Smoking from tailpipe during boost
 

Well I just got done installing my turbo setup and took it for a drive.. while getting in boost, i get quite a bit of whiteish smoke pouring out the tailpipe..

I'm assuming its actually blue-ish smoke and is oil burning.. anyways..

It's a brand new 16g turbo with megan mani/dp.. I was under the impression that the turbo had a built in oil restrictor but maybe it doesnt?

I put in a 323 GTX PCV valve but no difference.

The pan is tapped but maybe the drain isnt quite perfect? Ill try to post a picture in a second..

The only other thing i can think of is it has blowby, could it have that much extreme of blowby?

Is it an MHI 16G or a China special?

Got it off of ebay so im guessing china

One more thing i forgot to mention, the driver's side valve cover breather isnt yet hooked up to the intake path it just had a breather filter hooked up.. that couldnt cause it to smoke that bad tho could it?

Also, every once in a while when i get home and turn it off, there is a little bit of smoke coming off of the exhaust side of the turbo housing

could a bad pcv (clogged pcv port) allow oil to blow out of the breather onto the hot turbo/manifold? just spitballin' here

I just replaced the PCV and it made no difference

If you don't even have your driver's-side breather hooked up to a constant vacuum, then, yes, it could easily be causing smoking.

This is quite a bit of smoke.. I wasn't aware it would make that huge of a difference, the car is about 240 miles away i live on an air force base in louisianna and my car is in texas at my parents house.. so next time im in town ill try to rig that up and see what happens..

Well, if it's truly as much smoke as you say, then, yes, routing the breather correctly likely won't eradicate the problem entirely, but you should try it just for the heck of it.

What's the best way to do this? Route it back into the intake? Wouldn't that just pressurize the crankcase?

See this thread. https://www.miataturbo.net/forums/sh...ad.php?t=10930

What? bad advice.

Yes it would. The breather (driver side) should go before the turbo after the maf (if equiped)

Yes, route it to the intake; not a charge/intercooler pipe, but the one at the turbo inlet that'll see constant vacuum.

I'd double check the drain line is ok. triple check the PCV valve works (find air compressor). reroute the breather line. possible add restrictor in turbo (-4AN line?)

There isn't much vacuum at the turbo inlet. The airflow at that point in the system is a large volume of air with little vacuum or pressure. After the turbo before the throttle is mostly pressure and after the throttle is vacuum and pressure. If you have vacuum at the turbo's inlet then you have a blocked air filter.

you're still going to have 1-2 ~hg. Anything more than that and you have a restriction. Yes it's little, but yes that little bit of a vacuum helps pull the oil out of the turbo and helps seals the rings a bit better when in boost.

think about this: you're idling and you blow into your breather line, you'll see blue smoke out of the exhaust. You can blow enough pressure (about 15kPa at the extreme or 2psi) to force the oil back up into the turbo and start blowing past the oil seals into the exhaust.

At 2~hg. (as tested by Corky Bell at 9psi on his S1 kit) you're pulling about 1psi out of the crankcase, which will be just enough to help pull the oil out of the turbo, and in the least equalize the pressure different from compression loss or a leaking pcv.

in other words, it doesn't hurt.

in my case, I couldn't even put an catch-can on my breather line. The pressure drop from it was enough cancel the vacuum. Which lead to me burning smoke on decel out of boost. (I had bad rings). As soon as I removed the catch-can form the line and put it back driectly to the intake, the smoke was eliminated.

It's funny, huh, Scott...after lo these many years of preaching the benefits of correctly routing the PCV system, some people still don't buy it.

Update: I re-clocked the turbo so the oil return pointed more straightdown, routed the drivers side breather to the intake pipe right before the turbo, and put another turbo 323 PCV valve in..

One of those things fixed the problem, under boost i see no smoke pouring out of the tail pipe..

Next problem, after driving around town for a weekend quite a bit.. the oil and coolant was fine..

However, on the 240 mile trip home from texas to louisianna, it burned or leaked 5 QUARTS of oil.. wtf?

Rings? i have no idea, ill do a compression check this weekend but wtf is the problem?

Well i just took it for a drive.. its starting to smoke again in boost, but now it stumbles really bad when entering boost, which could be a totally different issue, or could it?

The thing only holds 3.6qts by the book... so I'd say you've got a problem.
I'm surprised nobody has asked you for your compression numbers yet. Do a compression check and report back.
Is there any oil in the charge piping?
Are you running a cat?

What do you mean pull the oil out of the turbo?

vacuum is suction....correct? So what happens when say you put a straw in a cup full of water and suck....the water travels through the straw into your mouth.

See...fixed the problem (combined with improving the oil drain). One of these days people will start listening to us, Scott...one day.

nah, that wont happen.


So greenday....whats up with it now? did you forget to tighten the oil drain or something? It it smoking the same way or could this possilby be because you ran without oil? stumble could be a number of things....retrace everything you did and make sure you didn't forget to tighten a hose or something.

Your absolutly right...

ok now back to the turbo. Where are you sucking oil from? The bearing housing?

Just got back from work, so i havent yet had a chance to look at it yet.. But anyways, it never ran more than a quart low on oil, it was fine all last weekend when i was driving around, but once i got on the highway i smelled oil burning so i pulled over frequently to fill up the oil

The stumble isnt really what im most worried about right now, its the oil.

On the drive home today i didnt smell or see any oil burning, but last night when i went to get gas i started it, let it idle for a few minutes, and saw what appeared to be smoke (possible condensation its been raining a lot here) pouring out of the tailpipe

Well i just went out and looked, and i know i tightened the oil drain, but for some reason the front side of the motor is covered in oil, i have no idea where it could be coming from.. but still like i said before, its burning out of the tailpipe on the highway

Basically the only things i could think it could be is either the turbo needs a restrictor on the oil feed ( i thought it had a built in one) Or its something to do with the engine (HG, rings, valves) something like that

Ill do a compression test this weekend or sometime this week if i have time tho