cygnusx1 Posted May 25, 2011 Author Share Posted May 25, 2011 (edited) Nope. Still smokes pretty good on heavy decel. I am losing my garage for a few weeks starting next week, as I work on a turbo swap for someone, so I'll just have to let it be for now. I may sneak in another compression test. This time I'll do a wet/dry test, and I'll yank that valve cover off that I "glued" on with Permatex2. I'll see if I can't tell if any of the valve seals lifted , and check torque/lash on the head again. If we can string together some decent weather, I'll put more seat time on it too. The turbo spools nicely now though! Is it possible that even though the dry compression numbers are all right on spec, that the oil control rings aren't controlling the oil? Edited May 25, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 26, 2011 Share Posted May 26, 2011 "Is it possible that even though the dry compression numbers are all right on spec, that the oil control rings aren't controlling the oil?" Oh HELL yes! I had a stuck control ring on #5 that would FOUL THE PLUG! I decided to "kill" the engine so took the boost up to 17psi and DROVE THE HELL OUT OF IT with the intent to kill it at an Auto-X and driving home one day... To my surprise, the smoking and fouling on #5 stopped after that. I must have unstuck it! Oil consumption went back to nil. I have an engine in my Fairlady Z that has over 225K miles on it now, and has PERFECT compression: first pump is almost 110, third pump is 185 steady and across the board. It also SMELLS of oil if you are behind it! Consumes oil over a quart in 1500 miles, and if I'm driving hard like Auto-X I can go through a quart in 500 miles! No real blue smoke unless it's in the morning, or after long decel. But for the way the thing runs...screw an overhaul! Oil is CHEAP! Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 26, 2011 Author Share Posted May 26, 2011 (edited) OK then I'll stop worrying about it then and get some more miles on it. Then I'll start flogging it around to scare out any bugs. It only smokes when I let off for a long coast. I guess I just shouldn't let off. Otherwise, it runs like a champ, except that it starts leaning out, during low load cells, as the engine bay gets hot. I don't think it's pulsewidth dropping off. I will datalog it tomorrow. I might need to bite the bullet and circulate the fuel rail. Edited May 26, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 26, 2011 Share Posted May 26, 2011 OK then I'll stop worrying about it then and get some more miles on it. Then I'll start flogging it around to scare out any bugs. It only smokes when I let off for a long coast. I guess I just shouldn't let off. Otherwise, it runs like a champ, except that it starts leaning out, during low load cells, as the engine bay gets hot. I don't think it's pulsewidth dropping off. I will datalog it tomorrow. I might need to bite the bullet and circulate the fuel rail. Not sure if anyone asked this, but did you put the breather screen back in the block? Just another thought. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 27, 2011 Author Share Posted May 27, 2011 (edited) Yes, I cleaned it all up and put it back in with locktite on the philip screws. I noticed something that I thought was strange today. I was charging the A/C so I had the compressor outlet pipe off for access. With the engine at idle I covered up the inlet to the intercooler with my hand, I felt no vacuum! I tried again and held my hand there completely sealing it off for about 25 seconds. No vacuum. I cracked the throttle a tiny bit and it nearly sucked my hand into the intercooler. Repeated this test but held my hand over the intake side of the "Cold Fast Idle vane valve thing". Vacuum built up pretty strongly there in 4 or 5 seconds. The engine was hot. So is my car breathing through the fast idle circuits, or the PCV circuits at idle, instead of the throttle plate? Normal or not? I wonder if my car takes too much air from the PCV circuits BECAUSE I have my throttle body pinched down to get a proper idle, due to air sneaking in from somewhere else? This could explain "dirty" air from the crank case getting into the intake plenum when the throttle is closed. Especially on heavy decel. Follow me? Am I way out of the ball park here? I know it's easy to test. I'll do it tomorrow...also going to put in another new PCV valve. The PCV valve for the turbo application has three positions right? Sealed under high vacuum, sealed under boost, and open during light cruise. EDIT: Forgot that the BOV was probably cracked open which is why I had no vacuum in the intercooler intake. DOH! Edited May 27, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
jamunm90 Posted May 27, 2011 Share Posted May 27, 2011 I'm not sure if this has been asked, but what oil are you using? Synthetic? If so, I would drain and swap to a regular oil for the next 500 to 1K miles. It will eventually break in with the synthetic, but will just take longer. It "may" fix the problem, but even a fresh stock rebuilt engine should not smoke like that unless you have blueprinted it and are running a racing spec rebuild with extra piston/ring clearance? I assume you measured your ring end gaps when you assembled it? It's possible that you simply have a bad oil ring in there someplace. I came across new main/rod bearings that were out of spec right out of the sealed package from a national brand. I sent them back and got another set...I think they were either mis-labled or mis-boxed but this kind of stuff does happen. I would put some more miles on it before you tear into the engine...it could seal up with some additional wear...Regular "dinosaur squeezings" oil will help speed up this process a bit.... Good Luck!! MB Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 27, 2011 Author Share Posted May 27, 2011 (edited) LOL yes I usually run Mobile 1 but I have some squashed dinosaurs in it now. Bored 0.020" over. My top two rings are gapped to 0.017" and piston clearance was set to 0.003" at the skirts. All ring gaps 180 staggered, not over the pin ends. Oil control spreader visually confirmed, not overlapped during assembly. It's a bit "gappier" than the FSM calls for but I do run 16-18 pounds of boost and occasional destructive track days. Maybe that's just it. 240 miles on it now and I "think" the smoke is a little less. I am sure my turbo is sealed up good now. Edited May 27, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 27, 2011 Share Posted May 27, 2011 Do you have an IAC valve in there? Is the MS controlling it or is it just plugging a hole? Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 27, 2011 Author Share Posted May 27, 2011 (edited) Just the Nissan electro mechanical fast idle valve. 12volts on it when the car starts up. It holds a 1500 rpm idle when it's cold and slowly drops to about 950. No MS idle control at all. My throttle stop screw is all the way down. I can't close the 240SX TB any further unless I file the lock nut on the set screw. It may very well be breathing too much idle air from the wrong place (crank case?). When I have some more play time with the Z, I'll disconnect/plug the PCV and drive it. Edited May 27, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
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