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bazhart
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Joined: 20 May 2009
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Location: Bolton Lancashire


PostPosted: Wed Aug 10, 2011 5:19 am    Post subject: Reply with quote

The worst scoring is always on bank 2 and always on the top of the engine (the opposite side to gravity effects which have nothing to do with it). The thrust side on bank 2 is the top where the coolant is exiting the cylinder (hence also hottest).

The thrust side on bank 1 is at the bottom where the coolant enters and is therefore coolest and almost never has scoring.

Just another example of well meaning posts that through lack of proper knowledge of the engine seem to contradict my posts when actually they are not only wrong but the complete opposite is true.

The obvious answer would have been an electric operated pump at low engine speed and a thermostat on the top of the engine block plus a re-routing of the entry point of the coolant on bank 2 - but it is too late for any of this to be applied to existing engines - hence I have been trying to think of ways to help those who presently do not have scored bores - to keep it that way without any expense or modification.

Ignore this advice at your peril (and if you do ignore it - please bring the car to me to fix it).


Baz
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spectraluk
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Joined: 30 Mar 2010
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2004 Porsche 996 Carrera 4S

PostPosted: Wed Aug 10, 2011 8:11 am    Post subject: Reply with quote

Perhaps this thread should be a sticky....?? - MOD anyone?
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Red993C4
Magny-Cours


Joined: 09 Dec 2010
Posts: 2723
Location: S. Wales


PostPosted: Wed Aug 10, 2011 11:54 am    Post subject: Reply with quote

@Baz: Interesting theory. Your work on the failed engines has naturally prompted you to put a lot of thought into the causes and possible remedies and your extensive experience has provided you with the observations on which to build up a well-founded theory.
I do have a question on your advice to 996 drivers based on your conclusions, but want you to understand beforehand that I'm just trying to pick your brain and not pick holes in your theory.

Since we're talking about cars capable of 0-60 mph in around 5 seconds, the unfavourable conditions prone to causing cylinder scoring in the most endangered cylinders would not last very long at all if the driver opens the throttle wide in an appropriately low gear, as the increased coolant flow and oil spray jets would kick in very quickly (though maybe still not quickly enough).
Don't you think that a more dangerous scenario based on your theory might be if a driver (starting from the same conditions) were to open the throttle wide from a low road speed in too high a gear, so that the pistons would experience a high lateral thrust load for a much longer period without benefiting from increasing coolant and oil flow, due to the leisurely rate of acceleration?
This would mean that the advice should really be not to "flog" the engine by opening the throttle wide in too high a gear for the speed or incline, particularly with a hot engine.
It would also explain why tracked cars which are regularly subjected to wide open throttle from a standstill while hot do not appear, as far as I am aware, to be over-represented amongst those suffering from cylinder scoring.

As I said, I'm not questioning the validity of your theory. I'd just be interested to hear your views on this interpretation of the possible conclusions to be drawn from it.
 
  
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Wattie
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Joined: 05 Nov 2006
Posts: 5668



PostPosted: Wed Aug 10, 2011 12:24 pm    Post subject: Reply with quote

bazhart wrote:
The worst scoring is always on bank 2 and always on the top of the engine (the opposite side to gravity effects which have nothing to do with it). The thrust side on bank 2 is the top where the coolant is exiting the cylinder (hence also hottest).

The thrust side on bank 1 is at the bottom where the coolant enters and is therefore coolest and almost never has scoring.

Just another example of well meaning posts that through lack of proper knowledge of the engine seem to contradict my posts when actually they are not only wrong but the complete opposite is true.

Baz


OK, I was obviously wrongly informed regarding which bank suffered the scoring, but I was certain I was told it was the bank where the thrust stroke was at the 'bottom' of the cylinder (if you see what I mean)!

I am still unconvinced about the water theory though... Is it not likely that the scoring is simply a result of gravity reducing the amount of oil available for lubrication at the top of the cylinder, then? I understand that the material used for the cylinder liners is different in water-cooled engines and could explain why they suffer more than air-cooled engines, perhaps?

The reason I am sceptical is that I don't understand how the bore can be hotter in a water-cooled engine, than in an air-cooled (or oil-cooled, if you want to be really pedantic) engine? Surely the water won't be hotter than if it wasn't any water there at all?

Maybe I am wrong, but I did study engine thermodynamics as part of my Automotive Engineering degree (albeit many years ago) and I am struggling to understand the physics here!

Either way - not thrashing the engine when there is insufficient oil pressure sounds like a good strategy to me!
 
  
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pawmaro
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Joined: 24 Apr 2011
Posts: 27



PostPosted: Mon Sep 12, 2011 6:25 pm    Post subject: Reply with quote

Buy a mercedes
 
  
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Maxie
Yas Marina


Joined: 11 Mar 2007
Posts: 8386
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PostPosted: Mon Sep 12, 2011 7:08 pm    Post subject: Reply with quote

pawmaro wrote:
Buy a mercedes


Well done, is that what you did?

~ Maxie wack
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GT4
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PostPosted: Mon Sep 12, 2011 7:43 pm    Post subject: Reply with quote

Maxie wrote:
pawmaro wrote:
Buy a mercedes


Well done, is that what you did?

~ Maxie wack


I think that's what he wish he'd done.

Just not an SL55 AMG circa 2005 nooo
 
  
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pawmaro
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Joined: 24 Apr 2011
Posts: 27



PostPosted: Fri Sep 23, 2011 8:51 pm    Post subject: like a racehorse Reply with quote

Yes nurtured never ranted from cold but still engine knackerd at 50k and no goodwill from Porsche. No warning just check engine light and a smoky left hand bank. Bloody rubbish now not like they used to be
 
  
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The Beast
Suzuka


Joined: 28 Jul 2010
Posts: 1159



PostPosted: Sat Sep 24, 2011 1:07 pm    Post subject: Reply with quote

Always a pleasure to hear you Baz.

All those who have experienced the exceptional quality of your rebuilt units can affirm that your experience in engine design means great gains for the owners of such cars.

After over 4000 miles (not including the oil change after 2000 mi run in) I have not needed to top up the oil, the temperature runs steadily at 80 even when going (not) full tilt up at 165 leptons, and the car purrs and gently whines as all those handbuilt cogs tooth and spool in tight lockstep after precision manufacturing from Hartech.

Speaking from experience, though, I must also say that it is a sorry state of affairs that Porsche have been stumped on build quality, and that all these years later there is no admission of the faults inherent in these engines. One expects issues in older cars but those younger 997's? Such a shame.

I have now passed on from the Porsche fraternity. ELA is the new owner and I can tell you he is very happy with his new unit - no Porsche Paranoia Syndrome for him!

It is a pleasure to have made your acquaintance Baz..



bye
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wizard993
Donnington
Donnington


Joined: 23 Jan 2008
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PostPosted: Sat Sep 24, 2011 2:45 pm    Post subject: Reply with quote

http://www.fvd.de/us/en/Porsche-0/-/-/-/item/item_details/VID_35299833-VCD_49660164-gid_256-sort_4-display_50-item_FVD10603700/ENGINE_-_Spare_Parts_-_Water_System-FVD10603700-997_Center_Radiator_Kit.html

If I had a manual 997 and planned to keep it for a while, I'd be giving this some serious thought.
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Xstyle
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Joined: 23 Dec 2011
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PostPosted: Fri Jan 13, 2012 11:05 pm    Post subject: Reply with quote

wizard993 wrote:
http://www.fvd.de/us/en/Porsche-0/-/-/-/item/item_details/VID_35299833-VCD_49660164-gid_256-sort_4-display_50-item_FVD10603700/ENGINE_-_Spare_Parts_-_Water_System-FVD10603700-997_Center_Radiator_Kit.html

If I had a manual 997 and planned to keep it for a while, I'd be giving this some serious thought.

Any further thoughts Baz?
 
  
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bazhart
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Joined: 20 May 2009
Posts: 1016
Location: Bolton Lancashire


PostPosted: Sat Jan 14, 2012 6:44 am    Post subject: Reply with quote

An extra radiator can only benefit if the thermostat opens at a lower temperature and then only if the ambient conditions are too hot for the std set up to cope.

Otherwise it makes no difference.

Baz
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bg259
Trainee


Joined: 29 Nov 2008
Posts: 80



PostPosted: Sun Apr 08, 2012 7:13 am    Post subject: Reply with quote

Baz, so what about a thermostat that opens at a lower temperature? Most open at about 87 deg Celsius if i remember rightly? On doing a little research
I found that gen2 cars thermostats open at a much lower 80 dec Celsius thermostat? And turbos even lower? Could this help these engine woes???
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GT4
Nordschleife
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Joined: 08 Nov 2008
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Location: Hertfordshire and Hampshire


PostPosted: Sun Apr 08, 2012 10:55 am    Post subject: Reply with quote

eh!

I think you'll find he's been fitting (and pioneering, certainly in the UK) that solution for years.

Has your grandmother ever eaten eggs?
 
  
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tregger
Österreich


Joined: 02 Jan 2010
Posts: 962
Location: pendle/lancs


PostPosted: Sun Apr 08, 2012 12:21 pm    Post subject: Reply with quote

GT4 wrote:
eh!

I think you'll find he's been fitting (and pioneering, certainly in the UK) that solution for years.

Has your grandmother ever eaten eggs?


perhaps a low thermostat could be retrofitted to your tolerance level Wink Laughing Laughing
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GT4
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PostPosted: Sun Apr 08, 2012 2:17 pm    Post subject: Reply with quote

It already has, but I still lose the HG when someone drains all the coolant.


Before I release my newest world-shattering discovery about the properties of mouldy bread on infected wounds, I might do some due diligence on prior works.
 
  
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ChrisW_Photographer
Newbie


Joined: 20 Nov 2012
Posts: 8



PostPosted: Wed Nov 21, 2012 3:39 pm    Post subject: Reply with quote

GT4 wrote:
Yet another reason not to buy a London car!



OH NO!! I've just bought a London car!! Does that mean I'm pretty much screwed!? Surprised The low 22000 miles on the clock that I bought the car for won't even help if this is all true!!
 
  
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floatingkiwi
Newbie


Joined: 06 Oct 2012
Posts: 38



PostPosted: Thu Dec 20, 2012 8:26 pm    Post subject: Reply with quote

I haven't heard any discussion vis 5w-40 instead of 0w-40 or castrol instead of mobil in this debate? Thoughts?

Matt
 
  
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GT4
Nordschleife
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PostPosted: Thu Dec 20, 2012 10:04 pm    Post subject: Reply with quote

"Don't go there" Dont know
 
  
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Zantaz
Suzuka


Joined: 14 Apr 2012
Posts: 1161



PostPosted: Thu Dec 20, 2012 10:48 pm    Post subject: Reply with quote

ChrisW_Photographer wrote:
GT4 wrote:
Yet another reason not to buy a London car!



OH NO!! I've just bought a London car!! Does that mean I'm pretty much screwed!? Surprised The low 22000 miles on the clock that I bought the car for won't even help if this is all true!!


Relax.....if you had a PPI/111 point check carried out as part of your purchase then it should highlight any problems that need to be addressed.

Check out Baz response on the 1st page...he provided a good analogy to how to deal with your car that could prevent this from happening.

"I like the analogy with an athelete/sportsman - warm up - then perform - then cool down progressivley - the trouble is you cannot avoid stopping when the lights are red, the junction is busy or the traffic in fron just stops - but you can avoid flooring it imediatley it the congestion free's up - just a suggestion"

You've got yourself a sweet mileage 997, the engine problem has occurred in a small number of 997's manufactured. Enjoy it, don't sweat it.
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