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Old 10-16-2012, 01:52 PM
  #31  
NoPasaran
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Originally Posted by kitwetzler
First thing I would do is check all the intercooler piping, especially the clamps. Sounds like you're getting a leak under boost.
that's exactly what it was. Left pipe from turbo was leaking, and I do not even know for how long, because everything on part throttle was fine. Only in 5th and 6ths gears on more than 50% throttle (and speeds above 125mph) did I notice the problem.
Old 10-17-2012, 12:23 PM
  #32  
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Originally Posted by NoPasaran
Heat soaks? I doubt that. I do not get into many jams, at best they are a few minutes long, and I do not live in a desert.

Stale gas? Only if it was pumped into my car already stale.

My tuner said that 3.6 engine stays clean for a long long time, one opens it after 30000 miles and it looks clean as a whistle, I assume this is because there is no DFI, that is one of the reasons I like 3.6TT.
Sorry heat soak in this context is, occurs, anytime the engine is shut off. It has nothing to do with how hot the climate is where you live/drive.

The running engine has some areas hotter than others and when the engine is then shut off the heat from these hotter areas will flow to cooler areas and this raises the temperature of areas of the engine that normally remain rather cool.

One particular area is the injector tips. They remain cool as the engine runs but when the engine is shut off they get hot as the heat from the hotter combustion chamber surfaces and exhaust valves flows into surrounding areas, components.

This heat soak tends to lead to deposits forming on or in the injectors.

If a car is used for short trips the engine is not run long enough, used hard enough for the fuel to remove/dissolve these deposits and they can build up over time to the point they create problems.

Premium fuel can go stale. For cars that are not used much the gas tank gets filled up and maybe a month or more can go by with the gas remaining in the tank.

The gas can be stale at the station as well, or on its way to being stale.

The recommendation is to buy gas from a busy station as its storage tanks are refilled more often thus its supply of gasoline is freshest. I've visited stations that are so busy they can get refilled several times a day. That's 4K to 8K gallons of gasoline per refill.

Engines can also be sensitive to different brands of gasoline.

Another issue that can arise is buying supermarket station gasoline. A gasoline test in the UK turned up that supermarket gasoline was coming from a mix of suppliers and while sometimes the gasoline was very good, as good as any station's gasoline, sometimes the gasoline was not as good.

A good tank of gasoline from such a station may be followed by another good tank or by a less good tank of gasoline.

If you are buying gasoline from a busy station and using the car regularly so the gas doesn't sit in the tank too long then you have nothing to worry about.

My limited exposure to the inside of these and other modern Porsche engines reinforces my belief if fed good/fresh gasoline, treated to regular oil changes and the car driven enough the engine gets used for something other than around the block trips, these engines remain deposit free as deposit free as they can be.

Sincerely,

Macster.
Old 10-18-2012, 02:18 AM
  #33  
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Originally Posted by Steamboat
Please help me understand, however, what an "engine cobweb" is and how one goes about "blowing them out".

Also, I've never heard of an ECU "dumping gas" or whatever so I'm not sure what that means.
I was going to stay quiet on this one and just enjoy the humour anyway...(and big lol aside for a second)... and, steam like yourself i also don't see these suggestions or explanations as having any credible reason for said problem, least of all being any form of cure you would exact on a high performance 997tt engine, let alone any engine for that matter....accepting the reported problem has since been diagnosed as a leaking boost issue and fixed.
This term cobweb is generally used by laypersons or bush mechanics but in reality these misfiring type symptoms can rarely be driven or thrashed out of an engine with any success beyond worsening the problem, damaging the engine, or blowing the engine to pieces in the process. If an engine has a problem then that problem really needs to be properly investigated to establish the precise cause, and the engine most certainly not continued to be operated least of all driven hard with some misconception the problem will miraculously remedy itself. And the ECU "dumping gas" is also a doozy (lol). Nopasaran, no offence intended, but where on earth did you come up with this one?
Old 10-18-2012, 03:01 AM
  #34  
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Originally Posted by Macster
Sorry heat soak in this context is, occurs, anytime the engine is shut off. It has nothing to do with how hot the climate is where you live/drive.

The running engine has some areas hotter than others and when the engine is then shut off the heat from these hotter areas will flow to cooler areas and this raises the temperature of areas of the engine that normally remain rather cool.

One particular area is the injector tips. They remain cool as the engine runs but when the engine is shut off they get hot as the heat from the hotter combustion chamber surfaces and exhaust valves flows into surrounding areas, components.

This heat soak tends to lead to deposits forming on or in the injectors.

If a car is used for short trips the engine is not run long enough, used hard enough for the fuel to remove/dissolve these deposits and they can build up over time to the point they create problems.

Premium fuel can go stale. For cars that are not used much the gas tank gets filled up and maybe a month or more can go by with the gas remaining in the tank.

The gas can be stale at the station as well, or on its way to being stale.

The recommendation is to buy gas from a busy station as its storage tanks are refilled more often thus its supply of gasoline is freshest. I've visited stations that are so busy they can get refilled several times a day. That's 4K to 8K gallons of gasoline per refill.

Engines can also be sensitive to different brands of gasoline.

Another issue that can arise is buying supermarket station gasoline. A gasoline test in the UK turned up that supermarket gasoline was coming from a mix of suppliers and while sometimes the gasoline was very good, as good as any station's gasoline, sometimes the gasoline was not as good.

A good tank of gasoline from such a station may be followed by another good tank or by a less good tank of gasoline.

If you are buying gasoline from a busy station and using the car regularly so the gas doesn't sit in the tank too long then you have nothing to worry about.

My limited exposure to the inside of these and other modern Porsche engines reinforces my belief if fed good/fresh gasoline, treated to regular oil changes and the car driven enough the engine gets used for something other than around the block trips, these engines remain deposit free as deposit free as they can be.

Sincerely,

Macster.
Actually ambient temperature has a lot to do with this "heat soak" term you refer to after an engine has been switched off. Where the ambient temps are hotter it takes much longer for the engine to cool off and it is on these occasions the engine temperatures can sometimes rise and stay higher for longer than say in cold weather....depending upon how hard the engine has been driven prior too and if any shutdown procedure was applied. But i'm not sure why soot would build up anywhere in that circumstance anyway?

Where injectors are concerned, fuel deposits that may build up in the lines, inside the injectors (from stagnating fuel sitting for extended periods in an unused engine) or, carbon build up around the exterior of the injector nozzle/tip from unburned fuel ultimately requires strip and clean to successfully remove. Often a cleaning fluid run can be run through beforehand to see if that fixes the issue. A lebanese tune up (which is the term i've sometimes heard referenced to as removing so called cobwebs by trying to thrash the misfiring out of the engine) will not remove injector related deposit build up....or any build up for that matter. If the combustion of the engine is faulty that is not an environment conducive to removing build up in fact to the contrary unfortunately. Where the combustion is faulty the carbon build up can only worsen because the fuel is not being combusted correctly/fully to burn any deposits away.
Old 10-18-2012, 04:13 AM
  #35  
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The ECU will dump fuel... Depending on the following conditions.

Per the factory Bosch documents we have two functions

FB LAMBTS 1.60 Detailed description of function
Task:
========
Protection of components (manifold, supercharger etc.) by mixture enrichment.
Principle:
========
An exhaust emission temperature which is too high can be lowered by an enrichment of the air-fuel mixture. By this enrichment,
more fuel reaches the cylinder than would be required for a stoichiometric combustion of the fuel. The fuel not burned
vaporizes at the cylinder walls and thereby cools these down whereby the exhaust emission temperature also drops.

The second is LAMFAWKR

This is Detonation/Knock Recognition based Fueling Enrichment.

When the knock sensors pickup detonation the ECU will reduce timing per each cylinder. At the same time depending on the amount of detonation the ECU will open up the injector duty cycle to provide similar results as the LAMBTS.
Old 10-18-2012, 04:58 AM
  #36  
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Yes i understand the functions of the various sensors and their relativity to the operation of the ECU. I was referring to nopasaran's comment in the context the ECU itself was "dumping gas" all on its own, without any elaboration to how and why.
Old 10-18-2012, 12:13 PM
  #37  
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Originally Posted by speed21
I was going to stay quiet on this one and just enjoy the humour anyway...(and big lol aside for a second)... and, steam like yourself i also don't see these suggestions or explanations as having any credible reason for said problem, least of all being any form of cure you would exact on a high performance 997tt engine, let alone any engine for that matter....accepting the reported problem has since been diagnosed as a leaking boost issue and fixed.
This term cobweb is generally used by laypersons or bush mechanics but in reality these misfiring type symptoms can rarely be driven or thrashed out of an engine with any success beyond worsening the problem, damaging the engine, or blowing the engine to pieces in the process. If an engine has a problem then that problem really needs to be properly investigated to establish the precise cause, and the engine most certainly not continued to be operated least of all driven hard with some misconception the problem will miraculously remedy itself. And the ECU "dumping gas" is also a doozy (lol). Nopasaran, no offence intended, but where on earth did you come up with this one?

Not all references to engine cobwebs come from laypersons/bush mechanics.

More than once I've encountered a car in a dealer's service bay and when asked what is the problem the tech has told me no problem found the driver just needs to drive the car more, a bit harder, suggesting (if not outright saying it) the engine needs its 'cobwebs' blown out.

In one case I watched as the owner picked up his car and drove off. Out of the corner of my eye I caught the SM kind of smiling and asked him what was funny.

He said the owner had brought the car in for some minor driveability issue and the tech checked the car out and found nothing wrong and advised the owner he just needed to drive the car harder. The owner indicated he understood and yet upon driving away he had the car in 4th gear in just a few car lengths after pulling away from the dealership service driveway, still in the parking lot. The engine might have been running at barely idle speed and probably that was all the rpms the engine ever saw.

Oh, another time a Cayenne was in (and I found out not for first time either) for mild driveabilty issues and of course the vehcle was checked out and no problems found and the customer was advised he needed to just drive the car a bit harder, Nothing gruesome of course, just up the revs once in a while, use a bit more throttle once in a while. The owner balked but when the SM suggested then he leave the car so the SM or one of the senior techs could drive the car the owner I guess got the message.

I get involved once in a while. I used to eat at a restaurant that was owned by a guy who owned a 2000 Boxster S. He spotted my Boxster of course and we started talking cars when I was there. His car had barely 20000 miles on it while my Boxster at that time had around 200000 miles. He was complaining about his car - nothing major, no CEL, no signs of anything remotely serious -- just that it just didn't feel quite right.

When I suggested he needed to drive the car more, use up some of that gasoline that had been in the gas tank since only God knows when you would have thought I had asked him for naughty pictures of his wife. Drive his precious Porsche more? No way!

But an otherwise healthy engine, showing no signs of any distress, appears to benefit from a prolonged drive.

As I have experienced more than once even though my cars serve as work commuters for my 60 mile (round trip mostly highway) work commute a longer drive of it just happens due to an ill family member around 100+ miles (round trip all on the freeway) the engines in both cars feel just a bit peppier near the end of the 50 miles. as I approach my destination.

Even before this 9+ months of weekly (or sometimes even nightly) 100+ mile drives at other times when heading out on a road trip and after having covered 100 or more miles at freeway speeds I notice the engine running particularly nice.

One time that really stands out was when I was in my 06 GTO on one trip to Huntington Beach (from Livermore) as I was approaching close to where I-5 (I had remained on I-5 all the way down and with my V1 had made pretty good time, if you know what I mean) and 99 come together I noticed the big (6.0l) V8 was purring like a kitten, and yet it would still roar like a lion when I nailed the gas pedal as I passed slower traffic going and over the pass and down into the LA basin.

Anyhow, I would never suggest, hope I have never suggested anyone take a sick engine out and as a "cure" blow out any cobwebs. Always the reason for the sickness/symptoms needs to be determined.

Sincerely,

Macster.
Old 10-18-2012, 12:33 PM
  #38  
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Originally Posted by speed21
Actually ambient temperature has a lot to do with this "heat soak" term you refer to after an engine has been switched off. Where the ambient temps are hotter it takes much longer for the engine to cool off and it is on these occasions the engine temperatures can sometimes rise and stay higher for longer than say in cold weather....depending upon how hard the engine has been driven prior too and if any shutdown procedure was applied. But i'm not sure why soot would build up anywhere in that circumstance anyway?

Where injectors are concerned, fuel deposits that may build up in the lines, inside the injectors (from stagnating fuel sitting for extended periods in an unused engine) or, carbon build up around the exterior of the injector nozzle/tip from unburned fuel ultimately requires strip and clean to successfully remove. Often a cleaning fluid run can be run through beforehand to see if that fixes the issue. A lebanese tune up (which is the term i've sometimes heard referenced to as removing so called cobwebs by trying to thrash the misfiring out of the engine) will not remove injector related deposit build up....or any build up for that matter. If the combustion of the engine is faulty that is not an environment conducive to removing build up in fact to the contrary unfortunately. Where the combustion is faulty the carbon build up can only worsen because the fuel is not being combusted correctly/fully to burn any deposits away.
If not allowed to get too bad, if the engine isn't left unused for an extremely long period of time increased driving can remove these deposits. Fuel has detergents and the violence of the fuel passing through the injector -- when more than the tiny bit of throttle the driver normally uses is used -- and the liquid and vapor cleaning action of the fuel in the combustion chamber can over a sufficently long drive and a few of these back to back can work to clean the engine of these deposits.

In some cases a fuel system cleaner can be used, is required, to deal with build up that can't be cured by more driving, at least not in an acceptable timeframe. A few times I've used Techron with noticeable and postiive results. But this is not a recommendation to use Techron on a regular or ongoing basis.

In the worst case, I came across a 993 Turbo S in a shop, this car was in because the owner had let it sit unused for 3 years and the fuel had dried out and formed deposists and created other problems in the fuel system that the engine would not start let alone run and the fuel lines, injectors, fuel pump and other related items had to be replaced.

Really I like to try to keep my cars' engines healthy organically. This I do or try to do by giving them regular/proper servicing and using quality fluids from oil to gas and beyond, and just using the car but in a fashion/manner that is legal and safe but takes into account these engines are a bit above and beyond the lump of cast iron found say an old pick up truck.

Once warmed up the Boxster or Turbo engine gets some revs. No bouncing off the rev limiter every shift but the engines see rpms in the upper reaches (above 3/4K) almost every trip. For the Turbo not a day goes by that it doesn't get to make some boost. A day without boost is like a day without sunshine and I strive to make every day sunny.

Sincerely,

Macster.
Old 10-18-2012, 02:29 PM
  #39  
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Originally Posted by Macster
For the Turbo not a day goes by that it doesn't get to make some boost. A day without boost is like a day without sunshine and I strive to make every day sunny.

Sincerely,

Macster.
exactly
Old 10-18-2012, 03:11 PM
  #40  
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Originally Posted by biglicks
exactly
+1!
Over - boost for me!! Every day....
Old 10-19-2012, 05:13 AM
  #41  
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Originally Posted by speed21
...Nopasaran, no offence intended, but where on earth did you come up with this one?
As I mentioned, I am not mechanic, just a driver, looking for info and maybe not expressing myself very eloquently, so, whatever...have this laugh on my account, it's on me, wisearse, if that is the only way you can get a laugh.
Old 10-19-2012, 05:22 AM
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Kevin, thanks for the info!
Macster, I've said it many times before, but thanks for taking your time explaining things in such extensive manner, always a pleasure to read your posts!
Old 10-19-2012, 07:11 AM
  #43  
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Glad the problem got diagnosed and fixed. My own data point here in this, from 24 years and about 330K miles of ownership.

Two indie P shop owners each with decades of experience have also vaguely described the benefit of the Italian/Lebanese/Tennessee(more later) tune up.

I drove a 993 to 120K miles, at which I had a top end rebuild done, due to worn valve guides, leaky chain cover, and just my own "while in there" obsession. This and the recurrent 993 SAI blockage will not be solved by an Italian or any other country of origin tune.

Drove it more till 161K miles when I sold it. During the 90 days prior to selling it, my TT had arrived and I was only driving the 993 once a month, perhaps just 20 miles to keep things ok. Not good enough. At the PPI a couple cylinders showed slightly high leakage. Indie took it out for a brisk spin and assured buyer all was ok.

Our Chief Engineer Bill Noe in the Sun Electric consumer products division late 70's asked our management staff for a volunteer car to demo the TN tune. Next I know I am revving my 1970 6.3L V8 MB 300SEL to around 4K while a colleague is pouring a cup of water down the air intake, and Bill is holding a white towel over the exhaust. Probably not safe given that loose deposits can end up elsewhere besides the exhaust, but I drove it another 5 years after that, no problems.

Test equipment has made huge strides since then, so first sign of problem, I am on my way driving or flatbed, to the shop with the test equipment and experience.
Old 10-19-2012, 11:32 PM
  #44  
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Originally Posted by NoPasaran
As I mentioned, I am not mechanic, just a driver, looking for info and maybe not expressing myself very eloquently, so, whatever...have this laugh on my account, it's on me, wisearse, if that is the only way you can get a laugh.
To be expected coming from someone who refers to Unlim 5000 car owners as just "rich posers" and slams the Greek guys in 997 Turbo Porsches as deserving to be stoned to death.

So yes, for someone who mocks others who are real performance enthusiasts, referring to them as merely "rich posers showing off", yet personally ponces around on 20's purely for vanity sakes complaining on the forums how he can't get satisfactory handling, whilst at the same time blaming the car/and brand, while trying to break 300 kph is somewhat contradictory would you not say? Hmmmm...

And as "just a driver looking for info", your best port of call would be to your nearest P tech really....not the discussion forums. Afterall what would "just a driver" do with the info anyway given you openly admit you don't have any real skill or qualification to exact any remedy on your own....

Last edited by speed21; 10-20-2012 at 12:18 AM.
Old 10-19-2012, 11:45 PM
  #45  
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Originally Posted by Macster
Not all references to engine cobwebs come from laypersons/bush mechanics.
True. But most do i've found.

More than once I've encountered a car in a dealer's service bay and when asked what is the problem the tech has told me no problem found the driver just needs to drive the car more, a bit harder, suggesting (if not outright saying it) the engine needs its 'cobwebs' blown out.
In the context of this thread i just didn't think blowing "cobwebs out" was appropriate given the symptoms expressed and the environment in which the problem was allegedly manifested.


In one case I watched as the owner picked up his car and drove off. Out of the corner of my eye I caught the SM kind of smiling and asked him what was funny.

He said the owner had brought the car in for some minor driveability issue and the tech checked the car out and found nothing wrong and advised the owner he just needed to drive the car harder. The owner indicated he understood and yet upon driving away he had the car in 4th gear in just a few car lengths after pulling away from the dealership service driveway, still in the parking lot. The engine might have been running at barely idle speed and probably that was all the rpms the engine ever saw.

Oh, another time a Cayenne was in (and I found out not for first time either) for mild driveabilty issues and of course the vehcle was checked out and no problems found and the customer was advised he needed to just drive the car a bit harder, Nothing gruesome of course, just up the revs once in a while, use a bit more throttle once in a while. The owner balked but when the SM suggested then he leave the car so the SM or one of the senior techs could drive the car the owner I guess got the message.

I get involved once in a while. I used to eat at a restaurant that was owned by a guy who owned a 2000 Boxster S. He spotted my Boxster of course and we started talking cars when I was there. His car had barely 20000 miles on it while my Boxster at that time had around 200000 miles. He was complaining about his car - nothing major, no CEL, no signs of anything remotely serious -- just that it just didn't feel quite right.

When I suggested he needed to drive the car more, use up some of that gasoline that had been in the gas tank since only God knows when you would have thought I had asked him for naughty pictures of his wife. Drive his precious Porsche more? No way!

But an otherwise healthy engine, showing no signs of any distress, appears to benefit from a prolonged drive.

As I have experienced more than once even though my cars serve as work commuters for my 60 mile (round trip mostly highway) work commute a longer drive of it just happens due to an ill family member around 100+ miles (round trip all on the freeway) the engines in both cars feel just a bit peppier near the end of the 50 miles. as I approach my destination.

Even before this 9+ months of weekly (or sometimes even nightly) 100+ mile drives at other times when heading out on a road trip and after having covered 100 or more miles at freeway speeds I notice the engine running particularly nice.

One time that really stands out was when I was in my 06 GTO on one trip to Huntington Beach (from Livermore) as I was approaching close to where I-5 (I had remained on I-5 all the way down and with my V1 had made pretty good time, if you know what I mean) and 99 come together I noticed the big (6.0l) V8 was purring like a kitten, and yet it would still roar like a lion when I nailed the gas pedal as I passed slower traffic going and over the pass and down into the LA basin.
I would agree with you macster that certain owners drive their cars in such a manner the engine never gets to operate as it was designed. But each symptom has it's remedy.....again referring in the context of this thread.

Anyhow, I would never suggest, hope I have never suggested anyone take a sick engine out and as a "cure" blow out any cobwebs. Always the reason for the sickness/symptoms needs to be determined.

Sincerely,

Macster.
That's fine. Anyway no offence intended....and thank's for your responses. I've always enjoyed reading your lengthy posts but found that particular one on the cobwebs a little out there...again in reference to the thread... hence my Lol.
Best.


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