Ok so please explain the pcv system to me. my throttle body is NOT from a gte, but a cressida and i am na-T. Circled in red is a connection on the throttle body that on a turbo car is connected to the valve covers. that connection circled in red is supposed to be doing what? blowing air out or sucking air in? mine blows air out but no air in. does that sound right? i always just had it blocked off since when i had the NA manifold i just had the valve covers connected to before the turbo and never had probs. is this the right way? if so i plan on using that port circled in red to connect to my isc (yes it works ive tried it)
explain the pcv system to me
- Thread starter viper92086
- Start date
The ISC is supposed to be connected to the accordian pipe(before turbo), boost would be a bad thing for the ISC(only meant for vacuum).
Your PCV system is correctly installed. Just block off the throttle body port and install an oil catch can in the line between the valve covers and the accordian.
Your PCV system is correctly installed. Just block off the throttle body port and install an oil catch can in the line between the valve covers and the accordian.
Fletch124;1111857 said:
Ummmm...NO!
The PCV requires TB vacuum to function correctly...and, it needs to be from the PCV port on the TB on a stock system. Plumb it anywhere else without a check valve and you will have a boost leak.
Also, the ISCV does not use vacuum...it uses metered air from the accordion hose.
The very best explanation/description I ever saw was made by JetJock (surprise surprise) but it's dissapeared into the slush.
jdub;1111862 said:
my TB doesn't have a check valve, its a cressida tb. on the cressida the valve covers are connected directly to the tb vs the intake piping. my pcv should be getting vaccum from before the turbo, just like the stock na setup right? also i have been using the isc after the turbo since i've gone na-t with no problems.
so i think i'm good then. thanks
I didn't say any of the stock TB's (Cressida or Supra) have a check valve. The GTE TB has an orifice to prevent boost from pressurizing the crankcase...the GE TB uses orifices as well, but the routing is different in the TB itself:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?Section=EC&P=5
The whole idea on the turbo is to allow vac from the TB to be the primary route for PCV vapor to be induced into the cylinders and burned. The motor is in boost only a small percentage of the time...when it is, PCV vapor is directed to the intake.
No, you're not "good" (where in the heck did you get that?). Doing what you suggested reverses the turbo design (7M-GE too) and will not work well at all. The vac produced from the intake is minor and nonexistent at lower RPM range. Like I said, the TB is the primary vac source...both on a GE and GTE engine. My advice is to get a turbo TB and route like a stock turbo motor...i.e connect the blue circle to the red circle.
Your ISCV need to get it's air from the accordion hose, after the AFM.
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?Section=EC&P=5
The whole idea on the turbo is to allow vac from the TB to be the primary route for PCV vapor to be induced into the cylinders and burned. The motor is in boost only a small percentage of the time...when it is, PCV vapor is directed to the intake.
No, you're not "good" (where in the heck did you get that?). Doing what you suggested reverses the turbo design (7M-GE too) and will not work well at all. The vac produced from the intake is minor and nonexistent at lower RPM range. Like I said, the TB is the primary vac source...both on a GE and GTE engine. My advice is to get a turbo TB and route like a stock turbo motor...i.e connect the blue circle to the red circle.
Your ISCV need to get it's air from the accordion hose, after the AFM.
jdub;1111894 said:
hmm ok ill source out a turbo tb then. another question is my car is burning oil i think, cause i noticed oil before the turbo and in the intake piping. would not having the pcv connected to the tb cause this? my car puffs some black smoke the first time i get on it everytime and little black smoke here and there. its on a maft basic in blow thru mode. does the pcv system have anything to do with this or do i just have possible blowby as well as a slightly rich condition because of my setup. i have the maft tuned via wideband to be 11.6 a/f under wot. motor has 74k orig miles if it matters.
thanks
oh yea and i know you keep saying its bad to have the isc after the turbo, but can you explain why? i can't see it causing any boost leak since the air is acounted for and not lost. i've seen several na-t guys run like that and not have probs. i myself have had it like that for 2 years and never had a idle problem.
oh yea and jdub even tho i'm gonna replace it anyway i'm curious to know why my tb would be letting air out of the orifice but not in. i can put my finger over the hole and idle or rev up the engine and air will escape but i dont feel suction at all. is it just a broken tb?
I would look at the turbo seals as the source of the black smoke...could be an initial rich condition too. Rings would give you more than a puff normally.
The TB plate should seal the plenum...if you block off the ISCV intake hose and PCV TB fitting, the motor should die. Routing the ISCV to the PCV fitting or anywhere else on the plenum deprives it of an air source at idle. If yours is running with the ISCV routed to the TB PCV fitting, you have a pirate air leak somewhere.
You also should have a flat shaped check valve under the ISCV...allows air into the plenum, but stops flow under boost. The GE motor does not have a check valve...you need it on a turbo.
At idle, you should feel vac at the PCV fitting...rev'ing it will reduce the vac up to positive pressure from boost. At cruise, you should be pulling vac. I am not that familiar with the GE or Cressida TB, but on a turbo motor it should behave as I described.
The TB plate should seal the plenum...if you block off the ISCV intake hose and PCV TB fitting, the motor should die. Routing the ISCV to the PCV fitting or anywhere else on the plenum deprives it of an air source at idle. If yours is running with the ISCV routed to the TB PCV fitting, you have a pirate air leak somewhere.
You also should have a flat shaped check valve under the ISCV...allows air into the plenum, but stops flow under boost. The GE motor does not have a check valve...you need it on a turbo.
At idle, you should feel vac at the PCV fitting...rev'ing it will reduce the vac up to positive pressure from boost. At cruise, you should be pulling vac. I am not that familiar with the GE or Cressida TB, but on a turbo motor it should behave as I described.
jdub;1111949 said:
turbo was just rebuilt by mdc about 1 month ago. if i take the hose off the isc the motor dies. it also has the check valve (the round disk with the flaps). as of right now the car is still setup as connected to the tb. it was originally connected to the coupler before the tb much like how the ge intake mani is set up. i dont feel vac at the pcv fitting (the tb port) but when i do rev it a little you can feel air escaping from that port.
i took comparison pictures a while ago since i had a busted gte tb and the cressida one. i beleive this first pic is the cressida
and this one is the supra
notice how the cressida has the tb port before the throttle plate. and i beleive the turbo one comes after the plate
cressida on the right
and this one is the supra
notice how the cressida has the tb port before the throttle plate. and i beleive the turbo one comes after the plate
cressida on the right
It does look like the Cressida TB has the PCV port before the plate...that's why it works when you hook it up to the ISCV per what I said earlier. It's also why you don't get vac at idle. I'm not sure how big the orifice is on the Cressida TB (or if there is even one there), but you can see it on the turbo TB by looking at the rear of the TB where the PCV fitting exits. No or too large an orifice (like I suspect on the Cressida TB) is not good.
I see you're running an EGR too...on the turbo TB the vac port for the EGR is just forward of the TB plate. This is what keeps the EGR from functioning at idle (as it should) on a turbo motor. Looks like the EGR port on the Cressida TB is behind the plate...that is not good either.
I see you're running an EGR too...on the turbo TB the vac port for the EGR is just forward of the TB plate. This is what keeps the EGR from functioning at idle (as it should) on a turbo motor. Looks like the EGR port on the Cressida TB is behind the plate...that is not good either.
hmmm, i just had to pass emissions and the car passed with no problems. does that usually mean everything is working? i mean nj emissions aren't strict, but they also aren't easy. maybe i'm on to something? lol i noticed that a couple of big dawg people with ffim's have their valve covers setup like mine. they connect before the turbo only. i know its not the right way but it seems like it works?
You're not listening...so do it however you want.
For the last time, the PCV is not going to work the way you have it set up. It's not going to work on the "big dawg" FFIM's that way either.
I'm done here.
For the last time, the PCV is not going to work the way you have it set up. It's not going to work on the "big dawg" FFIM's that way either.
I'm done here.
^ nah i got it i just need to source out a tb then i'll switch everything. i'm just trying to understand the differences of all the setups and how they work as wel as figure out alternate ways to keep the bay clean. thanks tho.
since there is no vacuum in the "accordian hose" there is no "P" in your PCV the way you have it hooked up. Also hooking the ISCV to positive pressure (under boost) doesnt make sense. Technically I guess it would work as it only really comes into play at idle, but its not correct. It should go to your "accordian hose" and simply wanting a cleaner looking bay is no reason to route it incorrectly.