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source of engine smoke?

Yesterday I was lucky enough to see some TV footage of my car on the track . I came 2nd in the race (only good one all day, in a car that was almost undriveable) from the rear, so the camera was following my car a lot. I could see a good deal of engine smoke and am wondering about the source.
The leakdowns are all 2-3%, the compressions within 5 psi on all 6.
I don't think it is rings. I wonder about valve guides (I have not had this engine apart). But normally I would expect that to occur on overun? while this occurs under load. So, I wonder about the Turbo. I have no real experience of turbos and never pulled one down. But they have the oil feed to the spindle. Is it possible to suck oil into the intake from here and feed it thru the engine.
If so, what would the symptoms be in the turbo. The spindle 'seems' tight - I can't get any play in it by feel.
It seems to happen when on boost - but will have to check the footage more closely. It certainly is not happening on idle - it is completely clean - but hard out there is a visible trail of blue smoke from the LHS of twin exhaust outlet.
Don't want to pull the engine down if the problem is not in there.
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Alan
Old 08-15-2008, 01:02 PM
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Blue smoke? if you mean black smoke sounds like it's going rich on you. What are your AFRs?
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Old 08-15-2008, 01:15 PM
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Alan, blue smoke on the overrun is normally the indicator of worn guides on an N/A car, as you say. Blue smoke under power normally means rings. Or excessive crankcase pressure (forcing oil past good rings). Do 930's even have PCV's?

As I understand it, compression rings are one of the first things to go with detonation - and someone here had photos of his amazing 157-piece top rings. I think this often doesn't affect leakdown or compression readings that much...

There is an oil seal internal to the turbo, I guess it's possible this could be leaking and allowing oil into the intake - in which case, this would be visible in the intake, no?

Causes of this on other cars are apparently poor turbo scavenge (e.g. clogged with coked/burnt oil deposits) or excessive oil feed (didn't some folks post here regarding turbo oil feed restrictors, which some folks didn't have?), either or both of which may result in oil getting forced into the intake and burnt in the combustion chamber.

Gotta be easier to check for that than to strip the top-end...

Here's a URL for Volvo turbo refurbish http://www.volvoclub.org.uk/faq/EngineTurboRebuilding.htm
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Old 08-15-2008, 05:16 PM
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Alan, do you have the ball bearing in the oil feed line? It's located underneath the oil pressure switch on the RH side of the engine.

Do you run your oil level hot in the middle of the two marks on the stick?
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Old 08-16-2008, 01:34 AM
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Nathan, I know nothing about a ball bearing in the oil feed line - I guess I should check. Is this the restrictor mentioned above. Can the turbo feed get excessive. (the oil pressure is 4+ bar at revs). Should there be a ball bearing sitting under the pressure switch - is this factory or after market?
Yes, it is blue smoke - oil.
If the top rings were gone, you would think it would show up in compression - after all - it is a compression ring?
I am topping it up during the day - usually put about 500 mls in it. I am topping it until the indicator gauge registers positive oil level under max acceleration. I noticed that often the indicator would drop to the bottom of gauge under full power. But not topping it right up.(It does have some annoying oil leaks from the cam seals too - which drop down onto the headers). But this is not the cause - you can't see any smoke until approximately it is on boost - ie many times it is running clean. I now have some video footage so can have a closer look.
Supposedly the engine had just been put back together when I got it, and the leakdowns etc look good - so I'm thinking the last possibility would be broken rings.
Looking for another cause. There is oil in the intake tract. I found it there in my post purchase strip down and posted a query. The answer was that this might be normal if driven hard?
Regards
Alan
Old 08-16-2008, 07:41 PM
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Alan, first of all you should only look at your oil gauge when it's idling on a flat and level surface, the same when you check your oil with the dipstick,, this is the ONLY accurate way to check it..
secondly, I still think you are going rich when you are under boost.. What are your AFR's ?? That is a key piece of the puzzle.. I'm having the same problem and it ( unfortunately) sounds like you've got a vacuum leak....
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Old 08-16-2008, 08:30 PM
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The boost AFrs are between 11.5 - 12. It is not fuel.
It is blue smoke. In fact since the footage has shown on national TV motorsport programme, a number of people (incl P owners) have contacted me to tell me the car is burning oil. The commentator kept speculating whether my car would last the race. But internally I reasonably confident the engine is in good shape - and I was not pushing it beyond 6000.
Irrespective of what the actual oil level is, (but it is about midway, and the gauge does not peg on warm idle on flat), I am not keen on running it under hard conditions without something showing on the gauge.
I don't know what the leeway is, but 'sump surge' or in this case 'tank surge' is something I'm not keen on if it means the engine runs short on oil for a brief moment. I figure as long as I have at least got the gauge registering under hard G's, the engine won't starve for oil.
My previous non P race car had special baffles made for the sump for this reason. You can loose an engine even under hard brakes. I don't know if it happens to P cars on the track, but I'm not keen to find out the hard way, and when there is nothing showing on the gauge, I have no idea where I am at that particular moment oil-wise.
I will have a look for a ball bearing in my oil line. I do suspect it is coming via the turbo, by whatever means. When I check the vid footage I should get a better idea.
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Alan
Old 08-16-2008, 10:43 PM
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Alan, forget the gauge in the dash. Use the stick when the engine is hot and at idle. The reason people run the oil between the two marks on the stick rather than at the top mark is due to hard cornering. In hard cornering it can cause the oil to come out of the top of the tank and get sucked in by the engine. The engine has its oil fed from the bottom of the tank so it is very unlikely to ever starve of oil. You have more chance of debris blocking an oilway as the oil is only filtered on the way out of the engine. To make things worse nearly all our cars don't even have the oil that comes out of the turbo filtered before it goes back in the tank...
And yes, the oil tank does have some kind of baffles. It's a good idea with these cars to remove and clean out the oil tank as carbon/sludge can build up in there and block the cam spray bars...
The sump of the engine is only used to catch the used oil and is then pumped back in to the oil tank via the filter.

As for the ball I was speaking of, yes, it is a stock part and is under the pressure switch. The banjo bolt which doubles as an adapter for the pressure switch has a special groove in it for the ball to hit.

OK, if you want to use the oil level gauge then as was said, just look at it at idle when hot. It takes a few secs for the oil in the tank to stabilise so it can give a reading anyway so red lights are pretty good for that. But IMO it's only really there to see that you haven't blown an oil line It's useless when you are driving on the track.
Oh, I think we solved your problem, it would seem you are running an extra gallon of oil
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

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Last edited by NathanUK; 08-17-2008 at 02:24 AM..
Old 08-17-2008, 02:17 AM
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Originally Posted by Alan L View Post
Nathan, I know nothing about a ball bearing in the oil feed line - I guess I should check. Is this the restrictor mentioned above. Can the turbo feed get excessive.
Yes, and yes.

930 Oil Drip Tank Fills When Engine Is Off -->Causes smoking
3.3 Turbo oil inlet


Quote:
I am topping it up during the day - usually put about 500 mls in it. I am topping it until the indicator gauge registers positive oil level under max acceleration.
Nope. Indicator gauge is usually quite accurate, but you have to appreciate that it's entirely meaningless except for when conditions are correct to check the oil on the stick; oil hot, level ground, leave at idle for at least 30 seconds for oil to return to the tank and any excess foam to settle etc.

Don't even look at the gauge at any other time (although it's a useful device for indicating the continued presence of oil in the system - once you know what it reads/should read with a correct oil level).

Speaking of "correct" oil level - a lot of people like to use a maximum fill level between the two lines. If you overfill (or the oil gets hotter than normal), it'll only puke out the breather into, if I'm not mistaken, the airbox.

Search for "mosquito fogger" in the N/A forum.

Quote:
Looking for another cause. There is oil in the intake tract. I found it there in my post purchase strip down and posted a query. The answer was that this might be normal if driven hard?
Regards
Alan
For some value of "normal".
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Last edited by spuggy; 08-17-2008 at 05:06 AM.. Reason: Added urls to turbo oil restrictor threads
Old 08-17-2008, 04:18 AM
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Thanks guys. My breather feeds into a catch tank, not the airbox. There is no oil in the catch tank. Scary thought the turbo oil goes straight back thru the motor.
I did flush the oil tank out (washed thru with high pressure petrol several times) when going over engine originally. Nice to know it has some baffles. I also suspect the way the line is configured it would be hard to starve the engine under load. Just don't want to be the first one to do so.
I will check the oil line for restrictor. (short of time at moment - pulled my SC motor last nite. Has slight 'tock tock' noise in one cyl when warm - not keen to drive it til I find source). Up to my ears in Porsche at moment.
Alan
Old 08-17-2008, 12:46 PM
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Hello!

If car smokes while accelerating in straight line and compression and leakdown is OK then it's probably your turbo bearings leaking into exhaust housing.

Reason for this can can be either excessive oil pressure feed, bad scavenging or plain old worn turbo.

Check for check valve (sic), check that scavenging lines aren't pinched. If everything is OK you might want to get yourself a new turbo. Maybe a Garrett GT35 or such?
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Old 08-17-2008, 02:00 PM
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Following the links above, it seems the ball bearing is a check valve to stop oil draining into the turbo on sut down - rather than restricting oil flow. Is that right?
I have no smoke on start up . the engine idles clean.
In which case my scavenge may be inadequate, or seals stuffed - correct?
I feel a turbo job coming on.
There is no detectable play in the turbo shaft - in either direction. So, the bearings may be OK, but the seal blown?
Alan
Old 08-17-2008, 03:01 PM
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I've just had a chance to see the video footage. It seems to be coming from the wastegate.
Does that make any sense?
There is definitely no smoke out the RHS of the car. The muffler is dual outlet. It runs clear coming off the corner (low throttle) then dumps blue smoke - about when the boost would hit - from what looks like underneath the car rather than out the back. It was not so apparent early in the race - perhaps the odd trace. By the end of the race, a visible blue haze, and a dense dump at onset.
Alan
Old 08-17-2008, 08:34 PM
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Hmm...if smoke comes out of wastegate then it's an engine problem. Wastegate dumps exhaust gases into air before they even reach the turbo, so if you are getting oil smoke from wastegate it's generated in the engine.

But I find it a little puzzling. A smoke created by broken rings or loose valve guides would come from pipes connected to both wastegate and turbo. Turbo cannot clean up the smoke.

Can it be a oil leak squirting onto hot headers on wastegate side when you accellerate?

My old car had leaky cylinder base and leaked some oil on headers while accelerating. Due to OEM header assymetrical design, drip from cylinder base will mostly spray one header.

You would like to raise the car and ask somebody to rev it while watching for leaks underneath.
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Old 08-18-2008, 12:12 AM
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Alan, the ball does restrict oil somehow. People have had problems and then fitted the ball - problem solved. The cut outs in the banjo bolt must restrict when the ball is pushed on to them. I think it might be a clever way of not just having a small hole that could get blocked with debris.
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Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

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Old 08-18-2008, 11:27 AM
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I say drain the oil & toss the filter. Replace the filter with a new one & refill with 11quarts of new oil (providing you are still running a stock capacity oil system). Drive it & see.

I have seen cars with overfilled oil levels (V8's), that idle great, run fine at lower RPM's, but then pack the top end with way too much oil at high RPM's & smoke like a Calcutta taxi cab.
Overwhelming the valve seals is easy when they are submerged.
Just a though & my .02 cents worth.

Mark
Old 08-18-2008, 12:02 PM
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Goran, There is a leak from the cam case above the header. It is enough to be annoying. But I was not keen to strip the top of the engine just to fix that. The vedors fix was lots of silicon around the back of the cam box. Some new seals when the engine was put back together might have helped.
I wondered if this is the cause - but could not relate it to the throttle behaviour. For instance it does not smoke on idle or as far as I can tell, low revs, or over-run.
I suppose it is possible that high revs = max oil pressure = max oil flow = max leaks, and it just happens to dump onto that header under those conditions? It seems to come out as tho it is under pressure tho - comes with a whoosh. Around boost intiation. I should check underneath and see if anything else is loosening up with boost - like you say - a base gasket.
How do you check if the turbo seals are OK? To eliminate that opotion.
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Old 08-18-2008, 12:47 PM
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It's hard to check the condition of turbo bearing seals. It either smokes or it doesn't. If it does, it usually smokes when turbo is hot. It's nothing you can open and take a look. Nearest indication is excessive shaft play.

It can be something easy. For example, my car had distorted rubber O-ring on the end of one oil-return tube that leaked only at high revs (when lot's of oil flowed trough it).

So your turbo might be OK, but something is is leaking oil on your headers.

Left pipe is wastegate and right pipe is engine, right? It sounds weird to see oil only come from wastegate exhaust pipe. Wastegate is situate before the turbo so if turbo was culprit, there should be no oil from wastegate. Also, if engine was emitting smoke, it should come from both wastegate and exhaust.

So that leaves the most probable cause: something is leaking on the left header. When boost is on, header gets hotter and it starts smoking more.

Things to check:

Oil return pipe seals.
Cylinder base
Head-to-cylinder
Valve covers.


You can remove left header and take a look. Chances are, you will find lot's of oil crud on the top.
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Old 08-18-2008, 02:09 PM
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Goran, There is a leak from the cam case above the header. It is enough to be annoying. But I was not keen to strip the top of the engine just to fix that. The vedors fix was lots of silicon around the back of the cam box.
Do you mean the back of the cam housing right next to the cylinder? chain ramp pins? Or the cam housing cover the one that is held by the 10mm nuts?
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Old 08-18-2008, 02:27 PM
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It is hard to tell from the freeze frame video - picture quality not good. May be better if I get copied to DVD. But it seems not to be the exhaust. It is definitely LHS engine only. Seems to be under car, and seems to shoot out in a burst and then continue until I throttle off.
There is no detectable play in the turbo. I suspect something like in your list. If a breather hose exited under the car at that point, it would look like that was the source. But the breather is in a catch tank.
I think I will have to pull the engine and chase the leaks.( As soon as I get my SC engine back in car).
Regards
Alan
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Old 08-18-2008, 02:31 PM
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