Smoke from exhaust with no load
 

Fresh rebuilt BP, new pistons, rings, valve seals ect... Car drives good, good power but when coming to a stop or just taking off normally in 1st I get a coulple puffs of greyish smoke from the tail pipe. Enough that it is a bit embarrassing. Strange thing is that it only happens sometimes, maybe 50% of the time. I thought maybe I fucked up rebuilding my turbo so I popped off the 16g and dropped in a known good 14b. Still seems to be doing it. Should be noted that I have both valve cover ports going to a VTA catch can, no pcv system. Any thoughts? I have a fair amount of soot coming outta the pipe on a cold start too. Air/fuels look good. Zero oil in charge pipes.

Ok, so it is still using 1qt every 60 miles. Catch can is empty, no oil in charge pipe.

Pulled the plugs today, all have signs of oil burning and ash deposits. I looked down into the cylinders and can see oil on all the piston tops, they are all wet... Car only smokes after decel, coming off idle and spits black outta the exhaust on start up. No smoke when cruising and only light, black haze when really on it. Ill try to do a leak down in the next few days. I had all the valve seals and a few guides done during the rebuild but i used felpro seals. What are your guys thoughts? Strange its all cylinders and pistons are wet... Leads me to believe it could be the valve seals... How could oil get on top of piston when its not running if it was rings.

https://cimg1.ibsrv.net/gimg/www.mia...62f30bd569.jpg

Oil on the throttle plate/intercooler would indicate leaking turbo, but decel puts it at valve stems. They are intake /exhaust specific and should "snap" when seated fully.

Ya the throttle butterfly and intercooler are dry so I know it's not the turbo. My machinist installed the valve seals but would assume he did the right. That said anyone can make a mistake. He is one of my best friends, said if I pop the cams out he would come by and install new valve seals again. I just wanna know what it is before i go that far.

I think it has to be stem seals. Decel, extended idle and right after startup are the times that stem seals will let themselves be known.

Ya I think deep down I know you are right. I think it is possible he mixed up the intake/exhaust valve seals. It would be a relief to be honest.

I'm pretty sure that has to be it. Your engine is using 1qt every 60 miles that's pretty significant. If it ends up being seals like you said that's a massive relief.

Just looked on rockauto, intake and exhaust valve seals are interchangable.

Just so weird that its every cylinder. I checked and the seals are interchangeable so he couldnt have mixed it up. I guess the could have been packaged wrong. At this point Im tempted to find a bp4w head.

Were the guides replaced when the head was rebuilt? Worn guides will have the same symptoms as bad seals.

A few of the guides were replaced but not all

I suspect either the remaining guides, or the rings never seated. Its possible to get smoke at startup from worn rings, same for off idle and on decel. My last 944 motor did the exact same thing with rings that were toast, and even it didn't burn oil that fast with track use only (the car basically fogged for mosquitoes every time you decel'd from WOT).

I'm just really hoping you are wrong. I've rebuilt probably a dozen engines and only had problems with the rings one time, that was because I was inexperienced and didn't measure the gaps. There is enough oil on the pistons with the engine off that I can soak it up with a fine tip paint brush. I've never seen valve seals leak that bad, was right after a 30 minute drive staying outta boost.

I did a quick compression test this morning, I didn't have my leakdown tester handy. With engine hot: 160, 160, 165, 167.

Really need the leakdown test, as a bunch of oil in the cylinder can mask compression issues.

Ya, I totally agree. I will say, I would find it strange that all the rings would be bad from a reputable company like arias and I'm getting next to nothing in my catch can. That said, it is totally in the realm on possibility. Leak down test can rule out the rings but it won't tell me if its the stem seals, it can tell if valves are sealing in the head but not if the stems are sealing. Car doesn't have the decel haze you are describing from your other car, I have experienced that before and yes it was rings. Right now I'm considering 2 options, 1) Order new valve seals from Mazda for $200 fucking dollars or 2) Find a bp4w head and just try that. I'm still open to suggestions however and obviously I need to do a leak down before I pull the trigger on either option.

At least it will rule out rings. Doesn't necessarily mean defective rings, could have been too much oil on walls during assembly/break in, wrong hone finish, etc. I'd be pretty surprised if you were losing a quart/60 miles from just seals. If you rule out rings, I'd probably sooner just swap heads.

Ya could be a bad hone finish or something. Part of me wonders if he forgot the valve seals completely, I may just pop the VC off and take a quick peek to see if they are in there. I agree that is an extreme amount of oil loss for valve seals, if you could see how much oil has pooled on the pistons you would be shocked. It pains me that I have so much into this head, my buddy replaced a bunch of valves, guides and resurfaced it then I replaced all the HLA's. I was going back and forth then about replacing the head all together, I really should have.

So I just looked at Kia for valve seals for 97 Sephia. Same part number as Mazda but they are $20 for a set at Kia vs $122 a set at Mazda. Crazy.

If you pull the intake manifold you could shine a light in and see if oil is running down the intake valves.

Great idea, I'll try to find some time to do that tomorrow.

Did a leak down test today. Results were 4% 9% 5% and 6%. Im gonna go ahead and do valve seals tomorrow.

That's not that great... where was it leaking for each of those? Rings?

I would say those results are pretty good and a big relief. All losses were past the rings. According to every piece of literature out there anything under 10% is considered excellent condition. Keep in mind, ring gaps are set relatively loose on this car as they should be so some blow by is expected.

I would be ecstatic with those numbers. A leak down doesn't tell you oil control ring condition though.

I would be leaning toward stem seals though.

Well good for three of them but 9% I would expect out of like a 125k mile street car.

Oil is in all of them though so seems like not related. Hoping it's the valve seals.

Changed the valve seals today, used the oem kia ones. Seems better but could be placebo, also needs some time to burn out the residue. Will know after I drive it to work tomorrow if it used any oil.

Anything appear wrong with the ones you took out?

6
Didnt fully inspect them but the ones I looked at seemed pretty normal.

So it's no better. Used a qt of oil on my way to work, it's weird because it doesn't even smoke much. Pulled the plugs, still a pool of oil on the pistons. I'm honestly done, I'm not gonna sell the car but I'm gonna put it away till the winter when I have time to do another rebuild. Pretty much gotta be the oil control rings at this point,

When you rebuilt the engine, how much was the oversize on the pistons? What brand pistons and rings? Did the machine shop assemble the bottom end? What were the tolerances?

83.50mm Arias pistons using the Arias supplied rings. I gave the pistons to machine shop for measurement but I assembled the bottom end. Not sure what p2w measurement he went with. I don't recall but I believe I set the gaps to 0.021. I should know better but I'm second guessing everything now and wondering if I installed the scraper rings all upside down. I obviously make the same mistake on all 4 cylinders whatever it was. I have a lift in the garage and a cherry picker so it isn't the end of the world to pull it apart, I'm just tired of working on it although my wife is insisting I should just fix it. I was gonna swap in my 6 speed soon anyway so I guess pulling the engine is ok. I'm honestly just glad I'm not gonna have to pull the oil pump, crank, water pump ect.. just checking and replacing the rings isn't nearly as much work as the full rebuild.

https://cimg7.ibsrv.net/gimg/www.mia...c5bbf7b9d9.jpg

What the fucking oil control ring gaps... How did i miss that? Well i guess im an idiot.

Looks like 0.21 on the money.

Pretty close. Maybe 0.40 even. Upper 2 rings were on the money, just the oil control rings were all kinds of fucked.

Some bad pitting from detonation, i assume from the excess oil. You can see how much oil was sitting in the cylinders at all times.

https://cimg2.ibsrv.net/gimg/www.mia...e6dc14cbcd.jpg

https://cimg7.ibsrv.net/gimg/www.mia...6ad3759ad2.jpg

Whoops. That sucks man...

Ya, it's shitty but it would be worse if I didnt see an obvious problem. So that's good lol. Good time to swap in the 6 speed too.

like so many rebuilds, things go wrong...

"fuc this thing, im selling it"


two days later.."ok so I took it apart and found this".


I live by this strategy.

Lol I told my father in law last night the miata is done for the year and Im burnt out. 2 hours later I had found the problem and ordered the parts. Haha there is no way I could let it sit for a year, I am too obsessive for that.

Look at Arias end gap recommendations for oil ring: 0.20" per inch of bore... Guess it was in spec :p

https://cimg0.ibsrv.net/gimg/www.mia...0ddaf128f1.jpg

Wonder if the missing 1/4" is in the oil pan.

I'm gonna take a good look. I also ordered a tapered wiseco ring compressor and new wiseco rings, time to do this right. I hate hammering pistons into the bore with cheap compressors.

Oil rings were all broken, bits were stuck in the ringlands.
https://cimg0.ibsrv.net/gimg/www.mia...2dfe766f4a.jpg

Better open those gaps up for round 2!

Ah. So gaps too small then. Or if they were proper, could have fucked 'em trying to drop the pistons in with that compressor that you're not a fan of.

Reassembly has begun. Using Wiseco xx rings this time, I can tell they are much better quality. Got gaps set last night. Ready to use the new ring compressor.
https://cimg3.ibsrv.net/gimg/www.mia...4c700470c6.jpg

Awesome man, get er' done

I put it all back together this weekend and put on 100 miles yesterday. Oil consumption is still there, I can still see oil on top of the pistons too. Even fouled a few plugs.

I would bet that if I pull it apart again the bottom rings will be broken. I made very sure to check and set all gaps and the install was smooth. Any chance this is a piston or bore issue? I didnt measure the whole bores and only checked ring gap 1/2" from top of cylinder. I feel like maybe the bottom rings get tight lower in the bore, butt and break. Anyone have any ideas?

Did you have the block bored or honed before installing new pistons? It's possible you're out of round/taper, but also possible that you've got the wrong gap for the type of piston. Just curious - are you running a 2618 alloy piston?

Ring install - are you sure all your rings are oriented properly? Most beveled rings need to be bevel down/indicator up, otherwise, they will scrape oil into the combustion chamber with each stroke. Does your wrist pin opening cut into your oil control rings? If so, that bottom ring that acts as a support rail will have a dimple that needs to be in the wrist pin opening. When installing the expander ring, are you sure the ends are butted, and not overlapping?

If you put new rings and an old cylinder, it's important to measure the wear. It won't be even from top to bottom or latitudinally or longitudinally.

This picture is related to a diesel engine but you get the idea.

http://www.marinediesels.info/repair...ar_pattern.gif

It's new pistons and the bores was recently punched over to 83.50mm when the pistons were installed. At this point it basically has to be a problem with the bores or a defective set of pistons. The only thing i can think of with the bores is maybe the bottoms weren't punched out all the way to 83.50 because the gaps at the top are right but maybe right at the bottom they are butting. It is unlikely but its gonna be something unusual.

Like you said, you could have cracked a ring or maybe the rings did not seat properly.

First set, all 4 pistons had broken oil rings and spacers so not a seating issue. Replaced that set and bought a tapered wiseco ring compressor, installed new rings. Oil consumption the same (1qt/60 miles), oil pooled on top of pistons that I can see through spark plug holes. So all 4 cylinders are using a ton of oil. It is all but impossible that I broke all the oil rings on all 4 cylinders twice although I do suspect they are broken again. Rings not seating I could see if it was a small amount of oil or a couple cylinders. The amount of oil used goes way beyond a ring seating issue. I've rebuild many engines so it is unlikely that suddenly I break the rings every time I install a piston, one piston sure maybe but breaking them all twice? I really doubt it.

All fair questions. Yes, 2618 alloy pistons. Block was bored and honed before install. My ring gaps are correct but I have no idea if the p2w is correct as I left that to my machinist friend. I will say, this engine doesn't have the cold rattle that I typically get with 2618 pistons. Wrist pin opening does not overlap with the oil control ring groove. I made very sure that the expander ring ends were butted and not overlapped.

Here is my piston spec sheet. I notice it says my oil control ring groove width is 4mm however my oil control rings with spacer is 2.8mm....that seems like a really loose fit. Thoughts? Or do they mean the ring groove depth?
https://cimg3.ibsrv.net/gimg/www.mia...cf84ab9098.jpg

I figured out the problem. They sent me 1.0mm 1.2mm 2.8mm rings. The arias rings that should have come with them are 1.2mm 1.5mm 4.0mm. Here you can see what they sent and the catalog where it says what i need.
https://cimg3.ibsrv.net/gimg/www.mia...1fa478623b.jpghttps://cimg1.ibsrv.net/gimg/www.mia...86c7727e58.jpg

Oh no, I hope they didn't destroy your cylinder surfaces!

Ya me too! It was fine after the first tear down and I have only put on 60 miles since the second tear down so I'm hoping I can just hit it with a ball hone. I'm working with my piston dealer and arias rep now, will let you know how they handle it. They seem helpful so far, I'm just waiting to hear back from the rep.

Yikes. Presumably they sent you the same ring package twice?

I ordered wiseco rings from another source the second time, but based on the size they sent the first time. I shouldnt have assumed the manufacturer sent the correct size i guess.