djamps

iTrader: (1)

130k on engine, 70k boosted. No smoke when cold, gives a short puff from right side when warmed up and engaging from a stop after idling (e.g. after red light turns green). There's also a puff at the onset of boost visible in rear view. You can smell oil burning pretty much always even though not visible. No oil in the intercooler or intake piping or catch can, and plugs look good. Burning about 1 - 1.5qt per 1k miles but makes 400+whp and good compression so I'm positive it's not burning oil in the cylinders...and it's coming mostly from the right exhaust pipe based on my bumper stains LOL.

I know I should just pull the test pipes off and check the turbos but it's a PITA... just curious what others might think and if it's even worth tackling. I'd hate to spend 1k+ rebuilding the turbos if it won't solve the OC.

my old honda used to smoke badly on cold startup when the valve seals went...is that typical when valve seals go?

Apparently has 5w30 oil (in it when I bought it), I'm thinking 0w40 might reduce the OC?

Thoughts for a cheap-scate trying to milk every last mile out of this? LOL

meatbag

iTrader: (9)

Easier to pull DP off and look then to change vavle seals.

djamps

iTrader: (1)

Can you look at the valves thru the manifold (plenum removed?) that might actually be easier for me having no lift.

DaveJackson

iTrader: (5)

At that rate of consumption it would have to be in the intercooler piping etc if it was the turbos, wouldn't it?

djamps

iTrader: (1)

One would think so...but the hot side piping is clean. MAF still looks brand new and intake piping is flawless while this issue has been ongoing for at least 10-15k miles. maybe it's coming out the exhaust side?

I guess my question would be what smoking behaviour of leaky exhaust valve seals vs leaky turbo seals?

If it were exhaust valve seals wouldn't it smoke more or less constantly depending on RPM and not just briefly during the onset of load or boost?

DaveJackson

iTrader: (5)

Just so we're clear in terminology, you're talking about valve stem seals (rubber/viton) not valve guides, (brass) right?
I've heard that hot temperatures and stomp on it after a long deceleration (tranny holding car back) down a hill. If it smokes a lot do a leak down and/or compression test to rule out rings after.
Then, it's PROBABLY valve seals but I think it could still be a broken top ring, so... It's tough to diagnose!

djamps

iTrader: (1)

I think so, whatever holds the oil back? I'm no engine expert.

Compression is 150-155 all the way across. Didn't bother with a leak down since as far as I know these numbers are typical for high mileage VQ's.

djamps

iTrader: (1)

I guess it's kind of impossible to know for sure what the problem is since both issues would theoretically dump oil into the exhaust at nearly the same point (one just before the turbo, the other just inside the turbo exhaust housing).

djamps

iTrader: (1)

Based on the power it 's making (over 400whp at 8psi with modest timing) and normal compression I'm reluctant to point at the rings or combustion chamber in general..

tcode

iTrader: (7)

My bet is on a bad oil piston rings.

DaveJackson

iTrader: (5)

It sounds crazy, but apparently the top ring can be broken and not affect compression. It's the scraper ring.

djamps

iTrader: (1)

If it's burning that much oil thru the rings (it's probably more like 1.5 - 2 qts per 1k miles at this point now that I think about it) should it be evident on the plugs? Also wouldn't the smoke be more or less constant?

jerryd87

iTrader: (4)

backwards the bottom three piece ring is the oil scraper ring the top two rings on a piston are compression rings, if the top one is broke the ring land is also probably broke and that engine cylinder is going to be trashed. alot of oil consumption issues come from too large of oil ring gaps, oil ring gaps not being staggered(each opening since its a three piece ring should be roughly12- degrees apart), or simply improper break in this is why i support the aggressive break ins, the entire thing with a soft break in is because of camshafts and wiping a lobe which wont happen with a high zinc oil. the rings get break in from rubbing on the cylinder walls and are 90% broken in within 10 miles, you get on the car the cylinder pressure increases and pushs the rings against the walls harder ensuring a proper seat and less oil consumption.

DaveJackson

iTrader: (5)

I think it should certainly be evident on the plug in the buggered cylinder. I have a fouled plug and I'm relatively confident that it's a valve stem seal, but I honestly can't say for sure...

djamps

iTrader: (1)

Well at least I know it's bank 2 I need to focus on, drove behind it and could see occasional puffs from the passenger side exhaust, nothing from the driver side. I'll pull the plugs (brand new as of 1000 miles ago) and see if any of them show signs of oil.

Am I correct that if they are clean then the rings are good and we're back to either exhaust valve seals or turbo leak?

boostedmaxima

If for some reason the turbo on that side isn't draining properly you could be getting smoke from that side.

djamps

iTrader: (1)

Interestingly today while changing the oil I noticed the passenger side drain line kinked slightly and pushing against a sharp metal frame piece (near where it connects to the drain pan) -- I'm surprised hasn't caused a leak over the years. The drain port on the oil pan is pointed too much upwards causing the issue.

Can the drain port connection (banjo bolt?) on the oil pan be rotated without much fuss or new gaskets? I tried but it felt like it required a breaker bar to loosen...

Resmarted

iTrader: (2)

Don't have much to contribute here... but if you were able to rent one of those fiber optic cameras you could stick it in spark plug hole. You could then rotate the engine by bumping your starter until you can see under the exhaust valves on the suspected bank. Might be tricky but it should let you see the valve seals. Just make sure you pull the camera OUT when you bump the engine over... don't want any more damage than necessary! PS if you're real clever you'd use a coat hanger to re-angle the camera UP to see the valve seals
this is what john wigs has to say from our forum (https://my350z.com/forum/9919639-post32.html)

djamps

iTrader: (1)

For the greddy turbo people, do I loosen the oil drain banjo bolt on the oil pan, adjust the angle then tighten? Or is there more involved?

DaveJackson

iTrader: (5)

Also, the tail pipe side doesn't correspond to an engine side if you have stock exhaust. (You might not, I'm just sayin).