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Recently finished my first turbo build. My exhaust is smoking pretty bad. im assuming its a draining issue. Im running gen 2 pt6266 ball bearing turbos. And I restricted the oil feed to .030. I called precision turbo they second my thought of it being a draining issue, and they suggested i don't use any restrictors.
I ran a test by draining the turbo straight down into a bucket, and i bored out my -10an to 1/2. To see if it still smoked. while testing, the exhaust smoked a lot less than before. I also tried the bigger .045 restrictor. And it smoked more than the .030. but it still smoked.
precision turbo suggested i use their high flow drains. there drains measure the same as my -10 15/32. But the base is machined with a taper.
do you think the high flow really makes a difference?
If you have a setup with very little vertical drop, the PCV system (or lack thereof) can make a big difference. Without seeing your setup, who can say what the problem is?
If you have a setup with very little vertical drop, the PCV system (or lack thereof) can make a big difference. Without seeing your setup, who can say what the problem is?
Im sure that my passanger side is pretty vertical. Driver side not so much.
But both sides smoke pretty evenly bad.
As for venting. Im venting both valve covers to a catch can.
Vent BOTH rocker covers to atmosphere.
Minimum 3/8" hose on passenger side to open mesh breather filter. Then, REMOVE ANY restrictor and run 1/2" id hose to vent driver side.. If you let that motor EAT, you've got to let it BREATHE too.
Route the driver side breather hose up and over the brake booster, then down to open about an inch below frame rail IN THE AIR STREAM, it will will draw more than twice the airflow out of crankcase than factory close PCV system: You're oil will stay clean longer, and rings will stay seated better, you won't have oil in your intake manifold, and your blow by gasses will not have a chance to back pressure your Turbo drains.
Closed PCV systems work on engines that suck. You don't want your engine to suck, do you ?
Last edited by Full Power; Jul 25, 2025 at 01:12 AM.
Reason: yes
Some will say they run ½” with no issues, but there are just as many (if not more) that have problems just like you. ½” drain ID is the issue IMO. Do you have abnormally high oil pressure?
I believe the restrictors are in the turbos them selves on those units which is why they say not to run an additional restrictor. Def not worth destroying 2 expensive turbos.
I’d do as they say and run without a restrictor and put properly sized drains on there. (i’d go ¾) AN fittings and lines are pretty poor choices for drains you should use thin wall tubing and high heat hose with clamps. There is no pressure, so AN fittings and lines are def not needed and they flow poorly as “Gravity drains” compared to thin wall tubing. 5/8” was enough to drain my journal T3 frame GT35s. But If you have to redo it all... I’d just step up to ¾. Then you know you won’t have an issue.
All the things mentioned above can def. help, but they don’t fix the root of the issue.
I can’t imagine that drain fitting you show will do much and I bet its not cheap. I’d buy one of the cheap 3/4 NPT threaded drains and go from there. Thin wall SS tubing or even ¾ copper tubing works well.
So I changed a couple things on the drain. I went with a high flow drain, now draining into the oil pan. And now the lines are more straight down compared to how it was. And I went with a .060 restrictor. And it still smokes pretty bad. Not as bad as before. But still pretty bad.
I can't believe that the hoses are not vertical enough. that its causing a back up.
Do you think I might have to much oil pressure?
im around 65-70 oil pressure. Precision turbo said that the turbo will take all the pressure that I can give it. But I think there has to be a limit on how much pressure the turbo can handle.
Here's some pics of the set up. Not the best pics. But my engine bay is pretty tight.
Last edited by duggravs; Jul 31, 2025 at 10:10 PM.
Interesting. Your drain situation looks much better than mine (barely any vertical drop and a long horizontal distance on mine), and I just get the barely noticeable puff of smoke at idle sometimes. At some point i the near future I plan to redo mine with hardline tubing, but it is what it is for now. Mine was worse before I hooked up the valley cover PCV port to vacuum (I have a check valve to keep boost out). I still have both valve covers vented to atmosphere. Is there a chance your returns are going in right where a baffle is, or where a lot of oil slings off the crank? I forgot to mention, mine is running 5w40 oil. I'm sure thicker oil would be harder to drain.
Interesting. Your drain situation looks much better than mine (barely any vertical drop and a long horizontal distance on mine), and I just get the barely noticeable puff of smoke at idle sometimes. At some point i the near future I plan to redo mine with hardline tubing, but it is what it is for now. Mine was worse before I hooked up the valley cover PCV port to vacuum (I have a check valve to keep boost out). I still have both valve covers vented to atmosphere. Is there a chance your returns are going in right where a baffle is, or where a lot of oil slings off the crank? I forgot to mention, mine is running 5w40 oil. I'm sure thicker oil would be harder to drain.
Here's a pic of my venting. I have both -10an valve covers venting to the catch can on the passanger side firewall. Even with 1 of the hoses disconected. Its still smoking pretty bad.
I don't know what else to do. Iv already spent pretty good money on redoing these hoses. I don't want to have to do it all over again.
I know its not what anyone wants to hear but it needs redone with a decent ID drain. Nothing else will correct the issue. And if you are gonna do it... go overboard as you don't want to do it a 3rd time. Get rid of the silly AN fittings and AN hose.
I run 5/8" on some puny gt3582s, no smoke, on my single setups I've always run 3/4" or even 1" if space allows. Never had a drain back issue. Just try to stay away from the cheap China AN stuff, I've measured some -10 at under .40"
This is one of the worst examples you can have location wise and it still worked well with no issues. Even with an immediate 90 and almost horizontal drain (both huge no no's) 3/4 copper pipe made this setup work. Large diameter is your friend.
Type M (thin wall) copper tubing and fittings are .875 ID. Type L is .785 ID
Ok I'm out of ideas. I replaced all the -10an stuff with 3/4 id hose and fittings. cleaned out the exhaust. And you'll never guess. ITS STILL SMOKING!!!!!!!!!
people are telling me to use a oil pressure regulator. And precision turbo is telling me not to. Becuse that will starve the turbo of oil. And that I'm still having a draining issue.
my thought is. At some point there has to be a max oil pressure that those seals can handle.
Here's a video of the smoke and set up
How well did you clean it out? Could it be residual? Its super hard to clean out oil residue. might need to go on a long cruise? Is oil in charge piping and exhaust?
How well did you clean it out? Could it be residual? Its super hard to clean out oil residue. might need to go on a long cruise? Is oil in charge piping and exhaust?
I used some pretty strong degreaser and let it sit over night. It cleaned up pretty good.
weird thing is that the exhaust side is dry.
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Turbo drain smoking issue 
