Valkyrie

Someone pointed out that my excessive blowby issues are being caused by the fact that my crankcase ventilation system is hooked up to a vacuum source (before the turbo).

I wonder if this wasn't done on purpose, however.

Any ideas?

BLUE TII

iTrader: (9)

Yes, pre- turbo is the oem location for crancase venting.

What is the use of the car?
When do you notice excess blowby?
What type of oilpan?
What is crankcase venting scheme (any catchcan?)

My experience is excess oil blowby can be caused by several issues.

1) Broken/stuck sideseals. This will cause excess pressure in the crancase and push oil into any sort of crankase ventillation no matter how good.
Solution- rebuild engine.

2) Stock oil pan and racing. This will cause excess oil sloshing up the oil filler neck into crankcase ventilation during hard cornering.
Solution- fully baffled/trap door oil pan with steep flat sides like Winchester or Built to Apex pan.
Half measure- more advanced oil filler neck baffle design (doesnt prevent oil slosh, bit keeps it out of crankcase ventillation).

3) Running overly rich at cruise. This will produce huge amount of crancase vapor, but it will be mainly gasoline and not oil. Its just at cruise that this rich running is an issue because engine and ancilliary parts are cool causing the crankcase vapor to condense in the intake.

I have been through all these crancase issues racing and have come up with this solution.
Winchester oil pan, big hose off both oil filler ports to baffled and vented oil catch can (no return to engine).

Only issue I have is excess gas vapor buildup in catchcan cruising in cold weather. If I drive 200 miles predawn to the race, I have to remember to dump catchcan before racing as my catchcan is in a cooler area of engine bay and the gas vapor condenses like crazy. You can light the liquid in catchcan on fire (tested).

When Im racing and everything is hot I get very little liquid building up in catcan.

I tried various baffling and filtering combined with venting catchcan back into engine and gave up because I wanted to keep inlet tract clean. That is why I open vent catcan and put uo with having to drain it.

Others let the condensed vapors drain back onto engine (using old rear turbo oil drain on single turbo).

I prefer to keep my oil cleaner/less gassy. If you are consistently getting oil hot enough at the track this isnt as much of an issue as the water and gasoline will cook out of the oil.

BLUE TII

iTrader: (9)

Made a little bracket with wing nut so its easy to drain the surprisingly nice cheap China catchcan everyo e in my area uses.

DaleClark

iTrader: (55)

I talked a bunch about the PCV system in this thread -

https://www.rx7club.com/3rd-generati...135405/page26/

The intake to the turbo is NOT a vacuum source. It is atmospheric pressure. That is how the car is set up from the factory.

Rotaries don't need much special for PCV, really just an atmospheric filtered vent. This compensates for the increase in pressure from the oil heating up.

Dale

BLUE TII

iTrader: (9)

Pre turbo is a vacuum source.

It is not a strong engine vacuum source like post throttlebody on the intake, but it pulls light vacuum when turbos are spooling hard.

If you adapt single turbo inlet to have a crancase nipple this vacuum can be even higher depending on your nipple location/angle/protrusion into TID.

Just having an air filter on the turbo inlet duct causes a decrease in pressure from atmospheric between the spooled turbo and the filter even if the crancase vent wasnt perpendicular to turbo airflow causing further low pressure area in crancase vent (siphon).

Valkyrie

It’s a track car, so racing. It has an aftermarket catch can (vented to atmosphere) and the wee stock catch (which I haven’t bothered to eliminate). The oil pan is stock, and I think it tends to get overfilled. This time I told them not to make sure not to overfill it.

My oil injectors also pull vacuum from the same source. I wonder if I shouldn’t be using a stronger post-throttle source of vacuum.

Should I unhook it from vacuum and return the catch can to the filler neck?

billyboy

Don't understand the mention of the stock catch can, unless that means the bulge in a stock filler neck - which might be part of the issue. How big is the aftermarket can, how big is the vent on that, how big is the line(s) running to it? Bigger is better in all those departments, most off-the-shelf stuff in that area is inadequate and just racey bling for street cars.

If running the oil injectors, I'd maintain the compressor face port, I'd ditch the line from the catch can running there unless there's some emission thing happening for dual purpose street/track.

BLUE TII

iTrader: (9)

TID is correct source for oil injectors- leave that.

Trying to work around the stock oil pan and the oil slosh up the filler tube is difficult.

Try capping both nipples on oil fill tube and drilling the top of the oil fill cap for the vent. Run a pipe with 90 deg barb fitting from oil fill cap up to where the hood just closes. Then run a single big hose to a vented catch can as high in the engine bay as possible.

You can get an exhaust exacuation set-up if the catchcan still fills too fast to complete your track session. But that will be smokescreen city and you might get meatballed.

Valkyrie

To confirm, the stock setup does return blowby from the lower of the two filler neck nipples, through brass lines, to the intake, but it would be best to eliminate this for racing purposes, right?
Maybe the vacuum is siphoning oil into the can?

The can doesn't fill up, I am just concerned about the oil that ends up in my engine bay near the catch can after every session.
It is probably coming from the nipple exposed to atmosphere, but it might actually have a different cause (oil cooler hose gaskets?).
I figure I can try directing that nipple into a coke can just to see if oil is coming out of it.
Hopefully filling the oil pan to the correct level will fix it, though.

On another note, I can't seem to recall if the turbo oil line has a restrictor. I had to replace the line, but I think I kept the original hardware in place. My new line came with two different sizes of restrictor.

It's the little plastic cylinder that runs above the spark plugs. At least I think it's part of the sump ventilation system.

The aftermarket can and its lines aren't especially big.

BLUE TII

iTrader: (9)

Yes, it is best for racing purposes not to connect the crankcase ventillation to the intake to eliminate the chance of oil ingestion.

The catchcan needs to be as high as possible, baffled and have the vent at the top of the catchcan so it will not blow oil out of the catchcan onto the engine bay.

I guess if you cant baffle the catchcan you could try a catchcan for your catchan as you suggest. It will have to be secure so it cant tip and spill oil onto the track or your tires.

billyboy

That's part of the fuel system between the charcoal canister and purge solenoid.

It appears you have an early filler neck if there's two nipples (UIM should have PCV provision). If reading correctly, you leave one nipple open? It will definitely blow oil out in that case. You might look to replace the neck with a aftermarket one to take a decent sized AN line and slow the air velocity.

Valkyrie

my car is a JDM 1996 “ver. 4”
both nipples have hoses, of course!
One goes to the intake, one goes to the catch can.

I directed a hose from the catch can vent into a beer can to just see if this is where my oil leaks are coming from.

j9fd3s

iTrader: (3)

i saw this on yayhoo Japan, and its a neat idea

BLUE TII

iTrader: (9)

Thats good!

Valkyrie

The car didn't spit any oil into the secondary catch can (read: ziptied beer can) during my race yesterday, so I think the issue was just an overfilled oil pan.
Hopefully there won't be too much blowby in the primary catch can this time.

On to my many other issues...