Recirc PCV or Exhaust scavenger???

[kracin]

ok, i want to switch styles, i hate getting oil in every part of my intake from all the vapors coming from my head and being pulled with vacuum to the intake... switching to the exhaust scavenger style that uses the venturi effect to pull vacuum with the exhaust flow in the downpipe/elbow

ok, so the question is, anyone have numbers or know which works better? anyone ever test the vacuum achieved at different rpms through both styles? or know which one works better for our cars.

i know that ive seen both run, but havent heard much, youd think that the intake style would pull more vacuum, simply because you pull more air through, but the venturi style usually pulls a lot too, and you dont need a high vacuum til high rpm anyway (for those that say theres not enoughe xhaust pull at idle) to prevent blowby.

thanks in advance

Ian

 

[IJ.]

Another option would be to use a Caddy electric vacc pump and vent this to the exhaust, benefit here being better ring seal as the crankcase is always under vacc. (to continue the discussion from "Data Base Error".... ummm I mean "SF")

 

[shaeff]

^ That's a very interesting idea, Ian. Do you know specifically which model(s)/year(s) have this pump? That might make for a good junkyard run. I haven't been there in forever!

 

[IJ.]

Shaeff: Sorry just rememebered a conversation on a domestic site awhile back on alternatives to the Moroso Vacc pumps and someone mentioned that late model Caddy's run a high capacity pump. (we already have a small helper pump mounted into the cruise control system)

 

[90T04]

The GM ones seals don't hold up well to oil vapor from what I have heard. Here is the one I am going to use. Its the smog pump out of a 1998 VW Jetta. I have read that the seals hold up much better to oil.

This bad boy sucks some major air volume. It will pull about 7 inches of vac. which is just about perfect for a PCV system. The downside is that it also draws a ton of amperage. Startup amps are at around 45A and it continuously pulls about 17A. I will get around the large initial amp spike by building a PWM driver to ramp up the current to full 12V.

I plan on using the normal engine vacuum up until I reach positive boost, and then use a trigger off of the Maft-Pro to turn on the PWM controller.

We shall see if it works. I have not figured out the plumbing or anything yet.

 

[NashMan]

venturi will wokr just fine but the poor fucker behind you will hate you to death

the only bad parts about exhuast dump is you will have to remove lines ever so often for cleaning since it will gum up from heat

or the comon way of befor turbo oily ic pipes or intake manfold with one way cheak vavle

the best thing you cna do is find out what are your goal for you car 500 all day long driven heavy as hell they tiwn exhuast dump wiht -12 is good thing to do remmber volume is you friend not persure

ok, i want to switch styles, i hate getting oil in every part of my intake from all the vapors coming from my head and being pulled with vacuum to the intake... switching to the exhaust scavenger style that uses the venturi effect to pull vacuum with the exhaust flow in the downpipe/elbow

ok, so the question is, anyone have numbers or know which works better? anyone ever test the vacuum achieved at different rpms through both styles? or know which one works better for our cars.

i know that ive seen both run, but havent heard much, youd think that the intake style would pull more vacuum, simply because you pull more air through, but the venturi style usually pulls a lot too, and you dont need a high vacuum til high rpm anyway (for those that say theres not enoughe xhaust pull at idle) to prevent blowby.

thanks in advance

Ian

 

[kracin]

venturi will wokr just fine but the poor fucker behind you will hate you to death

the only bad parts about exhuast dump is you will have to remove lines ever so often for cleaning since it will gum up from heat

or the comon way of befor turbo oily ic pipes or intake manfold with one way cheak vavle

the best thing you cna do is find out what are your goal for you car 500 all day long driven heavy as hell they tiwn exhuast dump wiht -12 is good thing to do remmber volume is you friend not persure

ya, ill be running 10-12 an size line to the exhaust dump, ive got a 1 way check valve setup in it and just got the bung welded into my downpipe right now, and the only thing that may stop it atm is that i might need to extend the pipe i have a little bit more to make it work right,

the engine will be pushing into the 700s when im done with it, hopefully on meth injection so i dont have to worry about any damn race gas being used all the time, keep it streetable and useable at high hp too. but everything is built for it except for a couple systems, and the new intake is next. so having exhaust dump would be suitable i think.... ill be checking the amount of vacuum i get from both the pcv to intake and pcv to exhaust scavenger with a cheap vacuum gauge hooked up to one at a time while driving and getting on it. and ill determine which ill go with from that, if i dont need the xhaust scavenger anymore then ill just cap it off and leave it at that.

 

[IJ.]

I like the switchable system 90t talks about Ian!

 

[Poodles]

Not to mention you can't run a cat, and it won't produce enough vacuum unless you're higher in the RPM range.

This is why they're used on drag cars...

 

[NashMan]

hench the word big boost all day long

me my self i useing rather simple set up tiwn -10 to a d block to a sinlge -10 to catch can to per turbo and or mana fold kidna tossing around ideas right now

it will do big power just not every day cauxe them v gasket's will leak


oh yae forgot to mention if your car rings seal great you will not hav emany issues at all if they don't then well you get the idea

 

[kracin]

Not to mention you can't run a cat, and it won't produce enough vacuum unless you're higher in the RPM range.

This is why they're used on drag cars...

i havent run a cat since i built the car, its straight 3" all the way to the magnaflow in back lol, if you run a cat your not gonna need to worry about a different pcv system anyway.

this car IS a drag car, in progress as well. and besides just like normal intake pcv styles, its the same as the exhaust scavenger almost, your not gonna pull rediculous vacuum off the bat through the pcv to intake unless your at high throttle also

but you don't need a lot of vacuum at idle, you need higher vacuum at higher rpm, which is what you get with both systems. you wont get a ton of blowby until you start upping the pressure with boost, and th emore boost you have the more exhaust flows or the more intake you have.

i have the bung already instaleld on my downpipe, going to clean up the connections today and install it back on my car, and ill be running both systems seperately at first and getting a vacuum gauge to test it like i said, and ill be sure to post some numbers, just want to make sure that its working at the optimum vacuum before i decide what to stick with.

 

[90T04]

your not gonna pull rediculous vacuum off the bat through the pcv to intake unless your at high throttle also

Wait isn't that backwards? I don't think you are going to pull any vacuum at high throttle. You will have the most vacuum at part throttle and idle.

 

[Poodles]

The stock GTE setup goes from vacuum at the throttle body, to vacuum before the turbo.

Yes, at closed throttle you have tons of vacuum at the throttle body...