Crankcase Pressure. FREE HP!

[TheKurgan]

so what you are saying is a breather in place of an oil cap is killing hp?

I don't see where in the world you got that idea. He was stressing that putting the crankcase in a vacuum increases horsepower due to less parasitic drag on the combustion stroke.

 

[2to3threE]

I don't see where in the world you got that idea. He was stressing that putting the crankcase in a vacuum increases horsepower due to less parasitic drag on the combustion stroke.

so basically what i got from it was that a breather will kill hp due to the fact its not vacuum.

so what is it. a breather is better or worse the the lines connected to the intake manifold?

also is a breather better than a oil cap?

 

[CandyRedGT]

Yea, clear as mud!!

YUP...for sure!! NO certain winners yet????

 

[07 Boss]

Actually the idea is to run a vacuum in the crank case. This allows the rings to seal better which helps keep the vapors cleaner. The pistons have to push less air if you maintain a vacuum in the crankcase and a good deal of HP is lost in pumping air in and out of an open breather system. So much that the pros run a extra pump just to pull a vacuum in the crankcase. The air oil separator a large one not the poopy little cans you see for sale allows any oil vapor to drop out of suspension so only clean air enters the intake and the amount of heat is negligible compared to the amount of cool air the engine takes in .

I have seen the effect of this on Ducati bikes on the dyno. Now I'll grant you that the Ducati twin is particularly susceptible to this because the pistons actually both go in the same direction during parts of their stroke so they displace a lot of air. But when people remove the check valve and run a K&N filter on the crankcase breather they loose hp. They gain hp by running the check valve and then into the air box where there is a slight vacuum.

Let me ask you this then. What happens when you have negative crank case pressure (vacuum) and the piston is moving the other way? Doesn't it have to work harder? Think about it. If you were to turn the motor without any combustion the volume of air inside the crankcase would be constant with no air going in and out of the breathers because as one piston is going down there is another going up. The air being displaced by one piston going down will be used to fill the void as another piston is moving up. I understand why it is an issue with a Ducati motor. IMO vacuum can be just as detrimental to HP as pressure. The only advantage to running a closed loop PCV system over breathers is that with the fresh air being introduced, and flowing through the motor, is that it will help clear the air inside of the motor. Less shit (unburnt fuel and exhaust gases) to get mixed in with your oil, and thus extending it's peformance life. But I think it is not enough of an advantage over keeping that shit out of the intake charge. Just change the oil a little more often.

 

[ZmanM3]

Let me ask you this then. What happens when you have negative crank case pressure (vacuum) and the piston is moving the other way? Doesn't it have to work harder? Think about it. If you were to turn the motor without any combustion the volume of air inside the crankcase would be constant with no air going in and out of the breathers because as one piston is going down there is another going up. The air being displaced by one piston going down will be used to fill the void as another piston is moving up. I understand why it is an issue with a Ducati motor. IMO vacuum can be just as detrimental to HP as pressure. The only advantage to running a closed loop PCV system over breathers is that with the fresh air being introduced, and flowing through the motor, is that it will help clear the air inside of the motor. Less shit (unburnt fuel and exhaust gases) to get mixed in with your oil, and thus extending it's peformance life. But I think it is not enough of an advantage over keeping that shit out of the intake charge. Just change the oil a little more often.

Thinking about it, you would have expanding combustion gasses that would off set that I think.

 

[2to3threE]

this is true, the crankcase would need vacuum on the upstroke, and pressure on downstroke.

therefore a breather would work better overall. thats what i am getting out of it.

 

[Fallenauthority]

Vacuum in the crankcase does in fact help free up hp. A lot of the oldschool big block dudes around here do it.

this is true, the crankcase would need vacuum on the upstroke, and pressure on downstroke.

therefore a breather would work better overall. thats what i am getting out of it.

Sent from my Droid using Tapatalk

 

[JeremyH]

Vacuum in the crankcase does in fact help free up hp. A lot of the oldschool big block dudes around here do it.



Sent from my Droid using Tapatalk

On an N/a big block, yes, thats why they run vacuum pumps.

But on a boosted mod motor there really is no need.

 

[Fallenauthority]

I disagree, might not be necessary but it would still be beneficial. IIRC a vacuum pump is used to evacuate blowby as well as help keep rings seated and sealed which in turn would increase power output.

Vacuum in the crankcase does in fact help free up hp. A lot of the oldschool big block dudes around here do it.



Sent from my Droid using Tapatalk

On an N/a big block, yes, thats why they run vacuum pumps.

But on a boosted mod motor there really is no need.

Sent from my Droid using Tapatalk

 

[striker 5]

I ran moroso scavenger breather caps and then ran hoses to the long tube header collector to suck out the pressure in the crank case on a 408 stroker I dont know if this would work on a 3v but it worked great on the 408

 

[JeremyH]

I disagree, might not be necessary but it would still be beneficial. IIRC a vacuum pump is used to evacuate blowby as well as help keep rings seated and sealed which in turn would increase power output.



Sent from my Droid using Tapatalk

I see your point but agree to disagree lol, if it really was a big deal on a 4.6L mod motor with the way we mod, we would all have run out and did the vac pump mod on our setups. The point is on a small boosted v8 breathers do the job just fine. And if you were losing any power in this case it would be neglible, but as most others have found out going to breathers on a boosted setup for our cars, actually frees up power. Really no need for vac in the crankcase when theres boost in the cyllinder, that piston is coming back down on the downstroke regardless if theres vac/atmosphereric in the crankcase!

On an all out n/a car/stoker etc, sure i can see a vac pump making a few hp. Im perfectly content with my breathers.

 

[2to3threE]

I see your point but agree to disagree lol, if it really was a big deal on a 4.6L mod motor with the way we mod, we would all have run out and did the vac pump mod on our setups. The point is on a small boosted v8 breathers do the job just fine. And if you were losing any power in this case it would be neglible, but as most others have found out going to breathers on a boosted setup for our cars, actually frees up power. Really no need for vac in the crankcase when theres boost in the cyllinder, that piston is coming back down on the downstroke regardless if theres vac/atmosphereric in the crankcase!

On an all out n/a car/stoker etc, sure i can see a vac pump making a few hp. Im perfectly content with my breathers.

 

[Fallenauthority]

Oh I agree it would be overkill for most but I was just saying it does provide benefit. For most of our needs breathers work perfectly fine. No worries we are on the same page, no major benefits seen on most setups but it still would provide gains on a balls to the wall setup most likely.

I see your point but agree to disagree lol, if it really was a big deal on a 4.6L mod motor with the way we mod, we would all have run out and did the

Sent from my Droid using Tapatalk

 

[JeremyH]

Oh I agree it would be overkill for most but I was just saying it does provide benefit. For most of our needs breathers work perfectly fine. No worries we are on the same page, no major benefits seen on most setups but it still would provide gains on a balls to the wall setup most likely.



Sent from my Droid using Tapatalk

 

[bmaxwell]

The Jaz can/breather has two. See my post #130. Excellent piece for $60. I have each side run to it via 3/8" hose.

I like your set up, I think I will copy it soon lol. . Thanks for showing us all the way you did it