oil breather tube
#11
10-03-2008, 10:09 AM
RE: oil breather tube
ORIGINAL: JimBlake
Flow thru the PCV valve is always in the same direction, towards the intake manifold. Exception would be under boost, if you have a turbo- or super-charger.
Its the other vent line, which Benji is talking about; THAT one can reverse its flow direction under wide-open throttle. Or, when bad rings cause enough blowby that the PCV valve cant suck it all out.
Im confused about that other line over to the left fender. Does that go to the cruise-control? If so, it shouldnt be coming from the crankcase vent.
Flow thru the PCV valve is always in the same direction, towards the intake manifold. Exception would be under boost, if you have a turbo- or super-charger.
Its the other vent line, which Benji is talking about; THAT one can reverse its flow direction under wide-open throttle. Or, when bad rings cause enough blowby that the PCV valve cant suck it all out.
Im confused about that other line over to the left fender. Does that go to the cruise-control? If so, it shouldnt be coming from the crankcase vent.
ORIGINAL: TexasHonda
All cars I've had will reverse flow into the intake (not through PCV), but from crankcase blowby pressure build-up combined w/ low manifold pressure under heavy throttle. You have to monitor crankcase pressure (pressure in valve cover) to see this effect. If there never was any reverse flow, you would never see gunk in the IACV or black carbon buildup all over the inside of the intake manifold. It would be nice and shiny.
All cars I've had will reverse flow into the intake (not through PCV), but from crankcase blowby pressure build-up combined w/ low manifold pressure under heavy throttle. You have to monitor crankcase pressure (pressure in valve cover) to see this effect. If there never was any reverse flow, you would never see gunk in the IACV or black carbon buildup all over the inside of the intake manifold. It would be nice and shiny.
#12
10-03-2008, 11:12 AM
RE: oil breather tube
Well, I was off base about the cruise control - thats on the firewall next to the fusebox. I was thinking of a different year or something...
How about a better picture of where that hose goes at the left fender.
How about a better picture of where that hose goes at the left fender.
#13
10-03-2008, 11:20 AM
RE: oil breather tube
How about a bird's eye view?
Jim, 6th gens have the cruise mounted on the left fender. In that picture above, the cruise control is mounted on the passenger side of the intake manifold; you can see the cruise throttle cable running across the front of the valve cover.
Jim, 6th gens have the cruise mounted on the left fender. In that picture above, the cruise control is mounted on the passenger side of the intake manifold; you can see the cruise throttle cable running across the front of the valve cover.
#14
10-04-2008, 06:10 AM
RE: oil breather tube
While reading this it occurred to me that installation of an oil trap in the PCV air inlet system would have long term benefits; reduced oil deposits in throttle plate/bore and IACV. The ones I've seen are simple compressed airmoisture traps convertered to trap oil mist. This may work well on the PCV air inlet as the volume of oil trapped would be small (infrequent drainings reqd) on an engine in good condition and not driven like a BOH.
good luck
good luck
#15
10-04-2008, 09:41 AM
RE: oil breather tube
At crankcase pressures below X, the PVC can flow enough volume to extract all the blowby gasses from the crankcase, and needs the inlet tube from the induction pipe to prevent it actually creating a partial vacuum in the crankcase. At crankcase pressures above X the PCV can't flow enough volume to extract all the blowby gasses, and the flow reverses through the induction breather tube (dumping oil vapour into the induction pipe in the process). The more blowby there is the more of it will be evacuated via the breather pipe rather than through the PCV, so it's worse with worn rings and low compression.
At WOT the vacuumin the plenum drops way off (i.e. air pressure rises substantially becaue the plenum isn't as isolated from atmospheric pressure by the throttle plate), so the 'suck' through the PCV is less, so more crankcase pressure and gasses escape via the breather tube than at lower throttle openings, i.e. the air pressure (still partial vacuum) seen in the plenum and in the induction pipe become far more equal, so both tubes become a viable escape route for the blowby gasses.
At WOT the vacuumin the plenum drops way off (i.e. air pressure rises substantially becaue the plenum isn't as isolated from atmospheric pressure by the throttle plate), so the 'suck' through the PCV is less, so more crankcase pressure and gasses escape via the breather tube than at lower throttle openings, i.e. the air pressure (still partial vacuum) seen in the plenum and in the induction pipe become far more equal, so both tubes become a viable escape route for the blowby gasses.
#16
10-07-2008, 05:43 PM
RE: oil breather tube
Well, my compter was fritzing on me and I'm just now getting the updates on this post. Ok, after looking at it a little closer (I STILL need to get a better picture) the vacuum line in question does NOT run over to the driver side of the engine bay. It runs to a sensor right behind the fuel rail and right in front of the Intake manifold. The wires of the sensor run into the conglomeration that is the wiring for the fuel injectors. I'm going to see if I can find a hayne's manual that points out what this thing is. In the meantime, I'm going to try and get pictures up tomorrow morning.
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