PCV, Just another Vacuum Parasite?

[Corpse]

Hello,

I do not view the PCV system to be useful in a well runnign engine, I do believe the crankcase needs ventilation though. i view PCV as a vacuum leak that sucks in bad air mixtures at times that I would prefer just be escaping through a breather into the atmosphere.

What is your take on this, I think it is just another useless vacuum parasite like power brakes and the Charcoal canister. Just another thing to cause engine inconsistency. I would like the only vacuum device on the engine to be the FPR and MAP sensor (Gen II/III). Power brakes can be run off of a vacuum pump and external Vacuum canister along with the interior HVAC vent door vacuum system.

-Dave

[RednBlack]

And what would run the vacuum pump

[Doubt_Incarnate]

you can use a scavenging effect from the exhaust system to pull the air from the crankcase. but it has to be done right. a "pan-evac" i think its called. then there is no pump to drive, ive never actually done it, but its supposed to work, pulls more air out so the rings seal better, blah blah + .01hp

[Corpse]

"but its supposed to work," - It does, many serious race engines use this method. It consists of a check valve tapped into the collectors and uses exhaust scavenging.

What would run the pump? 12V DC, Electricity. If you are edging on the fact that the alternator would cause more draw thus not allieviating the parasite, it is easily possible to run a relay based from a toggle switch on the Alternator's field coilwiring thus, turning the alternator off for extended periods of time.

-Dave

[RacerX11]

Care to elaborate the reason for all this? By running for extended periods of time with the alternator disabled, your voltage to the ignition system will be decreased, thus decreasing its efficiency, and the resulting loss of power could more than offset the gain from not running the alternator.

Marty

[geoffinbc]

This sounds like another project doomed to be over engineered and under built.

If you want to, vent the damn PCV to atmosphere. Same with the canister

Get a vacuum pump off a diesel engine to run the booster or convert to an electric/hydraulic booster.

However a Booster, PCV and Canister do not cause vacuum leaks if they work right. The fumes release from the PCV and Canister are fuel vapors so whats wrong with that? Save our enviroment.

[Corpse]

"your voltage to the ignition system will be decreased, thus decreasing its efficiency, and the resulting loss of power could more than offset the gain from not running the alternator. "

I used to run a conventional battery, now I have a Optima so, it will have enough power for shoret periods of time. I'm not talking about leaving it off for that long, just a few minutes at a time under acceleration.


"Save our enviroment." - No, I am strongly against this. People in the past made it what it is today, and we will make it worse for tommorrow, when we are no longer here.

"This sounds like another project doomed to be over engineered and under built." - Umm, how would it be under built, we are talking about something that is extremely simple to work with. Vacuum systems.

My plan was to vent to the atmosphere. I just wonder if it is worthwhile, which it should be. i of course, am not looking to see any difference, everything works as a system though so, every little detail counts.

"'do not cause vacuum leaks if they work right." - I am not saying vacuum leaks, which they are somewhat of, just parasitic devices. The only place vacuum should be allowed to be released from the engine is at the throttle body, which is necessry as an engine runs on Air and fuel. heh

The reason I find it necessary to not draw vacuum from the engine is that, any release of vacuum will change the charge in the intake side of the engine, IE: an unwanted irregular condition.

Just like the EGR, that was a horrible device, and the CAT. The only emmissions control I am looking to have is the computer controlling the engine.

The fuel vapors that you mention being released are not accounted for, which makes them a bad thing. the computer is essentially being screwed with when outside forces try to change it's working conditions.

-Dave

[RacerX11]

"your voltage to the ignition system will be decreased, thus decreasing its efficiency, and the resulting loss of power could more than offset the gain from not running the alternator. "

I used to run a conventional battery, now I have a Optima so, it will have enough power for shoret periods of time. I'm not talking about leaving it off for that long, just a few minutes at a time under acceleration.

-Dave

It doesn't matter what kind of battery you have. When the alternator is actively charging, your ignition system is getting a full 13.8volts. When it is disconnected, you will be getting 12volts or less. This couple volt drop can cause a power drop. I'm not talking draining the battery, I'm just talking charging versus not charging. Under short periods of acceleration is when you need the full ignition system power the most.

Old school drag racers used to try running the 1/4 without an alternator, but were actually slower because old ignition systems were even worse performers under low voltage conditions.

Marty

[Corpse]

Hmm, interesting. I figured it was more of an actual throuput issue. but, i can understand somewhat as you are trying to get a high voltage spark as opposed to high amperage.

I was just figuring the battery would help as it is better on it's output potential. Well, I'll see how it goes, I'm sure the difference wont be too much as the cylinder Air/fuel charge isn't too extreme in my engine. I do have a ton of spare relays. maybe I should get creative and just use 6-20 AMP relays off the alternator and have a switch for five of them, limiting the alternator's draw to just ignition and perhaps some other vitals.

that isn't something I want to do too soon. I already don't have much space for relays, i need to reloace the battery to the trunk. I relocated my washer tank and I plan on the coolant tank but, that is more of a pain, with the long hoses and the level of the container. Little annoyances are the cost of a more refined engine bay operating environment. I have too much time on my hands.

Thanks for the valuable insight, I just hate engine parasites. If you think about it though, having the belt drive nothing but a pulley, the tensioner and the alternator (Switch off) may be worth it's while until a conjure something more efficient up. i still need to get another pump for the PS though. Or significantly lower the draw of my current one as I am looking to do.

-Dave

[Guest]

This is a first, parasitic loss from a PCV? :roll eyes:

You will actually get BETTER performance incorporating it, think about the vacuum pumps that racers use, to pull a measuarble amount of vacuum from the crankcase. On a stock Ford 302, this simple modification is good for 15 HP. I know the PCV will not pull as much vacuum, but that ilistrates the point. It's JUST an emmisions device, in the aspect of buring or eliminating gasses, but also in mechanical performanbce as well. Easier for the pistons to moved down in the cylinders during both the intake and power strokes. Better ring seal will also help overall power output.

I would surmise that running an electric vacuum pump to pull crankcase vacuum (which I don't believe is your intent for the pump), will have a higher parasitic draw then just running the PCV or the plenum connected brake booster signal, and even that HVAC control. Beleive me, I've done a lot of research on the same ideas, and the Vacuum source from the Plenum itself IS the least parasitic. About the only reason people use the vacuum pumps is with rather large or long duration cams, where vacuum is very low.

And for the record I am also one that would like to try and at least lessen the damage we are doing to our environment.

Another thing to think about, untuned I made 218 HP and 270 Ft/lbs at the wheels in my truck, with Charcoal canister Cat, my EGR was not hooked up at that pont but is now, it runs much smoother and fuel ecomy went way up, also had more low end pull.

[RednBlack]

You can spend 300 bucks and do this.. http://www.auto-physics.com/ I prefer to stay with the stock, since I do have to drive it on the street. I like your theory though. There are several I have thought of. Choking the return line. Unplug the coolant sensor. Seriously, I like your thinking. No theory can ever be proved over the net. Has to be on the track.

[Corpse]

Hmm, i could screw around and use a few transistors, diodes and a 15 Volt Voltage regulator I have... I wonder how much juice the ignition system uses.

I guess a 230Watt capable system providing 15 Volts may work well. That would be very easy to assemble aswell. thanks for the idea. I shall try some R&D.

So much thought to do, so little time... (not really..)

-Dave

[sharkey]

as for an evac system, yes, it does work. all it takes is putting the tube into the collector on your headers and run the hose up to the valve covers. im guessing your not running headers though. also if you want to take the vacume away from your brake booster, then find a turbo grand prix and take the booster from that, its hydralic from the power stering pump. this will cause more drag on the power steering pump though. if you ran a vacume pump, it causes more strain on your alternator. what about shutting the alternator off??? most drag cars have gone back to running an alternator. most were finding with all the emectrical stuff on the car (gauges, fuel pump, high powered ignition systems, vacume pump, water pump, ect) by the time the burnout is done and you stage, by half track your at 11.5 volts, and most ignition systems take a dump around there, so you lose power. most racecars use dual high amperage batteries.

what im getting at is there is no way to get rid of the parasitic loss, you just have to minimize it. now going nuts taking all the emissions controll off isnt gonna do anything. if you stick to your map sensor and brake booster, your not going to gain power. you have to remember, when you go WOT, your vacume goes away because the throttle blade if allowing the air in (path of least resistance).

[imported_germ]

well, not sure if this will help you guys or not...

but my PCV has been removed for a few months now. all i did was plug the vacume line, remove the PCV valve from the intake and replace with the filter.

i also did the same thing with the rear valve cover and that stupid ass plastic hose that runs to the intake pipe.

i did this to avoid putting pressurized air from the turbo into the crankcase because the PCV valves didnt seem to hold 12 psi to well without leaking boost.

[Froggx]

well, not sure if this will help you guys or not...

but my PCV has been removed for a few months now. all i did was plug the vacume line, remove the PCV valve from the intake and replace with the filter.

i also did the same thing with the rear valve cover and that stupid ass plastic hose that runs to the intake pipe.

i did this to avoid putting pressurized air from the turbo into the crankcase because the PCV valves didnt seem to hold 12 psi to well without leaking boost.

Is there any negative effects do having PCV vent to the atmosphere like this as I was planning on doing the same thing to avoid pressurizing my crankcase.