• From: Detroit Metro
  • Registered: 2018-02-10
  • Posts: 12

Topic: air - oil separator for crack vapors experience for turbo'd cars?

Howdy folks.... Hoping to see if anyone else has some experience with air - oil separation issues. New engine, measured leak down is 2-3% for each cylinder, 2.0 L Ford....
We are having some blow-by oil issue that we cannot seem to get a hold of. Put in a fancy Perrin AOS normally seen on subi's hoping that would help alleviate our blowing all the oil out into the catch can issue. While it reduced it, there is still an issue we have over time at even moderate boost levels where we are blowing out too much oil vapor. The Perrin is an interesting design of concentric circles as well as a bottom screen (actually sponge is more accurate) before the supposed to be free of oil vapor is discharged (in our case into a catch can - not back into intake or turbo inlet).
We are running the Ford Zetec Focus engine, just hoping some of you fellows had maybe run into similar things in some of your set ups?

  • From: Newport News, VA
  • Registered: 2015-12-23
  • Posts: 621

Re: air - oil separator for crack vapors experience for turbo'd cars?

Prodiclson wrote:

Howdy folks.... Hoping to see if anyone else has some experience with air - oil separation issues. New engine, measured leak down is 2-3% for each cylinder, 2.0 L Ford....
We are having some blow-by oil issue that we cannot seem to get a hold of. Put in a fancy Perrin AOS normally seen on subi's hoping that would help alleviate our blowing all the oil out into the catch can issue. While it reduced it, there is still an issue we have over time at even moderate boost levels where we are blowing out too much oil vapor. The Perrin is an interesting design of concentric circles as well as a bottom screen (actually sponge is more accurate) before the supposed to be free of oil vapor is discharged (in our case into a catch can - not back into intake or turbo inlet).
We are running the Ford Zetec Focus engine, just hoping some of you fellows had maybe run into similar things in some of your set ups?

I had a significant (texas tea-style) blow by issue on a totally unrelated engine. New rings on a dingle ball hone with a hard overheat fixed that problem. Induced several others... but that is neither here nor there.

That guy
  • Zacks
  • Ripened Lemon
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  • Registered: 2022-10-17
  • Posts: 111

Re: air - oil separator for crack vapors experience for turbo'd cars?

Leak down (and compression) tests don't really tell you about the oil rings.

I didn't have any luck with a catch can, never tried a proper seperator with return.

I don't race a turbo car but I've owned several.  Someone I worked with raced a turbo subie and said that at his boost levels blow by was inevitable (this wasn't Lemons, I think time attack 400whp or something silly)

I've had luck with thicker oil.

I'm not convinced turbo blow by is a solvable issue especially without new rings ect.

  • From: Detroit Metro
  • Registered: 2018-02-10
  • Posts: 12

Re: air - oil separator for crack vapors experience for turbo'd cars?

Engine is fresh, maybe 30 hours now.... was honed, new ring etc... but perhaps the rings didn't seat right, good point.
We did go to a thinner oil with the engine being fresh and tight, but maybe a thicker oil will help.
I was concentrated a bit on the subie side of things since a lot of turbo experience there racing, but not much endurance that I could find. The Perrin guy was disappointingly not very helpful tech-wise. We looked at a vac pump but maybe my brain cannot wrap my head around that helping unless the ring seal is that bad..?

Thanks for the thoughts Gents

  • Jimmy
  • Ripened Lemon
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  • From: Collegeville, Pa
  • Registered: 2019-06-19
  • Posts: 134

Re: air - oil separator for crack vapors experience for turbo'd cars?

I am a little familiar with big turbo diesels.. You would be amazed of how much blow by they have and still run very well. If you were running the blow buy into the intake ( ie PCV valve ) you might not even be aware. Oil consumption is more of an issue . If its not using too much oil ( what ever your comfort level is ) and its not missing  - it might be ok.

Cordoba
  • From: Detroit Metro
  • Registered: 2018-02-10
  • Posts: 12

Re: air - oil separator for crack vapors experience for turbo'd cars?

We are not running into intake, just to atmosphere through now an air oil separator (Perrin) and into catch cans.
The oil in catch can is reduced, but still an issue as we push too much over time and would need to add more or blow up engine. I keep running into Mann Hummel Provents on search engines, trying to reach out to them for possible help but they seem to be more of an OEM supplier - not looking to sell one unit to some Lemons racer knucklehead.

One of the questions I had for both Mann and Perrin was about the oil drainback line. In my head, having the drain below the surface of the oil level in the pan would make more sense, that way the drain does not simply become another crank case vent and the oil cannot drain because of the pressure / velocity in the drain line. In our case, we ran a -8 drain line to try to allow both crank case vapor and oil to cross flow - but honestly unsure if this is OK. We had a check valve (from flying Miata but Mann one looks identical) in the drain line where it would not allow crank case vapors to push up, but it didn't seem to drain as well in our limited testing. I was hoping to get from Perrin tech that system would operate better under manifold vac (our case likely turbo inlet or vac pump) but got nothing to be honest.
Still just scratching my head a little....

  • From: SF Bay Area
  • Registered: 2012-01-06
  • Posts: 721

Re: air - oil separator for crack vapors experience for turbo'd cars?

Have you checked your turbo for oil leakage to the compressor-side?

Capt. Delinquent Racing
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  • From: Detroit Metro
  • Registered: 2018-02-10
  • Posts: 12

Re: air - oil separator for crack vapors experience for turbo'd cars?

Not with this new engine this year, turbo took a dump last year and has been gone through... The few times We have popped off the piping, at least to the throttle body, I cannot recall seeing any residue or film that could only come from compressor.

I have been wondering if with the crankcase pressure from blow by is affecting turbo oil drain, will likely put a gauge on valve cover cap to see if we are seeing pressure at higher RPMs. We really don't spin the engine much, generally shifting at ~6000 but occasionally we go passed that on certain tracks or certain spots where its harder to shift / easier to hold. The oil drain just goes into midsection that is between oil pan and block on the zetec. Same for the air oil separator honestly - about 1-5" ish from oil pan.

We were just at NCM and I did see a little oil film that could have come from the exhaust on the car, but was not conclusive... we were having some other issues and could have been some from gear box or under hood that just spread at speed