To cap or not to cap (PCV related)::Leak down 10/24/09l::

[MA70Snowman]

Okay I'm abreviating this ALOT.

I have a fresh rebuilt engine.
550 ccs
MAFT PRO running speed density
big T4 turbo (I don't think specs are important)
T4 tubular exhuast
HK$ wastegate dumped into downpipe
4" filter/intake pipe (NO BUNGS)
stock intake manifold
AFPR


issue:
So i got a good tune on my car. could kinda keep a steady Idle around 400-600
drove around. cruising i'm seeing 14.1 AFR, under boost 12ish
idle around 15

During my build I put on NA valve covers to clean up the engine bay to go w/ my COP ignition setup and had plans to run a FFIM. well my funds ran low and I didn't get the FFIM so wh en I bolted it all up the throttle linkage runs RIGHT OVER the Valvecover ports that I had tapped w/ -10 AN fittings that i was goign to run SS lines for a CC setup. SOO.. i've been running w/ both of thoses ports open w/ 2 small filters kinda... Rigged ontop of them There's no pre-turbo port because of the upgraded intake pipe (the port that the PCV system ran to on the accordian hose) Well after I got my tune I was under the hood and realized that I totally forgot about the port on the TB that the PCV system went to. So i figured i'd cap it.. NOW the car runs like ass. My logic. I figured I tuned the car w/ that extra air comming in. so I tried tuning a little leaner. for the life of me I can't get it stable yet.. I've DUG all over these boards regarding the PCV sytem and I'm pretty sure I understand how the system works.
So stock... the TB port was actually brining AIR into the sytem from the Filter.. correct? so theoretically I'd want to leave that port Open right? as at idle w/ the TB closed that air is still coming into the engine across the valve cover ports. (of course brining the valve gases w/ it) so my reasoning is I should UNCAP it.

so c urrently i'm thinking of taking another filter and popping that onto the port, would that be okay?
also. the two valve cover ports. am I hurting my engine leaving them open?
do I need vacuum on those ports for crank case pressure? I'm pretty sure I've seen a couple setups similar w/ 2 filters on them as well (of course this doesn't mean its right either)

Any input from some of the more techincally informed would greatly help out thanks guys.

 

[hvyman]

to have a properly working pcv system you need both ports(tb and accordion) into one port on the cc and the both valve covers going to the other port.

if you have a filter on the tb that will be a vac leak. if you have filters on the valve covers your not getting the vacuum you need to pull the gasses out of the engine.

--------]--]---------


the ] = valve cover ports and the -- = the lines running to the tb and accordion pipe. you need both ports so at all times you have vacuum to the valve covers to pull vapors from them. if you just use the tb port there will be times when your not getting vacuum to pull vapors. if you just use the accordion hose there will be a lot of times when your not pulling vapors from the valve covers. and when you don't have a proper pcv system you will eventually build up to much pressure and hopefully just blow a main seal.

 

[gaboonviper85]

Dear op

turbo cars must have crank case evac! Plumb the system back up like stock or do a proper catch can system...either way it needs to be run to the throttle and infront of the turbo! The pcv keeps vac on the motor which keeps oil "in the motor!"....putting those filters on the valve covers is BAD!

Do not put a filter on the throttle port as that's gonna be a huge boost leak and it will probably explode on boost anyway. Do more research on the pcv system as it's actually very important on ALL motors!

Have a bung welded onto your preturbo intake for your pcv system!

 

[rayall01]

Since I infer from your list, that you're still using the stock computer, you will never get it to run right without EGR. The TCCS requires the use of EGR.

 

[dumbo]

Running speed density, shouldn't really make a difference, computer can't see small leaks. So does it go back to running good when you unpcap it?? Either way you should set up the PCV system as it was stock.

 

[MA70Snowman]

Running speed density, shouldn't really make a difference, computer can't see small leaks. So does it go back to running good when you unpcap it?? Either way you should set up the PCV system as it was stock.

Actually Like I mentioned it ran VERY good w/ it uncapped thats why I'm asking these questions.

if you have a filter on the tb that will be a vac leak.

HOw is that concept different then stock?
IN the stock setup that hose going from the according across the valves to the TB. is pulling air directly from the air fiter its taking OPEN AIR.. metered or unmetered doesn't matter in the speed density setup.
HOWEVER, I do agree w/ it being a boost leak. and that was the initial reason for me capping it. as stock that boost pressure would just be fed back into the turbo helping to spool the system.

Seems like I will be swapping my old turbo Valve covers on for the mean time so I can actually plumb my ports back how I had them.

 

[dumbo]

Does it run shitty only at idle, or while driving too? It really shouldn't make a difference, thats strange. And as for a boost leak there is an orifice in there so it's only a slight leak, and not something to worry about, but you don't want to suck in unfiltered air there.

 

[MA70Snowman]

Does it run shitty only at idle, or while driving too? It really shouldn't make a difference, thats strange. And as for a boost leak there is an orifice in there so it's only a slight leak, and not something to worry about, but you don't want to suck in unfiltered air there.

Well when I firs capped it the engine straight died. was tough to start had to put the foot on the gas for awhile hold it at about 1500 rpms then after about 30-45 seconds I could get it to ROUGHLY idle. The drivability definatly suffered. stuttered on accel . stumbles and some times dies on the decel. and cruising can be lurchy. I uncap it.. it all goes away. and the more I think it about it.. it should make a difference. because thats more air into the chambers which changes your A/F mixture. specially at idle when the TB is closed. thats why I threw my original post out there. and I agree about unfiltered air thats why I contemplated a filter for a little while.

 

[dumbo]

Do you know forsure if the ISC valve is working, because I think that should handle your idle and what not. But I'm not sure, I could be way off.

 

[IJ.]

Blocked/clogged breathers in the NA covers?

 

[MA70Snowman]

Do you know forsure if the ISC valve is working, because I think that should handle your idle and what not. But I'm not sure, I could be way off.

Yeap. 100%, tested per the TSRM. and during cold I can feel it pulling vac if i pull the line off. and warm it closes.

Blocked/clogged breathers in the NA covers?

I'm guessing you're talking about the vents on the inside of the valve covers that LEAD out to the ports on top.. if that is the case, I would have to say no, not clogged. based on the fact that after she's warm I can see gases comming out of the ports before I had filters on them.

Anyway. I took alot of the advice on here. and Swapped on my old ugly Turbo valve covers at least until I go FFIM. I found a thread and Ripped IJs set up for the valve cover/catch can setup.

Valve covers T together. then run the the catch can. that leads to a T w/ one side going to a port I tapped into my pre turbo intake Pipe. and the other go ing to a one way check valve that then goes to the intake port. the check valve of course set to allow vaccum into to the manifold and not allow boost out. My battery was drained at the time. So I will attempt a start up tomorrow afternoon, and re-tune. (If anyone thinks the above setup is incorrect please set me right. but I'm pretty sure its a mirror of IJs setup.)

 

[dumbo]

Sounds about right. I think that old man knows a thing or two
Let us know how it goes

I`m gonna see how mine reacts to plugging and unpluggs the tb port as I also running maft pro spd+dens. When I`m home that is.

 

[jdub]

Are you using the stock ISCV? Do you hear it step open when you shut the motor down?

Is it routed to the intake or did you put a filter on it when you switched to SD?

Has the ISCV and the check valve under it been cleaned (or replaced)?

I suspect the air you had entering the TB from the PCV port was supplementing idle air from the ISCV...in fact, this is what it does on the stock system. You are correct, when you set the MAFT Pro up for SD with the port unplugged, it was "seeing" the air induced from the TB PCV port and it should. If you install a stock PCV, the problem should go away.

 

[MA70Snowman]

Are you using the stock ISCV? Do you hear it step open when you shut the motor down?

Is it routed to the intake or did you put a filter on it when you switched to SD?

Has the ISCV and the check valve under it been cleaned (or replaced)?

As mentioned I tested and verified it according to the TSRM. And everything I could get my hands on was cleaned during the engine rebuild.

I suspect the air you had entering the TB from the PCV port was supplementing idle air from the ISCV...in fact, this is what it does on the stock system. You are correct, when you set the MAFT Pro up for SD with the port unplugged, it was "seeing" the air induced from the TB PCV port and it should. If you install a stock PCV, the problem should go away.

That was my thoughts too. I'm curious to see how she acts now. but won't be able to play w/ it till after work today. will definatly let everyone know.

 

[jdub]

To clean the ISCV, it has to be removed from the manifold and the motor removed from it's aluminum base (3 screws). The check valve is under it in a recessed circular slot. Is the ISCV air path still routed to the intake like stock?

You really do need to get the PCV under vac from the TB.

 

[MA70Snowman]

To clean the ISCV, it has to be removed from the manifold and the motor removed from it's aluminum base (3 screws). The check valve is under it in a recessed circular slot. Is the ISCV air path still routed to the intake like stock?

You really do need to get the PCV under vac from the TB.

Yeap, I dismantled the ISCV. I was very meticulous on this engine build. Also including the fact that I was dead set on powdercoating anything I could pull apart and stick in an overn w/ out it breaking.

AND w/ the current setup the PCV SHOULD be under vac unless i'm misunderstanding my setup.

TB port -> PCV valve -> T -> Catch Can -> T -> Valve covers
.................................^
.....................Pre-turbo Intake pipe

 

[IJ.]

Silly question but is the PCV facing the right direction?

 

[adampecush]

Also, where did you route the line off your ISCV? It sounds like you have nothing routed to the intake tube. Unless you are running MAP, you will have problems introducing air after the MAF (both ISCV and PCV).

The stock PCV and ISCV systems are not "air leaks". They are re-introduced after the airflow meter.

 

[MA70Snowman]

Also, where did you route the line off your ISCV? It sounds like you have nothing routed to the intake tube. Unless you are running MAP, you will have problems introducing air after the MAF (both ISCV and PCV).

The stock PCV and ISCV systems are not "air leaks". They are re-introduced after the airflow meter.

Yes. Speed Density is a MAP, so NO the ISCV is not routed to the intake pipe. that has a Filter on it.

Silly question but is the PCV facing the right direction?

Honestly... with some of the stuff i've seen on these forums.. thats not entirely a silly question. But per your referance in another thread. I put the PCV right infront of the throttle port that so its open when there is vacuum TO the TB and closed when the system gets under boost, so that the vacuum is comming from the pre-turbo pipe.

Are you using the stock ISCV? Do you hear it step open when you shut the motor down?

Is it routed to the intake or did you put a filter on it when you switched to SD?

Has the ISCV and the check valve under it been cleaned (or replaced)?

I suspect the air you had entering the TB from the PCV port was supplementing idle air from the ISCV...in fact, this is what it does on the stock system. You are correct, when you set the MAFT Pro up for SD with the port unplugged, it was "seeing" the air induced from the TB PCV port and it should. If you install a stock PCV, the problem should go away.

jdub - I honestly wasn't aware there was an "other then stock" option lol. so yeas i'm running the stocker. and as mentioned before I am running a filter on it. I honestly didn't see a difference between a f ilter or running it to the pre-turbo pipe.
and you suspected exactly what I'm suspecting after reading more and actually thinking about the issue.

Well as mentioned I installed the PCV system. after about 30 minutes of fiddling (re-did base timing, re-tuned) I was able to get it to hold at idle w/ a 14.1 AFR. it was REALLY rough when it was cold, so I'm not sure if thats still going to be an issue as by the time I did have everything setup, it was warm. I'm guessing I'll have to do some more playing around while its cold or play w/ the Afterstart on the MAFT pro. Drivability is MUCH improved. no jerking at partial throttle, comming on/off the clutch is smooth. only rarely will it die during decel, like coming up to a stop sign/light, but I blame it entirely on a rough tune. haven't played w/ boost yet, as I'm still tuning low/mid, after I get a good setup there i'll move onto the High.

 

[dumbo]

Run it like stock, and be done with this problem. Not to mention no cons what so ever.