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Pdx dl

Yep, full exhaust.

Been thinking about the pcv. On my old domestic vehicles there was a filtered air intake routed to one valve cover and an “exhaust” (pcv) on the other. On the Volvo we exhaust the crankcase through the flametrap, but is there a crankcase “intake?” Or, assuming zero blow by, would it draw a vacuum on the sealed crankcase?

Raw unburned oil fouls catalytic converters and makes emissions skyrocket. That's why crankcase vents are put on the intake nowadays.

Isn't the engine an air pump? So if the case can vent then your vacuum on an NA engine should come from the intake side, no? Or am I not getting it?

Putting the outlet of the PCV valve on the exhaust stream creates a strong venturi effect. The hole itself is located in a strong low pressure area; so the more exhaust stream there is, the more engine vacuum you will have. It is terrible for emissions, as above.
 
I checked the Bentley, it looks like the Redblock has a ?sealed? PCV. I also read that the turbo cars don?t use the flame trap. Can I remove it? IPD says it?s to: ?protect against possible crankcase explosions due to a backfire.? This must be an intake side backfire. And with the turbo, the vacuum line is separated from the intake by the turbo.
 
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I was looking at the turbo PCV system in detail while putting my '85 B21FT back together. The "flame trap" or "flame arrestor" is the mesh screen that prevents fire (e.g. intake manifold backfire) from getting into the block. On high proof alcohol (everclear, 151 rum) there's a flame trap on the opening to prevent accidents:
Rum-bottle.png


In the non-turbo setups, the flame trap is a plastic mesh within the PCV lines. In the turbo setups, the mesh isn't needed (not quite sure why). The vent off the oil separator gets split into a bigger line to the pre-turbo intake hose, and a smaller line to manifold vacuum. Some posts say that the manifold vacuum line isn't needed.

The breather box drains directly back into the block. The catch can gets what's left over (or could replace the breather box if the catch can drains well to the block).
 
Further thoughts: does the aftermarket catch can do the same thing as the factory oil separator (flame trap box)?

Essentially yes...both are intended to condense oil out of crankcase vapors and drain the oil back to the block and route the vapors back to the intake in order to burn them during normal combustion.
 
I was looking at the turbo PCV system in detail while putting my '85 B21FT back together. The "flame trap" or "flame arrestor" is the mesh screen that prevents fire (e.g. intake manifold backfire) from getting into the block. On high proof alcohol (everclear, 151 rum) there's a flame trap on the opening to prevent accidents:
Rum-bottle.png


In the non-turbo setups, the flame trap is a plastic mesh within the PCV lines. In the turbo setups, the mesh isn't needed (not quite sure why). The vent off the oil separator gets split into a bigger line to the pre-turbo intake hose, and a smaller line to manifold vacuum. Some posts say that the manifold vacuum line isn't needed.

The breather box drains directly back into the block. The catch can gets what's left over (or could replace the breather box if the catch can drains well to the block).

The B21FT does not use a vacuum line. Fitting has a vacuum cap installed. Only the B23FT/B230FT engines have one, but the housing is still empty. On the past five B21/23FT engines I've had, the trap housing was deleted with the breather hose connected directly to the breather box and going to the elbow just after the airflow sensor assembly. First engine I dealt with that had that setup was a dealer-maintained B21FT installed in a 1-owner 1982 242T. Did the same on the B23FT that was swapped into it, and have done the same on subsequent K-Jet turbo engines. No problems.
 
^^^ Thanks John, that really helps make sense of the conflicting info I've seen -- why the flame trap housing with split big/small nipples is listed for B21FT, and why my old one had the small nipple melted/glued closed. Any idea why the B230FTs use the small nipple with a manifold vacuum line?
 
Interesting between, what I call, an "open" and "closed" PCV system. Visible on my old truck (way left) is the crank "intake" (K&N on passenger VC). I suppose on some level this could influence the air / fuel ratio. Perhaps that's what the PCV valve (PCVV?) is for?


Picture%20035-M.jpg
 
On the rally car PCV system, I made it more like a "normal" pcv system.
I drilled a small hole (1/8in) in the bottom of the oil cap. I then disassembled the cap, and stuffed it with filter foam. Stock oil box to catch can, then catch can to the pipe right after the air-filter.
This allows filtered air to travel through the cap, all the way through the engine, both oil separators, and then it get's a slight vacuum pull into the intake. Kept it really clean and worked well.
You can also add a restricted barb and tee the last breather into the intake manifold to pull even more vacuum, but if there's a leak anywhere in the system it'll throw off the fuel metering if using a MAF.
 
Funny how steel rimpz have come back to some extent. I recall Corvette rally's being the hot ticket in school. Still a nice looking set up. Nice that the aftermarket has brought out modern sizes on the old school stuff.
 
Funny how steel rimpz have come back to some extent. I recall Corvette rally's being the hot ticket in school. Still a nice looking set up. Nice that the aftermarket has brought out modern sizes on the old school stuff.

:nod:

Used to be you had to weld heavy barrels from trucks to your hubs or band them, and screw with the offset.
 
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