Bore scoring on refurbished engine
Discussion
mollytherocker said:
It's due to various crap materials and a poor block design in terms of coolant flow management isn't it?
Yes poor thermal efficiency and a weaker bottom end hence all Higher output variety's use mezger still (inc current 991 RSR)Manufactured for a third of the cost too.
Gary11 said:
mollytherocker said:
It's due to various crap materials and a poor block design in terms of coolant flow management isn't it?
Yes poor thermal efficiency and a weaker bottom end hence all Higher output variety's use mezger still (inc current 991 RSR)Manufactured for a third of the cost too.
itsybitsy said:
yes but the 997.2 turbo is in excess of 500bhp and the 991 turboS has 560 hp on the dfi lump not the mezger!
Very true but is redesigned and only similar not the same as earlier engine and has no longevity/reliability data yet time will tell,its not used in any competitive cars ASFAIK.Gary11 said:
itsybitsy said:
yes but the 997.2 turbo is in excess of 500bhp and the 991 turboS has 560 hp on the dfi lump not the mezger!
Very true but is redesigned and only similar not the same as earlier engine and has no longevity/reliability data yet time will tell,its not used in any competitive cars ASFAIK.itsybitsy said:
yes not the same as m96/7 engine hence porsche is using the basic but improved dfi(ie crank, rods etc) as the base for new gt3.but as far as i am aware the turbo is the same as 3.8 n/a dfi
Only on the road car surprisingly AFAIK the competition cars still use the Mezger unit I dont understand the homologation implications for Le Mans etc.
hartech said:
Sorry guys will reply to all questions next Monday too much on this week good questions though need some time to reply to hope you can be patient regards Baz
Baz any chance you could answer some of the outstanding questions im thinking of having the ims bearing upgraded but would like your views on this before I proceedTrying to catch up now so here are a few answers - sorry for the delay.
Regarding the wisdom of fitting a replacement IMS bearing when there are no signs of it failing - there has been a lot posted on here under the topic "IMS bearing sellers" that I would only have to repeat and it might be easier for you to get a balanced view of things to read that first (and save me some time as well!).
Mt view is that the statistics make it very unlikely to fail in your ownership and as it is expensive to replace - may be worth risking - but better still to get some insurance/warranty type cover (there is a lot available) of which our Lifetime Maintenance Plan is one. You will find on that posting some controversial responses and arguments about our policy on this - because we are trying to take a responsible position to the difficulty of customers fitting our kit (by not putting it on general resale) which others seem incensed about!
Regarding the 3.4 and bore scoring - most of the 3.4 engines had a different piston coating that was phased out (we understand due to health and safety reasons) and it has not re-appeared and we cannot get it reproduced anywhere. That original coating was also used on the 924S, 944 range and 968's running with Alusil.
It looks like Lokasil is probably either more aggressive or less able to retain the hard crystals - so needs the best possible piston coating to survive.
Various plastic coatings (sprayed on or screen printed on) replaced the original ferrous coating only in the last few 3.4's manufactured.
The earlier ones with the earlier pistons we have not seen score any bores but the later ones (or any early ones fitted with later pistons) have but rarely.
At the same time as fitting the newer pistons with the less durable coating the engine sizes and loads of later cars increased and the coolant volumes reduced - thus exacerbating the situation and therefore not really surprised they fail.
We are testing different piston coatings to try and find one that would enable us to re-bore Lokasil and save everyone the costs of new Nikasil cylinders - but it will take time to conclude if there is an alternative or if the only viable option is to fit Nikasil cylinders. Getting such special pistons manufactured, fitting and testing them for enough miles then stripping, inspecting and analysing - is an enormous task and unfortunately takes time - very frustrating but someone needs to do it to bottom this issue and find the final answers.
Regarding collection and delivery - if you are on our Maintenance Plan most rescue organisations will deliver a non-runner up here FOC (but worth checking first).
I do think a general 5% failure rate is about right but I think it will increase with time as mileages increase and values fall making the need to viable rebuild options more important in the future. Fortunately buying prices seem to reflect the concern and partially compensate for the risk.
This is however 5% over several owners so say 5 owners = 1% chance in one ownership and then only about 2% seem to be IMS failures - so quite a low risk indeed. Whereas cylinder bore scoring or cracking is inevitably linked to loads and mileages - the IMS bearing that lasts say 60K may well then last longer because the seals that originally kept the oil out and the metallic debris in - wear - increasing oil in and debris out so the percentages may get better with time for a few years.
It is impossible for a small business like ours (or probably even for Porsche) to absolutely test every potential cause of bore scoring and all the remedies to establish the exact causes. It is necessary to apply some automotive engineering experience to each possible potential cause to see if there is a greater or lesser likelihood of that being more or less significant.
We originally put our thoughts about causes on the Internet over 10 years ago together with our suspicions for the future and so far have not been found wanting but there is still a lot to research and understand - especially the reports of newer Alusil engines scoring bores that seem quite ominous.
As always I will share my thoughts and findings with those that value it (despite the unwarranted attacks by those not involved or qualified that think they know better).
If I have missed answering any other points raised please ask again and I will do my best to help.
Baz
Regarding the wisdom of fitting a replacement IMS bearing when there are no signs of it failing - there has been a lot posted on here under the topic "IMS bearing sellers" that I would only have to repeat and it might be easier for you to get a balanced view of things to read that first (and save me some time as well!).
Mt view is that the statistics make it very unlikely to fail in your ownership and as it is expensive to replace - may be worth risking - but better still to get some insurance/warranty type cover (there is a lot available) of which our Lifetime Maintenance Plan is one. You will find on that posting some controversial responses and arguments about our policy on this - because we are trying to take a responsible position to the difficulty of customers fitting our kit (by not putting it on general resale) which others seem incensed about!
Regarding the 3.4 and bore scoring - most of the 3.4 engines had a different piston coating that was phased out (we understand due to health and safety reasons) and it has not re-appeared and we cannot get it reproduced anywhere. That original coating was also used on the 924S, 944 range and 968's running with Alusil.
It looks like Lokasil is probably either more aggressive or less able to retain the hard crystals - so needs the best possible piston coating to survive.
Various plastic coatings (sprayed on or screen printed on) replaced the original ferrous coating only in the last few 3.4's manufactured.
The earlier ones with the earlier pistons we have not seen score any bores but the later ones (or any early ones fitted with later pistons) have but rarely.
At the same time as fitting the newer pistons with the less durable coating the engine sizes and loads of later cars increased and the coolant volumes reduced - thus exacerbating the situation and therefore not really surprised they fail.
We are testing different piston coatings to try and find one that would enable us to re-bore Lokasil and save everyone the costs of new Nikasil cylinders - but it will take time to conclude if there is an alternative or if the only viable option is to fit Nikasil cylinders. Getting such special pistons manufactured, fitting and testing them for enough miles then stripping, inspecting and analysing - is an enormous task and unfortunately takes time - very frustrating but someone needs to do it to bottom this issue and find the final answers.
Regarding collection and delivery - if you are on our Maintenance Plan most rescue organisations will deliver a non-runner up here FOC (but worth checking first).
I do think a general 5% failure rate is about right but I think it will increase with time as mileages increase and values fall making the need to viable rebuild options more important in the future. Fortunately buying prices seem to reflect the concern and partially compensate for the risk.
This is however 5% over several owners so say 5 owners = 1% chance in one ownership and then only about 2% seem to be IMS failures - so quite a low risk indeed. Whereas cylinder bore scoring or cracking is inevitably linked to loads and mileages - the IMS bearing that lasts say 60K may well then last longer because the seals that originally kept the oil out and the metallic debris in - wear - increasing oil in and debris out so the percentages may get better with time for a few years.
It is impossible for a small business like ours (or probably even for Porsche) to absolutely test every potential cause of bore scoring and all the remedies to establish the exact causes. It is necessary to apply some automotive engineering experience to each possible potential cause to see if there is a greater or lesser likelihood of that being more or less significant.
We originally put our thoughts about causes on the Internet over 10 years ago together with our suspicions for the future and so far have not been found wanting but there is still a lot to research and understand - especially the reports of newer Alusil engines scoring bores that seem quite ominous.
As always I will share my thoughts and findings with those that value it (despite the unwarranted attacks by those not involved or qualified that think they know better).
If I have missed answering any other points raised please ask again and I will do my best to help.
Baz
Alex the answer is "probably" because the Nano oil releases better lubricating properties from the additives at higher temperatures and so IF the primary cause turns out to be localised hot spots and overheating of the oil in particular areas of the cylinders that damage the piston coating and/or Lokasil matrix - then that very feature will provide an additional protection. The difficulty is knowing if the critical temperature is as high as the temperatures that the Nano oil works best at.
My opinion is that it is and therefore is worthwhile doing but I doubt I will have the ability to think up a way to test this and it may require longer term testing and general feedback before I can confirm absolutely that benefit.
Baz
My opinion is that it is and therefore is worthwhile doing but I doubt I will have the ability to think up a way to test this and it may require longer term testing and general feedback before I can confirm absolutely that benefit.
Baz
I think the ideal scenario is to apply as many common sense items including altering driving style as you can ,plus as many upgrades as possible Im sure its got to be a good way forward.I havent heard of any "Improved repaired" units failing Im sure Baz and co would say if there were!
G
G
The problem with the Lokasil in the standard Porsche bore - in our experience and understanding - relates to variable preform quality, degradation, the change to "plastic coated" pistons and general distortion and ovality increasing blow by and piston temperatures - combined with high cylinder temperatures at some stages of driving age, mileage, driving styles, increases in engine capacity and output and ambient conditions etc.
I think the lowest mileage we have seen problems is under 17K and more often than not nearer 35 to 40K (although we know the scoring takes place many thousands of miles before it is obvious).
Crankcase halves should be matched so both sides should be new with a replacement bottom end but if anything else is not (pistons etc) that life expectancy would be shortened.
Alloy Nikasil cylinders that secure a machined location at the top of the block (converting it to a closed deck) will last much longer and pistons survive brilliantly running in Nikasil (that works even without a piston coating) , so that combined with changes to coolant systems etc should result in a much longer lasting repair.
If such a bottom end repair using st andard bores is done under warranty - I guess it is better than nothing or paying for it but given equal choice and similar cost - a properly rebuilt engine with alloy Nikasil top hat cylinders would always be likely to last longer.
Baz
I think the lowest mileage we have seen problems is under 17K and more often than not nearer 35 to 40K (although we know the scoring takes place many thousands of miles before it is obvious).
Crankcase halves should be matched so both sides should be new with a replacement bottom end but if anything else is not (pistons etc) that life expectancy would be shortened.
Alloy Nikasil cylinders that secure a machined location at the top of the block (converting it to a closed deck) will last much longer and pistons survive brilliantly running in Nikasil (that works even without a piston coating) , so that combined with changes to coolant systems etc should result in a much longer lasting repair.
If such a bottom end repair using st andard bores is done under warranty - I guess it is better than nothing or paying for it but given equal choice and similar cost - a properly rebuilt engine with alloy Nikasil top hat cylinders would always be likely to last longer.
Baz
Edited by hartech on Friday 19th September 20:30
Edited by hartech on Friday 19th September 20:31
Firstly I'll echo what Baz said you'll get all 6 bores new as both crankcase halves get replaced together, they are a matched pair, together with the pistons that are damaged. I think they change the rings on the non-damaged pistons as well.
Yes you should get another engine that has xK miles in it.
Yes you should get another engine that has xK miles in it.
I agree - I think a rebuild with Porsche cases must be better marginally than piling more miles on an existing engine - but the reason I mention our rebuilds is because using the comparisons of a rebuild without identifying that you are referring to a rebuild with standard Porsche cases in each post could confuse some readers into thinking you are comparing all rebuilds and since our rebuilds can eliminate ALL of the faults with the standard engines I listed above, I think it is only fair for me to point that out a Hartech rebuild should be even better still.
Baz
Baz
anonymous said:
[redacted]
Not too clear I'll admit, If your engine has done say 45K miles from new before it bore scores then you have every reason to expect the same again. Talking to our local OPC the rebuild from bore scoring is new cases (matched pair) replacement pistons for those in the scored bores. New rings (I think) & obviously new bearings & gaskets. So your engine has had the clock wound back. I'd expect a decent amount of miles from the rebuild. Once rebuilt I would then run heavier oil as recommended by Hartech for their rebuilds & would reckon on that postponing the bore scoring the second time around. In my 986 I already run a 15W/50 oil for the same reason.
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