Sooty left tails pipe
Discussion
Hello everyone.
I recently traded my faithful old 996 for a 2006 997 Carrera 4 (3.6). I have noticed that there is a little bit of smoke on start-up but I had that with my 996. What is concerning is a sooty left tail pipe and surrounding body work. This has only become apparent recently after I topped up the oil.
Oil usage seems normal. I have done about 500 miles and not noticed high usage.
48,000 on the clock
Idles perfectly and pulls really well
Porsche sports exhaust
Has had all the IMS and RMS work done
Any ideas? Bore scoring or Oil separator?
Should I take it to Porsche or an independent?
Thanks
Garry
Smoking from one side is a sign of bore scoring but it usually starts with minor scoring and can take many thousands of miles before it becomes serious - and the previous advice is right - but many who carry out a bore scoring check are unused to seeing the difference between vertical polishing lines and actual scoring (made more difficult by the light from the camera reflecting in the cylinder bore) so make sure the people checking have seen it all before and know the difference.
Ticking or tapping noises can be very misleading and are rarely caused by piston slap (only if the scoring has become really bad).
I have written a lengthy technical explanation about this that will become available when our new guide is finished - but briefly it can be caused by any one of a long list (which is anyway not exhaustive).
To reduce emissions and fuel consumption - tickover speed is set at the lowest possible speed that will not invoke torsional variations in tickover speeds between firing impulses that are large enough to cause camshaft chain snatch impulses too big for the unsophisticated hydraulic chain tensioners to restrict especially at tickover when the oil pressure is low. The IMS transfer shaft and long camshaft chains can make this worse (see youtube "RollRing" chain tensioner video).
Those hydraulic chain tensioners are nothing like as functional as those fitted to later original air cooled engines and the design can actually promote a cyclic pulse in the tensioner that restricts the oil pressure at tickover. Some models allow a metal to metal connection between the tensioner piston and the tensioner blade that ticks as a consequence at tickover speeds.
Anything that results in an uneven combustion force in an individual cylinder compared to the next cylinder to fire (or compress) can unbalance the tickover from the designed parameters when it was new. So anything like a leaky exhaust, carbon build up on a valve, coked up spark plug, cracked coil, worn injector and of course a scored cylinder reducing compression (especially on tickover) can exacerbate that balance and promote a tick (but when it does the tick is more often caused by the wear on the piston making it more sloppy in the cylinder bore and tilting enough at TDC to rock making the edge of the piston crown touch the cylinder head).
The firing order of the engine results in the difference between a firing stroke and a compression strike moving along the crankshaft in such a way that there are some sequences that create a twist and snatch over a greater distance than others - increasing the snatch to the camshaft drive chains.
The engine speed is measured once/crankshaft revolution and if it is too high or too low the ECU changes a setting to correct the error. But there are three firing impulses/engine rev and so between each firing 120 degree angle (or two or three together) the engine can speed up and slow down and an adjustment is needed that cannot always be perfect for the required minor change and so sometimes that ticking noise can be heard to come and go as the ECU tries to find a setting to keep the overall tickover where it wants it to be.
The ECU is programmed to reduce the tickover speed as the engine coolant gets hotter - so often - leaving a car ticking over for long periods promotes a tick (because the coolant speed is low and the amount/proportion feeding into the cylinder block is low - resulting in higher temperatures and this lowers the tickover speed even more).
The exhaust manifold gaskets are a very poor fit and the exhaust bolts are notorious for corroding so that they no longer pinch the gasket and seal the joint. Even a small leak (especially into the ECG recirculating channels) can make a noise exactly like a metallic tick.
Even making one cylinder more powerful than another or one side of the engine bank fire better than the other can promote a tick.
It is not uncommon for any sports car engine that has been built to need the tickover to be raised a little to reduce tickover camchain snatch due to the engine generally having less rotation resistance with age and allowing greater speedup and down variations between tickover firing strokes.
Sometimes switching the air-con on and off or engaging drive in a tiptronic - can change the tickover "tick" (or get rid of it) even though the engine is ticking over at the same speed - because it increases the resistance of the alternator and air-con pump drive (or inertia of the crankshaft mass in a tiptronic) and this can damp out the crankshaft cyclical delta speed variations.
Sometimes a small piece of metal or gasket material can enter the inlet and sit on top of the piston where it touches the head. This has been experienced before when engines have been rebuilt by those you avoid completely stripping and meticulously cleaning all the inlet system before reassembly (because they assume that the parts that were damaged when say a valve is bent or a valve seat is damaged cannot possibly make their way up into the inlet system. I know it sounds impossible - but believe me those small pieces can get anywhere and everywhere and just lifting off the inlet system and re-fitting it after other work is not good enough.
Generally I would only pay attention to any ticking noises on tickover by allowing them to encourage me to get the bores properly checked - rather than to jump to conclusions - because more often than not - it is not a sign of a mechanical problem that anything much can be done about.
However a more sooty nearside tailpipe is a good clue to bore scoring even if the engine runs perfectly well, quietly and has no oil consumption increase.
I hope yours is OK and if it is fitting a low temperature thermostat and avoiding a heavy right foot after a hot rest period - will all help prolong life before wear of the piston coating results in scoring.
Baz
Ticking or tapping noises can be very misleading and are rarely caused by piston slap (only if the scoring has become really bad).
I have written a lengthy technical explanation about this that will become available when our new guide is finished - but briefly it can be caused by any one of a long list (which is anyway not exhaustive).
To reduce emissions and fuel consumption - tickover speed is set at the lowest possible speed that will not invoke torsional variations in tickover speeds between firing impulses that are large enough to cause camshaft chain snatch impulses too big for the unsophisticated hydraulic chain tensioners to restrict especially at tickover when the oil pressure is low. The IMS transfer shaft and long camshaft chains can make this worse (see youtube "RollRing" chain tensioner video).
Those hydraulic chain tensioners are nothing like as functional as those fitted to later original air cooled engines and the design can actually promote a cyclic pulse in the tensioner that restricts the oil pressure at tickover. Some models allow a metal to metal connection between the tensioner piston and the tensioner blade that ticks as a consequence at tickover speeds.
Anything that results in an uneven combustion force in an individual cylinder compared to the next cylinder to fire (or compress) can unbalance the tickover from the designed parameters when it was new. So anything like a leaky exhaust, carbon build up on a valve, coked up spark plug, cracked coil, worn injector and of course a scored cylinder reducing compression (especially on tickover) can exacerbate that balance and promote a tick (but when it does the tick is more often caused by the wear on the piston making it more sloppy in the cylinder bore and tilting enough at TDC to rock making the edge of the piston crown touch the cylinder head).
The firing order of the engine results in the difference between a firing stroke and a compression strike moving along the crankshaft in such a way that there are some sequences that create a twist and snatch over a greater distance than others - increasing the snatch to the camshaft drive chains.
The engine speed is measured once/crankshaft revolution and if it is too high or too low the ECU changes a setting to correct the error. But there are three firing impulses/engine rev and so between each firing 120 degree angle (or two or three together) the engine can speed up and slow down and an adjustment is needed that cannot always be perfect for the required minor change and so sometimes that ticking noise can be heard to come and go as the ECU tries to find a setting to keep the overall tickover where it wants it to be.
The ECU is programmed to reduce the tickover speed as the engine coolant gets hotter - so often - leaving a car ticking over for long periods promotes a tick (because the coolant speed is low and the amount/proportion feeding into the cylinder block is low - resulting in higher temperatures and this lowers the tickover speed even more).
The exhaust manifold gaskets are a very poor fit and the exhaust bolts are notorious for corroding so that they no longer pinch the gasket and seal the joint. Even a small leak (especially into the ECG recirculating channels) can make a noise exactly like a metallic tick.
Even making one cylinder more powerful than another or one side of the engine bank fire better than the other can promote a tick.
It is not uncommon for any sports car engine that has been built to need the tickover to be raised a little to reduce tickover camchain snatch due to the engine generally having less rotation resistance with age and allowing greater speedup and down variations between tickover firing strokes.
Sometimes switching the air-con on and off or engaging drive in a tiptronic - can change the tickover "tick" (or get rid of it) even though the engine is ticking over at the same speed - because it increases the resistance of the alternator and air-con pump drive (or inertia of the crankshaft mass in a tiptronic) and this can damp out the crankshaft cyclical delta speed variations.
Sometimes a small piece of metal or gasket material can enter the inlet and sit on top of the piston where it touches the head. This has been experienced before when engines have been rebuilt by those you avoid completely stripping and meticulously cleaning all the inlet system before reassembly (because they assume that the parts that were damaged when say a valve is bent or a valve seat is damaged cannot possibly make their way up into the inlet system. I know it sounds impossible - but believe me those small pieces can get anywhere and everywhere and just lifting off the inlet system and re-fitting it after other work is not good enough.
Generally I would only pay attention to any ticking noises on tickover by allowing them to encourage me to get the bores properly checked - rather than to jump to conclusions - because more often than not - it is not a sign of a mechanical problem that anything much can be done about.
However a more sooty nearside tailpipe is a good clue to bore scoring even if the engine runs perfectly well, quietly and has no oil consumption increase.
I hope yours is OK and if it is fitting a low temperature thermostat and avoiding a heavy right foot after a hot rest period - will all help prolong life before wear of the piston coating results in scoring.
Baz
Thanks very much Baz, your information is really appreciated. I owe you a beer! 
The soot only occurred after I topped up the oil, could an over-fill cause this issue?
I have read a few things about oil separators, could this be a cause or would that create an issue with both pipes
I have booked it into Tewkesbury Porsche Centre next week for it to be looked at and for a major service, breaks and aircon service.
I was going to ask them to do the 111 check with a view to getting a Porsche warranty. is this worth it?
If it needs major rebuild work would you recommend a Porsche Centre or independent?
I have noted your advice on avoiding a heavy right foot after a hot rest period. With that noted, I use the care daily, should I drive it as normal?
The soot only occurred after I topped up the oil, could an over-fill cause this issue?
I have read a few things about oil separators, could this be a cause or would that create an issue with both pipes
I have booked it into Tewkesbury Porsche Centre next week for it to be looked at and for a major service, breaks and aircon service.
I was going to ask them to do the 111 check with a view to getting a Porsche warranty. is this worth it?
If it needs major rebuild work would you recommend a Porsche Centre or independent?
I have noted your advice on avoiding a heavy right foot after a hot rest period. With that noted, I use the care daily, should I drive it as normal?
In connection with the above - I was just wondering where the words "tick over" derived from.
We use the expression "things are just ticking over" to mean everything is running smoothly - not doing anything dramatic but no issues". Using this to describe how things keep running smoothly must have derived first from engine tick-over
So where did "tick over" come from to describe and engine idling?
Could it be that it came from the slowest possible speed that the engine runs without snatch or ticking noises because going back a few years it was always possible to adjust the tick over using a throttle screw and if you slowed it down too much the engine started to shake in the mountings or if it had a chain camshaft drive - or gear reduction to the camshaft - it would start to "tick".
I guess "tick-over" could mean just that - the slowest speed that the engine will run at without creating a "tick"?
Any other ideas?
Baz
We use the expression "things are just ticking over" to mean everything is running smoothly - not doing anything dramatic but no issues". Using this to describe how things keep running smoothly must have derived first from engine tick-over
So where did "tick over" come from to describe and engine idling?
Could it be that it came from the slowest possible speed that the engine runs without snatch or ticking noises because going back a few years it was always possible to adjust the tick over using a throttle screw and if you slowed it down too much the engine started to shake in the mountings or if it had a chain camshaft drive - or gear reduction to the camshaft - it would start to "tick".
I guess "tick-over" could mean just that - the slowest speed that the engine will run at without creating a "tick"?
Any other ideas?
Baz
Looking at the dictioniary the definition is operating but not moving...
tick over
vb (intr, adverb)
1. (Automotive Engineering) Also: idle Brit (of an engine) to run at low speed with the throttle control closed and the transmission disengaged
2. to run smoothly without any major changes: keep the firm ticking over until I get back.
n
(Automotive Engineering)
a. the speed of an engine when it is ticking over
b. (as modifier): tick-over speed.
tick over
vb (intr, adverb)
1. (Automotive Engineering) Also: idle Brit (of an engine) to run at low speed with the throttle control closed and the transmission disengaged
2. to run smoothly without any major changes: keep the firm ticking over until I get back.
n
(Automotive Engineering)
a. the speed of an engine when it is ticking over
b. (as modifier): tick-over speed.
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