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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 495
Location: Scotland


PostPosted: Mon Nov 11, 2019 11:47 am    Post subject: Reply with quote

Ian I do not come here to "debate" I leave that to the politicians....look where that gets us..!!! (-:

I come here to learn, and boy have I learned a lot...THANKS... Trying to remember any or all of it is the hard part.. Duh!

Seems obvious that the inefficiency of the AOS system is the issue with the DI engines...Quite where Porsche or anyone else might go with that who knows..?

Seems taking a step back might be the next step forward... if you get what I mean... ? (-:

IF the inlet tract and valves HAVE to be de-coked at circa 70k miles to overcome a considerable drop of in efficiency (?)... Forgive me but that does not seem to be...err...terribly efficient..?

The idea that spark plug threads are required to project into the combustion chamber for some reason seems to hint at cost cutting in the design process...?

So the exposed threads pick up carbon, which causes problems when trying to remove the spark plugs..?

How so, would seem to be the next question..? On trying to remove the plugs does the carbon jamb in the cylinder head threads risking damage to them as opposed to the harder material of the spark plug threads..?

Is the process for removal one of working the plugs back and forward to try to release the carbon from the exposed threads allowing the spark plug to be removed and the freed off carbon to end up where ..???

I guess my simplistic thought processes might lead me to add a couple of extra compression washers to the spark plug to ensure that the threads did not end up in the combustion chamber to collect carbon deposits...

Another rather obvious thought might be that perhaps Porsche engineers decided for that the best performance outcomes the PRECISE point at which the spark MUST be generated is in the present position in the combustion chamber...? IF that were the case, the exposed threads that seem to hold carbon so well, could be removed from the spark plug body and that area of the spark plug body smoothed off, similar to diesel pre-heat plugs..?

My thinking on the risks relative to the disruption to the engine ancillaries and bank balance involved in the de-coke process was more related to items that may be broken or damaged to get at the inlet tract, the stuck injector being one example, but it seems to me that water cooled Porsches have rather a lot of gubbins that requires to be disturbed, unbolted, unplugged and removed, compared to simpler designs of the past..Shrug..! Jeez even one electrical connection on a sensor disturbed, can cause issues, let alone a broken/corroded bolt or stud....?

All that aside... on using compression via a slow turn on the engine.... As you guys know I have never put hands on a water cooled 911, but I have used pressure to remove and replace valve springs on a Porsche engine to avoid removing the head, I think I explained the process some time back on this forum.. Combine that with an injector imitating a missile mentioned previously, and it seems possible that a bit of thinking out of the box might be worth a try...ONLY if the forces in play are WELL understood...

Compressed air can be used to start diesel engines the size of a house, so spitting out an injector seems a possibility, as to how that process might be controlled.... there may be ways and means worth trying...? (-:

Ian, if you are reading this, I am flattered, please take no time to reply to my innate ramblings.... I am as ever just thinking in type, in an attempt to keep my brain from seizing up.. Old
 
  
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davidjf7
Imola


Joined: 21 Oct 2010
Posts: 787
Location: Hertfordshire


PostPosted: Mon Nov 11, 2019 12:23 pm    Post subject: Reply with quote

Interesting thread!

My 997.2 is now over 72k. Bought it at 20k 6.5 years ago, and having run another car for most of that period, have now made my 911 my daily, so the mileage is piling on.

Haven't noticed any loss of power or uneven running yet - fingers crossed.

DeMort - where is your Indy?
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7581
Location: Brighton


PostPosted: Mon Nov 11, 2019 7:57 pm    Post subject: Reply with quote

AOS is probably the best that can be made so its a case of live with it .. a small amount of oil is never going to be an issue .. erm .. well in this case and long term then perhaps it is ! it's still Porsche design though so it's what we have regardless .

Change debate to discuss .. just a mechanic here so i don't always get the correct wording Smile

de coke is what we used to do back in the day .. that was down to poor fuel and oil .. this is a new design that has designed the same fault into it ..

What we are trying to find out is what if any difference it will make and what we can do about it ... no facts as of yet .

The spark plugs are in that position for a reason .. i can only guess at that so we just deal with the end result ..

That being said these have been a problem to remove from 4 years old .. Boxster and 997 G2 ( DFI ) .. we undo .. do up .. undo etc to remove .. i've had one at 6 years ( missed plug change ) that i couldn't get them out at all .. did in the end but that's on another thread how i did it .

The cyls will have a certain amount of carbon in them .. a tiny amount from the plug threads makes no difference .. it will just get blown out with the exhaust .

Carbon to the point of a build up jamming a piston , snapping a chain .. yup i've seen it once .. not on a DFI car though .. G1 cayman .. never did get to the bottom of the reason for that but it was certainly due to an excessive amount of carbon build up on the piston crown .

Compression to remove it .. we considered all options and an engine drop was the best in the circumstances .. a long answer to go into the reason though and time is limited so forgive me there for not explaining it Smile
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 495
Location: Scotland


PostPosted: Mon Nov 11, 2019 8:49 pm    Post subject: Reply with quote

I hoped to raise questions for others to consider Iain, and not to elicit answers directly from you...

I will cease and desist on this topic.. BTW there is no such person as JUST a mechanic...!!!

As well as being a highly skilled mechanic/technician you are also a teacher with rather large pupil numbers in your cyber class... worship
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7581
Location: Brighton


PostPosted: Mon Nov 11, 2019 9:08 pm    Post subject: Reply with quote

lol .. bless you .. but you can ask any questions you like and i'll do my best .. time is the enemy here though .. never enough of it .. and with that i bid you goodnight !!!
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My Daughter's Crowdfunding has hit the target .

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She's not going until july 2020 though .



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lk993
Monza


Joined: 06 Mar 2008
Posts: 157



PostPosted: Tue Nov 12, 2019 6:48 am    Post subject: Reply with quote

Mr De Mort, thank you for your input, for me this sort of mechanical / technical side of things is an very interesting aspect of a forum.

Dare I ask, are or will these issues be the same for the 991.2 series of engines? (Carbon build up and spark plug protrusion)
 
  
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davidjf7
Imola


Joined: 21 Oct 2010
Posts: 787
Location: Hertfordshire


PostPosted: Tue Nov 12, 2019 10:12 am    Post subject: Reply with quote

I'm using this thread as an excuse to use more of my rev range than usual

Cop
 
  
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James M-S
Suzuka


Joined: 11 Apr 2017
Posts: 1111
Location: Derbyshire

2009 Porsche 997 Carrera 2

PostPosted: Tue Nov 12, 2019 11:11 am    Post subject: Reply with quote

davidjf7 wrote:
I'm using this thread as an excuse to use more of my rev range than usual

Cop
Grin
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Phil 997
Le Mans
Le Mans


Joined: 05 Dec 2015
Posts: 15566
Location: Bournemouth,Dorset

2009 Porsche 997 Carrera 4S

PostPosted: Tue Nov 12, 2019 2:31 pm    Post subject: Reply with quote

davidjf7 wrote:
I'm using this thread as an excuse to use more of my rev range than usual

Cop


Floor Floor Floor
_________________
911 Owners,Some Invest In The Future,
Others Enjoy The Moment Today.
 
  
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FZP
Estoril


Joined: 18 Jan 2015
Posts: 3872
Location: Cheshire


PostPosted: Tue Nov 12, 2019 4:06 pm    Post subject: Reply with quote

Phil 997 wrote:
davidjf7 wrote:
I'm using this thread as an excuse to use more of my rev range than usual

Cop


Floor Floor Floor

Since when does one need an excuse Bandit
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997.2 Carrera 2S GT Silver/Cocoa.
 
  
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Hertsdriver
Nürburgring


Joined: 12 Nov 2018
Posts: 469
Location: Hertfordshire/London

2004 Porsche 997 Carrera 2

PostPosted: Tue Nov 12, 2019 4:41 pm    Post subject: Reply with quote

Am I being naive or just stupid in my assumption that if the coke build up is very bad on the piston crown, and the combustion area in the cylinder head, then this could result in a potentially fatal increase in compression ratio if not cleaned? Dont know
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7581
Location: Brighton


PostPosted: Tue Nov 12, 2019 7:50 pm    Post subject: Reply with quote

lk993 wrote:
Mr De Mort, thank you for your input, for me this sort of mechanical / technical side of things is an very interesting aspect of a forum.

Dare I ask, are or will these issues be the same for the 991.2 series of engines? (Carbon build up and spark plug protrusion)


This will affect any car that uses direct fuel injection and as people have said .. BMW / Mini already offer a cleaning service with these engines ..

Porsche don't though .. access is very limited hence we are trialing different methods in an attempt to come up with a solution to clean these .

spark plugs .. i've not had a problem with 991 yet but i'm afraid i don't often service cars so haven't changed many .. they do come out on the DFI engines but it's a bit of a struggle on G2 997 / 987 .




Hertsdriver wrote:
Am I being naive or just stupid in my assumption that if the coke build up is very bad on the piston crown, and the combustion area in the cylinder head, then this could result in a potentially fatal increase in compression ratio if not cleaned? Dont know


This affects the valves .. the piston crown / cyl head will be the same as any other car and as such will have a normal amount of carbon build up .. But if you are cleaning the valves then it makes sense to do the same to the cylinders Smile

main issue .. no fuel injected into the inlet track .. its injected into the cylinder direct so there is no fuel to clean the valves .. hence the carbon build up .

Also .. a carbon buildup in a cyl .. it won't affect compression ratio but if it gets to a sensible amount it will end up jamming a piston .. carbon does not compress very well .. to much on a piston crown and it will hit the head putting a lot of strain on the timing chain .. end result is it will snap .


Seen it once and that's since these engines came out .. so about 10 years and once ! .. already mentioned it above but that was on a G1 cayman and i never found the reason for the carbon build up .

In short .. don't worry about this for now .. work in progress and we will give an answer when we have one .

Trust me .. when i think there's a problem .. ie G2 tensioners then i post about it ...... a lot Very Happy
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My Daughter's Crowdfunding has hit the target .

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 495
Location: Scotland


PostPosted: Wed Nov 13, 2019 2:41 pm    Post subject: Reply with quote

OK, OK...so I promised not to post any more on this thread...Apologies Ian.. But this link kinda saves reading rather a lot...?

https://www.youtube.com/watch?v=PS8riAae_bM


Job done Iain.. Question

Last edited by Luddite on Wed Nov 13, 2019 7:29 pm; edited 1 time in total
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7581
Location: Brighton


PostPosted: Wed Nov 13, 2019 7:02 pm    Post subject: Reply with quote

Can you edit your post and add this link and not the very large one please Smile


https://www.youtube.com/watch?v=PS8riAae_bM
_________________
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My Daughter's Crowdfunding has hit the target .

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 495
Location: Scotland


PostPosted: Thu Nov 14, 2019 10:02 am    Post subject: Reply with quote

Again, apologies to Ian.... Knowing you are not keen on diesel engines you may not have come across the work Cummins have put into AOS efficiency improvements, but then diesel engines have been using direct injection for rather longer than petrol....

https://www.cumminsfiltration.com/eme/opencvfilters

I guess the Porsche AOS would have been thought efficient enough till bore score issues showed up and pushed the AOS beyond it`s initial design capabilities to some degree....? Perhaps with the 997.2 the bore scoring issue has been hopefully resolved, though with the introduction of Direct Injection, perhaps it might be worth revisiting AOS design in search of improvement after all... hmm..?

No response required, just thinking in type..
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7581
Location: Brighton


PostPosted: Thu Nov 14, 2019 8:11 pm    Post subject: Reply with quote

Let's just say i started life as an apprentice on trucks .. British Telecom is where i started life .. 22 mechanics in the workshop .. a very large operation ..

You couldn't breath in the workshop in the mornings when we had to run them to get the air brakes off !!

Government said these were better for the planet than petrol at the time .. boy how we laughed .. shame we were proven true and the manufacturers stopped work on the lean burn engines at the time .. perhaps governments should try talking to the people that know about these things instead of just bringing in regulations ..

But as usual i digress ..

AOS and we are stuck with it .. there is no other alternative ..

This brings me to my main point here .. we have been discussing this at work .. obviously ...

it's not the oil that actually causes this .. there is always a fair amount of it in any inlet track on porsches .. probably more than most people realise ..

It's the contaminants in the oil ..

Going to say that again .. the debris for want of a better word in the oil that collects on the valves due to no fuel injection to help wash it off .

Why .. well perhaps we have gone full circle .. perhaps a 2 year oil change at circa 20K miles is not helping this ..

we are kinda leaning towards a one year oil change .. which is already done in other markets will help reduce this effect .

it's just a thought .. but it's a logical one .

bore score is a separate issue from this with different reasons and hartech can explain this and has already done so far better than i can .

Thanks for altering the link .. i do hate the oversized pages after a long link has been added Thumb
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My Daughter's Crowdfunding has hit the target .

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7581
Location: Brighton


PostPosted: Fri Nov 15, 2019 7:10 pm    Post subject: Reply with quote

A few pictures of the original gun we used and then the new gun which is far more versatile .. you need to get it at many different angles so this should help .

The original adaptor to fit the hoover and walnut gun on was made out of an existing inlet manifold we cut up .. the new adaptor is a custom made 3D printed one ..

Have to admit this 3D printing is pretty damn clever .. made to our measurements and will make hoovering out the old shells far easier.

Picture also of the walnut we use .. as you can see it's pretty much granules .

we have a chemical one to try which once used you spray some magic stuff and it dissolves anything that's left in the cyl / inlet manifold .

Trialing everything basically to see whats best .
_________________
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My Daughter's Crowdfunding has hit the target .

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

7pm - 9pm

Now At An Indy.
 



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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7581
Location: Brighton


PostPosted: Wed Nov 20, 2019 9:15 pm    Post subject: Reply with quote

Some news on this front ..

The demo of the first machine didn't turn out as well as expected .. we will have to drive the car for 100 miles and then strip it again to see what if any difference has been made , that's what we have been told anyways ... first strip after 1.5 hrs cleaning .. well no point posting pictures to be honest but we will see .

we all live in hope .

Plus side .. the customer we did the walnut clean when the engine was dropped ..

His report ..

Idle is a lot better ..

Performance seems sharper ..

The engine feels tighter .. his words ..

Mpg is difficult but he felt it was less .. hard to explain this but its subjective to how its driven .. i get the feeling he doesn't push the car to its limits but either way .. this is what he said .

Engine feels tighter is what i think is the difference as i take that to mean closer to a new engine .

We are atm going down the walnut clean route , after a guinea pig atm .. one person in mind .

we have another machine to demo but as they work on similar principles then i'm not convinced atm .. preventative and cleaning seem to be different things .. imho but we will see.

Over all im a bit disappointed but it's still early days .. things like this do tend to take a while im afraid but we will get to the bottom of it .

just IMHO and from what i have seen , i'm sure these machines have a purpose and im unqualified to say either way , as a preventative or a means to stop this if used regularly then im sure they are fine .. my problem is it doesn't seem to clean the system when it is bad ... we still need to do 100 miles though .
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My Daughter's Crowdfunding has hit the target .

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 495
Location: Scotland


PostPosted: Sat Nov 23, 2019 4:42 pm    Post subject: Reply with quote

Thanks for the heads up Ian.... Thumb
 
  
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