D chunk cylinder failure- early signs?
Discussion
Manks - this is a very difficult subject to analyse and give answers to. Most do have early signs but we have not inspected enough to quantify an answer directly that would be reliable although we are working on it.
You must remember that Lokasil is a new material and a new technology (holding silicon pieces in a matrix using various binders and matrix formula).
We are presntly undertaking a massive research project into the whole area of failures and reasons why - but it takes time to collect and then collate data and you need a lot of answers to reliably find conclusions.
We are also at the same time being pragmatic by concentrating on fixing the engines with the problem and finding less expensive ways to do the most reliable repairs possible while tryinmg to minimise a re-occurence (or extend the life expectancy compared to a new but unmodified engine) and find products and changes that will extend the life of an existing engine without scoring by selling or fitting our low temperature thermostat.
We are at the same time investing in suitable equipment for honing bores and measuring the results so we can reproduce the right finish etc and this is helping us collect the information that may eventually improve our understanding of the failure.
For a tiny private business - this is as much as we can cope with at present.
Baz
You must remember that Lokasil is a new material and a new technology (holding silicon pieces in a matrix using various binders and matrix formula).
We are presntly undertaking a massive research project into the whole area of failures and reasons why - but it takes time to collect and then collate data and you need a lot of answers to reliably find conclusions.
We are also at the same time being pragmatic by concentrating on fixing the engines with the problem and finding less expensive ways to do the most reliable repairs possible while tryinmg to minimise a re-occurence (or extend the life expectancy compared to a new but unmodified engine) and find products and changes that will extend the life of an existing engine without scoring by selling or fitting our low temperature thermostat.
We are at the same time investing in suitable equipment for honing bores and measuring the results so we can reproduce the right finish etc and this is helping us collect the information that may eventually improve our understanding of the failure.
For a tiny private business - this is as much as we can cope with at present.
Baz
Hi Baz,
Without pulling any punches and getting too technical whats your honest opinion of this engine?
Please put aside the chemical unknowns re locasil technology,could you give an opinion on bore cracks,ovality, hotspots under load and the crankflex issues we have discussed.I dont want to include RMS as thats another story!
Im starting to think its a flawed design am I wrong to think that these engines are a disaster waiting to happen?....even at silly low mileages I would aprreciate your opinion here.
G
Without pulling any punches and getting too technical whats your honest opinion of this engine?
Please put aside the chemical unknowns re locasil technology,could you give an opinion on bore cracks,ovality, hotspots under load and the crankflex issues we have discussed.I dont want to include RMS as thats another story!
Im starting to think its a flawed design am I wrong to think that these engines are a disaster waiting to happen?....even at silly low mileages I would aprreciate your opinion here.
G
Gary - it is honestly difficult for me to reach a conclusion like that.
I think the cars are absolutely brilliant and that the engines are fantastic (especially the 3.8 versions).
Ok we get several/week to fix and many more enquiries but I cannot equate that to the massive numbers that are apparently running perfectly OK.
Many other manufacturers of "modern" engines running at higher temperatures with similar damped temperature guages are also begining to have similar problems and I wonder if the demands of emmision standards have pushed manufacturers a little too far in trying to meet them so running engines basically so hot inside that they are more vulnerable than they used to be.
Ever more power, better fuel consumption and low emmisions are the main aim today and it is difficult while manufacturing costs must be cut and manufacturers are responding to demand for more and more modern products with shorter lifespans.
The engines we see have good points and poor ones. The poor ones could have been designed a little better and we think the mods we do (like closing the deck, lowering the crankcase temperature etc) improve the engines, while it seems that crankshaft bearings etc in the ones we see have a shorter life expectancy than they used to. But then they used to burn more fuel and give lower outputs at greater fuel consumption too (partly because the insides were heavier) and they did cost too much to make (hence Porsche never making much profit until this new design came along).
I believe there are some isolated problems in the Cayen engines and even the Panemera (which we expect to be looking at soon) so it is really a question of weighing up the the performance and cost against - what is probably fair to say - a lower average life expectancy than they used to run at before an engine rebuild (which is now generally available).
You must form your own conclusion and your own way of expressing that - but there are actually many other cars in a similar boat - you just havn't heard about them yet.
Baz
I think the cars are absolutely brilliant and that the engines are fantastic (especially the 3.8 versions).
Ok we get several/week to fix and many more enquiries but I cannot equate that to the massive numbers that are apparently running perfectly OK.
Many other manufacturers of "modern" engines running at higher temperatures with similar damped temperature guages are also begining to have similar problems and I wonder if the demands of emmision standards have pushed manufacturers a little too far in trying to meet them so running engines basically so hot inside that they are more vulnerable than they used to be.
Ever more power, better fuel consumption and low emmisions are the main aim today and it is difficult while manufacturing costs must be cut and manufacturers are responding to demand for more and more modern products with shorter lifespans.
The engines we see have good points and poor ones. The poor ones could have been designed a little better and we think the mods we do (like closing the deck, lowering the crankcase temperature etc) improve the engines, while it seems that crankshaft bearings etc in the ones we see have a shorter life expectancy than they used to. But then they used to burn more fuel and give lower outputs at greater fuel consumption too (partly because the insides were heavier) and they did cost too much to make (hence Porsche never making much profit until this new design came along).
I believe there are some isolated problems in the Cayen engines and even the Panemera (which we expect to be looking at soon) so it is really a question of weighing up the the performance and cost against - what is probably fair to say - a lower average life expectancy than they used to run at before an engine rebuild (which is now generally available).
You must form your own conclusion and your own way of expressing that - but there are actually many other cars in a similar boat - you just havn't heard about them yet.
Baz
Thanks for the reply Baz.
I in my my 30 odd yrs in the motor trade (jesus!) have not heard of and cannot remember an engine with so many potentials for disaster,I can only think of the "nicasil" issues around 99-02 regarding the excess sulpur in fuel which caused problems for jaguar BMW ect loosing compression,or the old sohc straight six 2.9 jaguar engine that was just bad,I really need to get some difinative figures for the scale of this/these issues as to be fair people dont normaly post on forums to say how good a particular engine is,whatever your or my opinion Baz there are a lot of threads now running on the internet via various forums in for me unprecedented volumes,your comment regarding possible scoring @40k compounds my thinking that we perhaps have a major issue.I can only imagine the problems getting worse with DFI gen2 engines as there is established data on such engines needing regular decokes ect unless the internals are drastically different not a cheap job on any engine let alone a 911.
Thanks again.
G
I in my my 30 odd yrs in the motor trade (jesus!) have not heard of and cannot remember an engine with so many potentials for disaster,I can only think of the "nicasil" issues around 99-02 regarding the excess sulpur in fuel which caused problems for jaguar BMW ect loosing compression,or the old sohc straight six 2.9 jaguar engine that was just bad,I really need to get some difinative figures for the scale of this/these issues as to be fair people dont normaly post on forums to say how good a particular engine is,whatever your or my opinion Baz there are a lot of threads now running on the internet via various forums in for me unprecedented volumes,your comment regarding possible scoring @40k compounds my thinking that we perhaps have a major issue.I can only imagine the problems getting worse with DFI gen2 engines as there is established data on such engines needing regular decokes ect unless the internals are drastically different not a cheap job on any engine let alone a 911.
Thanks again.
G
Edited by Gary11 on Friday 15th April 09:19
Continuing the early part of this discussion, some data from my science lab (the kitchen).
Investigating the operation of the standard 996 C2 thermostat...
Water...Length of
temp c..thermostat body (mm)
Ambient....65mm
70c........68mm
80c........71mm
90c........73mm
115c.......77mm
She was not in the housing at the time so its hard to assess the actual opening point where flow to the rads starts however for me the most interesting fact here is that the movement is quite small. The total movement from initial opening, say for arguments sake at 83c, through to the cooling fans switch-on at 102c is probably only 5 or 6mm.
I think this adds to the case for fitting the lower temperature thermosatat from Hartech as not only will the running temperature come down (any idea how much Baz?) but additionally the thermostat will have moved more (assuming its got the same temp:mm ratio) and so the thermostat orifice will be wider which means more coolant flow out to the rads -which is what I want.
Investigating the operation of the standard 996 C2 thermostat...
Water...Length of
temp c..thermostat body (mm)
Ambient....65mm
70c........68mm
80c........71mm
90c........73mm
115c.......77mm
She was not in the housing at the time so its hard to assess the actual opening point where flow to the rads starts however for me the most interesting fact here is that the movement is quite small. The total movement from initial opening, say for arguments sake at 83c, through to the cooling fans switch-on at 102c is probably only 5 or 6mm.
I think this adds to the case for fitting the lower temperature thermosatat from Hartech as not only will the running temperature come down (any idea how much Baz?) but additionally the thermostat will have moved more (assuming its got the same temp:mm ratio) and so the thermostat orifice will be wider which means more coolant flow out to the rads -which is what I want.
Well done for "Fiddling" - interesting isn't it?
Our thermostat research was not for "D" chunk failure (because we had a solution to that with the replaceable cylinders and restraining rings) but was when we realised that the coolant flow and balance had been altered in the engines with scoring problems.
As well as doing the same tests you did - we rebuilt two engines (with and without coolant flow mods) with temperature sensors fitted in strategic places and made up a wiring loom to a set of temperature guages and tested them with different thermostats - recording the results. Generally our thermostat ran 10 - 12 degrees C cooler and held the temperatures lower for longer under sudden hard acceleration and driving. The engines never reached the very high temperatures the standard set up did.
However - as many other of my posts in different forums have revealed - engine cooling is not the simple issue most expect. Many others ideas about speeding up water pumps and increasing the air flow to the radiators etc - I have explained - may actually run the engine hotter - and the response rate and cooling affects are not always as easy to predict as they would seem.
However - the older type of racing engines and many newer Porsche engines - run cooler as well - so I really think the lower temperature thermostat is a good investment.
It may well be that the Lokasil stability may be increased with the engine running cooler - but by now - most engines have run at the higher temperature for so long - I doubt it would make any noticeable difference.
Such testing is incredibly expensive for a small business like ours. First we have to buy a car or two (in this case) - strip and rebuild the engine and fit special parts - then drive it around under test for a long period in different conditions and then reach conclusions. With so many different models and variants, different capacities and performance etc - we couldn't possibly reproduce every scenario - and have to base our conclusions on a limited set of tests and conditions.
However - there is little doubt that - not only does the low temperature thermostat improve operating conditions and performance - but it also is reassuring to know it is in there doing a protective job all the time.
For such a small cost - it seems a no brainer to me - (and for the same cost reasons is never going to make us a return on the investment we put into finding something to help) - but something had to be done to help reduce the numbers failing and this is surely a soundly based and inexpensive modification that does that.
Baz
Our thermostat research was not for "D" chunk failure (because we had a solution to that with the replaceable cylinders and restraining rings) but was when we realised that the coolant flow and balance had been altered in the engines with scoring problems.
As well as doing the same tests you did - we rebuilt two engines (with and without coolant flow mods) with temperature sensors fitted in strategic places and made up a wiring loom to a set of temperature guages and tested them with different thermostats - recording the results. Generally our thermostat ran 10 - 12 degrees C cooler and held the temperatures lower for longer under sudden hard acceleration and driving. The engines never reached the very high temperatures the standard set up did.
However - as many other of my posts in different forums have revealed - engine cooling is not the simple issue most expect. Many others ideas about speeding up water pumps and increasing the air flow to the radiators etc - I have explained - may actually run the engine hotter - and the response rate and cooling affects are not always as easy to predict as they would seem.
However - the older type of racing engines and many newer Porsche engines - run cooler as well - so I really think the lower temperature thermostat is a good investment.
It may well be that the Lokasil stability may be increased with the engine running cooler - but by now - most engines have run at the higher temperature for so long - I doubt it would make any noticeable difference.
Such testing is incredibly expensive for a small business like ours. First we have to buy a car or two (in this case) - strip and rebuild the engine and fit special parts - then drive it around under test for a long period in different conditions and then reach conclusions. With so many different models and variants, different capacities and performance etc - we couldn't possibly reproduce every scenario - and have to base our conclusions on a limited set of tests and conditions.
However - there is little doubt that - not only does the low temperature thermostat improve operating conditions and performance - but it also is reassuring to know it is in there doing a protective job all the time.
For such a small cost - it seems a no brainer to me - (and for the same cost reasons is never going to make us a return on the investment we put into finding something to help) - but something had to be done to help reduce the numbers failing and this is surely a soundly based and inexpensive modification that does that.
Baz
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