15psi on a 13g? [1G]

[Oblivion02]

I was wondering if anyone has had any success boosting a 13g up to 15 psi, and if so, what have they done to get there? Does this boost level affect efficiency? If not, what is the most you have been able to get out of it, and how?

 

[kenamond]

By all means, start another topic about it. If you're one of the belivers of "pcv is for ring seal" you don't deserve that wiseman title. Please do a little research on the history of PCV, learn why the system is in place, and consult some professional racers and engineers in regards to its importance (or more like the lack thereof). Nothing short of an air pump has any worth in PCV. The stock system and any variation of it that you choose to come up with only functions when it doesn't need to and never when it does. It is for nothing more than compliance with the federal regulations mandating that cankcase ventilation be scavanged and not dumped to the atmosphere.

The "V" in PCV stands for...? And I don't care much about the history of PCV systems, though I've read articles about why they're on cars. The bottom line is that they serve a purpose other than emissions for our cars.

If your car is purely for the track, you can get away with no PCV system. I wouldn't recommend deleting it on a DD. If you just vent them, there's nothing to ventilate the fuel and exhaust fumes in the crankcase. All you have is more blowby that forces the old fuel/exhaust out the vents by displacing it with yet more fuel and exhaust. There's nothing pulling fresh air through the crankcase.

Any time the IM sees less pressure than the crankcase, it draws it through the VC breather which comes from the intake pipe downwind of the MAS which is clean, filtered, metered air. And your IM sees vaccuum quite a lot of the time.

This isn't just theory; there are plenty of folks out there who had oil reeking of gas, and they find out their problem was that they modded their PCV so that it stopped ventilating the crankcase.

So whoever's reading this should take both sides of this story into account and decide for themselves whether they should just vent their crankcase or maybe add a check valve and some non-vented catch cans to preserve the PCV functionality while keeping oil out of the intake and eliminating the non-robust PCV valve all at the same time.

 

[CTP]

The "V" in PCV stands for...? And I don't care much about the history of PCV systems, though I've read articles about why they're on cars. The bottom line is that they serve a purpose other than emissions for our cars.

The history is important because if it weren't for the federal government requiring PCV, no cars would have it.

The V stands for ventilation which is exactly what the two holes in my valve cover are doing. The P stands for positive, which is a good thing, but not possible when needed unless using an air pump.

If your car is purely for the track, you can get away with no PCV system. I wouldn't recommend deleting it on a DD. If you just vent them, there's nothing to ventilate the fuel and exhaust fumes in the crankcase. All you have is more blowby that forces the old fuel/exhaust out the vents by displacing it with yet more fuel and exhaust. There's nothing pulling fresh air through the crankcase.

The oil ends up carrying away the vast majority of the combustion blow by products whether your crank case is positively vented or not. Hence the need for oil changes.

Any time the IM sees less pressure than the crankcase, it draws it through the VC breather which comes from the intake pipe downwind of the MAS which is clean, filtered, metered air. And your IM sees vaccuum quite a lot of the time.

This is incorrect. The PCV valve is designed for prevent air from flowing through during A: periods of high vacuum (to preserve idle quality and prevent plug fowling) and B: periods of low vacuum (to prevent damage to performance).

This leaves your crank case seeing positive ventilation under one condition only, and it happens to be the time you need it least, moderate vacuum, i.e. when lightly cruising.

The PCV system provides no positive ventilation during periods of high load which is also when you need it the most. In addition to not providing any positive ventilation, the stock setup (and any crazy, 15 catch can and filter derivation of it) provides only one, very small vent hole for high load situations (the breather inlet). Obviously, this is the most important time to have adequate ventilation because it is when you're experiencing the most blow by and thus highest crankcase pressure. This is exactly why people with high horsepower cars run large vent holes off their valve cover with... you guessed it.... no PCV.

This isn't just theory; there are plenty of folks out there who had oil reeking of gas, and they find out their problem was that they modded their PCV so that it stopped ventilating the crankcase.

Maybe they should try 3,000 mile oil change intervals like the rest of the world that keeps up on maintainence.

So whoever's reading this should take both sides of this story into account and decide for themselves whether they should just vent their crankcase or maybe add a check valve and some non-vented catch cans to preserve the PCV functionality while keeping oil out of the intake and eliminating the non-robust PCV valve all at the same time.

I'd ask them to consider just how useless a stock setup PCV system is before spending time, effort, and money to try to "improve" on a design that doesn't even do what the majority of people here think it does.

 

[kenamond]

Lol

The PCV valve is a check valve and a metering orifice.

At idle or decel or any other condition where the IM is at lower pressure than the crankcase, the PCV valve opens and permits a limited amount of air to enter the intake manifold. When this happens, it will draw out fumes from the crankcase, and this will be replaced by fresh air drawn through the VC breather (which happens to also be metered). That ventilates the crankcase (you might want to check on the definition of ventilate; it's not synonymous with vent). When the IM pressure exceeds the crankcase pressure, the PCV valve closes (or is supposed to) so that you don't boost the crankcase. Then all blowby has one way out: VC breather.

What you're describing is just venting, and there is *NO* source of fresh air: no ventilation. So you don't get the "V" in PCV.

And that's a big cop-out to accuse everyone who ended up with fuel in their oil of infrequent oil changes. You have absolutely no evidence one way or the other.

I agree that when these motors' performance is pushed, the VC breather is not sufficient for venting the crankcase pressure. It's not uncommon for folks to enlarge/add breathers. I've heard of others wanting to add a pump to ventilate the crankcase, too. But for a lot of us, the PCV can be made to function with minimal effort.

I'm done here. Post any other arguments you have in the "Stupid PCV question" thread so that it can be debated in a PCV-related thread. I welcome any other comments you have; maybe I'm missing something.

Sorry to clutter your thread Oblivion02 - I'm guilty of frequent digressions.