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Discussion Starter · #1 ·
I was talking with a mechanic who used to run drag cars, and he said that he used a small vacuum pump off the crankcase to put a partial vacuum into the oil system, providing more thorough lubrication of the engine. He also said the oil cannot be suspended in a vacuum (floating in mid air), so it will naturally jump to your cylinder walls, providing better lubrication. I have been trying to find some supporting info for this online, but am having no such luck.

The breather tube needed a catch-can for any escaping oil, but he claimed it really made a difference in power and responsiveness. Anybody shed some light on the science behind this one? If there is any?:confused:
 

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Here are some good threads to start off with...
http://k20a.org/forum/showthread.php?t=24360
http://k20a.org/forum/showthread.php?t=37555
http://k20a.org/forum/showthread.php?t=23732
http://k20a.org/forum/showthread.php?t=47339
http://k20a.org/forum/showthread.php?t=47359

The breather tube you mention is the one in the valvecover on the LHD side correct? That would not be the best place for a vacuum port, but you can run the catch can there to trap the oil residue that is coming from the valvecover to the intake. Just put it before the PVC.
 

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Discussion Starter · #3 ·
I think he was talking about lower down closer to the crank, bottom end not head. Thx for the links, gonna hgave a read through in a few minutes here.
 

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Before adding a vacuum pump to your motor or thinking about it, you really need to know how it will benefit you and what you will gain from it. IF done properly, and setup properly, you can pull 20"+ vacuum no problem. There are a few added benefits to running a vacuum pump on the motor, but there are a few things you need to do as well to make it work correctly.

Can you name off a few ways this will benefit the motor and or make more HP?
 

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Discussion Starter · #7 ·
Got it now. Thank you for those links to when Niko was doing some digging. That makes total sense to run it from the top of the engine, less oil loss. Using a one way check valve and a catch can, with the e-vacuum pump, I should be able to draw a good vacuum (5-7") with en electric pump. Will control the pump digitally as well, but thats later...

I like the idea of the exhaust-siphon to generate a negative pressure in the crankcase, but I'll be building a NA Frank, so I don't think I'll generate the exhaust pressures required to pull the necessary vacuum.

Thanks SIGNALPUKE, and as the motor is still in the early stages, I'll post up later how she turns out (dont hold your breath on it, could be a few months) I'm a student, no cash, just lots of ideas and drive...

As for benefits, I have read to expect a 2-5% HP gain, but I don't expect to see a huge margin, just hoping that this will generate a better lubricity between my rings/pistons and the cyl walls.

I also like the idea of dry sump, but need to do some more reading into that as well. If you're pulling hard through corners, conventional oil systems tend to run lean, if I am not mistaken, (without oil pan baffles...) whereas a dry sump would help keep a consistent flow of oil to all parts, right? (Please correct me if I'm out of line) Probably pretty important when you're hammering down on second pulling out of a corner at 8500rpm, to have ample oil going to your head and block.
 

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Why do you guys think that breather tube connects to the intake.........:rolleyes:
I have 2 theories;

1. To supply fresh and filtered air to the motor to displace the vapors/oil that are evacuated from the crankcase. This would be the Helm's manual's description for it, and it would make sense, as relative pressure between the crankcase and the intake manifold is what drives the PCV valve to evacuate crankcase vapors....ie air removed from the motor has to be replaced by something in order for the PCV valve to function properly.

However, I have seen the infamous HT tests were it was realized that on an N/A b series with basic bolt-ons, crankcase pressure was evacuated via the breather hole on the valve cover at high loads as well. The motor was apparently healthy, but I'm not sure other factors weren't involved in the result.

So maybe it's also for;

2. Evacuating the crankcase under high load conditions when the PCV valve is unable to do so. The vapors would be recirculated back into the intake tract and burned.


What disadvantages would there be to using a vacuum pump to reduce windage loss?

Is there a maximum amount of vacuum that can be pulled from the motor before parts of the motor start to lose their longevity?

patfetchko are you at UVIC? I really miss BC :eek:
 

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You can definitely make power with a vacuum pump just as you can with a dry sump or combination of the 2 (some pro stocks use both). You don't see vac pumps in the street class because they haven't been legal. If you don't spend a lot of time working on sealing the motor up, you won't pull much vacuum. These are pretty leaky.
 

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If you don't spend a lot of time working on sealing the motor up, you won't pull much vacuum. These are pretty leaky.

exaaaaactly!

this is the biggest problem I have seen from people trying to use a vacuum pump. A Vacuum pump is trying to remove all the air from inside the motor. if you dont keep air from being able to get into the motor, then you may not get anywhere with the pump, and may not get any HP out of it. Sometimes this does involve different crankshaft seals, or modified ones, or modified placement...:)
 

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Discussion Starter · #13 ·
Not yet, I'm a Mech Eng Tech waiting to bridge to UVic from Camosun. Yea, BC's great, I don't mind visiting Alberta, but thats as far as that goes. And for its good for work.. But back to the issues...

To achieve power out of the combustions chamber, it needs to seal to the piston can be forced down, right? So, if we have a seal good enough to keep that pressure in the chamber to push the piston, then I would think that it would also hold true for a negative pressure from the crankcase.

I don't think the rings would act differently under vacuum, as you have pressure differences both ways during your strokes already, but I do agree that the engine would have to be sealed very well.

Can anybody explain to me how oil acts in a vacuum? I'm going to leaf through some fluids texts and see if I can find anything... G'night
 

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Now im not exactly sure but i think they are trying to say the bottom end is not perfectly sealed to hold high vacuum. Because of the PCV systems they have in turn made the oil seals weaker because they don't need to stand up to such high pressure as the older engine without PCV systems did. Now i know vacuum is different but it is a pressure none the less its just pulling the seals rather then pushing. But i believe the concept is the same. once again correct me if I'm wrong please
 

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The oil behaves differently enough that you don't have to run an oil scraper if you have the oiling system worked out, and losing that ring set can have benefits. I think around 40% of the frictional losses in your engine are at the rings. Between that and the decreased crank windage you can gain a worthwhile amount of power...which is why you see guys spending big money on dry sumps. It also takes power to turn the pump, so if you don't have the motor sealing up then you could be breaking even if you aren't pulling enough vacuum. If you just took your average K motor and bolted a dry sump on, you would probably see 7 in of vacuum and probably won't see a power gain because of the losses from turning the gear pump.
 

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The oil behaves differently enough that you don't have to run an oil scraper if you have the oiling system worked out, and losing that ring set can have benefits. I think around 40% of the frictional losses in your engine are at the rings. Between that and the decreased crank windage you can gain a worthwhile amount of power...which is why you see guys spending big money on dry sumps. It also takes power to turn the pump, so if you don't have the motor sealing up then you could be breaking even if you aren't pulling enough vacuum. If you just took your average K motor and bolted a dry sump on, you would probably see 7 in of vacuum and probably won't see a power gain because of the losses from turning the gear pump.
Any pics of your setup Luke? Ive seen people run smog pumps but they dont pull much vacuum. Which electric vacuum pump would you go with?
 

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I just run the dry sump. I was talking about NHRA pro stocks running a small oil pump and vacuum pump. Not all of them do it, I don't think. Some of them run an aluminum helical 6 stage, or they used to. They pull a lot of vacuum though.
 

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I just run the dry sump. I was talking about NHRA pro stocks running a small oil pump and vacuum pump. Not all of them do it, I don't think. Some of them run an aluminum helical 6 stage, or they used to. They pull a lot of vacuum though.
So someone in my situation running a S2K pump or type S pump a vacuum pump would be a wise investment? Not baller enough for a dry sump. :eek:
 

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So someone in my situation running a S2K pump or type S pump a vacuum pump would be a wise investment? Not baller enough for a dry sump. :eek:
agreed. would it be a wise to invest in something like that? what would do you think the life would be on something like that if it were used for a daily driver rather than a sunday cruzer or a drag car? Would it be practical?
 

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I suspect the hot oil will boil in a vacuum... a true vacuum, which you won't have. However, if it boils even partially that would be very bad for lubrication.
 
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