PCV Modification with Vapor Separation

[skagwayroadie]

Mark, the only thing you would do is the PCV modification.

The brake booster and everything else still is connected to the vacuum - you haven't even touched those.

The vacuum of the entire system is increased by just doing the PCV modification. Therefore, since the brake booster is still connected to the vacuum system and the vacuum is increased, the brake vacuum should be increased and the brakes should work better.

On another topic, you mention a vacuum pump arrangement, that is something that probably could be done too. If virtually every vacuum driven item in the car was operating from an electric vacuum pump, we would be able to get maximum vacuum in the engine - would be interesting to see how strong of a vacuum we could make going that route.

Thanks Aaron,

I get what you are trying to illustrate, the concept is simple enough. But on my 20 year old truck, the booster is connected to the PVC, and to no other source of vacuum. I have not worked on any car that was different than this, but I am not a automotive mechanic/technician.

Yes, I did initially think of an vacuum pump as I was reading the whole thread as some race cars do this to eliminate drag and thus reduce HP loss in racing applications from crank driven components. I gained a noticeable amount of power removing the fan clutch and went to a e-fan for a daily driven vehicle example.

[Aaron Murakami]

Ok - on my car and my friend's cars, the blow-by is directly connected to the PCV valve and that is it. All the other vacuum lines are connected to other parts of the manifold I believe.

[skagwayroadie]

Well, now we are getting somewhere. I do have on one bank of my v-6 where the blow by is vented to the intake piping. On the PCV valve a line goes to the vacuum booster and another to the intake tree, that controls heater functions and cruise control etc. So, this vacuum system is still being used, just accessed in a different way from yours, with the same effect. Knowing this then, how does this affect how we go about performing this mod as I am a bit confused now.

[Aaron Murakami]

On my car for example, the blow-by goes to a Y splitter. One side went to the PCV on the manifold and the other side went to the intake like yours (before the throttle body of course).
So I just plugged the manifold and plugged the tube from the Y splitter that went to the PCV. So the blow-by only has one exit and that is to the intake air box.

If you have the booster going straight to the PCV, I wouldn't do anything to it unless you knew more about the whole setup.

I really haven't seen those setups. Being that the PCV is a one way valve that only opens in the direction towards the manifold in order to suck the blow-by into it, I'm not sure why any booster or anything else would be connected to it.

Also, PCV's fail because of gunk building up, etc... and if a brake booster relied on vacuum from the PCV, that would be a serious safety hazard if suddenly your booster had no vacuum due to a clogged PCV. Would not be a fun surprise. I doubt any auto manufacturer would use the PCV for anything other than simply sucking the blow-by into it. I'm not an auto tech either but this is my best guess so far.

[skagwayroadie]

Got it Aaron!
I think I know what to do now. You description was clear and coupled with your initial post descriptions, I think I can make it work. We are talking about the same thing in different ways...different perspectives. I play around with my truck and do some testing and see what happens.
Thanks for taking the time to share and clarify...I love this kind of stuff!

[Aaron Murakami]

Ok - cool! Post a diagram if you can of whatever you wind up doing. Could help someone with the same setup.

[adurer]

There is a very simple way to know how much vacuum there is in our engines and I don't know why Aaron didn't mention that. It's called vacuum gauge. Every engine in good order has an intake manifold vacuum AT IDLE of 17-22 inches of mercury (inHg). So anyone can measure what vacuum gain he gets by plugging the PCV pipe to intake manifold.

But the real problems Aaron doesn't see (or deliberately omits) are these:

- all vacuum is depleted rapidly the moment we push the accelerator, because the throttle valve opens and thus atmospheric pressure 'rushes in' equalizing manifold pressure
- we need a MUCH higher vacuum to vaporize fuel at room temperature, much higher than any normally aspirated engine can achieve eventually ONLY AT IDLE.

So my opinion is we might get some minor fuel economy only when idling, but sadly we don't idle too much...

[vzon17]

But the real problems Aaron doesn't see (or deliberately omits) are these:

- all vacuum is depleted rapidly the moment we push the accelerator, because the throttle valve opens and thus atmospheric pressure 'rushes in' equalizing manifold pressure
- we need a MUCH higher vacuum to vaporize fuel at room temperature, much higher than any normally aspirated engine can achieve eventually ONLY AT IDLE.

So my opinion is we might get some minor fuel economy only when idling, but sadly we don't idle too much...[/QUOTE]

Actually not true my vacuum stays very high most of the time unless I really push on the throttle very hard. You loose some of the vacuum but never all of it. Unless you floor it.

[Aaron Murakami]