Help needed to identify cause of smoke
09-30-12, 05:01 PM
#1
Help needed to identify cause of smoke
Hey all, I just got back from the Carlisi Memorial BBQ at NJMP and need some help diagnosing a problem that developed with my car during the second day at the race track. I'm far from knowledgeable about this stuff so I'm going to dump all my observations here in the hopes someone knows what's going on.
The first two sessions of the day were fine. The car was running strong and there were no problems. I came off track and parked the car. When I went out for the next session, the car started billowing smoke when I started it up.
The smoke is definitely oil being combusted. It is *not* the brownish smoke you get when oil leaks directly into the exhaust stream and is vaporized. It is *not* fuel or coolant smoke.
I've noticed a smaller amount of smoke like this before 1 in 10 times when I start the car. I have always attributed it to pre-mix at the bottom of the fuel tank being sucked up and dismissed it. This smoke was MUCH more significant.
I took the car back out on track hoping that driving would clear it up like it has in the past. The car seemed to run fine but billowed smoke for a few seconds every time I boosted and then upshifted or lifted.
I came in, and checked my catch can. It was full. I thought that may be the cause of the smoke since the turbo would be pulling the soup straight from the can. I emptied the catch can, started the car, and it continued to billow smoke.
I took the car back on track and it continued to smoke under boost when shifting or lifting.
I drove the car around the paddock and it was billowing smoke on idle and under slow driving.
I took it out on surface roads and the smoke eventually cleared up, as long as I stayed out of boost.
I drove on the highway all the way home and as long as I stayed out of boost, there was no smoke. Any amount of boosted causes smoke to come out after the upshift or lift but NOT while boosting.
Observations:
- Engine sounds good, runs good, makes good power.
- Engine pulls good vacuum.
- Water temp, oil temp, oil pres all good.
- Car runs a solid 10 psi, never overboosted.
- When I got off the track and drove around slowly, I noticed that there is a new hissing sound between 0 and 5 psi. Above 5 psi the hiss gets a LOT louder. I haven't identified the source but I don't think it's a significant boost leak because I didn't notice any lack of power on the track. May be internal to the turbo/engine.
- No real amount of oil consumption over 150 miles of highway driving home keeping out of the boost completely.
- The catch can seemed to fill up unusually fast at the track. I thought that was the reason for the smoke but once emptied, the problem continued. Can did not fill up at all during the 150 miles back on the highway.
(I have a '95 style PCV system with catch can inline between the oil filler neck and the stock turbos)
- The turbo outlet intercooler pipe is a bit oily, but not unexpected considering I let my catch can fill up and have been at the track running the car hard for 2 days.
- No appreciable amount of oil in the intercooler when stood on an end-tank and allowed to pool.
So at this point, I'm either looking a blown turbo, a problem with the PCV system, or some sort of oil leak internal to the engine. I have yet to drop the downpipe and see what's going on there since I just got home. What really confuses me is that the car boosts fine (albeit with that new hissing sound) and only smokes after the lift. It doesn't constantly billow smoke anymore because I've been staying out of the boost but I imagine if I took it back on track and then idled it, it would billow constantly for a few minutes straight. I also can't help but wonder if letting the catch can get full and then tracking the car may have contributed to/caused the problem or whether it was a symptom of a problem that was already present.
Any thoughts would be hugely appreciated. Thanks!
The first two sessions of the day were fine. The car was running strong and there were no problems. I came off track and parked the car. When I went out for the next session, the car started billowing smoke when I started it up.
The smoke is definitely oil being combusted. It is *not* the brownish smoke you get when oil leaks directly into the exhaust stream and is vaporized. It is *not* fuel or coolant smoke.
I've noticed a smaller amount of smoke like this before 1 in 10 times when I start the car. I have always attributed it to pre-mix at the bottom of the fuel tank being sucked up and dismissed it. This smoke was MUCH more significant.
I took the car back out on track hoping that driving would clear it up like it has in the past. The car seemed to run fine but billowed smoke for a few seconds every time I boosted and then upshifted or lifted.
I came in, and checked my catch can. It was full. I thought that may be the cause of the smoke since the turbo would be pulling the soup straight from the can. I emptied the catch can, started the car, and it continued to billow smoke.
I took the car back on track and it continued to smoke under boost when shifting or lifting.
I drove the car around the paddock and it was billowing smoke on idle and under slow driving.
I took it out on surface roads and the smoke eventually cleared up, as long as I stayed out of boost.
I drove on the highway all the way home and as long as I stayed out of boost, there was no smoke. Any amount of boosted causes smoke to come out after the upshift or lift but NOT while boosting.
Observations:
- Engine sounds good, runs good, makes good power.
- Engine pulls good vacuum.
- Water temp, oil temp, oil pres all good.
- Car runs a solid 10 psi, never overboosted.
- When I got off the track and drove around slowly, I noticed that there is a new hissing sound between 0 and 5 psi. Above 5 psi the hiss gets a LOT louder. I haven't identified the source but I don't think it's a significant boost leak because I didn't notice any lack of power on the track. May be internal to the turbo/engine.
- No real amount of oil consumption over 150 miles of highway driving home keeping out of the boost completely.
- The catch can seemed to fill up unusually fast at the track. I thought that was the reason for the smoke but once emptied, the problem continued. Can did not fill up at all during the 150 miles back on the highway.
(I have a '95 style PCV system with catch can inline between the oil filler neck and the stock turbos)
- The turbo outlet intercooler pipe is a bit oily, but not unexpected considering I let my catch can fill up and have been at the track running the car hard for 2 days.
- No appreciable amount of oil in the intercooler when stood on an end-tank and allowed to pool.
So at this point, I'm either looking a blown turbo, a problem with the PCV system, or some sort of oil leak internal to the engine. I have yet to drop the downpipe and see what's going on there since I just got home. What really confuses me is that the car boosts fine (albeit with that new hissing sound) and only smokes after the lift. It doesn't constantly billow smoke anymore because I've been staying out of the boost but I imagine if I took it back on track and then idled it, it would billow constantly for a few minutes straight. I also can't help but wonder if letting the catch can get full and then tracking the car may have contributed to/caused the problem or whether it was a symptom of a problem that was already present.
Any thoughts would be hugely appreciated. Thanks!
10-01-12, 08:20 AM
#3
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Most everyone I know who tracks these cars with a twin turbo setup fills there catch can because they fill the oil to the top. I was tracking my TT car last weekend with the oil 1/3 the way up the dip stick and no oil accumulated in the catch can at all. Stop overfilling the oil 
My 1st guess is the smoke is from your turbos and the whining is from the turbos as well. If you have smoke right away I'm guessing the primary turbo is dead and you can take off the plastic 90 intake pipe to feel for play and if it's not the primary take off the aluminum intake pipe to the secondary turbo and feel for shaft play. I'm guessing one or both are not doing right. I have a really good set with less than 10k miles, ZERO cracks on the manifold and perfect shaft play
More importantly though how was the Carlisi meet and I hope you had fun
My 1st guess is the smoke is from your turbos and the whining is from the turbos as well. If you have smoke right away I'm guessing the primary turbo is dead and you can take off the plastic 90 intake pipe to feel for play and if it's not the primary take off the aluminum intake pipe to the secondary turbo and feel for shaft play. I'm guessing one or both are not doing right. I have a really good set with less than 10k miles, ZERO cracks on the manifold and perfect shaft play
More importantly though how was the Carlisi meet and I hope you had fun
10-01-12, 10:29 AM
#4
Hey Fritz, thanks for the info. I do fill up my oil all the way but I have one of the RESpeed baffled oil filler necks which does help an awful lot with the oil draw-through on right-hand turning courses. I will check out the shaft play of the compressors as soon as I get a chance. I'm still trying to figure out why they only smoke AFTER boosting and not during. I'll be happy if it's just the turbos and not the motor. Then all I have to do is evaluate whether I want to go with a rebuilt/replace of the stock sequentials, go BNRs, single, etc. :P
The event had a great turnout of FDs, but not a whole lot of 1st and 2nd gen folks. 5 FDs took to the track along with just a handful of other cars. Probably the most under-subscribed event I've been to before, but at least there weren't any trains/congestion :P
The event had a great turnout of FDs, but not a whole lot of 1st and 2nd gen folks. 5 FDs took to the track along with just a handful of other cars. Probably the most under-subscribed event I've been to before, but at least there weren't any trains/congestion :P
10-01-12, 10:42 AM
#5
hey armitage, well honestly i had the same problem as yours , i dont smoke when fully boosting , but soon as i let go i hear a pop then the mosquito control rx7 is known around my block! well i removed my turbos swapped to a single, that wasnt the issue , we prob have the same symptoms but completely opposite problem. but my coolant and possible oil seals are shot on mine, cause it eats up all the coolant and i leak alot of oil. id say honestly rip your engine out and inspect it , its the best thing to do
10-05-12, 12:17 PM
#6
Hey Fritz, thanks for the info. I do fill up my oil all the way but I have one of the RESpeed baffled oil filler necks which does help an awful lot with the oil draw-through on right-hand turning courses. I will check out the shaft play of the compressors as soon as I get a chance. I'm still trying to figure out why they only smoke AFTER boosting and not during. I'll be happy if it's just the turbos and not the motor. Then all I have to do is evaluate whether I want to go with a rebuilt/replace of the stock sequentials, go BNRs, single, etc. :P
Read this link.
https://www.rx7club.com/single-turbo...lained-727476/
Excerpt below.
On the compressor side, generally there is some kind of oil splitter which throws oil away from the seal as it is spinning. Because the piston rings and the splitter are dynamic seals, when the turbo is spinning faster, the better the seal operates.
The oil leak is driven by pressure, like any other fluid flow. When the oil pressure inside the center housing of the turbo is higher than the air pressure outside of the seal, the oil wants to travel outside to the air passage. The air that is holding the oil back on the compressor side is the compressor outlet pressure and for the turbine side, it is the turbine inlet pressure. That is because it is the air pressure that is behind the wheel (depends on wheel geometry and air pumping by the wheel too). This is why turbos leak more at idle/low load conditions and leak less when under full load/boost. The picture below is a depiction of the oil leak path.
The oil leak is driven by pressure, like any other fluid flow. When the oil pressure inside the center housing of the turbo is higher than the air pressure outside of the seal, the oil wants to travel outside to the air passage. The air that is holding the oil back on the compressor side is the compressor outlet pressure and for the turbine side, it is the turbine inlet pressure. That is because it is the air pressure that is behind the wheel (depends on wheel geometry and air pumping by the wheel too). This is why turbos leak more at idle/low load conditions and leak less when under full load/boost. The picture below is a depiction of the oil leak path.
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10-05-12, 01:12 PM
#8
an easy way to see if it's the turbos or not is to pull the turbos and fire her away. you'll be able to tell if its an oil control ring by watching the exhaust ports. It'll be Loud...and Awesome..but you'll know right away if you see even combustion from the front and the rear rotor housings. If you see one much stronger than the other...and oil..which one or if both of the oil control rings are toast.
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