Cayman GT4 - Porsche now accepting deposits. (Jan 2015.)
Discussion
fioran0 said:
The setup with the "integrated dry sump" is certainly what I would call a wet sump from looking at the system design and from having seen inside an M96 engine. An advanced wet sump no question but still a wet sump.
While you are correct regarding oil tank location (it can technically be anywhere for a dry sump), Im not convinced that the image you present of oil slopping around in the crankcase is quite precise enough to classify sump designs.
I would be curious to know if you have any examples of a true dry sump oil system utilising an internal engine tank cast into the engine case on a car? I had a think but couldn't come up with one. (for clarity, since some on piston heads enjoy getting wound up, thats not some sort of challenge but an actual question).
Your oil temp warm up statement is a curiously one dimensional one.
Looking at the wikipedia page you linked, its first paragraph is:
"A dry sump is a lubricating motor oil management method for four-stroke and large two-stroke piston internal combustion engines that uses additional pumps and a secondary reservoir for oil, as compared to a conventional wet sump system using only the main sump below the engine and a single pump."
The "integrated dry sump" exactly fits the second description for the wet sump while the dry sump engines most assuredly fit the first.
From what you say I too would classify it as a wet sump, however fancy it is divided from the crankcase. As far as I am concerned, practically speaking unless the tank is connected to the sump via a scavenge pump, and is physically sealed from it, it's wet sump. Baffle and divider plates don't count. (I appreciate my description was - deliberately- simplistic, but lots of posts have focused on the oil tank location as the defining argument)While you are correct regarding oil tank location (it can technically be anywhere for a dry sump), Im not convinced that the image you present of oil slopping around in the crankcase is quite precise enough to classify sump designs.
I would be curious to know if you have any examples of a true dry sump oil system utilising an internal engine tank cast into the engine case on a car? I had a think but couldn't come up with one. (for clarity, since some on piston heads enjoy getting wound up, thats not some sort of challenge but an actual question).
Your oil temp warm up statement is a curiously one dimensional one.
Looking at the wikipedia page you linked, its first paragraph is:
"A dry sump is a lubricating motor oil management method for four-stroke and large two-stroke piston internal combustion engines that uses additional pumps and a secondary reservoir for oil, as compared to a conventional wet sump system using only the main sump below the engine and a single pump."
The "integrated dry sump" exactly fits the second description for the wet sump while the dry sump engines most assuredly fit the first.
Regarding "one dimensional" I assume you mean it warms the oil up when you want it to but doesn't cool it down, which, to some extent an external tank might. While that's true, any engine that we are likely to be concerned about will have an oil cooler which will perform that task. Without one an external tank does have an advantage (and was doubtless a consideration on early bikes).
And other cars with an integrated dry sump - no I can't think of one either - but I would think as much a cost issue as a design one.
I wonder where my post went? iPhone meets stubby finger failure i suspect.
Absolutely, Its more a case of looking at the overall design than getting too hung up on the tank location which is precisely the point you were getting at with your posts. An external tank makes it somewhat easier with respect to guessing what approach is used, but as you said, it doesn't need to be externally mounted to make it dry.
I couldn't think of anything either on a car using an internal tank which was why I asked, I wondered if you had something in mind when you typed. It would have been interesting to look it up if there had been.
I have a faint memory of something in the Mezger book about him looking into doing something with an oil tank for an engine in/on the transmission with the fluid passing through the interface between the two and o-ring sealed. I'm reaching as I can't remember exactly but I should look it up again and see what he was on about and if my memory is even correct.
Apologies ref the one dimensional confusion. I was meaning that saying an internal tank was better based on an ability to warm up oil faster was to ignore other aspects. The same internal tank may cause oil temps to get too high for example either by its location (and the forces that drove it to warm oil faster) or by limits to its oil capacity versus an external tank with more room.
Absolutely, Its more a case of looking at the overall design than getting too hung up on the tank location which is precisely the point you were getting at with your posts. An external tank makes it somewhat easier with respect to guessing what approach is used, but as you said, it doesn't need to be externally mounted to make it dry.
I couldn't think of anything either on a car using an internal tank which was why I asked, I wondered if you had something in mind when you typed. It would have been interesting to look it up if there had been.
I have a faint memory of something in the Mezger book about him looking into doing something with an oil tank for an engine in/on the transmission with the fluid passing through the interface between the two and o-ring sealed. I'm reaching as I can't remember exactly but I should look it up again and see what he was on about and if my memory is even correct.
Apologies ref the one dimensional confusion. I was meaning that saying an internal tank was better based on an ability to warm up oil faster was to ignore other aspects. The same internal tank may cause oil temps to get too high for example either by its location (and the forces that drove it to warm oil faster) or by limits to its oil capacity versus an external tank with more room.
Steve Rance said:
If the Gt3RS does have a 'completely new engine' ( I know, we've heard it all before) then it's probably for homologation purposes which may make it less likely that the GT4 is a potential platform for a motorsport project. An indication will be whether it has a dry sump or not. I hope that it has.
The latest forum banter is that the new RS engine is the 9A1 GT3 block but with upgraded internals, and that it is still only Euro 5 compliant.The GT4 engine is a 3.8 with 380hp - deliberately detuned so that it does not tread on the toes of the 911 Carrera S, which is expected.
Take these with a pinch of salt - we will know for certain soon enough
TheAnimal said:
The latest forum banter is that the new RS engine is the 9A1 GT3 block but with upgraded internals, and that it is still only Euro 5 compliant.
The GT4 engine is a 3.8 with 380hp - deliberately detuned so that it does not tread on the toes of the 911 Carrera S, which is expected.
Take these with a pinch of salt - we will know for certain soon enough
How is it likely to be detuned? Lowering the redline or making it produce a little less torque? I hope they give it a 7.4k redline (at least). The GT4 engine is a 3.8 with 380hp - deliberately detuned so that it does not tread on the toes of the 911 Carrera S, which is expected.
Take these with a pinch of salt - we will know for certain soon enough
100bph/litre is a high output for an NA engine.
TheAnimal said:
The latest forum banter is that the new RS engine is the 9A1 GT3 block but with upgraded internals, and that it is still only Euro 5 compliant.
The GT4 engine is a 3.8 with 380hp - deliberately detuned so that it does not tread on the toes of the 911 Carrera S, which is expected.
Take these with a pinch of salt - we will know for certain soon enough
The new Cup S needs an homologated engine if it is to race in the GT3 catagory as the M engine doesnt have the relavent emmisson capabilities. So basically Porsche have a chassis without an engine. That - I believe - will be the purpose of the homologated 991RS. The M engine will still be used in GT4 and GT2. The bad news is that I am told that the motorsport division of Porsche have no current plans for the Cayman in thier motorsport program. The GT4 engine is a 3.8 with 380hp - deliberately detuned so that it does not tread on the toes of the 911 Carrera S, which is expected.
Take these with a pinch of salt - we will know for certain soon enough
Steve Rance said:
The new Cup S needs an homologated engine if it is to race in the GT3 catagory as the M engine doesnt have the relavent emmisson capabilities. So basically Porsche have a chassis without an engine. That - I believe - will be the purpose of the homologated 991RS. The M engine will still be used in GT4 and GT2. The bad news is that I am told that the motorsport division of Porsche have no current plans for the Cayman in thier motorsport program.
But this goes against two separate interviews in the press with Porsche management 
bcr5784 said:
As you may have gathered my background is more in bikes than cars. My early biking days were with Royal Enfields which are (genuine) integral dry sump engines - even to this day!
Bikes are something I havent ever done anything with. Well save for a dalliance for a week when I ended up with the wrong AIM data logger kit and had to dialogue with bike racers to rehome it. It was a Yamaha specific kit with loom etc that seemed a waste to cut up and bin half of. I will have a read on the Royal Enfield engines when I get a chance though. Sounds interesting.fioran0 said:
Bikes are something I havent ever done anything with. Well save for a dalliance for a week when I ended up with the wrong AIM data logger kit and had to dialogue with bike racers to rehome it. It was a Yamaha specific kit with loom etc that seemed a waste to cut up and bin half of. I will have a read on the Royal Enfield engines when I get a chance though. Sounds interesting.
You might find it more "cautionary" than interesting. Dry sumps and bike engines have not always worked so well. Dry sumps were used - at least in part - to maximise ground clearance/keep the engine as low as possible (for handling reasons). The trouble is a small capacity sump on a single cylinder engine (in particular) gives pumping issues. This leads to power losses and - as Royal Enfield and other British bike owners know - oil leakage. Not to mention "wet sump" when oil drains from the tank via the pump back into the sump. Not an issue I had with my Royal Enfields - but did with a BSA.bcr5784 said:
You might find it more "cautionary" than interesting. Dry sumps and bike engines have not always worked so well. Dry sumps were used - at least in part - to maximise ground clearance/keep the engine as low as possible (for handling reasons). The trouble is a small capacity sump on a single cylinder engine (in particular) gives pumping issues. This leads to power losses and - as Royal Enfield and other British bike owners know - oil leakage. Not to mention "wet sump" when oil drains from the tank via the pump back into the sump. Not an issue I had with my Royal Enfields - but did with a BSA.
HaHa. That sounds like the sort of interesting read I might just like. UH-Matt said:
If the GT4 is a de-tuned 3.8 , this surely leaves scope to tune it back up very easily to 400bhp+ ?
A detuned 3.8 does not sound exactly sound thrilling. Gt3 gets the best, even porsche were calling the 7 lump the masterpiece and the Cayman gt4 to make do with a detuned big standard 991 even if it does make 400bhp will it have the racy feel of the gt3 or just be a fast (but not too fast...) caymanGassing Station | Boxster/Cayman | Top of Page | What's New | My Stuff