Vacuum pump for performance

[Rusty67]

I read an article in a performance magazine a while back about using a vacuum pump to increase HP. I was looking for an old thread on the forums that had some info about it but I couldn't find it.

By using a pump to generate vacuum in the crank case, at least in theory, windage is reduces and the internal parts don't have as much resistence. Also, other vacuum powered accessories in the car would benifit it low vacuum were a problem.

In that thread, diesel pumps were mentioned. Apparently some of the Ford deisels came with these type of pumps. I was thinking about this and I came up with another idea for a pump that could be used.... maybe.

Would it be possible to use a smog pump to generate the vacuum ? Basically all a vacuum pump is doing is sucking on one side and blowing on another to create the vacuum right ? Since smog pumps basically do the same thing would it be plausable to use these to do the same thing if it was plummed in properly ?

 

[tos]

i'm not an engineer but i dont see any advantage to hooking vacuum up to your crankcase. if anything i think it would srew up your crankcase ventilation which is a positive pressure. if you have a pcv valve in your system it would cause it not to vent properly (open when it should) Maybe if you were to remove it and block the pcv to carb you might be ok but would also depend on whether you have a closed or open vent system. I think youd likely be sucking oil vapors into your pump. Windage can be improved by using a windage tray which keeps the excess oil away from your rotating crank. Your normal engine vacuum is created from your intake system (top half of your engine) and is sometimes reduced when you install performnce cams and intakes. Thats where the vacuum pump comes in to run accessories like power brakes and such. I wouldnt suggest a smog pump , those things have huge blades in them and will put a drag on your engine. Probably more loss than gain with one of those.

 

[SoCalCruising]

Many hi-perf/race engines use some sort ot active ventilation system. It maught be a pump or Moroso sells a system that hooks into the header and uses the venturi effect to pull crankcase vacuum.

The only serious side effect is a significant reduction in splash oiling. If you follow through, you should study the other mods that are recommended in order to restore oiling to certain engine compnents that rely on splash oiling. For example, piston pin oiling would be done actively through an oil passage in the rod, fed from the rod bearing. What I do not know is at what vacuum level (mild vs moderate vs heavy) these mods have to be done. It may well be that mild vacuum will not pose a problem, but you will also have less benefit. Lastly, a mild/moderate perf street engine proobably won't see much improvement, anyway, from positive crankcase ventilation (vacuum).

tos: the pump's output is directed to a catch can because you are right that crank case vapors and oil mist are evacuated and need a place to go.

 

[Rusty67]

I'm thinking of using a setup like this for 2 reasons. If I don't have enough vacuum to run my power booster that I don't have yet. Definately for the next engine I build which will be much more on the wild side. I figure if the pump generates enough extra HP to break even from the longer belt and assessory drive tension, then it is a worth while upgrade because it relieves interal pressure and makes it easier for the engine to turn. Plus it would give more then enough vaccum for other components.

I know nothing about passive oiling. Something like that is exactly why I wanted to post about this on the boards so I can get an education from the more experienced. I tend to only know just enough to get myself in and (sometimes) out of trouble. An upgrade like this is sure to have other side effects I wouldn't even know to consider.

The use of a smog pump, if theisable, would be a GREAT way to do it because (at least on the 5.0s) the serpentine brackets I've got have a spot right there for it and I wouldn't have to do any mods to the accessory drive. Also, for those concerned about wieght, the smog pump is not very heavy at all.

 

[SoCalCruising]

Well, using the belt-driven vacuum pump and making all the other needed mods would be a lot tougher than just adding an '86 Seville, or similar, electric vacuum pump. Or even just a vacuum cannister like I have. Anyway, that's the conclusion I came to when I was building my 331 and planning for power disc brakes.

Others can add to the list, but (at the least) piston pins and the cam rely on splash oiling, and the piston is also cooled by splash oiling. There's bound to be a good dissertation on this somewhere on the web.

 

[Rusty67]

For example, piston pin oiling would be done actively through an oil passage in the rod, fed from the rod bearing. What I do not know is at what vacuum level (mild vs moderate vs heavy) these mods have to be done.

I assume you would have to machine the rod and make sure the bearing lines up on each rod ?

I was hoping someone might know a little more on how much vacuum is benificial/too much. I was talking to a friend about it today and he said something to the effect of, well if you have too much you can always put a regulator on it to make sure it never passes a certain amount of vaccum. A good idea I think.

 

[D.Hearne]

Forget the Smog pump. I tried that with a Canfield headed 302 that was spun up to 7500 rpms regularly. The Smog pump sucked up excessive amounts of oil and then imploded from the (too many)rpms. Not to mention it was a noisy little ****, I had to fab a muffler for it. It seemed like the motor made a bit more power, but I never dynoed it or track tested it (ET's) The Nascar racers use em, or so I've read somewhere, probably the same source you did.

 

[Rusty67]

Wouldn't puting a regulator or restrictor on the line keep the pump from sucking too much out of the crank case ?

 

[gtss]

Does a PCV system not accomplish the same thing, after all it is a valve controlled hose connected to manifold vacuum.
you could experiment with different valves to control the amount of vacuum being created.
I can see the exhaust header method evacuating vapors and mist, however I don't know(being a Canadian) what the California emissions people would think of raw oil vapor being dumped out the exhaust.
Old. like really old, engines used to use a simple down pipe which used vehicle speed to create a siphon type draw to evacuate oil vapor fromthe crank case.

regarding a pcv system, perhaps the down side is the oil vapor entering the combustion process, harder to calibrate air fuel ratios with raw hydrocarbons entering from the crank case????

however would the horse power gain be enough to make up for the parasitic draw of a belt driven pump?

And for the record yes the older 7.3L and even the old 6.9L diesels used a mechanical vacuum pump to supply vacuum for the brakes.
the more current diesels (ford anyway) use an electric pump for a vacuum source, and use P/S based Hydra boost for brake assist

Just some thoughts...
gtss

just had another thougt, regarding the NASCAR set up, do they not run a dry sump system , which would then affect the entire discussion, and perhaps necessitate a different vacuum/ ventilation system

 

[Rusty67]

Hmm... interesting stuff.

I was planning on building a dry sump motor eventually. Not my next 302 thats in the works right now but the 351w I wana build a few years down the line. I havn't done much research on dry sump but I would immagine you are right about that setup having some of the same issues as an additional vacuum pump.

 

[rbohm]

adding a vacuum pump to a big block chevy built for racing(i forget the specs) added 35hp on the dyno. there are proven hp gains to be had by lowering crankcase pressure. parts that depend on splash oiling dont seem to be affected.

 

[Rusty67]

rbohm, do you think that adding a system like this to an average motor would yield enough HP/tourque to at least compensate for its addition. If it at minimum would "pay for itself" in power then I think it is worth it because it is lightening the load on the system overall. Wouldn't this, at minimum, make the hole motor last longer ?

 

[rbohm]

i believe the system would not only pay for itself, it would add power even on a street engine. how much over and above the power required to turn the pump i dont know, but an educated guess would be something like 10-12 hp gain on the average street engine. as to whether the engine would last longer, i cant say, but again and educated guess would be not really. remember that the friction loads will remain the same, you just reduce the parasitic losses from positive crankcase pressure, and since street engine dont develope the same internal pressures that a race engine does, the gains are going to be smaller. overall i think the addition would still be a benefit.

 

[mustangman1974]

it also helps seal the piston rings which is why it produces more power. The PVC system does the same thing, however under hard acceleration there is little vac. to accomplish the sealing. You have to also consider it will wear the piston rings and cylinder walls more because of the better fit. I would not recommend it on something driven everyday.

 

[Rusty67]

Interesting link:
http://www.dragstuff.com/techarticles/vacuum-pumps.html

The article says 2 things that really interest me. One being that if you stay under 15" of vac that there will be no problems with the internal oiling system. This can be easily achived by puting a regulator in where the breather normally goes in the valve cover. Second, the article says that by modifying a stock Ford pump some racers have been able to get reliable service that outperforms the aftermarket pumps.

The estimated HP loss from running this pump system is 1HP from the pump which is less HP then adding it will make. Your gain overtakes your loss. I would hope that it would also take care of the HP loss created from the longer belt, which in a serpentine system is 2HP at most. So if the system makes 3 or more HP then I suppose it is worth it.

The important thing the article doesn't talk about is HOW to modify the stock pump. Anyone out there got some info on this ? The only "hint" it gave is that the inlet and outlet should be opposite each other, top to bottem.

 

[Rusty67]

Forget the Smog pump. I tried that with a Canfield headed 302 that was spun up to 7500 rpms regularly. The Smog pump sucked up excessive amounts of oil and then imploded from the (too many)rpms. Not to mention it was a noisy little ****, I had to fab a muffler for it. It seemed like the motor made a bit more power, but I never dynoed it or track tested it (ET's) The Nascar racers use em, or so I've read somewhere, probably the same source you did.

Did you try puting a baffle in to restrict the oil flow into the lines ?

What other pumps could be used that are found on stock applications ?