996 Engine Strong vs. Weak

I have searched for a 996 for quite some time and have driven dozens of examples in that time, both 3.4 and 3.6 liter motors. I was always amazed how a car may seem "fast" to me one day then I would drive another example of the same car on another day and not think its that quick. I have read on several occasions here on this site that people claim to have "strong" motors vs others. What does this mean? What are the tolerances from porsche on hp from the factory? I always thought that Porsche was very conservative and had tight measures. I had not driven many examples back to back on the same day but have others here done so and if so have you seen differences where a particular car seems noticeably stronger than some other same model? Could it be some are just out of tune or is this just a product of how they came out of the factory? What do you guys think?

I think what you may be experiencing is the difference in suspension on different cars. Some "looser" cars tend to create an illusion of a slower ride, etc.

My car feels fast on some days and slow on others.

I find my car is like a women, some days a great ride, others i would rather drive something else!!

My car has been said to be exceptionally fast when it was stock. It would pull 3.6l by a bit. Whetehr it does now with more miles and more mods is tough to say. Sometimes the car feels slow to me sometimes not. I find it feels slow depending how I drive it. If I am trying to use power not in the powerband and don't downshift then it seems somewhat down on power. However this is only when the car is cold and oil is not yet to temp. I usually drive the car how it's supposed to not abusively but I like to not lug it either. It also makes a big difference to me at least as I feel everything on the butt dyno, whether it's cold or hot out. If it's 70 or below the car goes great. If it's 78 or above it goes fine but I can tell that because of the crappy 91 gas it is retarding the timing. I used to run the mix with 100 but there isn't anywhere around in SD that has it at the pump that's close or where it's reasonably priced otherwise.

I'd be willing to bet that if you took ten 996s of the same year, put in the same fuel and put them on the same dyno on the same day you would find their power to be very close to identical. However, gas, air density and weight can all have a huge effect on how fast a car is on a given day. My 996 race car with a full tank of gas at the beginning of an enduro feels like a pig compared to qualifying with a couple of gallons. The 100 lbs makes a big difference. As mentioned, air temp/density also has a big impact as does the quality of the gas. I really think it's these factors that account for fast vs slow rather than some engines being faster. Jim

totally agree!!!!!!

LOLOL I hear that! Though i do agree, and it must be the suspension between my C4 and my C2. The C4 seems faster and stronger then the C2... though both are same year and same motor.

Interesting I actually find unless I am just a wierdo and there are other factors to blame, that the car doesn't run as strongly with under 1/4 tank, as full or anywhere above? Well regarding the variance in engines, I would tend to agree assuming they are mass produced and not by hand like cup engines. I remember reading somewhere that cup engines used to be signed by the assembler, and some dyno'd higher which led teams to seek that particular assembler. Porsche then disallowed the signing of the engines because of this. I do feel however that my car has always been "unordinately fast". I never thought much of it until other very seasoned P car owners pointed that out. I also feel that how someone treats the car will also vary how much power the car looses over time etc. I.e. if a car is properly broken in and always warmed up before it is driven hard, I would expect less wear than if someone doesn't adhere to the break in procedure, and doesn't warm the car up prematurely wearking the cylinders, rings, guides, seats, etc.

+1

the fuel bump is getting old... i tried a 2001 996 today, it doesn't feel like fast. don't know why. maybe the summer tires and the temp. is like 30?

No question a tired engine will loose power. I don't get the 1/4 tank thing. Maybe you are just a weirdo.

I have always felt my motor was put together pretty well, no leaks and strong on power. I figured there are regular engine assemblers and master engine builders at Porsche, when the best aren't busy with TTs and GT3 engines they will buid a m96 motor.I think I got lucky. Makes sense to me, but I'm a crazy old F.

I don't think the average butt-meter can reliably tell the difference between engines in different cars. Different options can significantly affect weight including tires, wheels, seats, Litronics, different years, etc. I can tell the difference between full tank and empty, and it pulls harder when on empty. If you're not sure, get a G-meter for $100. I've made probably at least 100 runs, and it maps pretty nicely depending on temperature, tank fill, weight, and mods. I see a difference in ditching the spare tire, for example. With that said, there is some variability, though. Sometimes the ECU just says go; other times it seems to be acting lazy. That could be possibly due to our crappy gas and the ECU thinking, "I'm not sure this time."

I also ditched the spare and have a plug kit and compressor in the car. I do know that the ECU supposedly is a learning type and if you drive it like grandma it will respond like grandma. I have pulled the battery cable for 20 min after I do any maintenance like clean maf, or tb, or air filter, whatever, and it definitely is different. Also after a nice spirited mountain drive the car even around town is much more responsive. This could be just cleaning out the plugs and the like though

On normally aspirated engines, a change in density altitude will affect the performance of the engine, especially in its ability to produce horsepower. It's the reason why a piston propelled airplane will need a longer runway to take off on hot humid days as compared to cold and dry weather. The heat and humidity will decrease the amount of O2 per cubic foot of air. Therefore on hot humid days even if you are at sea-level, your engine will feel like its at a higher elevation (where the air density is lower). The opposite is true: generally on colder drier days, the engine will behave or suck air more efficiently and therefore feel with more horsepower or at its optimum hp even though you may be at sea-level, behaving like you are below sea-level where the air has more available O2 than on what aviation people call standard day (or something to that effect). I used to be a private pilot (up until I married 7 years ago and now with children) and density altitude is a very critical factor that is considered in aviation every time a prudent pilot is about plan their flight. You don't want to overload your airplane on a very hot and humid day with a runway that is short. You would run out of runway before you have enough speed to take off, all because your engine is not producing all the horsepower it is rated for, and it behaves like if you are taking off from Denver, Colorado even though you may be in San diego CA. Turbocharged or supercharged engines will not feel this change in density altitude up to point, meaning that the envelope of performance is wider. Mostly because the turbos will compress the air into the engine and increase its performance. Also, don't forget what the engine's computer does to retard the ignition once it detects pinging.

Example of the density altitude factor frm my 172P POH: 0 deg C at SL, 795 ft ground roll and 1460 ft to clear 50 ft obstacle 40 deg C at SL, 1065 ft ground roll and 1945 ft to clear 50 ft obstacle Don't forget the engine management system will lean the mixture with high density altitude. Pilots do this with a mixture control **** to get maximum rpm when the density altitude is high and the runway is short.

the 99 has motronic 5.2 which "learns"... I'm not so sure about model years 00 and beyond which use motronic 7.x - less parameters in this system for tuning...

i believe the only thing that learns is the tiptronic tranny, not the engine.