Stalls When Slowing Down, Or When Revs Drop

[phat_man]

I did bother to read it and just made a commentary about what normally happens on this forum when stalling or atmo bov's are mentioned. I have no opinion one way or the other. Perhaps you'll notice that I wasn't replying to your post, denoted by the quote in my post.

fair enough, i miss interepted what you were trying to say, ma bad.

update* i unblocked the PCV, but i still have this problem, im not sure why its stalling out, it cant be my fuel pump or my bov as it wasnt doing this before.

thanks, issa.

[GeeTR]

...I can spend the time to explain how it works

Hey dood,

Nature always tries to equalize, from one extreme to another, be it heat or particulates suspended in liquid. So osmosis, or equalization of a concentration through a semi permeable membrane... (tea through a tea bag into hot water, or water through your kidneys, 02 and C02 through aveoli in your lungs) or hot air from one room to another etc.

When the cylinder charge burns, some gas leaks past the piston rings into the crankcase, that's called blow by. Clearly engines work cus the pressure in the cylinder is higher above the piston then below is, so the piston moves down. Having pressure from blow by below the piston, in the crankcase then lowers the pressure differential, decreasing performance and causing issues with blowing out seals, dip stick etc etc.

The factory setup has a pipe from the cam cover to the intake pipe, then when under boost ingests the blow by, creates a little vacuum under the piston, increasing performance slightly.

On the over run, or when you back off the accelerator and the revs are dropping, a small one way valve opens and suck the blow by from the crank case as well. The one way is there, so when on boost, pressurized air doesn't go back into the crank case.

People remove the cam cover to intake pipe connection, as older cars have more blow by, and ingesting and burning these "already burnt oily gases" lowers the quality of the in cylinder combustion. This why you see ppl use filters on the cam covers (V8's) and just bleed that blow by to the atmosphere. This is illegal though, as the blow by is technically combustion gases that haven't gone through the cat.

Aftermarket, people use a container (oil/air separator) full of stainless steel wool, and route the gases through that, and then have a filter on the oil/air separator (which technically isn't legal either)

Keep in mind that in the stock setup, when on the over run, the PCV valve opens and wants to ingest air from the crankcase AND from the stock pipe to the intake pipe. Seeing as there's already vacuum in front of the turbo, and the pipe is "behind" the AFM, the PCV is ingesting air that's ALREADY BEEN METERED by the AFM… so AFR's stay the same, the ECU doesn't get confused. The issue is when people leave pipes open, or what not and the PCV pulls air from effectively a "leak"

Hope this makes sense. Search SAU, been covered many times, with lots of pictures and theory how people setup after market setups. Once you know what's going on, make sure your setup, is setup correctly otherwise you'll be stalling etc.

Rough outline, hope it helps

Michael

Edited February 27, 2008 by GeeTR

[phat_man]

thanks alot GeeTR, your a champion.

i get what you mean now, so its stalling because its sucking in air which isnt accounted for by the air flow meter. isnt this bad because its sucking it in from the top of the head?

or does it need to be pressurised, thats why its in front of the turbo compressor standard.

thanks alot, issa.

edit: so just putting a filter over it wont stop my stalling problems?

Edited February 27, 2008 by phat_man

[GeeTR]

thanks alot GeeTR, your a champion.

i get what you mean now, so its stalling because its sucking in air which isnt accounted for by the air flow meter. isnt this bad because its sucking it in from the top of the head?

or does it need to be pressurised, thats why its in front of the turbo compressor standard.

thanks alot, issa.

edit: so just putting a filter over it wont stop my stalling problems?

No worrys man

Well Im not really saying what its doing, as Im still not sure how your fab guy has made the pipe, some pictures would help.

Airs not getting sucked into cam cover breathers, as with the engine running, there’s still going to be some blow by.

Dont mean to palm you off, but its insanely simply concept, thats better shown with pictures.

Check this link... http://www.skylinesaustralia.com/forums/Ca...68174.html&

and all doubts should be alleviated. Hell, the issue, this thread was started for might not even be this

[phat_man]

No worrys man

Well Im not really saying what its doing, as Im still not sure how your fab guy has made the pipe, some pictures would help.

Airs not getting sucked into cam cover breathers, as with the engine running, there's still going to be some blow by.

Dont mean to palm you off, but its insanely simply concept, thats better shown with pictures.

Check this link... http://www.skylinesaustralia.com/forums/Ca...68174.html&

and all doubts should be alleviated. Hell, the issue, this thread was started for might not even be this

thanks for that, i had a read, i think i get whats going on.

now someone asked a question which no one answered in that thread and i want to know sort of the same thing.

i had the pcv pipe that used to run into the air intake pipe bunged, now i unblocked it and it sucks air in, should i put* a valve on it so it can't* suck air in, but so it can* blow out? or should i leave it as it is and just put a filter on it, it still idles abit funny but the computer is learning, and sometimes it stalls before the computer can correct itself.

so basically does it have to breath, or does it just have to blow out?

edited*

thanks alot, issa.

Edited February 28, 2008 by phat_man

[joeyjoejoejuniorshabadoo]

we need a stock bov smiley

[lighty01]

best bet is to get the maker of ur inlet to put 2 nipples to attach the stock hoses on.

my mates rexi made a winding noise when we blocked the vaccum like coming from his rocker cover to the inlet.. im pretty sure your having the same issue.

[phat_man]

thanks for that, i had a read, i think i get whats going on.

now someone asked a question which no one answered in that thread and i want to know sort of the same thing.

i had the pcv pipe that used to run into the air intake pipe bunged, now i unblocked it and it sucks air in, should i put* a valve on it so it can't* suck air in, but so it can* blow out? or should i leave it as it is and just put a filter on it, it still idles abit funny but the computer is learning, and sometimes it stalls before the computer can correct itself.

so basically does it have to breath, or does it just have to blow out?

edited*

thanks alot, issa.

edited so it makes sense.

[GeeTR]

thanks for that, i had a read, i think i get whats going on.

now someone asked a question which no one answered in that thread and i want to know sort of the same thing.

i had the pcv pipe that used to run into the air intake pipe bunged, now i unblocked it and it sucks air in, should i up a valve on it so it can suck air in, but blow out? or should i leave it as it is and just put a filter on it, it still idles abit funny but the computer is learning, and sometimes it stalls before the computer can correct itself.

so basically does it have to breath, or does it just have to blow out?

thanks alot, issa.

The plenum mounted one way is simply a source of vacum on over run. If you dont intend to set it up legally, then just block it off.

All your trying to manage really, is the fumes wafting out of the cam cover breathers. At minimum you need to stick a filter on there, just to stop crap from falling in.

Your best best to prevent oily mist all over your engine bay, is running the pipes from those cam breathers to a oil / air separator, which your well versed on now and run a pipe from the separator under the car somewhere, left open.

Again, this isn't legal, but allows the motor to breath, doest make your car ingest oily air under boost (when it matters) Iv seen the PCV connected to can, and another one way on the open end as well.

Cheers

Edited February 29, 2008 by GeeTR

[phat_man]

thanks alot for the help mate, i finally got a picture of my engine bay as it is now.

as you can see the pcv pipe on the right is just open, it was bunged but its just flowing freely. whats my best bet;

just put a filter on the end of it?

put a filter and a one way valve so it cant suck but it can blow out?

put a catch can so its just connected to the open pipe, and the other hose on the catch can goes under the car?

or put a catch can with a filter on it so i block the lines from the plenum going to the head, then connect it so it connects to both the knobs on the head?

im lost atm, thanks again for the help. issa.

[phat_man]

the last catch can setup im talking about, would that be the best way to go about it?

[phat_man]

update.

i blocked the pipes where the red is, and i put a makeshift fliter on where the yellow is, it fixed the idle alot better, but it still sometimes idles lower and stalls when i slow down???

what else could it be. im pretty sure its got to do with that, as it started happening straight after i installed the intake pipe.

[phat_man]

Thank you everyone for you help. i have found the problem to my idling issue... well actually my cousins mechanic found it.

it was a seizing throttle body, it was getting caught on all the shit stuck in there, so he gave it a good clean with some carby cleaner and i was on my merry way, its still seizing up a little, its just the last of the grim getting sucked away... i hope anyway. at least its not stalling anymore and idles properly.

thanks alot, everyone esp to GEETR for your help.

cheers, issa.