997 Gen 2 DFI Engines - Woes finally sorted?

997 Gen 2 DFI Engines - Woes finally sorted?

Author
Discussion

mollytherocker

Original Poster:

14,348 posts

175 months

Friday 6th May 2011
quotequote all
Do these engines mark the end of the much discussed weaknesses, i.e; liner cracking, bore scoring and IMS failures?

Can we now buy with confidence?

Or is it too early to conclude? Is coking up a real issue on these engines?

MTR

drmark

3,807 posts

152 months

Friday 6th May 2011
quotequote all
No coking it is not a real issue because there has yet to be one confirmed case of it happening - despite lots of dire predictions on this forum. That said, it is still early days and only time will tell.
Prepare for the stampede of clairvoyants...

shoestring7

5,948 posts

212 months

Friday 6th May 2011
quotequote all
If you're really worried, the 2.9l Cayman/Boxter uses the new engine without Direct Injection.

SS7

HoHoHo

14,850 posts

216 months

Friday 6th May 2011
quotequote all
If you're really worried

a) Don't buy one
b) If you do, get a warranty

Either way it then doesn't matter.

mollytherocker

Original Poster:

14,348 posts

175 months

Friday 6th May 2011
quotequote all
I am not worried. I am interested in whether these engines have finally been 'fixed'.

MTR

HoHoHo

14,850 posts

216 months

Friday 6th May 2011
quotequote all
mollytherocker said:
I am not worried. I am interested in whether these engines have finally been 'fixed'.

MTR
I don't know the answer to that (not that you expect me to wink )

But what I do know is that regardless of real world statistics, the scaremongerers (word?) will find a reason to make everybody st themselves about their P&J going bang.

Personally I'm bored of reading threads with people asking questions about if their car will either lose money or go pop. Cars will always lose money and some engines will go pop. It would be interesting to know what the real world percentage is of 996/997 engines that have had the faults we all assume our own cars have. One thing to bear in mind is the cost of the warranty is not very expensive and if Porsche were replacing loads of engines and whatever else that keeps breaking, it would be a whole lot more than it is.

I'm not having a dig at you Sir, and I think we should start a 'My car is really reliable, and I love it' thread!

mollytherocker

Original Poster:

14,348 posts

175 months

Friday 6th May 2011
quotequote all
HoHoHo said:
mollytherocker said:
I am not worried. I am interested in whether these engines have finally been 'fixed'.

MTR
I don't know the answer to that (not that you expect me to wink )

But what I do know is that regardless of real world statistics, the scaremongerers (word?) will find a reason to make everybody st themselves about their P&J going bang.

Personally I'm bored of reading threads with people asking questions about if their car will either lose money or go pop. Cars will always lose money and some engines will go pop. It would be interesting to know what the real world percentage is of 996/997 engines that have had the faults we all assume our own cars have. One thing to bear in mind is the cost of the warranty is not very expensive and if Porsche were replacing loads of engines and whatever else that keeps breaking, it would be a whole lot more than it is.

I'm not having a dig at you Sir, and I think we should start a 'My car is really reliable, and I love it' thread!
I appreciate and respect that you are not interested in this topic.

I am though from a technical point of view, and I would imagine that many other Porschefiles are too.

MTR

HoHoHo

14,850 posts

216 months

Friday 6th May 2011
quotequote all
mollytherocker said:
HoHoHo said:
mollytherocker said:
I am not worried. I am interested in whether these engines have finally been 'fixed'.

MTR
I don't know the answer to that (not that you expect me to wink )

But what I do know is that regardless of real world statistics, the scaremongerers (word?) will find a reason to make everybody st themselves about their P&J going bang.

Personally I'm bored of reading threads with people asking questions about if their car will either lose money or go pop. Cars will always lose money and some engines will go pop. It would be interesting to know what the real world percentage is of 996/997 engines that have had the faults we all assume our own cars have. One thing to bear in mind is the cost of the warranty is not very expensive and if Porsche were replacing loads of engines and whatever else that keeps breaking, it would be a whole lot more than it is.

I'm not having a dig at you Sir, and I think we should start a 'My car is really reliable, and I love it' thread!
I appreciate and respect that you are not interested in this topic.

I am though from a technical point of view, and I would imagine that many other Porschefiles are too.

MTR
No problem wink bye byebye

JLJ

402 posts

196 months

Friday 6th May 2011
quotequote all
HoHoHo said:
If you're really worried

a) Don't buy one
b) If you do, get a warranty

Either way it then doesn't matter.
How dare you offer such sound and practical advice on a thread of this nature! Do you know nothing about these types of threads?? Either re-post, using an appropriate measure of panic and impending engine related doom, or go elsewhere. wink

Ian_UK1

1,495 posts

160 months

Friday 6th May 2011
quotequote all
HoHoHo said:
Either way it then doesn't matter.
If these engines coke-up like other DFI engines, yes it bl**dy does matter! I don't want a car that only makes 300BHP in a couple of years time because of the valves being choked with crap and Porsche doing a 'What problem sir...'? I'll put good money on Porsche NEVER decoking one of these engines under warranty.

For the moment, this whole topic is on hold until I get (or someone else gets) a borescope down the inlet tract of one of the DFI engines and we can assess the extent of the coking problem. There will be one as all DFI engines (and Diesels) have this issue to a greater or lesser extent - it's just a case of how much and what effect it has on the engine's output.

As for the machanical issues - yes the DFI engine seems to have cured all the previous generation's ills. Anecdotally, there's no tales of woe on forums across the world and technically, they addressed all the right parts of the engine. Below are some excerpts from the Porsche Technical manual about relevant changes to the new engines:

Engine
A totally redesigned generation of engines is used for the new 911 models. As on
the previous model, these engines have a different displacement -
a 3.6-litre flat-six engine is used on the 911 Carrera, while the 911 Carrera S has a
3.8 litre flat-six engine.
Although the displacement is the same as on the previous models, the performance
and torque have been increased significantly, while fuel consumption is reduced by
approx. 15%.
This was primarily achieved through the use of direct fuel injection (DFI), by reworking
the intake and exhaust system and by improving the engine internally in order
to reduce friction and drive losses. By reducing the oil pan height, it was possible to
lower the installation position of the engines by approx. 10 mm, thereby lowering
the vehicle’s centre of gravity and improving driving dynamics.

Crankcase
The new 911 models feature a two-part, vertically split crankcase with an integrated
crankshaft thrust block. The advantage of this design is that smaller components
can be used, while the separate bearing saddle with cast-in cast iron elements is no
longer needed, thereby reducing the overall weight of the engine.
The actual crankcase on the new 911 engines is made completely of an aluminiumsilicon
alloy (ALUSIL).
This procedure offers the following advantages:
• With ALUSIL, the crankcase can be made from one cast, without cylinder
sleeves and without having to coat the cylinder bores afterwards.
• ALUSIL is an excellent heat conductor and thus allows high specific engine
output values.
• ALUSIL has excellent friction properties. Since the pistons and piston rings
slide on the exposed silicon crystals, they have a low tendency to seize.
• ALUSIL does not present any recycling problems because the crankcase
does not include any foreign materials, e.g. cast-in cast iron cylinder sleeves.
The listed advantages of the alloy are certainly important arguments in its favour.
Indeed, the low-pressure chill-casting procedure, which has since proved to be the
best solution by far for casting ALUSIL, is an important prerequisite for reliable,
mass-produced crankcase cast parts.
Cylinders are now connected differently in the cylinder-head cover area. The individual
cylinders, which originally stood freely in the water jacket (open deck design),
are now connected by a closed cylinder deck (closed deck design). The advantage
of this design is high cylinder stability, particularly the cylinder shape (roundness
and low cylinder deformation) over a wide load and temperature range. This has the
added advantage of reducing friction and thus reducing fuel consumption. Even
piston and piston-ring sealing has been improved as a result of the higher retention
of roundness of the cylinders. The entry of oil from the crankcase into the combustion
chambers and the entry of the fuel-air mixture from the combustion chambers into
the crankcase is reduced. This both improves consumption and reduces performance-
inhibiting overpressure caused by blow-by in the crankcase.

Crankshaft/crankshaft bearings
The drop-forged crankshaft runs in eight bearings and has twelve counterweights.
Main bearing 4 is designed as a thrust bearing. Axial play is determined by two
thrust plates, which are inserted at the left and right of the bearing.
The main bearings are designed as plain bearings with a diameter of 63 mm. Main
bearings 1/3/5/7/8 are smooth bearings, while main bearings 2/4/6 are grooved
bearings. These grooved bearings supply oil to the lubrication points of the crankshaft
bearings.
The drive mechanism for the two drive chains for the camshafts and demandcontrolled
oil pump is located on the pulley side.

Piston cooling
The piston crown temperature in the 911 Carrera engines is reduced by means
of piston injection cooling. The spray nozzles are forced-fitted into the crankcase
and cannot be replaced. To ensure the necessary engine oil pressure at low revs
and high engine oil temperatures, these spray nozzles only open at a higher oil
pressure.

Chain drive
Another special feature of the new generation of engines is that these engines no
longer have an intermediate shaft. This drive shaft, which was fitted between the
crankshaft and the camshafts on previous models, was required in order to reduce
the transmission ratio and thus the dynamic forces of the timing chains. Through
the use of new, high-performance timing chains, it was possible to simplify the drive
mechanism for the camshafts in spite of higher revs, thereby reducing the weight of
the engine significantly by removing the intermediate shaft. Together with an additional
crankshaft bearing location, this allows greater stability and a significantly higher
engine speed potential.

Oil supply
The oil supply in the new generation of engines has been essentially redesigned
with the following objectives in mind:
• To ensure the supply of oil even during very high lateral and axial acceleration
• To reduce friction and drive losses
The main differences between the new oil supply system and that used on previous
models are as follows:
• Additional oil extraction point in the cylinder head
• Electronic demand-controlled oil pump
• Additional watertight sheetmetal panel between crankcase and oil pan
Compared with the previous models, the new 3.6 and 3.8-litre engines have not
only one, but two extraction points in each cylinder head. In addition, the new 911
engines now have a total of 5 oil pumps instead of 3. These are located in the oil
pan and are driven by a shared shaft. They include 4 extraction pumps for the
cylinder heads (2 per cylinder head) and a new demand-controlled oil pressure
pump.

As you can see from the above, almost all the points that have been described by Hartech and others (and identified as potential weak points in the M96/7 engines) appear to have been totally redesigned. The exception, as it's not described in the technical manual (other than via a couple of diagrams) is the cooling system, so I have no way of knowing how the system is designed on the DFI motors or whether the idiosyncrasies of the previous generation engine are repeated.

mollytherocker

Original Poster:

14,348 posts

175 months

Friday 6th May 2011
quotequote all
Some great info there Ian, many thanks.

In terms of the general coking issues on this type of engine, what can an owner do to limit the issue?

MTR

drmark

3,807 posts

152 months

Friday 6th May 2011
quotequote all
With respect Ian - the coking subject is not on hold, it is non existent until such time as someone shows it to be an issue. Why be so negative about loss of power and Porsche not coughing up when no one knows if coking is an issue with these engines.

Why not act on your paranoia and get your car scoped as you said you would weeks ago. If it's coked then there is indeed a problem. If it's not then you can lay it to rest. But all this what if crap is such a waste of time and energy.

Phooey

10,870 posts

135 months

Friday 6th May 2011
quotequote all
I reckon mine is coked. Couldn't shake a Granturismo S MC-shift off my tail the other day. It was firmly locked-on upto 1.3 leptons frown

J-P

3,914 posts

172 months

Friday 6th May 2011
quotequote all
Phooey said:
I reckon mine is coked. Couldn't shake a Granturismo S MC-shift off my tail the other day. It was firmly locked-on upto 1.3 leptons frown
Hmmm... Or could be operator failure wink

C2'S'man

620 posts

189 months

Friday 6th May 2011
quotequote all
Phooey said:
I reckon mine is coked. Couldn't shake a Granturismo S MC-shift off my tail the other day. It was firmly locked-on upto 1.3 leptons frown
You should get a GT3, ooops, sorry, I forgot you used to have one!!!!
wink
g

J-P

3,914 posts

172 months

Friday 6th May 2011
quotequote all
I wrote to EVO about this some time ago. And they basically said DFI is great, dont worry about coking!

Edited by J-P on Friday 6th May 14:43

Ian_UK1

1,495 posts

160 months

Friday 6th May 2011
quotequote all
drmark said:
Why not act on your paranoia and get your car scoped as you said you would weeks ago.
Thanks for the compliment. A Doctor who obviously hasn't a clue what paranoia means! Let me educate you. Paranoia - "a mental disorder characterized by systematized delusions". Kindly explain to me how the simple, scientific understanding of the inevitable consequences of a known type of mechanical system can be systematized delusion? Denying the simple, well-understood science is delusional, not accepting it and trying to quantify its effects.

The reason I didn't get the car scoped is because my local independent didn't have a borescope that we could get pictures from. It has a tiny 2" screen that is too small and also too dim to photograph. And of course I daren't say on here that I've seen an issue then not put pics up to 'prove' it. I'd obviously have been lying and spreading unfounded myths about cars that in reality are completely perfect in every way. There you go - no paranoia here! biggrin

ScienceTeacher

391 posts

151 months

Friday 6th May 2011
quotequote all
drmark said:
With respect Ian - the coking subject is not on hold, it is non existent until such time as someone shows it to be an issue. Why be so negative about loss of power and Porsche not coughing up when no one knows if coking is an issue with these engines.

Why not act on your paranoia and get your car scoped as you said you would weeks ago. If it's coked then there is indeed a problem. If it's not then you can lay it to rest. But all this what if crap is such a waste of time and energy.
It is not unreasonable to anticipate this problem with the Gen 2 997. My understanding is that the problem affects all DFI engines petrol or diesel made to date to a greater or lesser extent. It is also not unreasonable to expect Porsche not to help based on their approach over the last 10 years with M96/7 issues. I have personal experience of extortionate service at more than one OPC and downright incompetence. I use Hartech and will continue to do so.
I am very interested in the preventative products that are on the market for DFI engines and how they work. Wynn's seem to be big in this area. Anybody any experience??

Edited by ScienceTeacher on Friday 6th May 16:17

TTwiggy

11,222 posts

170 months

Friday 6th May 2011
quotequote all
I've certainly heard some tales of woe concerning Audi's DFI engines - some older RS4s making about the same bhp as the previous gen S4!

I guess that at least with IMS, you have a perfect engine one day, and a bag of bolts the next, and depending upon your own situation (newish car with OPC warranty, or older car that someone like Hartech can rebuild) you just deal with it.

I'd be a bit peeved if I thought that I was simply getting used to the power of my shiny new car, only to find out that 100 odd horses had been coked up over time.

JLJ

402 posts

196 months

Friday 6th May 2011
quotequote all
Phooey said:
I reckon mine is coked. Couldn't shake a Granturismo S MC-shift off my tail the other day. It was firmly locked-on upto 1.3 leptons frown
That is worrying. A friend has one, a beautiful car and an exquisite noise. My 997tt absolutely slaughters his Granturismo S, even my 360 is quicker. A C2S should pull away from a Granturismo, albeit slowly. I had a C2S (gen 2) stay with me in the 360, was only a short blast, but seemed to be just as quick.