[PsychosIS_300]

A couple of weeks ago I was browsing through the forums and saw a thread about whether a breather filter is worth it or not. Someone recommended that if you want to make a real difference, you should attach your vaccuum that goes into your intake tube onto your exhaust. I forget who it was who said that, and I've tried searching for the thread, but with no result. My question is: Would this work? and how would I go about doing this?? If anyone has performed this modification, can you post pictures? I'm not even sure which tube on my intake is the vaccuum. lol And yes, I realize this would not be CARB legal.

 

[stjarvis]

Google crankcase evac system or something similar. Moroso makes a kit for it. You will need to hook it to a section of the exhaust that has little to no back-pressure or it will not work well (ie after cats).

 

[slodsm]

I have seen nice HP gains from doing this on turbo cars but very mild in N/A cars.

If you think of it like this, the crank case is sealed for the most part, when the piston moves down it is displacing air that is now forced to go to the other side of the motor and follow a piston up to maintain equal pressure.

In an N/A car with tight ring gaps and little blow by, using the exhaust to pull it out will benefit but not much. On a turbo car however with larger ring tolerances and larger piston to wall tolerances, more blow by equals more pressure the engine is fighting to move the piston down. Evacuation in that instance frees up HP that was being wasted to help force that piston down and is now using it to power the wheels.

 

[gcmbob]

Hold on now. I can see how that would make sense in an egine with one piston, but in multi piston engines one goes up and another goes down so in theory equaling out the pressures. Yeah? Im not saying there arent gains, cause i dont know.

 

[stjarvis]

It does balance, the gains you see from this are not from the pistons, they are from the crank rotating in a vacuum.

 

[gcmbob]

How can it be a vaccum? The exhaust never creates suction does it? This is the same idea as dry sumping but i dont see the mechanics of it.

 

[PsychosIS_300]

From my understanding, Its the angle of the inlet pipe of the vaccuum hose into the header or exhaust where it is connected creates a suction from the blow-by. I'm probably wrong, but I think that's how it works. It seems perfectly logical to me. Am I confused?

 

[HyperMKIV]

How can it be a vaccum? The exhaust never creates suction does it? This is the same idea as dry sumping but i dont see the mechanics of it.

it works like the wings of an airplane...the air flow is different on top the wing vs on the bottom, creating lift...the speed of the exhaust air flow can help create negative pressure if done correctly...

 

[gcmbob]

ok so you are counting on a venturi effect. the flow rushing past sucks air out of the tube going to the crank. Ok. I can see how that would be easy to screw up though. But if it works it works.

 

[HyperMKIV]

ok so you are counting on a venturi effect. the flow rushing past sucks air out of the tube going to the crank. Ok. I can see how that would be easy to screw up though. But if it works it works.

they've been doing this in drag racing cars for ages...

i really don't think it'll make that much of a diff on the IS unless it's heavily modified though... but hey, every little bit helps i guess...