USMC_DS1

Engine wear(cylinder lining) is actually address in the Hartech article. They position that low rpm is bad for the liner... has anyone else reviewed their tech doc n what r ur thoughts. I'm always interested in the 2nd or 3rd opinion especially if it's back by some credible references.

am722

I do most of my driving in 1st and 2nd and try to alter RPMs wildly between 500 and 7000. I generally am at peak RPMs approximately 40 feet from a stop light or stop sign, and if traffic is clear I will sometimes come to a dead stop in the middle of the road. I like to keep my brakes on their toes and my tires hot. I have a full HANS installed and I make passengers sign waivers before they accompany me to the grocery store.

These are performance cars, and as such, I perform in them. If you're not first you're last.

Quadcammer

Is this what you're referring to: "

However - because the torque at low revs is so much greater with these later engines the load on the piston/cylinder wall is much higher - even when a driver is not revving the car high (or therefore thinks he is not driving aggressively or near limits) simply enjoying good performance without realising the consequences – and so we find that a greater number of “more modest” drivers are experiencing this failure than
before. Furthermore it is a strange fact of piston wall lubrication that the most difficult revs to protect from “piston scuffing and bore scoring” is often at very low revs (where the later engines are
also producing more torque)."


If so, its basically useless. It provides no guide as to what RPMs qualify as "low" or "very low". They also do not elaborate on what type of load or throttle openings we are talking about.

its common sense that one should not heavily load a motor in high gear and low rpm. However, in light throttle steady state cruising, there is nothing at all with running at 2000rpm.

the added torque at rpms between say 1500 and 3000rpm certainly make the car easier to drive there, and I could not glean from the hartech article why they believe the engine experiences cylinder scoring or piston scuffing due to lack of lubrication there.

What I can tell you is that higher rpms put more stress on the rotating assembly. In addition, heavy acceleration (read load) at low speeds (read minimal airflow through radiator), can result in high CHTs and EGTs and that can cause the same scuffing and scoring.

The end result of all this is that if you drive in extreme ways (pounding the gas at low rpms, or constantly winding it out), there is the potential for damage. If you drive normally, at moderate rpms (say shifting between 3000rpm and 4500rpm) for the majority of the time, your engine will be just fine.

The notion that porsche engines are so different or special and must be run at high rpms for a long life is a myth.

CORSASCHNELL

Cold start: shift at 3K, normal driving: 4K, spirited driving: near red line.

Up shifts at low RPM ( aka lugging the engine) is never good practice. Internal combustion engines like "steady state", the more constant RPM results in higher efficiency and longer life.

Quadcammer

once again, what is "low rpm" to you. lugging a 997 engine requires you to be in almost triple digit rpms at a steady state

USMC_DS1

I'm also disappointed that Hartech did not specify what they mean exactly by "low RPM" but as an engine re-builder I'm taking their article with at least a grain of salt. BTW, I too have inferred that above 3k is a preferred shifting point, however, I've yet to see anything documented/published re which RPM band ranges are optimal to shift at.... So in reality anything we says is really just speculation. FWIW, I like shifting above 3k, the car just likes/feels right above 3k, but it would be great if someone actually had a report/article/reference to point to other than their opinion... of course, this is the internet so everyone is free to opine away.

crazycarlitos

before warm-up, i like to shift at around 3k

once warmed up, i shift around 4k or above.

for spirited driving, i shift around 6500 rpm.

i usually keep the car around 3500 rpm when driving around.

Whats the point of driving my car @2k RPM ? I might as well drive a Prius..

Fred R. C4S

A lot of you guys make me chuckle. As an old, worn out, retired Mechanical Engineer, I dare say there is probably not more than one of you who can actually define lugging.

Today's 3.8 liter engine with variocam, variable intake tracts, computer controlled ignition and injection is a totally different animal than say a 2.7 liter carbuerated 911 from the 60s or 70s. Those engines produced so little torque in comparison, that you had to be in the upper half of the rev band constantly in order to have the torque on tap or available to match the load your were applying to the engine. Today's engine is so much more flexible that a PDK can run on a flat level road at 1500 rpm or less around the subdivision. Put your foot down (ie ask for or put a load on the engine) and the gearbox will shift to 2nd or 3rd in a few milliseconds and you are at an engine speed that will develop more than enough torque to do the job.

You want lugging, try climbing a 10% grade from 1500 rpm in too high a gear (4th 5th or 6th depending upon your present speed). You can have the throttle wide open, but the engine cannot make additional torque available to accelerate the car. Cylinder pressures go up, temps go up, but your speed doesn't increase. In a worst case scenario, the car would actually buck and cough or even knock. Have any of you actually experienced engine knock first hand? If you've never driven a car built before the late 80s or early 90s I doubt it. I had a 72 Pinto beater that would knock so bad you thought it was going to throw a rod. Now THAT'S lugging!

CORSASCHNELL

Lugging to me is up shifting at 1500 RPM or when the engine is struggling to build up RPM's in higher gear. Proper up shifts are when the car maintains and builds up speed from previous gear selected.

crazycarlitos

fortunately, some of us do our own shifting. LOL

unlike PDK, we can't downshift in milliseconds to accelerate out of dangerous situation, if necessary.

manual 997 should be driven in optimal RPM range.. for safety and performance. 1500 RPM is NOT it. Most manual 997 drivers prefer 3-4k RPM on the streets.

I agree that our engines are not like the old P-engines..
but just because we have "variocam, variable intake tracts, computer controlled ignition and injection", it doesn't mean our engines are no-longer high-revving. Over the years, Porsche not only kept the exterior similar, they also made sure the driving experience is similar (and better) with each generation. Hence we have 997 GT3 with 435 HP @ 7600 RPM

compare that to:
Corvette ZR1 638 HP @ 6500 RPM
Camaro ZL1 580 HP @ 6000 RPM

fastm3

I really don't know what's good for the engine, but I do know what's good for me! That happens to be right between 4 and 5K, for most situations.

TxBob74

I am between 2500-4000 rpm probably 90% of the time. Never above 3K until oil temp is nearing 200F. Thankfully, Porsche lets 911 owners know this temp; why can't they put a similar gauge package in the 98X series? One of the reasons I traded my 2008 Boxster.

I am surprised that no one has mentioned the upshift light triangle that sits beside the digital speedo, at least on my 997.2. (The '08 Boxster did not have it). My impression is that if I followed the upshift light I would be in 6th at 35 mph. Absurd for a sports car and reminiscient of the analog "economy" mpg gauge on my 95 M3. At least Porsche gave us an antidote; it's called Sports mode.

Quadcammer

agreed completely. The "lugging" argument comes from 356 roller bearing motors. You really need to do something stupid to lug a modern car.

You aren't understanding his point. Firstly, with a manual, you should have the good sense to realize that 1500rpm is not the time to floor it. As such, you should have already downshifted. On the other hand, steady state cruising at 1500rpm is fine.

Please share with us what the optimal rpm range is, since you must know.

Furthermore, his point was that the newer cars develop so much more torque at low rpm that its not lugging to drive it at 2000rpm, not that the engine can't rev high.

Then again, what the hell is the obsession with revving high? All that does is put further stress on the engine. If you can make 500bhp at 6000rpm or 7500rpm, I'd much rather take 6000rpm.

Finally, your examples of cars that make between 150 and 200bhp more than the GT3 certainly doesn't make your argument very strong.

thats what its all about.

if you want to rev it cause its fun, do it and enjoy. Thinking that revving high is doing your engine any favors is silly. Don't worry about it and drive the bloody car how you want to.

wanderingwheelz

I'm still in the engine break-in period. This thread is killing me!!!!

I've only had my car past 4000 RPM a few times, and never as high as 6000 RPM.

I really need to get more miles on this thing.... Anyone near Delaware want to borrow it for awhile?

CORSASCHNELL

There was a little write up in a car magazine a few years back re break-in period. One guy who was picking up his Porsche from the factory via the Euro delivery program was told that new Porsche cars do not need break-in. Porsche asks for it so the "driver" gets used to the car in the first 1000 miles or so to avoid crazy mistakes due to unfamiliarity with the car's high performance levels.

True or not, I like to break-in a new engine, better safe then .......