gjnockie

Just passed 400 miles on my 991 Manual Cab and loving every mile!

It's obvious to me that Porsche has made some improvements to the 9A1 DFI engine since I have had my 997.2 09 S Coupe. I read somewhere that 150 engine parts have been changed or improved for the 991. I know that 5 hole injectors are one of the improvements.

My observations are as follows compared to my 09 which was year one for the 9A1.

1. Little to no oil consumption. My 09 at this mileage already burned more than a 1/2 quart of oil. My 991 has been full since day one.

2. NO SOOT. My 09's pipes were black and sooty at this point already. And the back of the car was covered in soot and black particles. The 991 is clean! Very pleased about that.

3. Much more free revving than my 09. I wonder why?

4. Fuel economy so far is fantastic. I am getting about 20 mpg around town.

5. Engine warms much faster and maintains a more constant temperature.

If anyone knows what some of those engine improvements are I am sure we would all be interested in knowing about them.

chuck911

Oil consumption comes down to ring seal, which in turn depends on engine loads during the first 20-200 miles or so. Brand new cylinders have a rough machine finish that is very fine and so wears off very quickly regardless of load. Only high loads can provide the pressure needed to press the rings into the walls forcefully enough to use the roughness to mate and seat the rings well. I did this methodically when my 911SC was rebuilt, and it has used less than 1 qt per 5k miles over 120,000 miles so far. So every time you've felt guilty for nailing it during "break-in" relax, those little bursts of joy were helping not hurting.

Another reason, and less certain of this but it makes sense, is all the changes in oil pumping technology. The new motor uses several electric pumps to deliver oil as and where needed. Its probably a lot harder for oil to seep past these several pumps and into the crankcase. If this is the case (and I'm not sure but it makes sense) then it would lessen or eliminate oil lost in the puff of smoke so often seen when starting up after being parked for some time.

Porsche studied motorcycle racing to help learn how to lighten everywhere. Lighter motors rev faster and easier, but they also tend to rough idle and takeoff, which is why flywheels are so important. DFI, together with fly by wire computer throttle control, gives such superb control it allows them to have both light, quick revving at the top end and smooth tractable control at the low end.

Engine warmup improves because they did the same thing with coolant that they did with oil, and not just for the motor for the transmission as well, and not just for coolant but for DFI and exhaust. If memory serves.... a lot of this is on their website... with cool movies and cutaway drawings.....

Mike in CA

With regard to engine warmup, although much derided ("I can't see the engine anymore!), the encapsulation of the engine plays a part not only in faster warm-up when dead cold, but in retaining heat between starts. Subsequent starts get to operating temp faster for lower emissions.

Nicoli35

I have really noticed the fast engine warmup, especially with the cold temps here lately, it is appreciated and wonderful.

SiNi

When you refer to warm up I presume you are referring to oil temp as opposed to coolant temp? Also what minimum oil temp do you consider to be "warm"?

rnl

At less than 32 degrees it takes 5 miles for the oil temp to break 75 degrees while the coolant temp is over 150

chuckbdc

I don't know the details but recall that Porsche literature pointed out that major advances were made in thermal management on the new engine. Something about internal coolant routing and underbody shrouding. I think emissions reduction of meeting requirements is a big part of it.

ArashApollo

Please keep posting guys! I love reading about this stuff.

ADias

PAG added a complex thermal management system with multiple thermostats to the 9A1. It was done for emissions purposes when the engine first starts cold. It all sounds wonderful, doesn't it? I won't get into the tradeoffs as this audience does not care for anything other than the proverbial corporate 'kool-aid'.

holminator

Porsche website comments are some of the things mentioned here: http://www.porsche.com/usa/models/91.../detail/drive/

chuck911

Uh, not following you. Especially the innuendo. There's some nefarious corporate agenda behind rapid warm-up?

holminator

I like Mounds but no Kool Aid for me unless you have some grape favor. Thanks. Just sayin.



http://youtu.be/s55QoIZScP4

simsgw

The biggest source of engine improvement is in the management of the engine by the computers, the... what's the Porsche jargon? DME I think. Digital Motor Electronics. They control at two levels. From one millisecond to the next, components are controlled using 'maps', which is a term I won't bother to explain, but it pre-computes the relationships between engine dynamics and the physical control components. Everything from injectors to valves to oil pumps and airflow control on the intake side. On the glacial scale of tenths of a second, the computers decide *which* map shall be active for each phase.

The 997.2 engine multiplied computer power by several times over the 997.1. Three times sticks in memory, but I don't promise that. This generation of engine has another increase in computer power, so they can use more pre-stored maps, maps of greater resolution, and apply more complex criteria to those 'glacial' decisions from one tenth second to the next about selecting new maps. That lets them do things like use injection strategies more subtle than the first-gen DFI rules. Which injectors fire [uh... 'inject' I mean] at which point in the combustion stroke is determined by computer and varies with load, engine temp, crankshaft speed, and so on.

That top-level programming evaluates our control inputs in light of the car's current situation to decide our intention. For example, we don't have a launch control 'button' like some cars.

The computers in that top-level loop, the glacial one, identify certain control actions in a particular pattern as being signs that we intend a maximum-performance launch. The engine begins to increase rotational speed, but a map is swapped in that holds the rpm steady at a certain point that I didn't notice. 4000 rpm or so. Think of that as "Ready, Set..." When we release the brake, a set of "Go!" maps is made active. Those ensure optimum tire slip, maximum effort shifts from the PDK with consistent throttle management, and so forth. At some point in the process, the 'routine' Sports Plus strategy blends in. The control maps used for launch, the "Go!" phase seem bulletproof. Very impressive. But I am able to confuse the "Ready, Set" maps. If we don't play our part, they get ... uncertain, anxious, in need of counseling... well, ineffective. Let's put it that way.

It's a case of having to trust the computers. You can't use human judgment, even experienced launch reflexes, without causing conflicts.

At the moderate speeds involved (for a computer), the various computers have ample time for all this even when approaching redline. That probably explains the easier rev'ing nature, which I've noticed also. Better torque management in that range. That's the performance end of the curve, and may have gotten pretty basic (i.e. predetermined') treatment in the 997.2 generation. Realistically, The essential phase is low rpm and particularly low rpm at low temps. These engines must be efficient in terms far more sophisticated than the old-fashioned horsepower per displacement measures. If they can't get the engines much more efficient, we won't be able to buy Porsches much longer. In my mind, the real issue is how much more they can extract without having to use forced induction, even on the Carreras. Makes me wonder whether we might see two types of induction distinguished for marketing purposes. TwinTurboBallsToTheWall (TTBTTW) turbos for the next gen Turbo model, and simple ForcedInductionButHardlyWorthMentioning (FIBHWM) for the Carreras. Oh, excuse me, that should be PTTBTTW and PFIBHWM. Ahem.

With reference to something else in this thread, I had been curious about certain aspects of the PDK shifting strategy, so I asked the Cayman project director at the West Coast Tech Tactics. The PDK Cars do not have a flywheel. That answered the question I had entertained, but it also shows how far they are going now to increase efficiency. Lower rotating mass is very important, but achieving smoothness without that customary stabilizing mass is a serious challenge.

They have met it, but it must have been the subject of some serious design studies several years ago.

Gary

SiNi

Ok but what oil temp do you regard as sufficient to drive the car aggressively e.g full throttle / high rpm?

fbroen

Thx Gary, very interesting.

SiNi, I wait until oil temp is up to normal operating temp before really punching it, but I suspect I am overly cautious there.