cygnusx1 Posted May 11, 2011 Share Posted May 11, 2011 (edited) The L28ET that I just rebuilt runs great. I put about 70 miles on it today "break in style". I have a concern because it smokes a little on decel. I am going to give the rings some more time to seat but I don't think it's ring related. I pulled the plugs and they are the nicest, light brown, dry, color I have ever seen in the car. That tells me that it might be the turbine seal. I figure when the engine is under load, the exhaust back pressure keeps the oil where it belongs, in the turbo core. On decel, the oil might be dripping into the turbine and making the blue smoke. It happens mostly when I come down from 4000+ rpm. When it coasts down to about 2000, the blue smoke begins to trail out. The head has only about 5000 miles on it since the rebuild, and the car does not smoke when it starts. I rebuilt the turbo during this engine build, but the shaft was a bit "rough" and pitted. I was not entirely happy with the shaft condition but I figured I would try it. I also didn't like the "looseness" of the seal on the turbine side. (this may be just me pointing the question). Does it sound like the turbo might be bleeding oil? Are there any other tests I can do? If I had a compression tester I would do that. The vacuum at idle is as good as I have ever seen it....and the plugs looks perfect. It smoked before the rebuild on decel too. I have the PCV valve connected to the block vent with some stainless mesh in the pipe, and have the valve cover vented. Upon doing some reading, I have to look into a better PCV layout, and an oil line restrictor. I am using the factory oil pipe right now. I also read that the new turbo seals need to build a "carbon dam" before they seal up well. Is that true? Dave Edited May 14, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 12, 2011 Share Posted May 12, 2011 (edited) Not having owned a turbo it seems to me that a lot of people with turbos going out pull an intake elbow off and see oil in there. Might be worth a shot. I don't think 70 miles is enough to break in rings, especially moly rings. I think smoke on decel is a sign of ring problems for NA cars too. Edited May 12, 2011 by JMortensen Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 12, 2011 Author Share Posted May 12, 2011 Not having owned a turbo it seems to me that a lot of people with turbos going out pull an intake elbow off and see oil in there. Might be worth a shot. I don't think 70 miles is enough to break in rings, especially moly rings. I think smoke on decel is a sign of ring problems for NA cars too. I'm going to pull the turbo outlet pipe to have a look. The plugs look so much cleaner than the grimy ones that i pulled out of the motor prior to the rebuild. In fact they look perfect now. I tend to think, that the plugs are not seeing any oil, based on their clean look compared to how they used to look. (same set of plugs). I hope it's the turbo because I won't mind letting it be for a while, if so. The top plug in this photo, represents what my plugs look like now. The oily one, represents what they looked like when I pulled them out before the rebuild. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 12, 2011 Author Share Posted May 12, 2011 (edited) Turbo compressor side appears clean and dry but I see some wetness around the end of the cartridge where it clocks to the turbine housing. I installed a restrictor in the oil feed line and checked torque at all the fittings. Will test tomorrow. I suppose I really need to give the rings more time to seat before I diagnose any further. I'll put on more miles tomorrow. Edited May 12, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 13, 2011 Author Share Posted May 13, 2011 (edited) I added a hose from the valve cover to the turbo inlet so that the PCV system should operate at well as the factory system did. I put on another 80 miles or so. It still smokes pretty good blue fog on decel from anything above about 3000 rpm. The plugs still look awesome and it runs really well. COmpression test will be next, followed by a courtesy valve seal change. I have at least three sets of new valve seals around. If compression is good, and valve seals don't solve the smoke, the turbo will get a new owner. Tapped into the turbo inlet pipe for the valve cover vent. Cheap and effective. Edit: I went back and checked the photos of the ring installation and it all looks good against the supplied chart. I specifically remember making sure the oil control spreader was not overlapped before placing the pistons in the block. I keep second guessing myself. (huge photo here: http://dcer.smugmug..../O/P1060561.jpg ) Edited May 14, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
Oddmanout84 Posted May 14, 2011 Share Posted May 14, 2011 Does your turbo have the stock oil fittings on it or a restrictor? Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 14, 2011 Author Share Posted May 14, 2011 (edited) I just added a restrictor the other day with no change in conditions. I am waiting on a compression tester which I think will show the rings are fine, hopefully... I mean, it runs great and the plugs are a beautiful color. Edited May 14, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
rags Posted May 14, 2011 Share Posted May 14, 2011 Come get my stocker turbo and see if it still smokes using that one. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 14, 2011 Author Share Posted May 14, 2011 (edited) Yeah Joe, good idea. I did this test and I need some help interpreting it. -Cold start, zero smoke. -Hard acceleration, zero smoke. -Heavy deceleration, smoke. -Hot idle, little to no smoke. -Shut down hot, and restart in 30 seconds, big cloud of blue smoke after start and rev. <---------- turbo seal dripping into turbine? Edited May 14, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 14, 2011 Share Posted May 14, 2011 Yeah Joe, good idea. I did this test and I need some help interpreting it. -Cold start, zero smoke. -Hard acceleration, zero smoke. -Heavy deceleration, smoke. -Hot idle, little to no smoke. -Shut down hot, and restart in 30 seconds, big cloud of blue smoke after start and rev. <---------- turbo seal dripping into turbine? It might be the turbo, but when I had a turbine seal leak on my turbo car, it smoked all the time, especially under load. It was so bad I couldn't drive it. What ring configuration are you running? The race motor I just built was still smoking a little even after two days on the dyno. When I pulled the head, I could see that the rings hadn't fully broken in yet. You can tell by the wear pattern on the cylinder walls. I'm running a total seal moly top, two piece 2nd, and standard oil control ring setup. It is making good power and ~250psi across all cylinders. Did you check the compression yet? Pete Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 14, 2011 Author Share Posted May 14, 2011 (edited) No, I am waiting for a compression tester. The piston rings are ITM as part of the ITM piston/pin/ring set. They were all gapped in the respective bores to 0.017". The gaps were staggered, alternating 180 degrees, all of them above the skirts. Oil control rings and gaps were confirmed properly setup before I clamped the ring compressor on them. The plugs are super clean and dry. I have heard that turbine seals will leak all the time if bad, but will leak most off throttle; similar to valve seals. They will pool oil in the turbine, to be burned off again, if the car is fired up hot again, a short while later. Next chance I get, I will pull the downpipe and look in the turbine housing for play and grime. So far, based on the great vacuum readings, strong power under load, with no visible smoke, and clean plugs, I think the piston rings are good. When I changed the ring seals and bushings in the turbo, I was not thrilled with the conditions of the ring groove and shaft. I did not document the measurements because I had no reference anyhow. They just looked a bit pitted and dull for precision fitment, to me. It probably smokes worse now that I cleaned all the coking out of it for the rebuild. I am tempted to plug off the turbo oil feed line and do some brief tests....bad idea or REALLY bad idea? Edited May 14, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 14, 2011 Share Posted May 14, 2011 Probably not a good idea to spin the turbo without oil pressure. Maybe the turbo needs a new shaft and seals at this point. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 14, 2011 Author Share Posted May 14, 2011 I am going to test everything no matter what. But I am hoping that my hunch is correct, and that the turbo has exceeded its usefulness. It's a unit that was "rebuilt "at least twice now. Generally when you have a problem after changing something, the first thing you do is blame the work you just did. In my case, piston rings and turbo seals were messed with. I have much more faith in the work done on the pistons than the turbo. I will get to the bottom of this next week. Quote Link to comment Share on other sites More sharing options...
Noddle Posted May 14, 2011 Share Posted May 14, 2011 (edited) Yeah Joe, good idea. I did this test and I need some help interpreting it. -Cold start, zero smoke. -Hard acceleration, zero smoke. -Heavy deceleration, smoke. -Hot idle, little to no smoke. -Shut down hot, and restart in 30 seconds, big cloud of blue smoke after start and rev. <---------- turbo seal dripping into turbine? Depending on what ECU you are running, but can you remove the turbo from the equation ? ie, remove the pipe from the turbo to the manifold ( or configure a temporary pipe to connect the flapper ), and then do a heavy decel, and see if it smokes ? if it sill smokes, maybe leaking valve guide seals Nigel Edited May 15, 2011 by Noddle Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 15, 2011 Author Share Posted May 15, 2011 (edited) Yes, I could do that because I run MS, however, the compressor side is bone dry. I think if it is leaking, it's on the turbine side, I can't think of an easy way to take that out of the equation. Thanks for the idea though! LOL. I thought about performing my 30 second hot restart with the nose of the car down hill and then uphill to see if there is a difference. I know it's a reach but....at least i am thinking. Edited May 15, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 15, 2011 Share Posted May 15, 2011 If the compressor was leaking oil you would probably see it on the plugs. Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 15, 2011 Share Posted May 15, 2011 Pull the O2 Sensor right at shutdown, watch the hole for smoke; sniff it while it cools down. The scent of carbonising oil dripping into a hot exhaust turbine is pretty unmistakable. If it's leaking bad enough, (big puff on 30 second shutdown?!?!?) you will likely see smoke pouring out of the O2 Sensor hole if it's close enough. You will smell it for sure. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 16, 2011 Author Share Posted May 16, 2011 (edited) Gotta get my nomex gloves ready. My O2 is close to the turbine exit. About 3" away, so it is a good point of view for sure. It makes sense that if there was smoke there shortly after shutdown, it's likely not coming from the combustion chambers. Yeah cold starts are always very clean, do a hot restart shortly after shutting it down and you get a big blue cloud that clears with a rev or two. On that note I suppose it's easy enough to pull the down pipe right off, and cycle it on-off and look inside. Maybe my cloths don't smell like burnt oil after all. It must be carbonizing oil. Is it pungent? Edited May 16, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
RB30X Posted May 16, 2011 Share Posted May 16, 2011 If the compressor was leaking oil you would probably see it on the plugs. Or it would sit in the intercooler. Its not an auto is it?? Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 16, 2011 Author Share Posted May 16, 2011 It's a 5 speed. Compressor side is bone dry. Confirmed at housing Quote Link to comment Share on other sites More sharing options...
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