Crankcase vacuum pump?

[Highside]

I was browsing MikesXS last night when I saw a PCV reed valve that claimed a slight HP increase due to the fact that it created a slight vacuum inside the crankcase.

(Cage)Racers have been doing this for years, except that they use vacuum pumps to get even more crankcase vacuum (20 in or so). On large V-8's, you can get over 20 HP increase with low tension rings and a strong vacuum pump. In Pro Stock, they use low amperage electric motors to run their pumps. The good thing is that this is basically FREE HP, that comes with an increase in gas mileage.

Has anyone heard of a vaccum pump, powered by an electric motor, that would be suitable for MC use?? I imagine you could get 2-3 free HP with it.

 

[Tomterrific]

Both pistons go down at teh same time. This pushes out great volumes of crankcase atmosphere. If a one way (check) valve is put in the breather hose, air goes out but not in. This is the pump you want and many 360° twins owners use some sort of valve. I use a power brake check valve myself, just like the one on my Triumph. The generic power brake check valves are only $5 at an auto parts store.

Tom Graham

 

[Highside]

Both pistons go down at teh same time. This pushes out great volumes of crankcase atmosphere. If a one way (check) valve is put in the breather hose, air goes out but not in. This is the pump you want and many 360° twins owners use some sort of valve. I use a power brake check valve myself, just like the one on my Triumph. The generic power brake check valves are only $5 at an auto parts store.

Tom Graham

Yeah, that probably gives 3/4's of the benefit of a vacuum pump, The pump just takes the same effect, and takes it to 11.

 

[Tomterrific]

The engine architecture of every engine except singles and 360° twins makes your statment true. But for a single or 360° twin, the self pumping is quite strong. Other designs have a piston going up when one is going down and need the auxilliary pump to get as much vacuum. In our case, I believe an auxillary would steal more power than it would gain. Don't know, just an educated guess.

Tom

 

[Highside]

The engine architecture of every engine except singles and 360° twins makes your statment true. But for a single or 360° twin, the self pumping is quite strong. Other designs have a piston going up when one is going down and need the auxilliary pump to get as much vacuum. In our case, I believe an auxillary would steal more power than it would gain. Don't know, just an educated guess.

Tom

I thought about this and I see your point. If you used a vacuum pump, it would make more powen until you got to BDC. As soon as th piston moves up, it has to fight against the vacuum to rise to TDC, then you would be losing the power you gained for a net gain of nothing.

Now I wonder how this would act on a 277 re-phase motor??

/scratches chin

(why don't we have a smiley for this??)

 

[XSLeo]

The vaccum in the crank case lets the rings seal better. Better seal is more power.
Leo

 

[Highside]

The vaccum in the crank case lets the rings seal better. Better seal is more power.
Leo

In theory yes, I'm not convinced that that's what's actually happening in the dynamic environment of the rings near the top the compression stroke and beginning of power stroke. All well seated rings have less than 1% leakage when you apply over 1,000 PSI to them.

Those gapless rings that they make for cars, can be assebled to have 0% leakage during a 100 PSI leakdown test, but they don't make any more power because when the engine is running at 1,000+ PSI, they leak the same as properly gapped racing rings.

 

[DirtyErnie]

Just gotta figure that crank-case is getting pumped down whatever the displacement of your engine is on each revolution. I know the case is fairly large, but there's a LOT of stuff inside, plus oil. 20"Hg = ~10psi or so. Not sure it would pump itself down that far.

Would it be worth it? Why not...

 

[ReycleBill]

At what point would a vacuum pump begin to draw the oil out of the engine?

 

[ReycleBill]

Could something like a windshield washer pump be used as a vacuum pump? They're certainly small enough and already 12 volt.