997.2 Engine Reliability
03-24-2015, 10:28 AM
#271
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03-24-2015, 10:59 AM
#272
Nordschleife Master
so you admit to having multiple negative 9A1 experiences a few years back resulting in a an engine rebuild …. yet in order to avoid making the same mistake (and hence all the drama on this thread) you are looking to purchase another vehicle with the exact same 9A1 engine? 
I'm not after money here! On the contrary, I'm just genuinely interested in buying a 997.2 for myself after coming from two consecutive 9A1 bad experiences back in 2010 that ended up on a teared down engine, which is all very well documented on the RL forum and elsewhere, and the last thing I want is to commit the same mistakes all over again.
03-24-2015, 11:04 AM
#273
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That being the case, I suggest CPO for caymanpowder
And on your third 9A1, you may want to refrain from diagnosing your own car. I have a sneaking suspicion that your multiple past engine failures may have had something to do with you doing your own troubleshooting, instead of leaving it up to the pros.
03-24-2015, 01:32 PM
#274
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03-24-2015, 03:00 PM
#275
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If I follow all the posts correctly I believe his issue was with two different 9A1 engines - the non-DFI 9A1 that was in the Cayman compared to the DFI 9A1 in the 997 and he's trying to get some feedback that would give him comfort that non-DFI 9A1 problems didn't carry over to the DFI 9A1.
03-24-2015, 04:47 PM
#276
If I follow all the posts correctly I believe his issue was with two different 9A1 engines - the non-DFI 9A1 that was in the Cayman compared to the DFI 9A1 in the 997 and he's trying to get some feedback that would give him comfort that non-DFI 9A1 problems didn't carry over to the DFI 9A1.
CaymanPower, if this is correct and you are looking for a 997.2, I suggest you move forward with confidence. Anything can fail, but I figure your odds for success with this car are unusually high.
03-24-2015, 05:12 PM
#277
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If I follow all the posts correctly I believe his issue was with two different 9A1 engines - the non-DFI 9A1 that was in the Cayman compared to the DFI 9A1 in the 997 and he's trying to get some feedback that would give him comfort that non-DFI 9A1 problems didn't carry over to the DFI 9A1.
03-24-2015, 05:16 PM
#278
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I suspect you are right, and the intensive probing is driven by past experience that could or would have any of us feeling as CaymanPower appears to feel. All I can say is that I drive my car with spirit, and I have no concerns regarding reliability. To support that, if there were significant problems with these motors, there would be a lot more chatter (there is no chatter).
CaymanPower, if this is correct and you are looking for a 997.2, I suggest you move forward with confidence. Anything can fail, but I figure your odds for success with this car are unusually high.
CaymanPower, if this is correct and you are looking for a 997.2, I suggest you move forward with confidence. Anything can fail, but I figure your odds for success with this car are unusually high.
03-24-2015, 05:21 PM
#279
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It is my belief that none of that afflicts the DFI engine except for, perhaps, some early models, MY09. I'm craving for a MY11 or later 997.2 !
Some of these early models are also notorious for DFI related problems in conjunction with a less than perfect engine cooling system, with bore scoring being the end result of fuel interference on the cylinder walls' oil film and overall oil quality premature deterioration. Excessive engine running temperatures or too low outside temperatures adds to the problem accelerating the wear process since these engines work with very tight tolerances as far as piston to bore clearances go -there's only a thin oil film preventing them to rub against each other - in order to cope with compression rates as high as 12.5:1 for the sake of better fuel-efficiency and emissions. Engine bank #1 being the most affected - normally, you would see smoke upon startup on the rear left tail pipes ONLY!!!
It is very easy to understand how this whole process takes place if we look at the 1st generation DFI system working principle:
In this process, electro-mechanically controlled fuel injectors inject fuel directly into the combustion chamber at a pressure of approx. 580 psi to 1740 psi (40 to 120 bar - in the 2nd DFI generation found on the 991 this value can be as high as 200 bar for better fuel atomization).
The spray cone angle and injection-jet orientation have been optimized to achieve optimum homogenization in the entire operating range. Within the injector, the fuel jet is twisted (rotated around the longitudinal axis - that's the swirl effect, one hole injector type, the 2nd DFI generation uses multi-hole injectors, as many as 6, one central and 5 peripheral, again for better fuel atomization). This rotation forms a conical cloud of fuel. The fine atomization produced in this way allows faster evaporation of the fuel.
The heat energy required to evaporate the fuel is absorbed from the combustion air, thereby cooling the air. This reduces the cylinder charge volume and additional air is drawn in through the open intake valve, which in turn improves cylinder charging.
Lowering the temperature reduces susceptibility to knocking and additionally allows the compression ratio to be increased.
High-pressure stratified charge ignition is used in the DFI flat-six engines in order to optimize cold starting with regard to fuel consumption and emissions. In this process, fuel is injected once into the specially shaped piston recess just prior to the end of the compression stroke when the engine is being started. This forms a stratified charge around the spark plug to ensure that an ignitable mixture is formed. This reduces both the amount of fuel required and the emissions during the starting phase compared to intake manifold injection.
Once the high-pressure stratified charge ignition starts the engine, the engine DME switches to the catalytic converter heating phase. In this operating state, multiple injection helps to bring the catalytic converter to the temperature required for optimal conversion of pollutants as quickly as possible.
To this end, the first injection of fuel takes place during the intake stroke and the second injection of fuel occurs into the piston recess when the intake valves are closed, just before the end of the compression stroke. The slightly lean air/fuel mixture can then be ignited at a very late point, thus increasing the exhaust temperature. The resulting delayed combustion and the continued exothermic oxidation of unburnt fuel (excess oxygen) even after the exhaust valves are opened produce a considerably higher exhaust temperature directly with the use of dual injection to heat the catalytic converters.
The high exhaust temperature quickly heats the catalytic converters to the temperature for optimal conversion of pollutants (for extreme cold conditions and short low rpm trips the engine goes through several cycles of this catalytic-converter heating phase with combustion chambers being exposed to more unburt fuel each time - proportionally to the higher cold air charge density, lambda value approx. 1.05 )
Engine operation at low rpms and high engine load leads to special requirements for the mixture-forming process within the engine. Here, triple injection takes place in the upper load range up to 2,500 rpm. Dual injection is performed up to 3,200 rpm. The amount of fuel required for combustion is distributed over two or three successive injection processes during the intake stroke (injection in synchronization with intake) This injection strategy further improves homogenization of the cylinder charge in the stated map ranges. In the other engine map ranges and in the range near idle, the engines are operated with conventional single injection during the intake process.
The spray cone angle and injection-jet orientation have been optimized to achieve optimum homogenization in the entire operating range. Within the injector, the fuel jet is twisted (rotated around the longitudinal axis - that's the swirl effect, one hole injector type, the 2nd DFI generation uses multi-hole injectors, as many as 6, one central and 5 peripheral, again for better fuel atomization). This rotation forms a conical cloud of fuel. The fine atomization produced in this way allows faster evaporation of the fuel.
The heat energy required to evaporate the fuel is absorbed from the combustion air, thereby cooling the air. This reduces the cylinder charge volume and additional air is drawn in through the open intake valve, which in turn improves cylinder charging.
Lowering the temperature reduces susceptibility to knocking and additionally allows the compression ratio to be increased.
High-pressure stratified charge ignition is used in the DFI flat-six engines in order to optimize cold starting with regard to fuel consumption and emissions. In this process, fuel is injected once into the specially shaped piston recess just prior to the end of the compression stroke when the engine is being started. This forms a stratified charge around the spark plug to ensure that an ignitable mixture is formed. This reduces both the amount of fuel required and the emissions during the starting phase compared to intake manifold injection.
Once the high-pressure stratified charge ignition starts the engine, the engine DME switches to the catalytic converter heating phase. In this operating state, multiple injection helps to bring the catalytic converter to the temperature required for optimal conversion of pollutants as quickly as possible.
To this end, the first injection of fuel takes place during the intake stroke and the second injection of fuel occurs into the piston recess when the intake valves are closed, just before the end of the compression stroke. The slightly lean air/fuel mixture can then be ignited at a very late point, thus increasing the exhaust temperature. The resulting delayed combustion and the continued exothermic oxidation of unburnt fuel (excess oxygen) even after the exhaust valves are opened produce a considerably higher exhaust temperature directly with the use of dual injection to heat the catalytic converters.
The high exhaust temperature quickly heats the catalytic converters to the temperature for optimal conversion of pollutants (for extreme cold conditions and short low rpm trips the engine goes through several cycles of this catalytic-converter heating phase with combustion chambers being exposed to more unburt fuel each time - proportionally to the higher cold air charge density, lambda value approx. 1.05 )
Engine operation at low rpms and high engine load leads to special requirements for the mixture-forming process within the engine. Here, triple injection takes place in the upper load range up to 2,500 rpm. Dual injection is performed up to 3,200 rpm. The amount of fuel required for combustion is distributed over two or three successive injection processes during the intake stroke (injection in synchronization with intake) This injection strategy further improves homogenization of the cylinder charge in the stated map ranges. In the other engine map ranges and in the range near idle, the engines are operated with conventional single injection during the intake process.
Last edited by CaymanPower; 03-24-2015 at 06:41 PM.
03-24-2015, 08:12 PM
#280
I hope it all works out well for you but I cannot understand why you ask for opinions. You argue with everyone including one of the preeminent Porsche engine builders, tell everyone they are wrong, and then answer your own questions. I have no axe to grind with you but that's just how this entire thread reads.
03-24-2015, 08:32 PM
#281
Rat Balls
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I hope it all works out well for you but I cannot understand why you ask for opinions. You argue with everyone including one of the preeminent Porsche engine builders, tell everyone they are wrong, and then answer your own questions. I have no axe to grind with you but that's just how this entire thread reads.
If he is this concerned about the reliability of the car before he has bought one, then he will have an ulcer after a few weeks when he's got his money in it.
Some people are just not made to own these cars...worse yet, their paranoid posts will eventually influence others not to buy one either...and that would be a shame.
03-24-2015, 09:27 PM
#282
Nordschleife Master
+997
If he is this concerned about the reliability of the car before he has bought one, then he will have an ulcer after a few weeks when he's got his money in it.
Some people are just not made to own these cars...worse yet, their paranoid posts will eventually influence others not to buy one either...and that would be a shame.
If he is this concerned about the reliability of the car before he has bought one, then he will have an ulcer after a few weeks when he's got his money in it.
Some people are just not made to own these cars...worse yet, their paranoid posts will eventually influence others not to buy one either...and that would be a shame.
03-24-2015, 10:54 PM
#283
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I hope it all works out well for you but I cannot understand why you ask for opinions. You argue with everyone including one of the preeminent Porsche engine builders, tell everyone they are wrong, and then answer your own questions. I have no axe to grind with you but that's just how this entire thread reads.
But you are forgetting a very important point, first and foremost, these so called preeminent Porsche engine builders are the ones who first argue with Porsche themself and tell them they are wrong!
Can you understand that?! Arguing against Porsche technical expertise, Porsche that race engines since almost the beginning of times?!
This is not rocket science you know... all it takes is some engineering background and some common sense to ask the right questions !
Engineering is the art of compromise... so, every engineering product is compromised somehow by definition. If it doesn't deliver you have to seek where the compromise has gone too far.
I seek thoroughly and I present my findings in a bold HONEST way hoping that someone chimes in and just proves me wrong!
If that doesn't happen I hold to my conclusions until contrary evidence. That's how I learn.
What I can't bare is fanboys or someone treating me like I was retarded, because you can't be rational with either of them!
Let me give you an example, every Porsche owner, every so called preeminent Porsche engine builder, Porsche themself all of them tell me that some smoke upon startup is normal on a Porsche horizontally opposed cylinder engine but I present two simple evidences and all the rationale behind the 'classic' explanation looses any possible credibility, although none of them are willing to acknowledge that:
A. Not every Porsche horizontally opposed cylinder engine smokes upon startup
B. There are some Porsche horizontally opposed cylinder engines that smoke from one cylinder bank only (I've owned two)
Next thing you know, you are being called paranoid or a troll.
03-24-2015, 11:35 PM
#284
Rat Balls
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Fair enough!
But you are forgetting a very important point, first and foremost, these so called preeminent Porsche engine builders are the ones who first argue with Porsche themself and tell them they are wrong!
Can you understand that?! Arguing against Porsche technical expertise, Porsche that race engines since almost the beginning of times?!
This is not rocket science you know... all it takes is some engineering background and some common sense to ask the right questions !
Engineering is the art of compromise... so, every engineering product is compromised somehow by definition. If it doesn't deliver you have to seek where the compromise has gone too far.
I seek thoroughly and I present my findings in a bold HONEST way hoping that someone chimes in and just proves me wrong!
If that doesn't happen I hold to my conclusions until contrary evidence. That's how I learn.
What I can't bare is fanboys or someone treating me like I was retarded, because you can't be rational with either of them!
Let me give you an example, every Porsche owner, every so called preeminent Porsche engine builder, Porsche themself all of them tell me that some smoke upon startup is normal on a Porsche horizontally opposed cylinder engine but I present two simple evidences and all the rationale behind the 'classic' explanation looses any possible credibility, although none of them are willing to acknowledge that:
A. Not every Porsche horizontally opposed cylinder engine smokes upon startup
B. There are some Porsche horizontally opposed cylinder engines that smoke from one cylinder bank only (I've owned two)
Next thing you know, you are being called paranoid or a troll.
But you are forgetting a very important point, first and foremost, these so called preeminent Porsche engine builders are the ones who first argue with Porsche themself and tell them they are wrong!
Can you understand that?! Arguing against Porsche technical expertise, Porsche that race engines since almost the beginning of times?!
This is not rocket science you know... all it takes is some engineering background and some common sense to ask the right questions !
Engineering is the art of compromise... so, every engineering product is compromised somehow by definition. If it doesn't deliver you have to seek where the compromise has gone too far.
I seek thoroughly and I present my findings in a bold HONEST way hoping that someone chimes in and just proves me wrong!
If that doesn't happen I hold to my conclusions until contrary evidence. That's how I learn.
What I can't bare is fanboys or someone treating me like I was retarded, because you can't be rational with either of them!
Let me give you an example, every Porsche owner, every so called preeminent Porsche engine builder, Porsche themself all of them tell me that some smoke upon startup is normal on a Porsche horizontally opposed cylinder engine but I present two simple evidences and all the rationale behind the 'classic' explanation looses any possible credibility, although none of them are willing to acknowledge that:
A. Not every Porsche horizontally opposed cylinder engine smokes upon startup
B. There are some Porsche horizontally opposed cylinder engines that smoke from one cylinder bank only (I've owned two)
Next thing you know, you are being called paranoid or a troll.
03-25-2015, 08:28 AM
#285
People are still responding to this guy?