I have a custom TT setup with AEM F/IC on my 03 Z. We are running a blow through setup and am having problems with the factory pcv system. It is hooked up just like factory with the exception of the drivers side rear hose is vented into the atmosphere.

At idle when the pcv is open it is basically a big vacuum leak and it goes lean. If I cap the pipe on the intake manifold and let it vent to the atmosphere it smooths out and my fuel trims correct properly. however then there is no pcv.

any thoughts on correcting this issue short of a pull-through system?

anyone foresee any problems with fully venting to the atmosphere? All kinds of BBC's are running around with no PCV. I dont have to worry about DEQ or emissions or any of that crap, im out in the boonies.

 

Hook the driver's side crankcase vent to the intake after the MAF and it will be registed air that is drawn through the crankcase.

If you are using MAP, it doesn't matter and I would recommend connecting the PCV to 2 check valves and have one valve go to the plenum as usual and the other to the turbo intake piping (post air filter). That way you maintain crankcase ventilation under boost and idle. Leave the driver's side open to atmosphere - it should only suck air in.

Main thing with turbos is not to increase crankcase pressure (to ensure best oil return flow).

 

I cant connect the breather tube after the MAF because it is a Blow-through system and under boost you would be pressurizing the crank case.

the AEM F/IC has its own MAP sensor but that doesnt change the factory ECU trying to correct the fuel trims by comparing MAF signal and O2 signals. So i need them to work together and that means no un-metered air entering the Intake manifold.

 

So right now your MAF is located after the turbos if I'm understanding correctly. Hmmm. Either you have to move the MAF further back (pull through) or compensate for the air being boosted in the feed to the driver's side vent, perhaps using a restrictor?

You could just get a real EMS and then you wouldn't have to worry about it.

 

tony t,

connect a hose to the driver side valve cover and connect the other end of the hose to the inlet side of your turbo compressor (between the the turbo and the air filter.) this way, the suction of the turbo will create a vacuum and suck crankcase pressure out of the driver side valve cover.

 

he said he cannot meter air that way. unless I misunderstood...

 

he has a blow through setup. it works perfectly.......just look at any greddy setup. that's how they are.

on a draw-through setup like on a JWT, you have to be careful about adding anything into the system after the MAF...or else the car doesn't knwo what's going on.

He isn't worried about how the air gets metered, Tony T just needs a way to attach a vacuum source (air intake side of turbo) to the driver's side valve cover so that he doens't pressurize the PCV system.

 

yes he is right, you really need the vacuum that the intake side pulls through and it doesnt matter if it is metered or unmetered.

a lot of the factory pcv on the passenger sides mess up as well...


put another inline check valve in there.

 

bbc's use these

 

those work too......they attach to your exhaust manifolds (or headers) and as the exhaust gases flow out of the motor, there is vacuum created at attached device. that device is hooked to your crankcase and helps to depressurize the crankcase.

of course, a vacuum pump is the shizzle! I haven't seen anyone hook one up to a z yet......but they are more of a racetrack item.

 

They will use those in full race applications when you dont have to worry about O2 sensors not to mention the oil accumulation in the exhaust system. But you can run a large breather in each valve cover though it can rob a little horsepower. Since most are carbeurated though, they wouldnt ever have my problem.

anyways I think I got it fixed. I ran the breather tube from d. side valve cover to a catch can and then connected both turbo inlets. I also put a check valve inline on the pcv. I guess the vacuum from the turbos keeps the pcv side from drawing in too much un-metered air.

Thanks for the constructive replies.

 

tony t..... you're a lucky guy. You had 4 of the most knowledgeable guys give you advice. Don't see many threads like this..

 

Check this out

http://www.et-performance.com/turbo.html

basically its 2 heavy duty check valves

 

Thanks again guys. I appreciate good help. Its not leaning out at idle and the trims are adjusting properly. Now if I can get my MAF voltage to stop fluctuating.

And thanks for the link blackbird, I am working on putting something very similiar right now

 

If you fixed the vacuum problem and the voltage fluctuates you may want to check the following. Not sure if this helps but if your MAF voltage is fluctuating you may be getting noise or feedback from the meter. From what I read above you have the MAF after the turbos which means that you are blowing through the meter. The turbulence created by the fast moving air may cause the MAF to meter or read improperly this is called noise or feedback. You want to make sure that you dont have any sharp bends or turns close to where the air enters and exits the MAF this will reduce the chance of any improper readings. It will also reduce any backwash in air when the throttle closes depending on the location of the blow off valve of course.

 

Sorry I also forgot to mention that the location of the blow off valve is also important on a blow through. The valve should be open under vaccuum at idle. So if you have the valve after the MAF sensor you are bleeding off metered air into the atmosphere creating a vacuum leak this would cause the voltage on the meter to fluctuate and create a idle/drivability problem.

 

My BOV is about 8-10 inches before the MAF and there arent any bends within around 7 inches from it. I am thinking I might just need a new one. at idle it will fluctuate around .2 volts. from just under 1 volt to around 1.2.