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I finally had some time get back at some of the car projects and noticed something a little concerning.
I am adding an oil cooler through a thermostatic sandwich plate form Chase Bays. I can pretty much only orient it this way. I am also adding a dual sensor for oil temp and pressure that is rather chunky and also hard to fit. Here is the test fit of everything. I will need to run 90* AN fittings coming towards the passenger side of the car and mounting the 13 row mishi oil cooler off the steering rack on the passenger side with a custom bracket.
Issues I see already... I don't think I can run my turbo oil feed line off the sandwich plate since I don't think oil would flow through there until it reaches 180*. But I can't fit the sensor in that NPT port and I can't spin the sandwich plate since the AN bungs contact the alternator or the block castings below it. Maybe I can clearance those protrusions on the block below the plate. Or I need to find another oil feed location. **EDIT** There is another NPT port on the other side so I'll put my sensor there and run the turbo feed from the T with the stock sender.
Now the concerning part...As I was looking at this stuff I noticed my block was covered in oil at cylinder 4. I had just driven the car and it drives fine. Even found a small pool on the undertray. Some oil coming out of the valve cover gasket in the same place too.
So now I'm back to being paranoid about this motor and the root issues I've had for years now. I still think the cylinders are oval shaped. Those black marks on the walls just aren't normal. But I think the symptom is just a lot of crankcase pressure.
Considering my options: 1. Add a check valve and return crankcase ventilation to the stock-ish scenario with a PCV to intake manifold and a closed air/oil separator on the other side to the pre-turbo pipe. https://www.jegs.com/i/Moroso/710/85496/10002/-1
Maybe I can do a swappable setup where I run the PCV on the street and just run the current system for track days.
2. Get an electric vacuum pump and just power it to pull vacuum at all times and plumb it into the valve cover. Maybe throw the air/oil separator in between VC and the pump. https://www.jegs.com/i/JEGS/555/63019/10002/-1
Some random big block guy said this to me at a meet that he uses electric vacuums to deal with excessive crankcase pressure. More research is needed.
3. Torque head bolts more... unlikely to do anything.
Helps evacuate the pressure more but doesn't provide and actual vacuum to pull it out.
5. Start saving money and building my spare 1.8 block since this one seems cursed.
On top of trying to address the ridiculous amount of blowby, I am also going to replace all the turbo lines with PTFE lines. Fab up a custom bracket for that oil cooler and get the lines made for that. Maybe I can get a pressure gauge on the dipstick to monitor actual crankcase pressure and see if thats really the culprit. I was also planning on a big brake kit this year and maybe even stiffer coilovers for the track but unless I can get this oil blowout under control that stuff might need to wait.
'til next time,
Matt
Last edited by MillaTyme91; Feb 28, 2026 at 10:05 AM.
Alright, I've done a bit of research and have a plan. First off, since the car is already a bit apart, I have to wire up the new sensor, create the bracket for the cooler and the lines. I'm replacing the turbo lines from regular AN rubber to PTFE for temp reasons; I should've done this initially but was ignorant to their usage. Then I will measure crankcase pressure by capping the valve cover breathers. Assuming its not an extreme amount that requires a better block, I will move forward with my plan to evacuate those gases. This is what I came up with:
Basically, two sealed air/oil separators. Passenger side will go to the intake manifold via this cool AN10 check valve I found - https://www.racetronix.biz/p/one-way...black/ckv-1010
This will provide vacuum to the crankcase under decel and idle conditions and will close when boost is entering the manifold and engine.
The driver side will go to another air/oil separator that is sealed. It will then split to two lines, one to the intake pipe between the air filter and turbo. And one to the exhaust. They both will have the same check valve between them. This should allow for slight vacuum scavenging when in boost and throttle conditions. This requires a kit that use a bung welded in to take advantage of the venturi effect. Faster air creates a low pressure zone and that in turn creates a small amount of vacuum.
If I understand fluid dynamics correctly (I don't), then the intake portion will be practically useless since the exhaust will have a stronger flow, especially in boost. But the way I see it, is redundancy at the cost of complexity and every little bit helps. I will apply the same bung on the intake, welded in at an angle and appropriately facing direction.
I will need to move my oxygen sensor on my exhaust so that the scavenge bung is downstream to avoid oil contamination and replace my cat with the test pipe. I might need to retune idle a little bit as well. Once these are all installed I will have to do another pressure check. In the case its not evacuating enough crankcase pressure, I will look more into electric or pulley driven vacuum pumps. Dry sump would be sweet but may as well pay for a new engine at that cost level. I know how ridiculous this is but part of me is kind of looking forward to the engineering of it and the other part really is tired of oil getting blown through the valve cover gasket or worse.
Running a passive VTA breather with two AN10 lines out of the valve cover doesn't seem to evac enough pressure for my motor. So I'm looking at maximizing it to limit the oil getting pushed out (presumably) my valve cover and cam seals.
Have you measured it by chance? I know the exhaust evac is big in the v8 world and Moroso sells a kit for it with a check valve. I'm leaning towards exhaust evac just due to engine bay space and lack of emissions requirements for me. I think I'll probably weld some bungs on both and test them and just see whats better.
Running a passive VTA breather with two AN10 lines out of the valve cover doesn't seem to evac enough pressure for my motor. So I'm looking at maximizing it to limit the oil getting pushed out (presumably) my valve cover and cam seals.
Have you measured it by chance? I know the exhaust evac is big in the v8 world and Moroso sells a kit for it with a check valve. I'm leaning towards exhaust evac just due to engine bay space and lack of emissions requirements for me. I think I'll probably weld some bungs on both and test them and just see whats better.
assuming you have the usual pcv and exhaust vents using 10AN VTA, whats stopping you from just adding another huge breather system by installing a quickvent cap and another VTA 10an can? Though you must have some pretty bad blowby if the single 10an setup isnt working. My motor is tired as hell with loose rings and was puking from everywhere before i installed those and it fixed that issue very quickly.
Adding the quickvent system would be just another giant place for extra blowby to go, slowing the speed of all the other air even more. just an idea
First off, I replaced all of my turbo lines with PTFE ones and threw some better heat sleeve on there. Unrelated to oil leakage but something I've wanted to do. I also finally installed an oil cooler, and had to move some things around with that. But I now have a working oil temp sensor too!
Custom built bracket, this took a while but was quite fun. First iteration leaked like crazy from the PTFE fittings so I just went back to some Vibrant performance CPE lines for their flexibility and "ease" of fabricating and no more leaks for the cooler!
Ok and now on to the intesting stuff regarding blow by.
I sealed off the catch can, made this little apparatus to measure pressure and then idled the car. It made about 1.25psi/2.5inhg as a completely sealed unit. This of course meant the pressure built up with no release. I saw smoke coming out of the tailpipe because oil was probably getting passed the turbo seal since its the weakest point.
So that told me I definitely have blow by but thats not a very good test. The next test was idling it with the catch can vented normally and revving it a bit. No pressure built at all, meaning my catch can is venting enough at idle loads.
After doing that, I wanted to know if it built up pressure under boost and maybe that was causing the oil seepage. Well this part really confused me because I set up the test and probably got some weird looks from others in traffic lol. Ran the line out through the hood vent and into the cabin to watch the gauge during pulls.
And to my absolute astonishment... there was no measurable pressure there either?! This has really perplexed me. The only thing I can think is that my catch can on the valve cover is indeed venting enough even at 17psi on a EFR6758.
My thoughts now, are that its gotta be building down in the pan. The reason I believe this is because I do smoke at idle randomly and other random times too, but not always. Confirmed by friends driving behind me. I'm thinking I probably want to try to measure this as well, so I'll work out a way to use the oil dip stick tube and hook up this gauge and line there.
Am I absolutely crazy if I drill into the oil pan and hook up some venting to there?! Obviously using grease to drill/thread, draining oil afterwards and using a check valve up to the intake manifold. This of course dependent on the results of the pressure test from the bottom of the block.
If your cam seals and VC are what’s leaking, and you’re building zero pressure in the crankcase measured at the VC, how would pressure in the bottom end affect the issue? Or are you looking to just alleviate the smoking at idle you’re getting?
I seem to remember EFR’s being very sensitive to oil drain diameter/routing. No issues there? Not on an EFR but I'm currently getting some smoke from my turbine housing at idle as well, despite now having a 6an and two 10an VTA vents on my car. Adding that second 10an vent stopped the oil seepage from my oil cap and dipstick tube but didn’t affect the smoke at idle. Straightening my oil drain routing is the next target.
I’m a little lost on how you plan to vent the pan. Having a vertical VTA tube going way above the pan height is one thing. Running a tube with a check valve to the intake manifold would just result in tons of oil getting sucked into the engine?
There is a reason that oems always vent from the valve cover. There is significantly less liquid oil suspended in the vapor mix up there . Don't reinvent the wheel, just refine it.
Reread the catch can thread. If you have not enlarged the passages in your valve cover, you're making a mistake. If you have not added some sort of a media within the valve cover passages for the vapor to condense upon, you're making a mistake. If you have not run both sides of the valve cover to your catch can, you're making a mistake. If you are still running PCV valve, you're making a mistake.
In rough terms, you are running three times as much air through the engine as the stock breather system was designed to handle because you're making three times the horsepower. Add three times as much breather hose and fitting capacity and allow the vapor speed to slow enough that the oil falls out of suspension and you will be in much better shape.
And yes, efr turbos are an absolute nightmare for oil drain and crankcase pressure problems. Do not use a threaded drain fitting in your turbo. It will not drain properly. Do not use too small a drain line or fittings with that turbo. Do not run it without some sort of a restrictor to prevent over oiling. Do not have any sort of low spot or belly in the line or fittings as it returns to tank. Do not position the turbo in a way where the chra is not perfectly level left to right and front to back.
I feel like that's a lot of do nots, but those are very picky turbos.
If your cam seals and VC are what’s leaking, and you’re building zero pressure in the crankcase measured at the VC, how would pressure in the bottom end affect the issue? Or are you looking to just alleviate the smoking at idle you’re getting?
I seem to remember EFR’s being very sensitive to oil drain diameter/routing. No issues there? Not on an EFR but I'm currently getting some smoke from my turbine housing at idle as well, despite now having a 6an and two 10an VTA vents on my car. Adding that second 10an vent stopped the oil seepage from my oil cap and dipstick tube but didn’t affect the smoke at idle. Straightening my oil drain routing is the next target.
I’m a little lost on how you plan to vent the pan. Having a vertical VTA tube going way above the pan height is one thing. Running a tube with a check valve to the intake manifold would just result in tons of oil getting sucked into the engine?
I'm not exactly sure where its leaking. I'm just thinking if pressure builds at the bottom and isn't alleviated through the oil passages to the top, it will cause oil to come out wherever. But yes, the idle smoking thing would be great to get rid of as well. My drain tube is straight but if its gravity drained only, a slight pressure differential in the pan will cause that drain to back up. That's what I think is going on, possibly with yours too.
Yeah probably, I'm doing research to see if there are any OEM blocks that do this and if they vent it through a port on the block or where. You're right, it probably would cause a ton of oil to come up. I'm still thinking it through haha.
There is a reason that oems always vent from the valve cover. There is significantly less liquid oil suspended in the vapor mix up there . Don't reinvent the wheel, just refine it.
Reread the catch can thread. If you have not enlarged the passages in your valve cover, you're making a mistake. If you have not added some sort of a media within the valve cover passages for the vapor to condense upon, you're making a mistake. If you have not run both sides of the valve cover to your catch can, you're making a mistake. If you are still running PCV valve, you're making a mistake.
In rough terms, you are running three times as much air through the engine as the stock breather system was designed to handle because you're making three times the horsepower. Add three times as much breather hose and fitting capacity and allow the vapor speed to slow enough that the oil falls out of suspension and you will be in much better shape.
And yes, efr turbos are an absolute nightmare for oil drain and crankcase pressure problems. Do not use a threaded drain fitting in your turbo. It will not drain properly. Do not use too small a drain line or fittings with that turbo. Do not run it without some sort of a restrictor to prevent over oiling. Do not have any sort of low spot or belly in the line or fittings as it returns to tank. Do not position the turbo in a way where the chra is not perfectly level left to right and front to back.
I feel like that's a lot of do nots, but those are very picky turbos.
Post 51 has the VC vents I drilled out. I've read that thread and I'm doing everything it says, hence why I'm not sure why there's so much oil getting out. The only thing that I haven't done is put steel wool in the baffles because that would only stop oil from getting to my catch can but it doesn't really get much anyways.
I am using a -10 drain that isn't kinked or not straight in any real way. I am using an external fitting from the housing to maximize internal diameter. I can take measurements but the housing itself is on the Kraken manifold and more than likely is horizontally straight. I thought the EFR has an internal restrictor, you're saying I should look at an in-line restrictor as well?
Maybe I should just throw that oil filler cap -10 bung setup like Bloopdog said if its really a volume issue. But I think my test shows thats not the case. Beyond that I could go to a -12 but if there's pressure in the crankcase, it doesn't matter how big the drain is.
There are large oil drain holes in the block and head, "crankcase" = oil pan, block, head, and valve cover, it's all the same pressure. I've been wanting to make a CAS delete plug with some NPT threads in it to monitor crankcase pressure. I currently have a 2.5bar MAP sensor but it's only reading a distant signal off a catch can. This is only really an issue/interest for us idiots running an EFR.
I was seeing ~.5psi positive pressure without the valve cover vented to the intake. I was seeing -0.5psi with it hooked up. I'd return to that if I were you. I did this all on the dyno before I added the sensor, and it actually picked up a decent amount of power (~12ish hp) with that simple mod. You can see the positive pressure on post #27 here: https://www.miataturbo.net/engine-pe...-105866/page2/
Sorry, I didn't go back and reread your thread. I just started from that fresh post talking about your problem. One of the local guys and I tried multiple times to solve his efr problem and it was very finicky. I just think they have very weak seals.
Circling back to the tube in the exhaust, they make O2 sensor defoulers. You can drill out the tip if it has one, stick a slash tube in it and JB Exhaust weld it. Make sure you mark the defouler showing the REAR of the car when installed, so you put the slash tube in correctly.
Also, you can put it in the rear o2 sensor location so you don't ruin the cat. Keeps everything reversible as well.
Six, no worries, thats why I linked the exact post . Pretty frustrating paying so much for a turbo that has issues like this.
Curly, that is absolutely incredible info thank you! I'm going to try the pre-turbo intake tube with a similar slash cut since I have a good tube length there. I picked up some argon and I'm going to try welding aluminum for the first time since my PrimeWeld 180 came with a spool gun.
I'm currently making the brackets for my two catch cans. One is done. But my first bracket I ever made broke. It was a hammered 90 degree with no heat and it held my EBC so I remade that. Then when pulling the vacuum hose off, I sliced my hand open when it popped off lol. I also have a couple other things I've been doing. Pics to come probably next weekend.
Circling back to the tube in the exhaust, they make O2 sensor defoulers. You can drill out the tip if it has one, stick a slash tube in it and JB Exhaust weld it. Make sure you mark the defouler showing the REAR of the car when installed, so you put the slash tube in correctly.
Also, you can put it in the rear o2 sensor location so you don't ruin the cat. Keeps everything reversible as well.
Solid idea, I like it thanks! I'm going to try doing the same principle on the intake tube first since its just more accessible and Curly has shown the exact results I'm hoping to see. Ideally I want both on the same catch can (intake and exhaust) to just have tons of vacuum but I think I'm running out of room for AN lines in my engine bay lol.
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. Pretty frustrating paying so much for a turbo that has issues like this.
