacuator on my car. Pics when I'm done. It will be run off the external dump.

 

[GalantGst]

I dont know much about this vacuume pump system. I know the other day I took out the pcv valve and put a straight fitting so it relieves more pressure.

What advantages do u get with this vacume pump?
Less crank case pressure right?

Like some one stated its a 40 hp gain how exactly do u gain hp with higher vacume?

Some one please school me about this.

 

[BluemeanieTSi]

I dont know much about this vacuume pump system. I know the other day I took out the pcv valve and put a straight fitting so it relieves more pressure.

What advantages do u get with this vacume pump?
Less crank case pressure right?

Like some one stated its a 40 hp gain how exactly do u gain hp with higher vacume?

Some one please school me about this.

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[MustGoFaster020]

I have some numbers for you guys. I did this a while ago so my numbers may be off a little bit, but should get you a good idea of what kind of a difference these can make in case pressure. I tried an old electric GM pump. It was dead though, it wouldn’t pull that much vacuum. A few other sites said it should be capable of at least 10in/hg, but mine would only pull about 4 in/hg when I hooked it up to the gauge. So keep that in mind.

For the testing I used the dipstick tube for my pressure tap. The gauge I used only went up to 1.8 PSI (50”water). The motor was in good condition, re-built 5-7K before I did this testing. Pulled 160-160-160-158 for compression. (stock size, 7.8:1 pistons)

Before: Both breather lines off the valve cover were run to my catch can, so nothing was helping the air get out. I was running 15 PSI for boost. At low RPM, the gauge just pulsed a lot. Cruising around 2700rpm on the freeway, case pressure would vary from .25-.35 PSI (7-10in/h2o) biased on load. When running the car hard in 3rd, case pressure would start at about 1PSI at 3500rpm, and build to 1.8PSI by 5000RPM, at which time the gauge was pegged and I let off.

After: I hooked the pump up to one line on the valve cover, and left the other going to the catch can. I did this because I figured the pump wouldn’t be able to flow as much air as was going to get past the rings. I also had no way to control the vacuum level if was able to pull all the air out. So at best I was looking for was 0PSI in the crank case. Cruising, case presser dropped down to around 3”h2o. (.1PSI) On the gas, The gauge wouldn’t go over 40”h2o (1.44 PSI) all the way up to 7K.

As for noticeable power gains, I was to busy watching the gauge and driving to pay attention.

 

[Bostedquest]

alot of the diesel GM cars had them, look at the "boats" they just about all had them. The 302s (yes GM made 302's) and 305's, they also had them.

A good pump will pull 10-12" vac.
And that should keep the crank case (especially on our 4) in the -#'s or -0-.

 

[Defiant]

I'm still curious about this whole deal. In the magazine article they mention a penny and a feather falling at the same rate in a vacuum. That's not just low pressure, that's most of the air molecules removed from the chamber. You're not going to get that in a crankcase- for one thing, you'll suck a crank seal either out of place, or you'll put enough pressure on the lip to burn it up. As a raw guess, what's the volume of a crankcase going to be, about the same as the displacement of the engine, maybe more? You're going to take quite a pump to pull that down to any significance. And I've still not noodled-out what all this is going to be doing to the rings.

 

[Bostedquest]

And I've still not noodled-out what all this is going to be doing to the rings.

it helps them seal better becuast they are only fighting 2 forces, combustion pressure, and friction. The lower pressure on the bottom side helps them to seal better, nearly ending any chance of blow by. Unless that is, there is no ring there to seal...

 

[Defiant]

it helps them seal better becuast they are only fighting 2 forces, combustion pressure, and friction. The lower pressure on the bottom side helps them to seal better, nearly ending any chance of blow by. Unless that is, there is no ring there to seal...

Hm. But my readings have told me the rings are blown to the bottom of the grooves before the pistons move, and the combustion pressure holds them against the cylinder walls from the inside with gas pressure. Hm.

 

[Bostedquest]

Hm. But my readings have told me the rings are blown to the bottom of the grooves before the pistons move, and the combustion pressure holds them against the cylinder walls from the inside with gas pressure. Hm.

That is true, but if you look at it this way...

There is combustion pressure above the rings.
It is bled to the inside behind the rings to push them out (sealing force).

But as the piston falls, it creates a deal of pressure UNDER the piston and piston rings inside the crankcase. That force does its best to counteract the sealing action the combustion pressure creates by removing sealing force.
That is the third acting force.

That downward pressure also creates a pressurized area that fights the downward movement of the piston. Granted it cannot do much to stop it, but it does create resistance to the downward force none-the-less.

Now remove that force, and the piston rings only contend with 2 actionable forces, friction and combustion pressure from above. Now if you also relieve that constant compression pressure from the revolving pistons, and you have a much smoother and mre efficent running engine.

Ok, back to school time...
We all know that every action has an equal and oppisite reaction right?
So the force on top of the piston creates a force to drive the piston down.
The theory above states that that action creates an equall amount of pressure below the piston. This pressure is somewhat relieved through the PCV valve, but NOT copmpletely.

But imagine if you removed ALL that negitive pressure? That is the theory behind the bennifits of the vacuum pump.

That is about as simple as the explanation gets.

 

[Defiant]

But as the piston falls, it creates a deal of pressure UNDER the piston and piston rings inside the crankcase. That force does its best to counteract the sealing action the combustion pressure creates by removing sealing force.
That is the third acting force.
That downward pressure also creates a pressurized area that fights the downward movement of the piston. Granted it cannot do much to stop it, but it does create resistance to the downward force none-the-less.

What about the rising pistons in other cylinders creating a low-pressure under them? Hmm?
It'll just move around in the crankcase.

Now remove that force, and the piston rings only contend with 2 actionable forces, friction and combustion pressure from above. Now if you also relieve that constant compression pressure from the revolving pistons, and you have a much smoother and mre efficent running engine.

If you can evacuate enough air to matter.

Ok, back to school time...
We all know that every action has an equal and oppisite reaction right?
So the force on top of the piston creates a force to drive the piston down.
The theory above states that that action creates an equall amount of pressure below the piston. This pressure is somewhat relieved through the PCV valve, but NOT copmpletely.

But imagine if you removed ALL that negitive pressure? That is the theory behind the bennifits of the vacuum pump.

jThat's the challenge. You aren't going to get all that much air out of the crankcase. True you'll remove some, but I'm curious just how much. I don't have any trouble grasping what it is they're trying to do, I'm just suspect on whether they can. It's one thing with a NASCAR engine spending so much of its time in a narrow rev band, but on a street car with crank speed constantly moving from 750-5000 rpm, or even a street/strip car making two or three runs every week, I don't know how well it's going to function. There's scads of whiz-bang tricks and methods done in racing (lever shifters, blocks with no cooling, no cooling fans, brakes that don't work under 500°, total-loss ignition..... hell, some of those guys don't even have air conditioning) that just don't apply to our corner of the "real" world.

 

[Bostedquest]

What about the rising pistons in other cylinders creating a low-pressure under them? Hmm?
It'll just move around in the crankcase. If you can evacuate enough air to matter.jThat's the challenge. You aren't going to get all that much air out of the crankcase. True you'll remove some, but I'm curious just how much. I don't have any trouble grasping what it is they're trying to do, I'm just suspect on whether they can. It's one thing with a NASCAR engine spending so much of its time in a narrow rev band, but on a street car with crank speed constantly moving from 750-5000 rpm, or even a street/strip car making two or three runs every week, I don't know how well it's going to function. There's scads of whiz-bang tricks and methods done in racing (lever shifters, blocks with no cooling, no cooling fans, brakes that don't work under 500°, total-loss ignition..... hell, some of those guys don't even have air conditioning) that just don't apply to our corner of the "real" world.

Well say that under normal situations the crankcase sees up to +2 Psi. If you have a pump that creates and holds 15" of vacuum, you have nearly eliminated that pressure that is there. That will allow more resistance free movement.

Some of those GM pumps create 18+" of vacuum when hard wired... that is some SERIOUS vacuum in under 2 CuFt of crankcase space... So yeah I would bet they have a pronounced effect if used right...

 

[Defiant]

Well say that under normal situations the crankcase sees up to +2 Psi. If you have a pump that creates and holds 15" of vacuum, you have nearly eliminated that pressure that is there.

In a normally-aspirated engine, you have that going on with the PCV valve at constant engine speeds.

That will allow more resistance free movement.

Some of those GM pumps create 18+" of vacuum when hard wired... that is some SERIOUS vacuum in under 2 CuFt of crankcase space... So yeah I would bet they have a pronounced effect if used right...

Okay, I'm not warring here, and I think you realize that. I'm seriously curious.

But you have a low-pressure area, not an evacuated one. And evacuation is the supposed goal. Just having a low-pressure chamber won't really be doing squat for you, will it? You still have those pesky molecules banging into one another and getting in the way of things, although there will supposedly be fewer. 18in Hg is barely halfway to being empty. And I'm still curious what that lower pressure is doing for the rings, if anything.
I realize these multi-million-dollar NASCAR outfits aren't doing too many thousand-dollar add-ons just for fun (although the sponsor tie-in is always a source of suspicion for me), and that they're very proprietary and secretive about which does what. I'm just curious.

 

[Bostedquest]

In a normally-aspirated engine, you have that going on with the PCV valve at constant engine speeds.
Okay, I'm not warring here, and I think you realize that. I'm seriously curious.

But you have a low-pressure area, not an evacuated one. And evacuation is the supposed goal. Just having a low-pressure chamber won't really be doing squat for you, will it? You still have those pesky molecules banging into one another and getting in the way of things, although there will supposedly be fewer. 18in Hg is barely halfway to being empty. And I'm still curious what that lower pressure is doing for the rings, if anything.
I realize these multi-million-dollar NASCAR outfits aren't doing too many thousand-dollar add-ons just for fun (although the sponsor tie-in is always a source of suspicion for me), and that they're very proprietary and secretive about which does what. I'm just curious.

I know your not warring...
I am just tring to answer questions.. I know how it works. I have used them in the past on other engines and they were a great help in reducing crankcase pressure and ring wear.

Ok... you see movement in the crankcase, both in parts, by air and by oil vapor. Granted an elect vac pump that we are talking about will never create a true vacuum, it can and does greatly reduce the built up pressure.

What I was saying about the rings is this...
Combustion forces them down. The movement of the piston moving down creates pressure that acts in the oppisite direction, trying to force them back up. Some of that pressure is moved to rising pistions, some is relieved throught the PCV valve, but there is still pressure there. Without some outside force acting to reduce it more, there will ALWAYS be pressure there.

I know that an elect pump can never create a vacuum, and that it cannot ever get the reading to a constant true -0- pressure. A guage may ready -0- but trust me, there is still pressure there, but it is less then 1% of 1 PSi, so it it ignored and thought of as -0-.

A test a person did earlier said that a bad pump pulled 4" vac.
Later during the test, the engine made nearly 2 PSi at 5K in the crankcase. (then RPMs were dropped. We will assume that the numbers would have kept climing regularly)

Later when the Pump was hooked into the system, the max pressure the crankcase got was 1.44 PSI all the way to almost redline (7K).

So let us assume that at 7K without the pump (low ball it) and say 2.3 PSi. That change with the pump is nearly 1 PSi (.9) And that was with a pump doing less than a 1/4th of what it sould have been doing. Now figuratively, the numbers say the pump at full compasity would create 3.6 Lb Vac. But that also means that it would be a true vacuum, which we know could not happen. But given that number, we can safely say that a propperly opperational pump would negate any pressure build up.

Now that lower internal bottom end pressure means less fighting the pistons and crank have to do to move. While it does little for the oil vapor in the case (get a windage tray to solve that)
That also means that oil blow by would nearly be eliminated, catch cans would be decorative, and honestly the lower pressure would be helping to suck the rings to the cylinder walls because...
1. the negitive acting pressures would then be removed
2. the lower pressure would then be tring to draw relief pressure from anywhere. What happens in a Neg/positive pressure situation? neg tries become neutral or become positive itself. So that neg pressure (in relation to the combustion pressure) would help suck the rings to the bottom of the grooves and keep them there.

 

[Defiant]

Interesting stuff.

I think your information was more informative than the magazine article was.

Thank you.

 

[Bostedquest]

Interesting stuff.

I think your information was more informative than the magazine article was.

Thank you.

Well if nothing else a little easier to understand about the pricipals of why to use one...

Not to mention ALOT shorter and more to the point

 

[herostar]

Why would an engine create the extra force in the crankcase requiring a pump? I'm curious because my stroker motor blows the dipstick out all the time, and I think this pump might help...

 

[Bostedquest]

Why would an engine create the extra force in the crankcase requiring a pump? I'm curious because my stroker motor blows the dipstick out all the time, and I think this pump might help...

read any of my replies/posts on this page (starting with #38)... all deal with the association, creation and solution of pressure (and its effects) in the crankcase.

If you are blowing out dipsticks, then you are getting some serious blowby...

I would first suggest removing the PCV and placing a "catch can" there...

It is not that an engine creates "additional" forces, they all create the pressure, just depending on BoreXStroke is just how much it actually creates.

But yes, a "Stroker" motor will produce more force then the original CID engine did.
The force created is in direct relation to the CID (Cubic Inch Displacement) of the engine in question.
So (taking a number from above) a stock engine creates 2.3 PSi at 5K RPM's. But your "stroker motor" added 33% more displacement... the new pressure number would be 33% higher, or 3.059 PSi. That is a hefty increase. So you would at the very least need a free-flowing catch can set up.

 

[MNGSX]

read any of my replies/posts on this page (starting with #38)... all deal with the association, creation and solution of pressure (and its effects) in the crankcase.

If you are blowing out dipsticks, then you are getting some serious blowby...

I would first suggest removing the PCV and placing a "catch can" there...

It is not that an engine creates "additional" forces, they all create the pressure, just depending on BoreXStroke is just how much it actually creates.

But yes, a "Stroker" motor will produce more force then the original CID engine did.
The force created is in direct relation to the CID (Cubic Inch Displacement) of the engine in question.
So (taking a number from above) a stock engine creates 2.3 PSi at 5K RPM's. But your "stroker motor" added 33% more displacement... the new pressure number would be 33% higher, or 3.059 PSi. That is a hefty increase. So you would at the very least need a free-flowing catch can set up.

The rings flutter more = leak with more stroke.. On a stroker the HP difference between a normal crank case and a high vacuum one is pretty big..

 

[Bostedquest]

The rings flutter more = leak with more stroke.. On a stroker the HP difference between a normal crank case and a high vacuum one is pretty big..

Trust me I know why they leak more...
I also know that a free-flowing crank vent will help alot with blowing out dipsticks...
If he would leave the dipstick not fully inserted it would also help alot with saving the valve stem seals...

One of the biggest reasons they leak more is because they (stroker motors) create more creankcase pressure below the rings, allowing them to fight the combustion pressure more.

When a crankcase has an excess of pressure, it will find anyway to escape. It that means working away at a low pressure gasket, it will do it. If it means blowing out through the PCV (and taking a large amount of oil with it) it will.

There are many things that are affected when you have too much crankcase pressure...
Any seals and or gaskets may be blown out...
It can actually prevent oil from draining down the head ports to the block (too much escaping pressure) Think of it as a straw, or tube with a bubble in it... the fluid can only trickle down at best.
Excessive ring wear rotating horizontally (edges moving up/down) in the ring groves.
Turbo, piston and valve failure due to oil blow by threw the PCV port.
It gets ugly fast... if it is bad enough...
I am not saying that all engines do it, but I have seen it happen both in N/A and turbo/supercharged engines...

Worst was a poorly done (302) 347 Ford stroker... He ended up loosing everything but the very core engine parts... (block/head/crank/rods/intake)

 

[Nos~4G63]

Very interesting concept, but i will wait for someone else in the DSM community to try this before I do.

 

[Car Cannibal]

I hear you on the vacuum pump but it would be easiest to add a real breather to the valve cover first.

The valve cover has two crappy ports to let air out, both which if you looked under the cover, are trapped by a maze of baffles which do not get direct access to air.

I would add a push in breather to the oil cap first and allow the head to vent more. Just machine the oil cap to accept one of the smaller breathers and push it in so that it does not hit the hood.

The vacuum pump is a great mod, if done CORRECTLY. Thats the issue, not starving the motor for an extra 10-20 hp.