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997 DFI valves coking up / injector fault .

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

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

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

:cop:

:floor: :floor: :floor:
 
Phil 997 said:
davidjf7 said:
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:
 
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:
 
lk993 said:
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 said:
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 :)

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 :D
 
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..
 
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:
 
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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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 .
 
After this post was used in a current topic i felt it best to explain why i have not as of yet continued this ..

If you look at the date then you can see that a few months after this the world turned to crap .. we lost 4 members of staff and are still running on little more than a skeleton crew .. we are managing as always and hoping to replenish our numbers soon , work has been very busy and unlike normal years there has been no slow down .

In which case with more staff projects such as this and a few others can continue .

For now a walnut clean is the best we have found but that involves an engine drop .. more time and we hope to find a better solution .

Thank you for reading .
 

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