OEM MSM PCV System Crankcase Pressure Test
 

I made this video a few days ago to test and see how much crankcase pressure was building up on my mostly stock OEM MSM PCV system. The only modification that I've really done to the system is placing the stock PCV valve in the return hose from the OEM catch can to the oil pan.

I did this by drilling and tapping my extra plastic oil cap and hooking it up to a boost gauge with high pressure lines and fittings that I had left over from my water injection setup. I also hooked my intake manifold pressure to a second gauge and placed them together on my window. For sort of a reference between boost/crank case pressure.

I'm not exactly sure what I was expecting to find. But it looks like it didn't get much higher over 2.5psi with 22psi of boost.

These are the results from a rebuilt engine with maybe 5-8k miles on it. Last time I checked compression a month or two ago, it was close to around 165 across the board(8.8 Wiseco pistons). Leak down #s are unknown.

This is 2nd and 3rd gear pull.

https://www.youtube.com/watch?v=

I had a longer 3rd gear pull, but my mount was really shaky and the numbers were the same.

EDIT: Uhh, the embeded thing didn't work, but the link auto shows the preview? I have the dumb.
EDIT2: Trying to figure out the embed code.

Here's the link. I'm not sure if I can get the embeded video to work out.

I guess I never updated this. I heard from sources that pretty much any pressure at all in the crankcase is bad. Let alone 2.5 psi. So I ended up performing some modifications to the baffling system in the valve cover. This information has been talked about before in various places.

I drilled out the hole on the one side of the valve cover to 1/2" and actually added another smaller hole while I was in there. The original was smaller than the extra hole I put in. Pulled out the smallish 90" fitting which I think is on the same side of the valve cover, drilled it out to 1/2" I as well and put a larger fitting in it.

One of the main reasons I did this was because I was tired of pulling my tranny replacing rear main seals that were never bad. Did this and no more leak. My cam seals never leaked though. I'm guessing under acceleration, oil was pooling to the back of the motor and was getting pushed out past the rear main.

Couple pics:

https://www.miataturbo.net/attachmen...ine=1440373132


https://www.miataturbo.net/attachmen...ine=1440373132


https://www.miataturbo.net/attachmen...ine=1440373132


https://www.miataturbo.net/attachmen...ine=1440373132


https://www.miataturbo.net/attachmen...ine=1440373132

And an updated video:

anything done on PCV side?

excellent test and the 1st time I've seen a video of it.
Thank you very much

I replaced the factory PCV valve with the 323 GTX replacement valve a while ago. I then put the factory PCV valve in the large tube that goes from the catch can down to the oil pan, assuming this should keep the oil from coming back up the line. There have been reports that this can happen under hard left hand turns.

The only other thing I did was, instead of using the rubber tube that goes from the port on the drivers side of the valve cover, through the strut tower brace over to the catch can, I used a 1/2" stinless line. I'm not sure this was necessary as I believe most the restriction was due to the small single hole in the valve cover. But I had the tube and decided to just keep everything 1/2" (drilled hole/fitting on valve cover/tube to catch can).

Looking at the second video again, it almost looks like the needle might have even moved a TINY bit towards the vacuum side.

I'll try to remember to take a picture of my engine compartment tomorrow and post it up. It looks pretty stock. The mess that a MSM stock under hood looks like.

Pic because people like pics. This was right before I drilled the valve cover and put the stainless tube in.


https://www.miataturbo.net/attachmen...ine=1440392203


And again, this is running 20+ psi with a larger turbo. Probably not really an issue on a stock turbo even maxed out.

I'm in the midst of doing this myself. I have the valve cover off and was planning to paint it when I decided to drill out the middle to driver's side hole like yours was done. Regarding the larger nipple you used, can I ask where you sourced it from? I'll probably need to do that as well since my car's been leaking oil out of the valve cover and rear and front seals.

Here's a picture from 10 min ago.

https://www.miataturbo.net/attachmen...ine=1440466364

You'll see in the picture, the 1/2" stainless tube I used. It's zip tied under the strut tower brace. The fitting I inserted into the side of the valve cover was one of the ends of the pipe that I cut off which had a bead. So I really don't have an answer to your question. We just had the pipe laying around our shop.

If I were you, I'd just use something like this and jb weld it in.

McMaster-Carr

Or the threaded type if that's your thing.

McMaster-Carr

Or with a 45 or 90 degree angle if you want. I think most will agree, this is one of those things that it doesn't hurt to go a little bigger. I could see someone making this out of 9/16 or 3/4 fairly easily if you wanted to get carried away.

Hope this helps.