I always thought the old "open her up and blow out the carbon" was BS

But I have to say, it has been well over a year, that I FINALLY had the time and opportunity to drive my 996 more than 15-20 miles around town or short interstate trips. (Just the facts of my life at the moment, not by choice) Got to take her on a 70 mile each way trip that included some smooth as glass tarmac on an interstate where the average MPH of the vehicles around me were in the 85MPH range. So there were sections where I was able to briefly pop her up over 100, and she performed beautifully. As it was 95F ambient, I was not too surprised to see the coolant temp, even with my low temp T-stat stay at around 190F estimated, with the AC on. Once at more moderate speeds, it very slowly crept down to the 180F mark. But the most revealing thing is how the engine idle, acceleration, even sound, are smoother than before the trip. I'm guessing there was some carbon build up, or perhaps the ECU was finally able to tune up a bit more? The difference is VERY noticeable. Not a bit of oil or coolant level change, and the oil is still super clean, no darkening at all. I know that sounds silly, but after doing so much maintenance on the engine, you always wonder until a really decent shakedown, that everything is tight and sealed as it should be.

Your experience parallels mine. I've reported often enough a good highway jaunt really perks up the engine. Goodness knows I get the opportunity to experience this almost every week cause I make a 50+ mile freeway run to a family member then back again. While I do not get the chance to touch 85mph (the limit is 65mph) and triple digits are out out out of the picture just 65mph (well, maybe to avoid being run over I up the speed to 75mph) is sufficient. Will also repeat that both of my cars get used for a 30 mile commute though the 30 miles does include some surface street driving. On a good day just a half a mile or so from my house to the freeway and around a mile or so from the freeway to my office.

Sounds like it was a great drive.

Did the same on Saturday, though longer trip and some track time too. These cars seem to love being used properly...engine is quieter and smoother, I usually get a little tiny valve tick at idle as the lifters don't fully pump up but that's all gone now and gearbox is smoother than ever.

+1 on this. I had my car for about a month. Went for a drive with a long time friend and enthusiast and let him drive on some great sections of road in CNY. The next day I was heading back home and everything just seemed..smoother. Couldnt quite put a finger on it but idle was smoother, shifting seemed easier...was like there was this pent up aggression in the car that just got released and it was relaxed again =)

Some of what used to pass as an "Italian Tuneup" is now the electronics adapting to a different driving style....before it relearns and goes back to the frugal, boring, everyday, driving-in-traffic style.

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X2, I was gonna say it could be the adaptation and short/long term trim levels being manipulated. I know some cars, you can do a certain procedure to manually reset the adaptation values for certain parameters such as throttle response.

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This adaptation is really quick and is an ongoing process. How quick? Well, the 1/4 mile guys say the 1st run is for the DME the 2nd run is for the money.

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get the poison out!

I use mine as a DD and I can definitely tell when it's time to hit the freeway. Too many short trips on surface streets and the car feels sluggish. Open it up for a long 65mph++ stint and it purrs like Porsche again. I love freeway on ramps!

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Sounds indeed like the DME making a huge difference. SO I wonder why the "boring" run parameters are incorporated for around town driving? The "performance" one sure seems better for any and all conditions! how long does this DME change last, I wonder? Exactly the same for me!! I need more time in the car on trips like this. What a blast.

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Yeah +100mph for over an hour is the fix not only the car but the driver needed made a boring near straight interstate run twisty and interesting...

I wish! I need some track time. I only had brief pulls to +100 when I was blocked in along side the 18 wheelers doing 85+, and had a car in front and behind me. I would let the car in front pull ahead at 85 while I slowed down to maybe 75 (which I'm sure irritated the driver behind me, but, oh well Then when I had a good maybe 1/8 mile open in front, I dropped to 4th, let her open up and left the cars behind me...well,way behind me.

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Nonsense. There is nothing quite as generous as giving the driver behind you the thrill of seeing 911 in full acceleration right in front of them!

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The DME adapts constantly as various inputs change. This is quite obvious when one starts a cold engine and it idles and warms up. At no time is the engine improperly fueled. I'm not the only one to have done this but I can say from my experience driving my Porsches in all kinds of driving conditions in all kinds of weather from near zero temps to triple digit temps from a few feet below sea level to nearly 9K feet above none of my Porsches has ever been caught on the wrong DME foot so to speak. Another technique to observe the DME adapt is to while the engine is idling remove the oil filler tube cap. This creates an air leak and while the engine initially reacts the DME in just a moment sorts out the fueling. This is at idle but at higher engine speeds the adaptation happens even quicker. Yet another example though one can't observe is when the knock sensors detect the signs of detonation. The DME adapts so quickly that the harmful detonation never occurs. Thus these engines can run very close to incipient detonation for thousands of miles with no harm. No slow to learn DME would result in that kind of engine longevity. While the quarter mile guys assign the 1st run to the DME, the DME doesn't need this. Under hard acceleration the DME goes open loop and then uses fuel/ignition maps that are designed to meet the torque demand of the driver. So whatever the DME has learned isn't used in this case. The benefit of an extended run at "speed" is the valve and combustion chamber deposits get removed -- washed or burned away -- over time and combustion improves.

Macster - another good, informative post. Thanks, dude

Yes, that makes solid sense, thanks. I know it had to do with the load on the engine. Obviously 5k rpm in 4th is under a lot higher load than 5k in 1st, 2nd, or 3rd, so there would be elevated combustion temps from the increased flow of fuel, and hot exhaust gases. I like Gonzos take on accelerating away. Too funny.