Shifting above 3500 RPM. Good for a 911 or not?

[CPBMD]

Hi All
I have been told by numerous enthusiasts on numerous occasions that it is important to shift gears at or above 3500 rpm's. They say that lugging the engine is very bad for a Porsche. I have also read in a book that it is even better to shift at 4500 rpm's. I have been doing this with my '89 C4 for a while only after the engine is warm. I am wondering if this is fact or fiction.
Thanks Cons

[TMc993]

I don't buy into the "Shift at 3500 RPM" theory or any other similar theory. I really have a difficult time believing that Porsche (Or any other manufacturer for that matter) would build a car for general street use that couldn't be driven below any given RPM level without damage.

I think this is just folklore that has been passed down from earlier times when there were no engine management systems like we have now. Even though the newest of 993s are now approaching 12 years of age, their engine management systems are quite sophistocated and significantly minimize the type of wear we saw back in the days when people used to brag about getting 70K miles on an engine before they had to remove the heads and do major repair.

From all that I've read, what is more important than shifting at any given point is keeping the oil at the appropriate level, getting the engine and transmission up to operating temp as quickly as possible after starting the car, then making sure that, over time, you drive at a variety of engine and transmission speeds.

That said, there's nothing like winding it up and hearing the sound of that big flat six is there?

[Matt Monson]

I've never understood why anyone would spend any amount of time driving outside of the powerband that the cam provides. When you are "on" the cam, the engine is both most powerful and most efficient. Driving below that threshold isn't going to hurt anything but not only will you have less power, and slower acceleration, but your fuel economy will go down.

I shift ALL of my cars between 4000-4500 rpm ALL the time. This is the same on my '68 911t, my '73 914 2.0l and my 2008 WRX. Sure, if I am cruising along at 45mph for a significant period of time, I'll shift into the highest gear where it doesn't bog (generally 4th) and run the engine at 2500 or even less. But when I am actually accelerating the car, whether casually or spirited, I always shift over 4000. Furthermore, running the engine up to 4000+ rpm does NOT require putting the pedal all the way to the floor. You aren't obligated to waste gas by going full throttle all the time.

[computamedic]

I can't believe you guys!!! I make a point of EVERY time I take the car out, I wait for the oil to get nice and hot and make sure I hit the red line at least a few times in every journey. That's close to 7,000 revs on my "chipped" car and even in traffic I'd usually be way over 4,000 revs unless it's moving at a snails pace.

These engines are designed to rev and thrive on it!! Letting an engine labour at low revs is bad for any engine - Porsche or otherwise.

Regards

Dave

[CPBMD]

Dave
That is what I like to hear. I shift around 3500 rpm most of the time. After reading your post I think I will do as you do and rev the engine to 6000 rpm a few times a journey. Thanks for the input.
Constantine

[CPBMD]

Hi Matt
Thanks for the response. You are correct about shifting on the cam. In 2nd gear when I hit about 5200 rpm's the car really takes off. It feels like a turbo is kicking in. That must be the cam effect you are talking about since my 89 c4 is not a turbo. After reading your comments I am going to make sure to shift in the 4500 rpm range from now on. It more fun to drive that way anyway.
Constantine

[TMc993]

Okay, I'm going to defend my statement. The original post said:

Originally Posted by CPBMD

.....that it is important to shift gears at or above 3500 rpm's. They say that lugging the engine is very bad for a Porsche. I have also read in a book that it is even better to shift at 4500 rpm's.

I didn't say that shifting at 4500 RPM all the time was bad...All I said was that I didn't by into the theory (And it is a theory) that one should shift at any ...3500...4500...Hell, let's go for 8500...given RPM level all the time or risk catastrophic engine failure. That's just bull****.

I know the engines are made to rev...I've owned three Porsches and am well acquainted with the make's traits....

But, I'll bet you this...If you guys were looking for a Porsche to buy, I bet if you saw an ad that said, "I reved the **** out of it every time I drove it!" you'd run in the opposite direction.

[afast16v]

Originally Posted by TMc993

Okay, I'm going to defend my statement. The original post said:



I didn't say that shifting at 4500 RPM all the time was bad...All I said was that I didn't by into the theory (And it is a theory) that one should shift at any ...3500...4500...Hell, let's go for 8500...given RPM level all the time or risk catastrophic engine failure. That's just bull****.

I know the engines are made to rev...I've owned three Porsches and am well acquainted with the make's traits....

But, I'll bet you this...If you guys were looking for a Porsche to buy, I bet if you saw an ad that said, "I reved the **** out of it every time I drove it!" you'd run in the opposite direction.

I agree with this comment...totally true

[Tom W]

Well, it's a question of if you are asking about shift points while accelerating or if you are asking about what rpm's should be maintained while cruising down the road.

I always shifted while accelerating at 5-6k once the engine was warm. It's more fun and it's where the power band is. I'm a firm believer in "life begins over 4500 rpm" for our cars.

The manual warns against lugging the engine (trying to accelerate from 2k rpm) but that does not mean you can't cruise down the road there, you just need to downshift before trying to accelerate. That said, I always cruised at about 3.5-4k rpm. Gas mileage suffered a little but I didn't have CEL issues from carbon build-up caused by putt-putting around and I could accelerate as required without a shift required.

I personally would avoid a car where it was not driven at higher rpms (as opposed to running from one that was).

[Rich L.]

The explanation I got from my shop on this topic had to do with oil circulation. The oil needs to be up to temp and the engine running at 3k+ RPM for the oil to be flowing nicely through the oil cooler in the nose. At lower RPMs the oil will circulate but not really fast enough to cycle the oil through the cooler fully. So if you run below 3k RPM all the time, some old oil can sit in the corners or the cooler and never fully warm up to match the rest of the oil and can develop some water in it which can rust the fittings up there between the lines and the cooler.

Note: I'm not an expert, just relating what I was told by someone I consider to be one.

Cheers,
Rich

[J Richard]

I think this is a carryover from the early years of the 911, my first a 67s didn't make any power below 3500rpm, and it would cough a spit unless you kept it "on the cam" the motor would lug badly if you didn't keep it in the proper rev range...but it was a blast to drive all wound up...

Every generation has gotten better with better bottom end and wider rpm range which has lessened the issue... the 964 and 993 almost drive like "normal" cars by comparison...that said, I drive mine on the street from 3K and up, and wind it right through the sweet zone every time on my way to the speed limit (or ok maybe a little more...) Yeeehaaa.....

[Chaos Theory]

I find the Porsche's I've driven (pre-90's air cooled) do not like to be shifted to the next gear unless you have a good amount of RPM's (~3500+), mine included.

Like others above I make a point of generally maintaining a cruising RPM of at least 3 grand, and I do take it to redline briefly every so often after it has reached operating temp.

I knew it just felt better and one of my friend's has eluded to what Rich has pointed out about the oil cooler, but I'm glad this thread came up so I could see other views.. Subscribed.

[Noah]

I never drive my car below 6000 RPM's, these are sports cars designed at the factory for high performance. If you lug the car around at 5000 RPM's you'll foul the plugs, create engine sludge, and cause pitting on the cam lobes. You have to drive "on the cam" which means 6000 RPM+.

[lupin..the..3rd]

If you take your gear ratios, and plot them as a logarithmic curve, overlay that on a horsepower graph (like what you'll get from a dyno run) and you'll see the ideal engine speed for each gear. For a 911 SC driving in 2nd gear, it is 5240 rpm. There's also a simple equation that calculates the laminar flow characteristics of the oil cooler vs. oil temperature and engine rpm:

[trak ratt]

Wouldn't it be easier to use the spread sheets on Instand-G?? That way you can just pick the correct one for your car/trans, enter the tyre size and there you have it!!! Graph of RPM / gear, and at the bottom the MPH / RPM

[forklift]

just get a tip and be done with it.

I try not to shift at all though since it wears on the trans. I strart out in 3rd and can make it to 4 different starbucks in 3rd.

[Rob in VA]

Also, be aware of using the steering wheel at full lock, especially when turning right. For whatever reason, Porsche designed the steering rack to be optimized for left turns. So, I usually plan my routes with a minimal amount of right turns. It's not too bad once you get used to it. Ideally you never want to use more than 30% of steering angle. Oh yeah, I never parallel park the car because it's way too abusive.

[PK Dorki]

Originally Posted by Rob in VA

Also, be aware of using the steering wheel at full lock, especially when turning right. For whatever reason, Porsche designed the steering rack to be optimized for left turns. So, I usually plan my routes with a minimal amount of right turns. It's not too bad once you get used to it. Ideally you never want to use more than 30% of steering angle. Oh yeah, I never parallel park the car because it's way too abusive.

You can fix that issue by inserting a thin plastic shim just to the left of the steering U-joint (in the smuggler's box). I have a spare one of these shims I can sell you for $40 (a 20% discount) which will solve your problems!

[Rob in VA]

Originally Posted by PK Dorki

You can fix that issue by inserting a thin plastic shim just to the left of the steering U-joint (in the smuggler's box). I have a spare one of these shims I can sell you for $40 (a 20% discount) which will solve your problems!

PM sent!

[lucittm]

You guys crack me up...

Mark