SR20DET valve cover hose with internal orifice

[SABLT194]

I'm having a bit of problems with my SR20DET. I have the crankcase (valve cover) vent line (with the internal orifice) running from the Valve cover to the intake tube. The intake tube fitting is located between the MAF and the turbo so and airflow from the crankcase will not be measure by the MAF. My car starts and idles like crap for about 5 or 10 seconds, then seems to clear up. Starts, runs and idles perfect when its up to temp. I plugged the line completely and the cold start problem went away. But, at WOT crankcase pressure builds and the motor starts blowing oil out the Valve cover gasket. I've made several different orifices trying to find a happy medium, but so far no luck. Anybody else run into this? Not sure why Nissan would put unmetered air into the system.

Regards,
Steve

[spl310]

How about a PCV valve inline?

[spriso]

Can you upload a higher-res image of the engine shot-- for some reason it looks like your AAC valve is not connected? (I see a plug on the purple idle adjustment -PS and AC load adjustment), but I can't quite tell if the other plug is connected-- which will affect your cold idle for sure!

EDIT: Looking at it again, it appears that your AAC valve is hooked up and just the purple plug is missing (which is ok).

Michael

[SABLT194]

Yes - I have the idle air valve hooked up. I left off the Air Conditioning fast idle valve. It's kind of crazy the way it behaves. I know it's dead lean (verified by Wideband) when it's going through it's crappy startup cycle. Need to see what kind of MAF output I'm getting as well.

[spriso]

You can easily remove the MAF element and clean it with MAF cleaner (use ONLY cleaner designed for air flow meters!)


As for the restrictor in the hose here is part of an old post that I did that might be helpful:


You can also see the valve cover breather hose that has been plumbed back into the intake. This is also very important if you want your car to run properly but this is not just an ordinary hose-- these are the details that you need to pay attention to:



The stock valve cover breather hose was not quite right to match up with our intake plumbing, so a replacement was sourced that fit our application much better. Inside the middle of the stock turbo hose is this brass bushing. Its job is to stop oil from leaking down into the intake, but still allow any air from the PCV system to be able to breathe into the intake to keep a good PCV balance.

To keep all of this happy, you need to put the restrictor back into the plumbing so you are not just sending down oil into your intake—not good! Cut the bushing out of the stock intake hose and liberally squirt down the inside of the new hose and press it into place (on the valve cover side of the hose!) Here is a shot of the restrictor before being pressed back into the new hose:

[SABLT194]

Thanks Michael,

I do indeed remember reading your docs about the restrictor. I think Sid probably hit the nail on the head. I need some type of lightly sprung PCV valve that will stay closed at idle and light cruise , then relieve crankcase pressure under boost.

Regards,
Steve

[Ed Mason]

Michael, Steve,
Michael, I need to purchase or get info on that hose you sourced. The original one I am using has turned to semi rigid plastic.

Steve, this may be redundant, but there is a pvc valve on the passenger side that vents the crankcase. I purchased a new one at the local auto zone,so you might check that. My car has excessive back pressure because the rings are shot and I compensate for it by running up the boost to about 14psi. So your problem may not be the hose and orifice. I get oil into the cold side of the turbo because of the excess crankcase pressure, but doesn't get into the MAF sensor element, yet. Another thing I read about on the blowoff return inlet into the cold air side of the turbo should be angled into the direction of the turbo inlet. This allow the excess air from the blowoff valve to go straight to the turbo and not some go to the MAF and be falsely read.
I am going to remodify mine as it goes straight into the cold air pipe.

[SABLT194]

Thanks ED,

If I remember correctly I just shortened the original SR20DET hose for mine. That may not be possible for you depending on where you put your vent fitting. I am running about 12# of boost and with the stock size orifice I have no problems with oil blowing out all over the place, not do I have a cloud of oil smoke out the exhaust. So, it seems all that functions correctly under high boost. I can also hear my BOV chuffing when I back out of the throttle, and BOV venting does not seem to cause anything funky with ECM fueling. My issue is only cold crank, cold start, cold idle (for about 10 seconds) and the BOV is fully closed at that point. I also have a cold tip-in throttle stumble (for about 1 minute or so). After everything gets even a little temp, all these issues go away. Starts, idles, and has throttle response like a champ. Just seems like when it's dead cold, the ECM fueling gets all befuddled for a bit. I will double check the PCV valve but I need to do some research on how they are suppose to work. Since the PVC is plumbed direct to the intake manifold, I assume the check valve should seat closed under manifold boost conditions , and open under high vacuum conditions (idle and light cruise) with again more un-metered air. Perplexing Indeed

On sourcing your hose- I would cut bend a coat hanger to the shape that fits your application. Then take a trip to NAPA, Autozone, Advance. Warm up to a counter guy and see if he will let you in the back to sort thru the hoses to find something close. Sometimes you can make one hose out of two. Just put a barb fitting at the splice and use a shrink sleeve (available from Jegs) to finish it off. That's how I had to do my top radiator hose, and my funky heater hoses. The shrink sleeves do work well and they don't look too bad IMO. If you look at my photo in the early post you can just barely see the shiny shrink sleeve on the top radiator hose.

Regards,
Steve

[Kevin Desirello]

The MAF is to close to the turbo.
The turbo is creating turbulance into the MAF.
Micheal sets his up with a bit of S a turn to deal with it.
I ran into this with my dads.
We moved it for wards and and the issues went away.
Kevin

[SABLT194]

Thanks Kevin.

Michael had suggested that to me quite a while back as well. Not sure why that would give me fits on cold start only. None the less, I'll test that by fabbing up some temporary elbow solution to verify that turbulence is indeed the problem. Space in that area sure is a premium. I originally wanted to get the air filter out from under the hood, but just found no way of making that happen. The other possibility is to place the MAF after the turbo. Boost thru MAF. I have seen others do this (not on SR20DETs mind you). I would suspect all MAF calibrations would go completely out the window. Not ready to go through that agony but interesting thought.


Regards,
Steve

[Kevin Desirello]

I dont think the maf will work running boost through it.
you would have to re map the ecu to do that.
also what did you do for the blow off valve the stock ecu calculates for it to be recirculated.

my later builds like caraddics Jon frampton we went with a stand alone and ditched the maf all togther.

[SABLT194]

Here's a good read on crankcase ventilation for boosted applications.

http://www.sr20-forum.com/information-l ... ition.html

[SABLT194]

Ok, So I ran a test to see if my cold startup problem is related to the rather short distance from the MAF to the Turbocharger. I fab'd up a temporary extension to put the MAF plenty far from the turbo. No change in startup problem. It cranks, stumbles, farts, and runs on one or two cylinders for a few seconds. Then it catches and idles like a champ. I also confirmed that during idlem The PVC valve indeed pulls a vacuum on the crankcase. There is almost no vacuum on the restrictor line running to the CAI tube next to the turbo. So Air flow direction is definitely from the CAI, thru the restriction, into the valve cover, thru the PVC valve, and on to the intake plenum. This air would indeed be metered.

Under plenum boost - the PVC valve should close, Blow by the rings would add pressure to the crankcase, and that pressure would be relieved by the restrictor tube from the Valve cover to the CAI.

Still lookin ??


Regards,
Steve

[spriso]

Weird.

Do you have the brake booster fitting blocked off (back of the intake plenum)-- looks like you have something strange plumed into that port. Also, what did you do about the two fittings on the underside of the upper intake plenum? Are they blocked off? Sounds like you have a vacuum leak to me.

Also, your photos are too small-- I can't tell if you have the hose connected before the throttle body to the underside of the intake plenum (cold air idle to the AAC valve).

Michael

[SABLT194]

Thanks Michael,

That is a boost transducer in the back of the plenum. The two small vacuum lines are both connected to my Synapse BOV.

I agree that I'm getting unintended airflow from somewhere. It's just crazy that as soon as it cleans up, it idles and runs like a champ.