ttreat

I have read numerous post saying to keep above 3000 rpms. Since I will be driving my new to me '01 back from North Carolina Friday I thought I would ask if this is applicable on the highway. According to some transmission info I have, cruising at 65 mph would be just shy of 2600 rpms. Cruising at 50 mph would be just shy of 2200 rpms. Are these rpms too low even for highway cruising. Obviously, I wouldn't want to lug up a steep hill at these rpms but for generally flat, rolling or downhill highways, is this really a problem?

ivangene

I stay clear of long periods in the 2900-3500 rpm since the variocam kicks in there... I either drive above that or below it....

if you find the rpm's are too low... just GO FASTER !
LOL
have a safe trip !

ttreat

I'm sure I will find plenty of opportunity to GO FASTER and be above 3000 rpms. I just want to know if I need to downshift when I slow down.

yasuro

in my 6 speed when i'm about 80 MPH in 6th gear (a good highway cruising speed, imho), i'm at about 3000 RPM. so fwiw, i think that it would be safe to run at that to maximize speed vs. fuel efficiency. i leave it to others more knowledgeable than myself to respond about the variocam question.

i may be mistaken, but i would think that porsche would have designed the car to be able to cruise at US highway speeds in the tallest gear without harming the engine. of course if you take autobahn into consideration, maybe porsche assumes cruising speed to be 120 MPH?

htny

I agree 100% w/ yasuro, if long distance on highway then top gear, that's what overdrive cogs are for!

Meister Fahrer

It's even better than that since German cars have always been designed to be able to cruise extended periods at top speed.

That even goes back to the old aircooled Bugs cruising at top speed of 72mph.

But I find it also cruises well at low rpms, just don't lug it under load obviously.

Again, the aircooled VWs and Porsches were designed to maintain higher rpm's for proper cooling as well.
Another benefit of water-cooled in a modern driver.

Shark Attack

My first look at the title of this thread I thought, "WTF whatever is safe" But I see this question actually has some point behind it.

I dont mean to hijack, but what do the varicams do and what exactly do they do when they "kick-in"

Tippy

This would apply more to air-cooled 911 engines rather than water-cooled due to having the fan spin fast enough to keep the jugs cool.

As stated above, as long as you don't lug the motor, you are ok.

But, you could argue against this point with stating a Tip car goes to 5th gear by 35MPH.

Macster

That the VarioCam kicks in at 2900 to 3500 rpms news to me. My info is it is active at low rpms (to around 1400 or so) and then comes back on above 5000 rpms to help with high speed cruising.

There is some protection against hystersis so the VarioCam doesn't stutter/shuffle between being active and inactive.

As long as one isn't constantly varying the Rpms over and then under the activation/deactivation speed the VarioCam system becomes active and stays active or it becomes inactive and stays that way as long as well as long as the Rpms remain constant and above or below the trigger point.

Sincerely,

Macster.

Macster

Don't worry about it. Just keep gear selection optimized to ensure you avoid lugging the engine. Then to conserve fuel run in the highest gear possible.

I can drive my 02 Boxster 2.7l 5-speed 2K miles from CA to the mid-west and never leave 5th gear while on the freeway -- from 80mph (west Tx daytime limit) to 75mph, 70mph, or even 65mph in Tx (night time limit) -- unless I come to a section of road work where the speed limit may be as low 45mph or I get caught behind some slow traffic and have to shift down to 4th until I can find time to get around the traffic.

(Drove my Turbo back and forth a couple of times and can and do leave it in 6th gear the whole time save for the same exceptions as I noted above.)

When you pull off freeway to fuel up give engine time to shed some heat it has built up running at freeway speeds. I closed throttle coast down the off ramp and then let engine idle a moment or so at gas station pump island before I shut the engine off.

Starting out cold drive easy for a few miles until engine/drivetrain get nice and warm. Even at freeway speeds this can take some minutes and miles, especially in cold weather.

Check oil level every fuel stop along with other vital fluids, just in case there's a problem. Car is "new" and unfamiliar to you so you want to pay close attention to vital fluids especially the first long trip or so. Carry 1 to 2 quarts of proper oil with you just in case you need to add some oil.

Sincerely,

Macster.

ivangene

I was told the trigger point is about 3200... is that wrong?
at any point - what I was saying to to avoid the constant activation and deactivation as you have pointed out as well....

we seem to agree, but at differant rpm's -

ttreat

I am always learning more about these cars but my original question was based on the concern of low rpms being a potential cause of the IMS failures. I was mainly concerned that I would not be able to identify that there was slight lugging at highway speeds and low rpms. I wasn't thinking about engine heat. I don't see how this would be any different from any other water cooled car.

It sounds like I should not be concerned. Great!

Macster

Not to sound mean but if you are concerned about low rpms causing an IMS failure you bought the wrong car. These cars spend almost all their time at part throttle or less (30% or less as do most other street driven cars) and believe me if low rpms has anything to do with IMS failures the engine will have plenty of chances for this to occur, unless you drive everywhere in 2nd and 3rd gear.

FWIW, my 02 Boxster has over 227K miles on it and I dare say it has spent more time at 3000 rpms and lower than most cars have spent at any and all rpms. As I mentioned in another post, I can drive nearly 2K miles at freeway speeds in just a couple of days (and have done so numerous times and continue to do so whenever I can get the time off from work) and almost all of this driving is with the engine running 3K rpms or lower. So far, after 227K miles, no IMS problem.

If you want to do something to calm your nerves, just elect to change the oil/filter more often. I change both my cars' oil/filter every 5K miles. Other than that, relax. Drive the car. Enjoy the car.

Sincerely,

Macster.

fpena944

One nice benefit of the high gearing in 6th gear is that you will get close to 30 MPG if you're taking it easy on your car.

For a vehicle with such high performance that is quite a feat!

ivangene

The better side of the car is if you try really hard you can get 10 mpg!!!

As Macster said, dont loose any sleep... change the oil often (once home) and keep taps on the fluids for the trip...

check tire pressure for sure !
(changing the subject yet again)