C4VetteLS1

Ack, i think i may have gotten a part i dont need now.

I just got my AMW catch can setup and i have an Metco Breather as well. I was just thinking i cant use both together can i? because the idea of the breather is to eliminate the PCV stuff as you cant use pcv with a open system (breather).

Or if i run the catch can i need to run the stock oil cap that seals the crankcase.

Can you guys confirm this is correct. Also which do you think would work better? Personally i would think the pcv setup with the catch can would work better to vacuum the crankcase pressure. Any opinions?

Cokeroker

iTrader: (9)

to me they are both "precautionary" in nature. I personally have both and have noted no problems with it. I honestly have only had the catch can in for like 500 miles and have not checked it for oil tho

NastySSoo

Ditto what Cokeroker said. I have noticed a major decrease in oil consumption which can only be attributed to the breather.

TKGN1

I have installed the kit both ways, sealed and with a breather. I run a breather and the catch can on my personal car, but the functionality will work either way. The pcv still is pulling crankcase pressure out, which is what you want. In essence, the valve cover filter is basically acting like the fresh air tube did, still allowing fresh air to enter and move through the crank case.
The breather buy itself (no pcv), IMO, can only evacuate the crankcase buy the pressure it builds up, therefore a positve pressure is created within the crankcase. That is why I'm a firm believer in the pcv (vac. pump, or some type of evac. system) to help remove the pressure. Drawbacks to the pcv is oil contamination, which brings us back to a catch can.
Hope that helped.

C4VetteLS1

If you have a breather which makes the crankcase a open system, how can the pcv work to control pressure/vacuum in the crankcase since the breather will negate any changes from the pcv? ( I could be wrong)


Also say you run your pcv from your drivers side valve cover (stock ls1 style), run it to the catch can, then to the port on intake correct. Then put a breather on it. Do you then cap the pass valve cover line that goes from the valve cover oil neck to the throttle body port?? or do you leave that hooked up?

jimmyblue

iTrader: (11)

If you do have a breather, then you don't want
to have the rest of the PCV attached to the TB -
cap off the bungs. Because otherwise it is a
source of un(MAF)metered air in your system and
will perturb mixture. And then since the PCV is
disconnected, the catch can is pointless.

TKGN1

on a stock LS1, the fresh air tube runs from the throttle body(atmospheric pressure/ no vacuum) to the valve cover, no restrictor or anything, just a straight line. If you disconected this port and added a breather, it will not change the amount of vacuum the pcv is pulling. The pcv itself is the controlling factor to the volume and vacuum the motor pulls on the crankcase.
The crankcase is still an open system basically, through which the "air" travels through the air filter--> throttle body-->fresh air tube-->crankcase-->pcv-->back into the intake.

If you were to put a breather on the valve cover, I don't think it would make to much difference if the stock fresh air line was connected or not. But, you definately need a fresh air source. I have heard of guys actually cavitating the oil pump by pulling vacuum on the crankcase without a fresh air breather, although that was with an external vac. pump. I would assume that the stock system could pull enough vacuum to cause problems without a fresh air source, but I havn't found a volunteer to try it on their car.

jimmyblue

iTrader: (11)

The PCV makeup tube comes from before the TB
but after the MAF, and the uptake tube is behind
the TB. There is no unmetered air path (unless you
have bad seals). Once you open up either end of
the PCV plumbing you can pull fresh air that isn't
known by the PCM. The spent gasses in the
crankcase are mixture-neutral (first order) but this
is not true of fresh air / vacuum leaks.

TKGN1

jimmyblue, good point, just curious if the amount of volume that passes through the pcv(if running a breather set-up) would actually throw off the pcm as unmetered air? Thanks for the insight.

C4VetteLS1, I'm still favoring the pcv set-up, not because of the catch can, but more for evacuating the crankcase.

NastySSoo

Im using both with no negative (only positive) effects!

BLK02WS6

iTrader: (2)

How does this setup sound? I took the fresh air line off of the TB and put the small K&N filter on it that used to be on my AIR pump line (filter came with my lid - AIR pump is gone). I then plugged off the TB fresh air connection.
I also have an LS6 valley cover with an empty glass fuel filter in the line before the PCV valve to see any oil - so far none. I have a catch can, but didn't get anything in it with this motor so I took it off.

The reason I did this is because I was actually getting oil in the fresh air line from the vavle cover to the TB. I don't understand why, but it was in there and even in the small cavity on the TB - none inside the intake at the PCV connection though. Is it possible to draw vacuum on the fresh air line even though it is on the inlet of the TB? Maybe at WOT? Doesn't make sense to me, but now it can't get to the TB for sure!

iateyourcat

Great info! I've been wondering about this and you've all answered every question I had.

Ferocity02

iTrader: (60)

The amount of air brought into the motor through the PCV line system is not nearly enough to throw off any readings whatsoever.

Viper

iTrader: (6)

"The reason I did this is because I was actually getting oil in the fresh air line from the vavle cover to the TB. I don't understand why, but it was in there and even in the small cavity on the TB - none inside the intake at the PCV connection though. Is it possible to draw vacuum on the fresh air line even though it is on the inlet of the TB? Maybe at WOT? Doesn't make sense to me, but now it can't get to the TB for sure!"

Mine does the same thing, so I put a filter in-line on that line to stop the oil. In combination with the AMW catch can I have, this system is working well now; no oil behine the TB and in the cavity, and I'm getting oil in the catch can. But I like the idea of a fresh air filter on that line off the passenger valve cover instead of going to the TB at all. When you folks speak of a breather, are you talking of one that replaces the oil fill cap on the passenger valve cover?

NastySSoo

Thats correct, screws on in place of oil filler cap.

TKGN1

Thanks for the clear up Ferocity02, I didn't notice a change on my car with an open breather and I'm running an LS1 maf. But, I will still do further research to be sure.

C4VetteLS1

Ok so would you all agree this is the correct way to run both:

1) Run the metco style breather, cap off the throttle body air line that used to goto the filler neck.

2) Run the pcv vacuum line (on ls1 style pcv) from driver rear of valve cover around and directly to the AMW catch can, and the other side of the catch can to the vacuum port on the side of the intake after the throttle body.

3) Plus both vacuum ports coming off the passenger side ls1 valve cover.

This is in a non ls6 pcv setup car.

NastySSoo

I installed the metco, installed the AMW catchcan, and left the line to the TB in tact.

TKGN1

just make sure you still use the pcv valve. All the LS1s I have installed the kit on, I simply removed the rubber line between the pcv itself and the throttle body and added the new lines and the catch can in between. Makes going back to the stock set-up real easy.
I agree with NastySSoo, won't hurt to leave the stock fresh air tube on.

C4VetteLS1

But do you plug off the driver side valve cover breathers? and just run the pcv from passenger side valve cover (or ls6 nipple on front if using ls6 valley cover) to the catch can.