MetalSolid

Has it been officially announced that the 997.2GT3s will have wet sump engines? Even though most drivers of these cars won't be effected by the change, the difference between a Carrera S & GT3 would become less compelling.

If true, I suspect the next RS will have dry sump, as the GT3 becomes ever more softer & main stream; as already seen even in these forums, people just want the GT3 name on a car with more power that looks "slammed".

Cupcar

Shown below is a diagram of the original dry sump system used in all air-cooled 911 cars.

In the later cars #8 the oil cooler was replaced with an oil filter- note that before this change there was no filter in the pressure loop and anything dropped in the oil tank would go directly to the bearings.

On the water cooled versions of the crankcase #8 was replaced by the oil tank and the oil filter moved to the top of the engine. Add in a couple of more spray bars for the 2 extra cams and 2 scavenge pumps in each cam box with separate lines leading to the oil tank and you pretty much have the changes made for the water-cooled application of the air-cooled crankcase.

Funny the A91 looks so much more complicated.

Alan Smithee

Perhaps history will repeat itself. The original RS had the same basic motor as the 911T, which was also available in the 914.

It would be great if all Porsche sports cars once again had competition-worthy drivetrains.

Cupcar

In further examination of the way the new DFI A91 engine is designed, it appears to me that with a few modifications it could be made into a full dry sump and to use Nikasil cylinder liners if required .

So, although the GT2/3 will use the basic A91 engine, the engine could conceivably be a very different version of the one in the normal 911.

Normal 911= "integrated dry sump", cast silicon cylinders, steel rods, cast pistons.

GT/Turbo Variant= dry sump, replaceable Nikasil cylinders, Titanium rods, forged pistons.

This would make sense for production line management of engines for all cars.

Time will tell.

Carrera GT

I did a quick Google on this and strangely couldn't find a dictionary of engine terms. My Google Kung Fu is weak.

Anyway, I believe a gallery is any line or casting designed to carry (fuel or lubricant) while a galley is designed to gather and direct lubricant.

All that said, I think the belly tanks are heat exchangers.

Given the strength of synthetic coolants, I think the design is meant to be simpler, with less parts, less weight, less complexity and less parasitic energy cost (pump energy and dead weight.)

For emissions, the engine temp needs to rise quickly from a cold start and be held at a higher temp for a cleaner burn. Using coolant to regulate the engine temp and oil more specifically to lubricate (with less influence over head temps) would help let a street engine get up to temp quickly. It seems to me that every second word out of Porsche is about emissions and government regulations. I imagine internal engineering projects need to address those talking points. It also seems that less and less of the street cars is directly from the race cars these days -- even the GT cars don't share the durability lessons learned in the Cup cars. I noticed an example of this recently when a GT3 lost the return line on the power steering fluid reservoir. This is a problem that has cropped up in some Boxsters/Caymans, but I didn't know it's the same mistake allowed to continue even in the GT3. It's a press-fit and it should be a threaded fitting. Really, it should be an electric power assist, but I can see that would take more crash tests or whatever nonsense.

I'll resist the temptation to preach to the choir on the lamentations of "purist" 911 devotees that Porsche stopped making the 993 ... : )

FTS

This is going to turn out to be just like the air vs. oil-cooled debate of the decade, Metzger vs. A91, isn't it?

NJcroc

There has been quite a bit of testing at Porsche with this engine and many of the components are revolutionary in design. The old design is indeed old and a new one is coming. Everyone just wants a good strong durable engine, I believe porsche has one coming

911rox

I think you'll find the Nikasil cylinder linings are actually etched into the linings by submerging the block into a solution containing whatever... The linings are therefore not replaceable per say...

The new engine blocks have Alusil cylinder liners that are created via a different process whereby the metal has something mixed in with it that is later exposed once the cylinder linings are etched.

The two processes are different and not interchangable. Motor racing (ie F1, superbikes etc) have traditionally used Nikasil to my knowledge. I suppose Porsche know better (as if! we'll wait and see)

911rox

The air vs water cooled debate was due more to sentimental reasons I believe. Sure the m96/ m97 had their issues but that was because Porsche didn't get them right. Watercooled engines were mainstream at the time amongst car manufacturers and were proven technology. I don't see that air cooled engines in general had benefits over water cooled, Porsche were just slow to change.

The GT1 metzger vs A91 debate is more so due to the fact that one engine is proven for many years in motorsport, has the necessary hardware to do the job (ie. dry sump, liners etc) and the other simply doesn't at this point. It may be a huge advance on the m96/m97 but for those serious track users it aint proven. It is a case of proven vs unproven technology...

I'm sure everyone would have felt a whole lot better about such a change if Porsche had gotten off their ***** and popped them into the cup cars etc a year or 2 ago to do the testing and show their worth to the consumer. Instead it seems they are planning to make us the ginni pigs... Hardly the best way of ensuring ongoing loyalty if they get it wrong!

GrantG

I believe that the current (old) GT3 has cylinders bolted to the crankcase like the aircooled cars, wherein the entire cylinders can be replaced (not the linings) and even replaced with larger displacement (bore) units.

911rox

Thanks GrantG, wasn't aware of that fact...

Chris

iLLM3

Agreed, beats me why they went through all of this development and hassle when they had a current masterpiece already.

Cupcar

Nikasil cylinders are made by electroplating nickel carbide onto aluminum, this process was developed by the Mahle company and was first used on the 917 Porsche in 1970 then first used for a production Porsche in 1972 on the Carrera RS 2.7.

Nikasil creates a very durable, particularly low friction, lightweight cylinder that can be used with a stronger forged piston. Nikasil is currently used by most, if not all, Formula 1 teams and by Ferrari and others in their high end street cars.

The 996 (non-Metzger) engine has Lokasil cylinders (really localized Alusil) which is a cylinder made of high silicion content aluminum which is cast as part of the engine block then is etched chemically leaving the silicon as the wearing surface. Alusil has not been as durable as Nikasil when used with forged pistons thus cast pistons are used. Alusil does not have the low friction surface for power development that Nikasil does.

Having a fully replaceable cylinder was a natural part of the design for the air-cooled engine since the cylinder had to be externally finned and exposed to air flow. When Porsche water cooled the air-cooled crankcase to create the Metzger engine, they merely removed the fins and bolted a water jacket around the cylinders. This retained the easily replaceable feature of separate cylinders and allowed easy use of a Nikasil cylinder and forged pistons.

Having a replaceable cylinder facilitates engine rebuilding for racing.

The new A91 engine has a closed cylinder deck- the prior 996 engine had an open deck- which would allow the easy installation of separate cylinder liners if Porsche wanted.

Porsche could also coat the cylinders of the A91 with Nikasil if they chose and not have a separate liner, but then the engine would be harder to rebuild.

Bill Verburg

here's the block, 2 pieces including the crankcase and cylinders

Cupcar

Bill can you tell how the bottom of the crankcase is enclosed?

Does that dashed line shown in the lower left of the parts diagram go to a bolted on cover?

The reason I ask is I wonder how one tightens the rod nuts after inserting the piston and rod from the top and figure one has to reach from below.

Also, it looks like the new oil pump may be mounted to the cover if there is one, making conversion to a full dry sump simple.