Cylinder Scoring - All you need to know!
Discussion
The new section 5 of our Internet based buyers guide has now been uploaded (see www.hartech,org buyers guide). You will need a lot of time and probably a headache pill or two if you want to read the whole lot in one go.
It has been written to inform anyone at any level of relevant knowledge (from a non technical owner to an experienced qualified engineer) - that is interested in the problem of cylinder scoring in 996 and 997 3.6, 3.8 and Cayman S engines - what the many contributory factors are and why.
Briefly it covers why it is easy to design an engine so bullet proof that it never ever goes wrong but it would then be very expensive and heavy as a result. With pressures on profitability, low emissions and higher performance - manufacturers have been under pressure to trim designs, weights, costs, emissions and fuel economy while increasing performance - which inevitably moves their products closer to reliability or longevity limits.
This section gradually explains how some systems that worked OK in air cooled 911's and the 944/968 range had small subtle differences when applied across into the M96 engines that individually seemed insignificant but actually pushed each reliability issue slightly closer towards the limit - but insufficient to cause a problem (in other words pretty well perfectly designed for the needs of the modern World). Many of the changes and weaknesses seem also to concentrate the problem on bank 2 (where most of the failures are).
When the later bigger capacity and more powerful versions were built - instead of changing some of those marginal issues to compensate for the additional heat and loads - it seems that they were either left exactly the same or in one case while moving in the right direction for reducing costs - went entirely in the wrong direction for reliability - resulting in engines running so much closer to that boundary - that some - after ageing and with some wear and tear taking place and after experiencing different driving conditions and styles - simply slip over the boundary and become damaged (usually on bank 2).
The scenario is typical of many other historical engines from different manufacturers that following a capacity or performance increase - search out and find the weak spots in a previously reliable design.
Usually a small but significant modification eventually appears on the market to fix the problem - but more often from smaller specialist organisations (that is presently taking place with these engines).
Because this initial engine range was actually so very well designed to run really close to - but still inside those "safety margins" - the increased performance applied to later models without other supporting alterations - has revealed a complex list of contributory weak spots - each even closer to the limits - such that a particular mix of sometimes different circumstances can push the engine over them.
It is therefore a complex problem requiring lengthy investigation and testing, proving good well founded solutions while exposing some other inadequate ones recently coming to the market.
This 25,000 word section explains each issue with both simple explanations and analogies backed up with technical and scientific facts so anyone should be able to grasp the salient points and realise that there are several issues to consider and several modifications that are beneficial during a rebuild and not one simple fix. It also includes further new developments that may help owners avoid the problem.
Before readers start with responding with typical criticism – please remember that I don’t need to write this stuff for my benefit (I already understand it) and furthermore if I spent the same amount of time and effort it took to write this section on promoting our business in other advertising or marketing ways – it would certainly result in greater financial rewards. It has been written to inform others about the problem – what we know about it and what we do about it – to prevent misleading alternatives from confusing owners – empowering them to make informed decisions if they need help or advice.
Although many with more experience would not need to read the whole of it to understand what it contains, I do not intend to respond to any criticism unless every word has already been read.
Best regards and happy reading,
Barry Hart
It has been written to inform anyone at any level of relevant knowledge (from a non technical owner to an experienced qualified engineer) - that is interested in the problem of cylinder scoring in 996 and 997 3.6, 3.8 and Cayman S engines - what the many contributory factors are and why.
Briefly it covers why it is easy to design an engine so bullet proof that it never ever goes wrong but it would then be very expensive and heavy as a result. With pressures on profitability, low emissions and higher performance - manufacturers have been under pressure to trim designs, weights, costs, emissions and fuel economy while increasing performance - which inevitably moves their products closer to reliability or longevity limits.
This section gradually explains how some systems that worked OK in air cooled 911's and the 944/968 range had small subtle differences when applied across into the M96 engines that individually seemed insignificant but actually pushed each reliability issue slightly closer towards the limit - but insufficient to cause a problem (in other words pretty well perfectly designed for the needs of the modern World). Many of the changes and weaknesses seem also to concentrate the problem on bank 2 (where most of the failures are).
When the later bigger capacity and more powerful versions were built - instead of changing some of those marginal issues to compensate for the additional heat and loads - it seems that they were either left exactly the same or in one case while moving in the right direction for reducing costs - went entirely in the wrong direction for reliability - resulting in engines running so much closer to that boundary - that some - after ageing and with some wear and tear taking place and after experiencing different driving conditions and styles - simply slip over the boundary and become damaged (usually on bank 2).
The scenario is typical of many other historical engines from different manufacturers that following a capacity or performance increase - search out and find the weak spots in a previously reliable design.
Usually a small but significant modification eventually appears on the market to fix the problem - but more often from smaller specialist organisations (that is presently taking place with these engines).
Because this initial engine range was actually so very well designed to run really close to - but still inside those "safety margins" - the increased performance applied to later models without other supporting alterations - has revealed a complex list of contributory weak spots - each even closer to the limits - such that a particular mix of sometimes different circumstances can push the engine over them.
It is therefore a complex problem requiring lengthy investigation and testing, proving good well founded solutions while exposing some other inadequate ones recently coming to the market.
This 25,000 word section explains each issue with both simple explanations and analogies backed up with technical and scientific facts so anyone should be able to grasp the salient points and realise that there are several issues to consider and several modifications that are beneficial during a rebuild and not one simple fix. It also includes further new developments that may help owners avoid the problem.
Before readers start with responding with typical criticism – please remember that I don’t need to write this stuff for my benefit (I already understand it) and furthermore if I spent the same amount of time and effort it took to write this section on promoting our business in other advertising or marketing ways – it would certainly result in greater financial rewards. It has been written to inform others about the problem – what we know about it and what we do about it – to prevent misleading alternatives from confusing owners – empowering them to make informed decisions if they need help or advice.
Although many with more experience would not need to read the whole of it to understand what it contains, I do not intend to respond to any criticism unless every word has already been read.
Best regards and happy reading,
Barry Hart
Excuse my ignorance but new to all this, just reading the interesting Hartech article and came across this, "ISSUES THAT RENDER THE Cayman S, 3.6 and 3.8 engines different to the 3.4’s and Boxsters.". Is the Cayman S referred too the Gen 2 one and the 3.4's the gen 1 one or is the cayman s one the Cayman 3.4's and the 3.4's referred too something else? If you can understand the question you are doing well and an answer would be much appreciated.
BertBert said:
so people who mend porsche engines for a living writing a 54 page guide on engines going wrong.
Is it just me...?
I know it all enables them to hopefully drum up more business by showing how competent they are but I personally think it is good of them to share there knowledge and hopefully educate us at the same time. Just my thoughts. Happy Christmas.Is it just me...?
Chris W - I would love to know more about the USA experience - which models and what problems and modifications etc (I do know their 3.4 996 cranks bend and snap) but having done my bit from what I know over here - perhaps you could research the position over the pond and let us all know what you discovered? It's about time someone else posted something constructive rather than picking over what we have provided.
doneitnow - OK perhaps I should have said the "996" 3.4's - but if you read it all I think you would realise that the main difference in the 3.4 Cayman S and the 996 3.4 is the change in the head gasket and therefore the more coolant flow to the cylinder head and equally as a result the less to the cylinder block which therefore runs hotter especially at the top on bank 2 where all the failures usually are.
Bert Bert - I am not sure how else you would expect anyone to be able to write so much about the subject unless they were the main rebuild specialists and see and handle more engines than anyone else while providing more solutions and having carried out more research? Would you pay more credence to someone with hardly any actual practical experience or proven success?
May I also repeat what I have often reported before - we do not need any more business - our success combined with the increasing failure rate is encouraging us to expand inside our existing building but we don't need to in order to make a living and with many other pressures of customers on our Maintenance Plan and the 2012 race team - that is absolutely not the reason why I have posted all this information.
The reason - as I have stated before - is simply that I read miss-information from other sources and as a result we often receive engines for their 2nd rebuild that have already been rebuilt once elsewhere. That doesn't mean I am trying to take all the work (we simply couldn't handle it otherwise) nor that some other solutions may be reasonably OK - but I just feel it is better for owners in trouble to be able to read all about what we do and what everyone else does and why. It is just interesting that there seems no other supplier of engine rebuilds willing or able to offer their reasoning and expanding upon their range of solutions and at least by my posting - owners can ask others reasonable questions about what they think of some issues and what they do about it and if after that they want to go elsewhere - that's absolutely OK by us.
I find that people that shy away from having the confidence to explain things fully and are not prepared to publicly explain everything out in the open usually either have something to hide or don't really know enough and don't want to expose that.
Remember the only people to benefit from our postings will be people in trouble and with a huge financial problem whatever they decide to do. Empowering them with comprehensive advice and information (fully backed up with technical explanations etc) cannot in any way harm their ability to go on and make the best decision they can in the circumstances.
It might well upset some that in providing this source of information - we may emerge as the most capable of providing the best answers - but how that can harm the very people in need of help - I fail to see - It only harms those providing less of a solution - and possibly not those needing one.
At least we are rebuilding engines to the satisfaction of owners every day of the week and continuing to explore more improvements all the time. Not sure why that deserves to be sniped at or our motives being questioned.
Happy Christmas day,
Baz
doneitnow - OK perhaps I should have said the "996" 3.4's - but if you read it all I think you would realise that the main difference in the 3.4 Cayman S and the 996 3.4 is the change in the head gasket and therefore the more coolant flow to the cylinder head and equally as a result the less to the cylinder block which therefore runs hotter especially at the top on bank 2 where all the failures usually are.
Bert Bert - I am not sure how else you would expect anyone to be able to write so much about the subject unless they were the main rebuild specialists and see and handle more engines than anyone else while providing more solutions and having carried out more research? Would you pay more credence to someone with hardly any actual practical experience or proven success?
May I also repeat what I have often reported before - we do not need any more business - our success combined with the increasing failure rate is encouraging us to expand inside our existing building but we don't need to in order to make a living and with many other pressures of customers on our Maintenance Plan and the 2012 race team - that is absolutely not the reason why I have posted all this information.
The reason - as I have stated before - is simply that I read miss-information from other sources and as a result we often receive engines for their 2nd rebuild that have already been rebuilt once elsewhere. That doesn't mean I am trying to take all the work (we simply couldn't handle it otherwise) nor that some other solutions may be reasonably OK - but I just feel it is better for owners in trouble to be able to read all about what we do and what everyone else does and why. It is just interesting that there seems no other supplier of engine rebuilds willing or able to offer their reasoning and expanding upon their range of solutions and at least by my posting - owners can ask others reasonable questions about what they think of some issues and what they do about it and if after that they want to go elsewhere - that's absolutely OK by us.
I find that people that shy away from having the confidence to explain things fully and are not prepared to publicly explain everything out in the open usually either have something to hide or don't really know enough and don't want to expose that.
Remember the only people to benefit from our postings will be people in trouble and with a huge financial problem whatever they decide to do. Empowering them with comprehensive advice and information (fully backed up with technical explanations etc) cannot in any way harm their ability to go on and make the best decision they can in the circumstances.
It might well upset some that in providing this source of information - we may emerge as the most capable of providing the best answers - but how that can harm the very people in need of help - I fail to see - It only harms those providing less of a solution - and possibly not those needing one.
At least we are rebuilding engines to the satisfaction of owners every day of the week and continuing to explore more improvements all the time. Not sure why that deserves to be sniped at or our motives being questioned.
Happy Christmas day,
Baz
An excellent piece of work.
My verdict? avoid these engines/cars like the plague. The risk is simply too great. Non GT2/3/Turbos will go down to banger money.
Porsche dropped a right royal testes. I would expect more from the creator of the G50 3.2 Carrera. Why expect anything less than bulletproof??
My verdict? avoid these engines/cars like the plague. The risk is simply too great. Non GT2/3/Turbos will go down to banger money.
Porsche dropped a right royal testes. I would expect more from the creator of the G50 3.2 Carrera. Why expect anything less than bulletproof??
Baz, I also would like to say thanks for all the constructive information you post.
A new engine from Porsche is really not the answer unless they themselves have done something to resolve the original problem.
My question regarding Gen II engines was based on the wide experience of failures that yuo will have, and some of the Gen II engines are certainly getting to an age where the Gen I engines were "blowing" ...
Information on the American Intermark series is limited to two seasons, first indications being very good --- but I am not sure in reply to questions regarding potential oil starvation at high G with non Mezger block engines, how the Intermark series have dealt with this --- or even whether they have needed to make any allowances whatsoever.
Having competed in the Porsche Club Championship I am now playing with a Cayman R and may some years down the line convert this into a track car. Unless Porsche do something in the meantime !
I therefore lay all my cards on the table
But I can tell you, on road tyres at a very wet Cadwell Park my Cayman R was devastatingly fast .. and I am still learnng it
A new engine from Porsche is really not the answer unless they themselves have done something to resolve the original problem.
My question regarding Gen II engines was based on the wide experience of failures that yuo will have, and some of the Gen II engines are certainly getting to an age where the Gen I engines were "blowing" ...
Information on the American Intermark series is limited to two seasons, first indications being very good --- but I am not sure in reply to questions regarding potential oil starvation at high G with non Mezger block engines, how the Intermark series have dealt with this --- or even whether they have needed to make any allowances whatsoever.
Having competed in the Porsche Club Championship I am now playing with a Cayman R and may some years down the line convert this into a track car. Unless Porsche do something in the meantime !
I therefore lay all my cards on the table
But I can tell you, on road tyres at a very wet Cadwell Park my Cayman R was devastatingly fast .. and I am still learnng it
Sorry I will have to get back with the price fitted when I get back to work on next Tuesday 3rd Jan. I gues it relates a lot to what else is being done at the same time - eg coolant change or a new radiator etc.
However according to GT4 (different web site and forum but the guy that explained about the way to see true dash coolant temperature using the on board computer and a brilliant source of Porsche information) - the GT3 Cup Cars are fitted with a 55 degree thermostat (almost the same as I was trying to get manufactured recently to fit to our race cars but was thwarted due to the numbers needed for manufacture running into thousands) - and if this is right not only will I try and get one to see if it can be fitted - but I think it totally vindicates our research and the content of our section 5 and justifies the fitting of our own low temperature thermostat for road use. It confirms what I had already written about racing with cooler engines and therefore substantiates our conclusions and all the work we have done to fix that problem - while throwing back in the faces of those arguing the cause is something else! how relevant it is to keep those cylinders cooler.
Baz
However according to GT4 (different web site and forum but the guy that explained about the way to see true dash coolant temperature using the on board computer and a brilliant source of Porsche information) - the GT3 Cup Cars are fitted with a 55 degree thermostat (almost the same as I was trying to get manufactured recently to fit to our race cars but was thwarted due to the numbers needed for manufacture running into thousands) - and if this is right not only will I try and get one to see if it can be fitted - but I think it totally vindicates our research and the content of our section 5 and justifies the fitting of our own low temperature thermostat for road use. It confirms what I had already written about racing with cooler engines and therefore substantiates our conclusions and all the work we have done to fix that problem - while throwing back in the faces of those arguing the cause is something else! how relevant it is to keep those cylinders cooler.
Baz
P50 said:
An excellent piece of work.
My verdict? avoid these engines/cars like the plague. The risk is simply too great. Non GT2/3/Turbos will go down to banger money.
Porsche dropped a right royal testes. I would expect more from the creator of the G50 3.2 Carrera. Why expect anything less than bulletproof??
So when will they go down to 'banger money'? They've been around for 14 years or so now, will it be soon?My verdict? avoid these engines/cars like the plague. The risk is simply too great. Non GT2/3/Turbos will go down to banger money.
Porsche dropped a right royal testes. I would expect more from the creator of the G50 3.2 Carrera. Why expect anything less than bulletproof??
And don't be too sure about GT3 TT etc. I've seen those in OPCs leaking oil like sieves so they're not perfect. It would be interesting to see their respective failure rates given the different quantities built.
DSM2 said:
So when will they go down to 'banger money'? They've been around for 14 years or so now, will it be soon?
And don't be too sure about GT3 TT etc. I've seen those in OPCs leaking oil like sieves so they're not perfect. It would be interesting to see their respective failure rates given the different quantities built.
It's obviously relative but I consider £3.75k with offers pretty cheap for a 2001 Boxster with a duff motor. And don't be too sure about GT3 TT etc. I've seen those in OPCs leaking oil like sieves so they're not perfect. It would be interesting to see their respective failure rates given the different quantities built.
http://www.ebay.co.uk/itm/PORSCHE-BOXSTER-S-3-2S-2...
When I was in my teens (I'm 41) the A/C 911's had very strong residuals. Tired/broken/rusty or not I can see W/C 6 cylinder cars eventually dropping to the situation I mention. But they'd have to be rough. What I mean is a 993 on the 1997 R plate with its guides gone or suchlike will be worth (and are) a huge amount more than a comparable 1998 R 996 with a problem of the same value.
These two cars are simply an example of how the market prices a two owner 54k mile manual cab 911 in sound condition. (I tried to get as close as I can on the Trader). I find it amazing the prices are in this situation. I don't think the 996 is a bad car but is it the reputation that has done this or the sheer volumes built? Or simply because the 993 is the last of the air-pumper? These are not S cars where the 993 is even stronger on prices.
A W/C with a bust engine worth less than the cost of the repair will mean it may be sold on to be dismantled. At some point.
http://www2.autotrader.co.uk/classified/advert/201...
http://www2.autotrader.co.uk/classified/advert/201...
Edited by P50 on Tuesday 27th December 09:57
Hi ChrisW - I hope someone has time to research the intermark series - for engine problems - it would be another source of useful information.
Over here head cracks seem likely and rear crank shells (due to the overhang of the cranshaft and it flexing at the rear).
The centrifugal force on cornering will send the oil across to the outer cylinder head chamber and could starve the oil pick up.
A deeper sump can help but one on the market has holes that allow the oil in the sump to leak out again on whichever side is the outside at the time.
We make one with baffles and flap valves in (used with success in our BRSCC Boxster series) now in production and available soon - but this should be used with a lower oil fill level to avoid too much oil pumping up into the breather system.
Regarding prices etc - I think a high mileage 996 or Boxster could be worth considering in one way and that is that really most older Porsches that people keep for ever and become classics have an engine rebuild at some stage and actually they are less expensive to rebuild that an air cooled or 944/968 air cooled engine (like for like). If the various weaknesses can be fixed at the samel time - it could make a lot of sense especially to people who can remove and replace the engine themselves - where rebuild prices actually start @ just over £2K + Vat (although more like £3 to £3.5K with various extras - but still good value).
Baz
Over here head cracks seem likely and rear crank shells (due to the overhang of the cranshaft and it flexing at the rear).
The centrifugal force on cornering will send the oil across to the outer cylinder head chamber and could starve the oil pick up.
A deeper sump can help but one on the market has holes that allow the oil in the sump to leak out again on whichever side is the outside at the time.
We make one with baffles and flap valves in (used with success in our BRSCC Boxster series) now in production and available soon - but this should be used with a lower oil fill level to avoid too much oil pumping up into the breather system.
Regarding prices etc - I think a high mileage 996 or Boxster could be worth considering in one way and that is that really most older Porsches that people keep for ever and become classics have an engine rebuild at some stage and actually they are less expensive to rebuild that an air cooled or 944/968 air cooled engine (like for like). If the various weaknesses can be fixed at the samel time - it could make a lot of sense especially to people who can remove and replace the engine themselves - where rebuild prices actually start @ just over £2K + Vat (although more like £3 to £3.5K with various extras - but still good value).
Baz
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