M20 crankcase pressure

[zaq123]

The black port on the left side of the airbox is just a plugged -6AN fitting. I had valve cover routed there originally before decided to introduce the oil separator. Now it just plugged hole. I actually going to put a vacuum gauge there to see how much vacuum if any gets created in the airbox ( I made a paper gasket for the box so it's sealed). Probably won't be any unless the air filter gets dirty?

Here is a gauge. gradated in IN H2O where 14 is about 1 inHg and the max 25 is 1.8 inHg (0.9 psi). The gauge holds maximum recorded reading until reset. I mainly want to see what it does because I'm using somewhat small(ish) cone air filter with the setup (not much space there with ABS unit) so I want to see if the air filter flows enough air for this 2.9L engine (no excessive vacuum in the airbox at WOT with 0.7+ psi being excessive for the clean filter ???).
Any thought on this? https://www.youtube.com/watch?v=J1pgbJJ3boY

Or I can just log and look at my map sensor reading ? I guess at WOT vacuum in the airbox and the vacuum block theoretically will be the same? What should MAP sensor read at WOT compared to idle? Ideally is obviously zero vacuum at WOT but what is the acceptable vacuum as not to be considered restricted air intake?

[zaq123]

Hmmm. so bitch tube to the separator, separator cyclone
to air filter, and bottom separator oil from separator to submerged dipstick?


t

I just actually read it lol..No, the bitch tube is still there and not affected.

The setup is : Value cover vent to the separator, separator into the air box, the bottom separator oil drain into the dipstick tube.

Here is a view from another side..

[zaq123]

i would use it out of the abundance of caution, however, if you have the same system/architecture as per S62 unlikely crankcase pressure can push oil up that far with a NA engine?

I'm going to test it and see what it does. Dipstick sits in the block about 3.5" inches (87mm) above the full oil level so I don't think there will be any suction of the actual oil. I was more concerned about crankcase oil vapors. I did some reading on S62 and like in m20, crankcase and the valve cover pressure/vacuum is very balanced to each other. S62 Oil separator has much larger vent line from the valve cover compared to its drain line so the flow of vapors is obviously not equal.

Here is a picture with my spare dipstick tube which shows the dipstick and how much it goes beyond the end of the tube in the block (87mm to the oil line)

[zaq123]

Hmmm. so bitch tube to the separator, separator cyclone
to air filter, and bottom separator oil from separator to submerged dipstick?

Yeah, I'd probably run one, too-
in theory the bitch tube should do all the pressure equalization,
and the ever- so- slight negative pressure of the intake will help when you're on low- throttle cruise.
But being open to intake, if oil ever backed up, that would be... expensive...

The 4 cylinder Alfa with IR and Spica had an interesting little catchcan that had a vacuum break on the
drain- I had one around for a long time, but lost it in the last move. Along with the oil filter cutter...
Those cars were a great source of 1- way fuel valves, odd little linkage parts, and fittings.

t

dipstick tube on m20 is not submerged into oil (similar to S62) hence my concern of some venting into the oil separator from where the oil will be draining from it. On S14, oil separator drain is submerged into the oil in the oil pan via 13 below, so technically no venting into the separator.

[digger]

I'm thinking the same, considering S14 design has oil drain tube submerged. However S62 doesn't have any check valves and it goes into the tube above the oil level?

i would use it out of the abundance of caution, however, if you have the same system/architecture as per S62 unlikely crankcase pressure can push oil up that far with a NA engine?

[TobyB]

Hmmm. so bitch tube to the separator, separator cyclone
to air filter, and bottom separator oil from separator to submerged dipstick?

Yeah, I'd probably run one, too-
in theory the bitch tube should do all the pressure equalization,
and the ever- so- slight negative pressure of the intake will help when you're on low- throttle cruise.
But being open to intake, if oil ever backed up, that would be... expensive...

The 4 cylinder Alfa with IR and Spica had an interesting little catchcan that had a vacuum break on the
drain- I had one around for a long time, but lost it in the last move. Along with the oil filter cutter...
Those cars were a great source of 1- way fuel valves, odd little linkage parts, and fittings.

t

[zaq123]

I'm thinking the same, considering S14 design has oil drain tube submerged. However S62 doesn't have any check valves and it goes into the tube above the oil level?

[digger]

to me i would probably use one

[zaq123]

Ok. here is my setup for the crankcase venting/oil separation with a return to ITB airbox. S62 oil separator that drains into the dipstick. Haven't tested it yet due to shit weather/lots of road salt at the moment. For those who is familiar with M20, should I run the check valve on the oil drain line to the dipstick since the dipstick is above the oil line in the pan? Not sure if the crank pressure will push any oil up into the separator while the engine is running. Something like this (link) or not needed for NA M20 in your opinion? https://www.lingenfelter.com/product/L200030000.html