i have a 93 240sx KA.
I just got (almost) finished with my shortened intake install. I have seen a lot of people just throw a breather on the hose after going to an aftermarket intake, with no reported idle problems. I have a few friends with sr20 sentras and they have the timing cover hose with just a breather also, and no idle problems.
My issue is after I hooked everything up and just had the timing cover open to the atmosphere. (all other hoses are connected properly no vac leaks) The idle would hunt alittle. nothing horrible, but my idle used to be rock solid, which i want it to be again.
I have no problem with just connecting it to the intake again but i am wondering if this is indicative of a problem with the PCV valve. When idling there is a considerable amount of air being pulled through it. i can stick my thumb over the hole and i have to pull alittle bit to get it to pop off (vacuum holding it on). We checked my friends sr20 and there is almost no air flowing through the timing cover hose. I know the sr is a diff motor but...
My question is: Is there supposed to be this much air flowing through the timing cover hose? if not, this is a PCV valve issue correct?
Putting the hose back on the intake is not an issue, nor is replacing the PCV valve, just wanna pinpoint a potential problem, thanks!
Timing Cover Hose
[s3] wrote:Are you talking about the crankcase vent hose?
yep! but the PCV valve is whats letting air be sucked into the intake manifold from the crankcase, the cams only swirl the air a bit in there.... they wouldnt be making it flow through.
i know the sr20 is a different motor but putting a breather on its valve/timing cover hose doesnt effect its idle. just seems odd to me, and ive seen no mention of it for the KA on these forums.
the "air" comes from the gap between the rings and the cylinder bore when the a/f mixture goes bang...a good engine has a little "air", a worn out engine has a lot of "air". this "air" wants out of the engine really bad, if you dont give it a way to get out...it will find a way, usually by blowing out the largest seal it can find..the rear main.
a vent with a filter to keep out bugs, dirt etc is more sanitary sloution but the epa guys dont like us going around spewing our "air" everywhere. so if you hook a vacuum line from the intake to your crankcase it will "positively" suck em out.....problem is that sometimes there aint always a vacumm in the intake.....a backfire could send the air right back to where it came from and blow all the seals out and even cause a crankcase explosion..
a check valve would prvent that from happening. other times the intake may have turbo boost in which case its a better idea to hook that line between the turbo and the air filter.
race cars use these check valves to keep negative pressure on the bottom side of the pistons for a little free horsepower
(p.c.v. valve) positive crankcase ventilation valve:ylsuper
a vent with a filter to keep out bugs, dirt etc is more sanitary sloution but the epa guys dont like us going around spewing our "air" everywhere. so if you hook a vacuum line from the intake to your crankcase it will "positively" suck em out.....problem is that sometimes there aint always a vacumm in the intake.....a backfire could send the air right back to where it came from and blow all the seals out and even cause a crankcase explosion..
a check valve would prvent that from happening. other times the intake may have turbo boost in which case its a better idea to hook that line between the turbo and the air filter.
race cars use these check valves to keep negative pressure on the bottom side of the pistons for a little free horsepower
(p.c.v. valve) positive crankcase ventilation valve:ylsuper