Latest generation 911 engine on test rig

[Bob Gagnon]

If I picture in my mind the water jacket that Porsche bolts over the cylinders to water cool the aircooled engine that is pictured in the diagram below as being a permanent part of the good old aircooled crankcase casting, the resulting picture in my mind is the crankcase for the new A91 997 engine pictured below it.

Also, it looks to me as though Porsche could easily modify that 997 chain drive oil pump and the bottom cover of the engine (if there is a bottom cover) to make a true dry sump engine.

Also, note the way that the cylinders fit into the water jacket in the diagram below, with the closed deck of the new engine (the old 996 engine had an open water jacket deck) Porsche could use either a cast in Alusil liner or separate Nikasil liner cylinder for the engine.

This would mean that the normal 911 could have a cheaper Alusil cylinder, "integrated dry sump" engine and the up market GT3, Turbo, GT2 could have a Nikasil cylinder, forged piston, full dry sump engine all using the same basic crankcase.

This would make production line sense to me, but I am just dreaming here.

[Brad Roberts]

I pay a monthly fee to access the latest online "PET" from Porsche. They have not announced it yet publicly, but I have had access since June 08. Since I pay for the service, we are allowed to use the pictures

I'm not sure how they are handling the bottom of the engine. Let me look!



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[Brad Roberts]

This is the "pan" that is shown going to that line.









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[Brad Roberts]

Here is the head:





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[Bob Gagnon]

There is a cover! I knew there had to be to get to the rod nuts.

It looks sculpted with a curve and vanes to scrape oil off the crank, this could make the spinning crankshaft itself an oil pump to clear the crankcase of oil. Very interesting.

Hmm, if the cover vanes connected to the oil storage points shown below in the diagram of the A91 oiling system shown below (added text is mine)...boy I would like to see one of these engines apart!!

[Bob Gagnon]

I finally got some factory literature about the A91 engine and find it to my mind at least to be a much better engine than its 996 predecessor.

Some things I found that were not discussed above:

DFI is really a neat concept and allows a 12.5:1 compression ratio and lower fuel consumption and CO2 output per horsepower. The engine is designed for 93 octane fuel, but will run on an octane as low as 90 with timing adaption done automatically through the knock sensor system. I am sure some power will be lost, so us California guys would do well to use some racing gas as a secret advantage for track use.

The engine is made using the same process as the 928, 968 and 944 engines with Alusil construction, not the problematic Lokasil construction of the 996. The text describes the block to have a closed deck construction unlike the 996's open deck, another design advantage.

The pistons are forged construction, the rods are forged with fractured off end caps.

The entire bottom of the engine is comprised of a huge bolted on aluminum sump (it reminds me of the bolt on extension sumps that 356 racers use) which contains the oil pump and has side chambers which correlate to what I circled as "oil collection points" in the oil system diagram I submitted above. The engine is still an "integrated dry sump" design but the sump is much better isolated from the crankcase than the 996 engine and has several cleverly formed sheet metal baffles to control oil slosh during cornering and braking. The part that is pictured above (Brad Robert's post starting "This is the "pan" that is shown going to that line") that I thought was the sump bottom cover is only one of these sheet metal baffles designed to scrape the oil off the crank and send it to the sump below it.

The key here is that this entire sump/oil pump assembly looks like it could be easily converted to a full dry sump design with only a bolt on kit to replace the sump and oil pump for racing use, and my bet is Porsche will do this for the GT3 and GT2 applications of this engine. If this is the case, look for racers to do this on cars not so equipped with a dry sump from the factory, Cayman, Boxster etc.

I will post pictures when I get time to go through the hoops it takes to post them here.

[Brad Roberts]

Bob,

you can email them to me, or you can post them on one of my other sites and just link to them This is how I do it for sites that don't allow uploads. I either FTP them to my server or just make a junk post on one of my other forums.

Thinking more about this.. it is dirt cheap for server space now. Why exactly does SD PCA not allow uploads in this forum?



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[Bob Gagnon]

Thanks to Brad, here is a picture of the oil sump/oil pump complex of the new 997 engine. Text has been added to identify what I think the components of the system are.

You can see how easy it would be to eliminate the oil storage beneath the engine and modify the oil pump to make the engine a true dry sump. The separate chain drive would conceivably make this conversion possible without removing anything but the part of the engine pictured below which could conceivably be done without removing the engine from the car!

The pressure pump is interesting in that it has a sliding gear which changes the overlap between the pressure pump gears to vary the output of the pump to the needs at hand for the engine at the time. This is controlled by a solenoid valve managed by the engine's computer.

[Brad Roberts]

I can see aftermarket oil pans in our future

Great shot!


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