Surge at around 3000RPM?

My '99 C2 996 Tiptronic, seems to be developing a slight engine surge around 3000 RPM. While not under load everything runs okay. But when accelerating in 2nd or 3rd around 3000RPM the engine goes from a noticably lower tone to a higher tone in a little surge rather than the normal smooth progression. I'm thinking that one of the sensors might be causing this or perhaps the Tiptronic box? Any ideas where to start looking? PS: I've driving in M not D.

Variocam

I use to have that, felt like turbo boost. I thought it was pretty cool, but it went away..

I bet it didn't go away, you just got so used to it that you don't notice it anymore. I don't unless I am thinking about it. Try light to moderate throttle through 3200 rpm in second gear. I think you will feel it.

THe variocam smooths out substantially when you use an oil other than 0W40.

What evidence do you have to support this claim?

Because it does in most cases. Timing is engaged more smoothly and does not jump. Proven by Porsche technician. Many people find that several symptoms disappear when then stop using 0W40 motor water. Not just Porsche vehicles, either. I do not understand why people insist that this is the preferred choice when only 2% of all the oils on the Porsche' ever changing approved list include 0W40.

In other words no evidence. I use Mobil 1 0W40 in my car and have had zero problems with this oil (including Variocam). The oil you continue to recommend is not on Porsche's most current list. I'll continue to fill with one of Porsches recommended oils. You are certainly free to fill your car with any sludge you choose.

So, your smoke at startup indicates that you have no problems? It is quite easy to prove that the 3.4 valve timing engages more smoothly when not using 0W40. Anyone with a data logger can do so and see the proof themselves. BTW, Porsche DOES NOT recommend 0W40. It accounts for only 2% of the approved oils by Porche. The vast majority of approved oil is a 5W40 weight.

Re-check the TSB, Porsche does recommend Mobil 1 0W40 on that list. The oil that you advocate is not on the list. Both of my cars operate very well with Mobil 1 and Porsche engineers obviously like how Mobil 1 works in Porsche motors (Mobil 1 is the factory fill). I have zero interest in arguing with you on this point (I like your posts, but you clearly have an "axe to grind" with oil selection). Porsche engineers obviously have their own opinions on the oils that should be used in their cars (the list of oils in the TSB is very clear). If you want to ignor the TSB and use a different oil that is certainly your prerogative. I will agree to disagree.

I did not recommend any oil in this thread. Read it again...... slowly. Also I will say it again....slowly....Porsche DOES NOT RECOMMEND 0W40. Stop reading what you want to see and read what is printed.

Read even more S L O W L Y. It is on their current list of recommended oils for the 996 (read the TSB for yourself) I am sorry if I mistated your position on oil. In past threads you have recommended oil that is not on Porsches current list. Have you changed your opinion on this?

Are you confusing "approved" with "recommended".

I am not confused, but you appear to be. In my posts I continue to use the term "recommended". Porsche has issued a TSB for the recommended oils (there are many) for the 996, Mobil 1 0W40 is on that list. I have never said M1 0W40 is the only oil on Porsches list. Once again, it is on the list of current recommended oils TSB. Have you changed your opinion from past threads where you recommended oils outside of Porsche's current TSB for certain driving conditions? To further clarify, I would not have any issue putting any of Porsches recommended oils in my cars. However, I have no interest in second guessing Porsche with an oil outside of their list. Why would I? My Porsches seem quite happy with Mobil 1 BTW, this is my last post on this issue in this thread. I have no interest getting caught up in an oil argument.

Well, just so there is no confusion, Porsche DOES NOT, repeat DOES NOT make any recommendation as to a specific oil to use. All they do is list those oils that they have tested and have met with their APPROVAL. They have not tested all oils and therefore no position is taken by them. Obviously. people are going to make their own decision (hopefully an educated one) on which oil to use. However, they should not be led to believe that Porsche RECOMMENDS any specific oil.

Well 199Porsche 911 is correct. Porsche currently lists 7 pages of approved oils I think 84 oils are on the list for all cars built since '84. TSB group 9, #1/05. Only a small fraction of the oils listed are 0W40 (13) and Mobil1 one is only a small fraction of the approved oils (3). And not all approved oils are available world wide. Some of the more familiar ones approved in North America are Castrol Syntec 5W40, Castrol GTX 5W-40, Mobil 0W-40, 5W-40, 5W-50, Agip 5W-40. So make an educated decision based upon the use of the car and your climate. Porsche does not recommend a particular oil, it factory fills its cars with a particular brand but does that mean the racers running Amsoil or somethiing similar are fools? Just my opinion. Todd

Thank god finally somebody to put that to bed.

... for today!

I did notice that there is a sticker on the engine compartment hood that says "Factory Filled with Mobil One" or some such garbage. There's only one reason that Porsche uses Mobil One as a factory fill, and it's spelled out for you right there with the sticker. $ I don't know the symbol for deutschemarks or euros or whateverthehell money they use over there this week, but Porsche did not put that little sticker on the car out of the goodness of their hearts. Exxon/Mobil paid dearly for that, let me assure you. But hey, if you want to think that's what you should use, then by all means do so. You'll make the marketing guys at E/M very happy. The stuff was $6/quart last time I looked. OUCH! Michael

MJB, what do you use instead?

Exxon 20W50 dino oil. It's on the approved, er, recommended, er, uh, well, it's on the list. Official OE filter though. And I was wearing my Porsche shirt and air-cooled hat (left over from my 993 days) when I changed it. Michael (AKA MJB)

I just got back from the kitchen to get my popcorn and a beer, did I miss anything? Tastes great! Less filling!

Ditto regarding 20/50 although I use Castrol. I've used it on all my Porsches since the 80's...running all of them to 200,000+ miles without issues. I haven't changed the oil in the 996 (I've put less than 1200 miles on since I purchased it) but I plan on using 20/50 in that as well. I have a hypothesis, born of experience, that tells me thicker is better. This is a faith based hypothesis that I'll never try to prove for sure and, as long as I'm not disproven, will continue to include as part of my regular pcar maintenance.

I've thought about this more since posting the message. I used to use 20w50 in my C4 Corvette. It was a track rat, and I beat the overlovin'**** out of it, that poor thing. I bought the car new and at around 16K miles turned it into my track car, major engine work, suspension, brakes. I had all manner of issues (it was a Chevy afterall) and problems due to the abuse on track; wheel bearings, ball joints, lost the power steering hoses, some electrical stuff, but other than worn valve guides and broken valve springs, not a single ittybitty bit of engine problems, even after driving in sub-freezing weather at Road America and other early morning winter events with that heavy oil. I'll never forget flying down the straights at RA at 120+ with snow blowing in the window. Brrrrrrrrrrrr. Michael

How dare you people use an oil other than those approved by Porsche! I guess there are fewer zombies who blindly follow anything Porsche says than some thought. Some people on this board frown on those that actually use their intelligence and make decisions based on their own experience and knowledge rather than blindly following marketing hype.

Here's the thing (and out of curiosity): why do you think that Porsche recommends 0W-40 fill then? Mileage? HP? Seriously, what do you think? And second, anecdotal evidence that's been espoused on here is fine and often worthy, but anecdotal evidence also was responsible for flat earth societies, bloodletting via leeches in medicine, mainframes instead of PCs, etc. I'm not trying to throw cold water on these experiences, but it's always worthwhile to question things.

Porsche DOES not push Mobil 0W40 at all. As a matter of fact, 95%+ of their approved list includes oils other than 0W40. Their factory fill is directly related to the amount of money Mobil gives them for using their product. That is not opinion, but fact and is a standard practice in the industry. Yes, in theory, a thinner oil will improve gas mileage as well as power. That is, unless it causes burning of the oil. In an emsision compliant car, this means that all this burned oil is being expelled out of the exhaust AFTER it has passed through the intake. This means the octane of the fuel in your car is reduced and the inatke air is hotter (power loss). In the short run, a thin oil may give you more power, but unless it also provides the maximum protection against wear, it won't give you power as long as it should. Among the componants at risk because of too thin of an oil are, guides, seals, bearings and journals, and so on. Many racers will use an ultra thin oil to maximize power, but their engines are rebuilt regularly. BTW, blood letting was sound medical practice and has been proven to reduce risk of many ailments, including heart desease. This is the reason given why premenepausal woman have fewer heart attacks than do men.....due to their regular monthly bloodletting. Risk level for men who give blood several times a year, also have shown to drop to the level of woman.

You missed my point; why do most US Porsche dealers fill with 0W40? I mean, even in light of a relationship with Mobil, they clearly make other alternatives, like the aforementioned 20W-50 and also a 5W-50 version. Why not use that formulation? I'm not even going to get into a discussion on bloodletting, but feel free to read this link from Wiki for more info.

Does a dealer care? Additionally. more and more dealers are using oil other than Mobil 0W40.

A dealer will likely do what Porsche recommends/suggests, though. I guess a study comparing the wear of an engine during average use in a cold and warm climate would be the only way to scientifically settle this debate.

Anyone know when I'll have to swap the PZeros for Michelins? Porsche-Partners

Getting back to the originalk question, is there any change in mixture/settings with Variocam that would emphasize the 'surge'.. I'm also seeming occasionally some 'hesitation' around the surge when I'm not positively accelerating.

My porsche independent mechanic switched me over to 15w50, saying 0w40w is too thin... I was hesitant but since he changed me over car runs smoother, and the variocam does not surge... plus my oil pressures are much better, with 0w40 when the care got into the 0 of the 180 the oil pressure dropped to near 1.1 bar, now I rarely go below 1.5 and above 4.5.

As I was asked.....where your proof? It cannot be true unless you have obtained a proclaimation from Congess that it IS true. I have tested dozens of engines running both 0W40 and 15W50 and, without exception, the engines running 15W50 idled better, valve timing switching was smoother, better throttle response, reduced or eliminated oil burning and leaking and engine was quieter. It is only a matter of time before 0W40 becomes the oil of choice for drivers living in sub-zero temps and/or the uninformed. Even a 5W40 oil smooths out the idle and helps in the variocam shifting. Therefore, if you are running 0W40 and have engine problems, many of us have given you a suggestion. It costs you nothing to try a better oil. I wonder when we will get word that Mobil has "reformulated" their 0W40?

I'm using 0w-40 and get this surge off and on... couldn't care less whether it surges or not (used to VTEC S2000 POWA!) as no one is telling me based on evidence whether it's a good or bad thing, but it sounds like it's a common thing... so why the heck would you use it as part of an argument to fill with a heavier oil to smooth it out if this is a normal thing?

Sorry to resurrect this thread but my car surges around 3200 RPM too. Should I be concerned?????

Ran a search and found that this is quite common and normal for the Variocam.

I thought I read somewhere (renntech? pano?) that you should avoid high viscosities (15W or the like) in the 996 because the variocam was designed to operate on lower viscosities that flowed faster through its passages or something.... I clearly remember reading that 15W+ was BAD for the variocam... NOt saying that's right, but I read it somewhere serious ;-) Personally, living in FL and frolicking at Sebring a lot, 15W50 or 20W 50 makes a lot more sense in my cars, but I've been afraid to use that in the 996 because of variocam - which incidentally is very noticeable and annoying on my car with the dealer's oil 0-40! I'm gonna go download that oil pdf and do an oil change myself, after all what is the worst that could happen, I just bought an extended warranty ;-)