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YOUR RESEARCHSafe highway RPMS
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Check oil level every fuel stop along
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Suggestion
Check oil level every fuel stop along with other vital fluids, just in case there's a problem.
Leading evidence: 'Check oil level every fuel stop along' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check oil level every fuel stop along' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
Take for granted the vario cam is changing the cams degree to negative numbers when at higher rpms.
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Suggestion
"Vario-cam" meaning variable cam where it will change the degree of the cam depending on your rpms.
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Suggestion
If you are experiencing a transient increase in rpms or acceleration, that is you are holding the throttle steady or steadily applying more pressure to the throttle and experience a momentary increase in acceleration that is not normal and that is not due to the resonance valve in the intake manifold opening or due to the VarioCam system being activated (at least assuming these are not malfuctioning and changing their state due to some mechanical or electrical malfunction).
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Suggestion
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.
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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?
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 !
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?
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.
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"
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.
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.
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.
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 -
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!
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.
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!
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)
Yeah but on roads you don't know you might get hit with the "fun tax" that pulls up behind you and shines these bright lights in your rear view mirror!
I think when I went on my DE I was in the single digits for fuel economy. What a fun use of hydrocarbons!!!
Yes, I really want to avoid the "fun tax".
I feel much better now that many of you have posted your opinions that cruising in 6th gear shouldn't be a concern. I thought it would seem rather sensless to have to cruise down the highway with the engine roaring just to keep the car from lugging. Otherwise, we might as well put Honda 4 cyl engines in our cars.
when i first brought my 996 home i did manage 11 MPG the first 2 days. basically i used ~13 gallons of gas and traveled 140 miles (my tank is a bit smaller because i drive a C4).
i still spend most of my local/city driving in 3rd gear. i cruise around town @45 MPH in 3rd at around 3000 RPM. i definitely avoid lugging the engine :P
Is it a "surge"? A transient increase in Rpms or acceleration? Or is just more like a bit there's a bit extra peppiness that continues?
These engines have a resonance valve in the intake manifold that is manipulated around the 3K rpm point to take advantage of the way the air moves through the intake system.
When this valve is opened, not only does this perk up the engine -- provide a bit of a boost in HP/torque -- the intake sound changes as well.
This is normal.
If you are experiencing a transient increase in rpms or acceleration, that is you are holding the throttle steady or steadily applying more pressure to the throttle and experience a momentary increase in acceleration that is not normal and that is not due to the resonance valve in the intake manifold opening or due to the VarioCam system being activated (at least assuming these are not malfuctioning and changing their state due to some mechanical or electrical malfunction).
Both the VarioCam and intake resonance flap are controlled by the engine controller.
Each has a specific rpm level at which a state is selected. (Other inputs also can affect if a state is selected, for instance coolant or oil temperature.)
Each has a specific rpm level at which the current state is deselected. The separation in rpms is several hundred rpms so unless you are accelerating the car up to and over 3K rpms then releasing the throttle and allowing the car to slow until rpms drop several hundred rpms below the activation rpm level there is something else going on. Probably something not normal, to state the obvious.
Under normal driving conditions, that is if you can manage to hold rpms constant within 200 rpms (or so) a state once entered will not be left again. The rpms must decrease or increase by around 200 rpms in order for a state change to occur.
Sincerely,
Mactser.
On long drives, I vary my RPMs by going into 4th and 5th periodically on my Tiptronic. I usually like to keep my RPMs about 3000-3500 all the time around town, using the manual mode, IF I kept my car in 5th on a long trip with 24-2800 RPMs, I would wory about lugging the engine. I know when my wife drives the car only in auto mode, afterwards, when I drive it it seems sluggish and takes a few minutes at higher RPMs to clear out the slugglishness. After a business trip, I can always tell when my car has been drivem in auto mode because it doen't have that spark it usually has when I drive it regularily in the manual mode at least 3000RPM or higher.
I hope you have heard of how you can advance (+) and retard (-) the ignition timing so that this explanation might register. The cams spins in relation to the crank spinning with the pistons on it. The difference of cam spin to crank is expressed in degrees ie + or -. If you go negative with the cam degree then it places more power in the higher rpms. + degreeing puts the power band lower in rpms. "Vario-cam" meaning variable cam where it will change the degree of the cam depending on your rpms. So it's a game of always having the best power the engine can throw out. Take for granted the vario cam is changing the cams degree to negative numbers when at higher rpms.
Now hehehe the advancing and retarding the ignition is the opposite concerning where it puts the power. Advancing ignition sparks early so that by time a faster spinning engine fully ignites the fuel the piston is near top dead center and not sparking late in the combustion cycle. Just remember they are opposite in power dabbling.
My personal opinion? rpms are related to cops saying stop doing that or pointing laser guns on the hwy. Other than that just cruise it and stay away from doctors or they'll have you gulping meds the salesmen recently offered them kickbacks for selling.
IIRC all M96 water cooled engines came with VarioCam, which is variable intake valve timing.
VarioCam Plus came in circa 2004 (?). (My 03 Turbo has it and it appeared on other engines afterwards not before, so I'm guessing the 2004 number.)
VarioCam Plus is intake valve timing with intake valve variable lift control as well.
I have an intake lifter from a VarioCam Plus engine on my office desk. Very cool device.
Sincerely,
Macster.
The sluggishness is just the Ecu having adapted to your wife's style of driving. I'd be worried if when you got in car after wife and engine not sluggish but just the opposite. Would mean she's been out doing a bit of street racing or cayon carving, the bad girl!
2400 or so rpms not lugging engine unless you're climbing a steep grade. Even then as long as you don't give engine full throttle but ease it on a bit until rpms climb that is not lugging engine.
Porsche knows as well as anyone can how these cars are driven and has designed the engine and transmission to deliver good torque at lower rpms, though of course then engines do pull well to redline and deliver the goods when asked.
Sincerely,
Macster.
My advise is just drive it. If it has been sitting take it easy on it till the rubber and plastics have sealed back up. Rubber and plastic do a little shrink or expand game at times when lacking normal usage. Just drive it and don't feel bad if you....well.....sort of open it up
The cars a killer so don't expect it to fall apart from easy cruising. BUT if you give us time to set up the youtube video cameras we will advise you to stay in top gear using 5-7000rpms. Just give us the route and I'd be glad to hang back behind you videoing
Or worse... your wife is letting someone else drive the car...
(Did I say that outloud??? j/k...)
Enjoy the car - if the IMS worries you that much, you should have bought a different car...
Rudy
for US, 2002+ for variocam plus on NA cars, 2001 for turbo
basically all the 3.6s
per Porsche "VarioCam Plus combines intake-side camshaft control (VarioCam) and intake- side valve lift switchover (Plus). The valve lift control system consists of switchable flat-base tappets on the intake side actuated by an electro hydraulic 3/2-way directional control valve. The intake camshaft provides two different cam profiles with corresponding valve lift curves to act as required by selectively switching the relevant cams. The flat-base tappets have two nested lifters which can be locked together with a pin. The inner lifter is in contact with the small cam and the outer lifter with the large cam. A hydraulic compensation element takes care of any dynamic valve clearance adjustments."
