997 Gen 2 DFI Engines - Woes finally sorted?
Discussion
Ian_UK1 said:
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.
So... probably enough time has passed, plenty of cars with decent miles on now, did it work?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.
Any feedback notes on Porsche's homework? I'm very ignorant about the engine that followed the M97
Very nifty 
I think everybody has just been waiting for the problems and certainly from the GT4 Clubsport side I have seen nothing but good news ...
Engines stripped after three seasons with nothing to be done other than the consumables of a rebuild .... oil temperatures over 150C with the solution being an oil change after each race day (how surprising!) resulting in a willingness to disconnect the distracting high temp oil warning ... so far so good ?
It is also interesting that the 718 Clubsport still uses the 981 engine in X51 tune, and unlike GT3 Cup and RSR, it's all un-lifed ... so based on 10 years experience in the field Porsche themselves voted in favour of the Gen-2 engine for this race car.
I think everybody has just been waiting for the problems and certainly from the GT4 Clubsport side I have seen nothing but good news ...
Engines stripped after three seasons with nothing to be done other than the consumables of a rebuild .... oil temperatures over 150C with the solution being an oil change after each race day (how surprising!) resulting in a willingness to disconnect the distracting high temp oil warning ... so far so good ?
It is also interesting that the 718 Clubsport still uses the 981 engine in X51 tune, and unlike GT3 Cup and RSR, it's all un-lifed ... so based on 10 years experience in the field Porsche themselves voted in favour of the Gen-2 engine for this race car.
I started looking for a Gen 2 S manual 18 months ago. I had 3 cars inspected by an independant specialist and two of them were rejected.
The first looked stunning from the outside and ticked all the boxes, low milage, guards red and Sports chrono but the thing struggled to idle sounded lumpy and the seller refused the person inspecting a test drive which raised alarm bells.
The 2nd was due to be sold to a well known 911 specialist for stock and they were inspecting it for their own reasons but gave me a phone call out of curtosy as they knew I was in the market. It failed a bore score check on one of the rear cylinders and I was told to avoid it if it came back on the market.
3rd time lucky I ended up with a single owner car with slightly more miles than I would have liked (but below the average) amazing over rev report and genrally cherrished motor.
The first looked stunning from the outside and ticked all the boxes, low milage, guards red and Sports chrono but the thing struggled to idle sounded lumpy and the seller refused the person inspecting a test drive which raised alarm bells.
The 2nd was due to be sold to a well known 911 specialist for stock and they were inspecting it for their own reasons but gave me a phone call out of curtosy as they knew I was in the market. It failed a bore score check on one of the rear cylinders and I was told to avoid it if it came back on the market.
3rd time lucky I ended up with a single owner car with slightly more miles than I would have liked (but below the average) amazing over rev report and genrally cherrished motor.
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