Venomous S

So I guess we still do not have the fresh air thing resolved, whether this is essential or not?

xviper

OK, here's my take on this. And I'm open to counter ideas.

The PCV system on this car (and others) uses vacuum to "help" draw out oil vapours from the crankcase and inside the valve cover. This is for those times when there is minimal crankcase pressure. During those times, manifold vacuum can be quite high (as high as -22 psi) and it can generally run at -10 psi. I don't believe it's all that good to run that kind of vacuum inside the engine (and outside the combustion chambers), so they put in that front breather to draw air in to equalize the negative pressure.
However, when there is sufficient crankcase pressure, the oil vapours are going to come out the PCV and front breather on their own.
In the case of F.I., we've introduced an extra variable - that being positive boost pressure from the outside that can get into the engine via a bad valve (not good as this compounds any positive crankcase pressures that already exists).
IMO, if you place a one-way valve on both the PCV AND the front breather, you are elimininating that avenue of negative pressure relief during some of those times when manifold vacuum far exceeds crankcase pressures (like when doing high engine braking).

Scorpion

That's why I just use a Supra PVC, all metal construction and since I've put it in, I have yet to pop the dip stick out which happend constantly with the stock honda unit. Best part, it was $4

fperra

And here is my take on it. The PCV system we see in all emission control cars today is designed to prevent the blow by gases from being vented to the atmosphere as they were in my more youthful days (anyone remember valve cover breathers). The PCV system is not a performance enhancer. Because it recycling the blow by gases into the intake manifold, the octane rating of the fuel is reduced. The extent of this reduction depends on how poorly the piston rings are sealing. The blows by gases also add heat to the intake charge - another bad thing. But we have to live with the PCV system to keep Al Gore from going into another one of his rants. And you still have all these negative affects with the Krank Vent system.

So let

Venomous S

I don't think you are using this KV stuff as you mentioned earlier but basically if you were installing the KV on your car, you would only install it on the PCV side and leave the front breather alone to maintain that pressure equalization.


And SCORPION

The supra pcv valve is supposed to be stronger than Honda's not allowing + pressure to flow into the crankcase?

Scorpion

I believe it is, it's designed for a factory boosted car. Looking just at the constuction of the valve it's 100% metal compaired to the 100% plastic Honda unit. I tested it before I put it in, I set the regulator on my air compressore to 20psi and it blocked it. The Honda one made a little whistle.

Kremlin

fperra, I think you've convinced me... Along with the krankvent mini kit for my Comptech SC/AC, do you recommend getting an oil catch can or anything like that?

Venomous S

I am still trying to get the whole picture and its hard being sleepy here.

Ok so what is the difference between the PCV system (gases in valve cover area) and the KV system (gases at back of pistons)

I think i'm missing something here. With either of the 2 systems (PCV and KV), don't the blow-by gases escape from the back of the pistons, down into the pan area and eventually they travel up to the valve cover area since it is where the vacuum source is found so that's the blow-by escape route in both scenarios?

fperra

That is correct. The only difference is the Krank Vent does it more efficiently. That's why you definitely want a catch can with the Krank Vent.

stitos2k

This thread just gave me a headache. I found this searching the web.

http://www.honda-tech.com/zerothread?id=1199935

Has a pretty good explanation of crank case vacuum etc etc.