3000 rpm

[ksjohn]

I read somewhere a while back that the M96 engine has a natural vibration at 3000 RPM and you should avoid maintaining that RPM for an extended period.

I have a 99 with a 5 speed, and it just happens that 73 mph is 3000 RPM.

Can anyone confirm that maintaining 3K RPM is a bad thing?

Thanks

[flaps10]

I read that too at some point. It does seem to have a harmonic at 3000, and that rpm does come at inconvenient points in each gear. As to whether it's harmful, I've flown planes that have placards and yellow arcs that were stay out zones so it causes me to avoid sustained operation. But it's not in the manual that I've found and other than interewebs stuff I've not read much

[rick3000]

I have never heard of the 986 having a natural vibration at 3000RPM. Excessive vibration at 3000RPM is normally an indication of a failing motor mount.

[thstone]

I think what you're hearing is advice to keep the engine above 3000rpm to avoid IMS bearing problems. The IMS bearing is rumored to fail earlier if the engine is driven at low rpm (<3000rpm) on a continual basis (supposedly especially bad is lugging the engine at low rpm).

I have no idea if this bit of Boxster-lore has any real validity but if you do a search on the IMS bearing I am sure that you can read all about it.

[NewArt]

And I've read that tips have a lower rate of failure and they tend to run at lower revs than 3000 automatically !

[jdraupp]

Originally Posted by NewArt

And I've read that tips have a lower rate of failure and they tend to run at lower revs than 3000 automatically !

That's because there were less cars built with tip. Don't believe everything you read.

[Tcar]

Originally Posted by NewArt

And I've read that tips have a lower rate of failure and they tend to run at lower revs than 3000 automatically !

Tips never lug. They downshift.

[jluetjen]

I'm pretty sure that a vibration at 3000 RPM is the front engine mount. I replaced mine and it largely fixed the problem. I say largely because it is still slightly there, but I discovered that I put my mount in upside down. Why?

(...Going from memory, it's been a couple of years since I replaced this...)

The original 986 mount that I took out was clearly shot. When I went to our host to by a replacement I discovered that the 986 mount has been replaced by the 987 mount. Great. I ordered mine and installed it aligned the same way as the original and the problem was massively improved. But still with a slight resonance at 3000 RPM.

Looking again, I discovered that there is an alignment notch cut into the outer tube of the mount, which should align with the bracket on the engine. It looks like the 987 mount is installed rotated 180 degrees from how the 986 mount was mounted.

Think of it as a circular tube with a thick rubber insert shaped like an "A" installed. The 986 mount had the "A" installed this way: ^

The 987 mount was marked to have the A installed this way: V

I've never gone back to fix it since it's a minor annoyance. I doubt most people would even notice. But one day if I'm in there, I'll flip it over.

The cost of the mount isn't alot -- so don't sweat the scare stories about the dual mass clutch. If you're careful, you can even replace the mount without draining the coolent system and removing the coolent hoses which are near the mount.

[BIGJake111]

I do notice a vibration that happens only in 6th gear and only when my foot is entirely off the gas at 3k rpm. If I have my foot at all on the gas no vibration but if I let off there is a vibration until the revs drop.

I'm assuming it's just my motor mount getting old though.

[ianacole]

I seem to notice a slight vibration/flat spot at about 3200 RPM, if I'm just cruising. '97 manual.

[particlewave]

IIRC, the variocam kicks in at 3200rpm, which is why there is s flat spot and why it's advised not to maintain that rpm.
I'm not sure if it applies to all 986 models...

[Meir]

Let me share my 2 cents.
I have been following this forum (and others) for the past 6 years.
The first time I read about the vibration, was in one of Jake Raby posts about the potential reasons for the IMSB failure.
If to be honest, no one really convinced me with the true reason for the failure. Although there are a liot of theories out there, there is no logic explanation (to me) why some fail and some don't.
The only theory that made a sense to me, is the one presented by Jake, talking about the vibration at the 3000 RPM range.
If I remember correctly, he mentioned that the flywheel is acting as a harmonic balancer, and there is a natural vibration due to the tension on the IMS to crank chain.
He also implied that low mileage cars are more prone to failure under the assumption that they are not driven hard enough. Also explain some documented cases of multiple failures with the same driver, to suggest the way you drive your car contributes to the IMSB failure.
Up to here, these are words of my memory, so I might not be 100% accurate (and I apologize for that) with Mr. Raby words.
To speak from my personal experience, I can tell you that there is a significant vibration in the 2700-3200 RPM range. It is mostly noticeable on deceleration. (Meaning when the engine RPM drops from 3200 to 2700) and RPM fluctuation.
On my ex 99 base, the flywheel was completely shot at 160K miles.
I could clearly feel the vibration at the above mentioned RPM range, and it was gone, as soon as I installed a new flywheel, just before e I sold the car.
Since then (and if to be honest also before) I try to keep the RPM on the 3000-4000.
It is also more fun, although less fuel efficient.

[Jager]

Replace the Dual Mass Flywheel.

[Dlirium]

Originally Posted by Jager

Replace the Dual Mass Flywheel.

With What?

[Jager]

Originally Posted by Dlirium

With What?

A new Dual Mass Flywheel.

I use LUK brand.

[Retroman1969]

Sigh. I ignored a lot of doom advice and scare stories when I bought these cars and I guess I'll have to ignore this too if I plan on getting any sleep. Mine seems to gravitate to 3000 rpm for all things and I assume has done it for all its 162,000 miles. It shifts between 2500-3200 rpms 90% of the time in normal driving, and cruising on the highway at typical speeds (65-75 mph) falls right around the 3000 rpm mark as well.
If that's really it's unhappiest place to be, then I'd have to file it under the "major design flaw" category.
Honestly, I've never noticed any vibration.

[boxxster]

It's surprising to me that people are having vibration issues with these engines. It's a pretty well known fact that a flat 6 configuration is inherently balanced, or at least should be in theory. I never cruise at 3k, usually 2500-2800 so I haven't really noticed this on my car.

FWIW, I found this excerpt which was written about a 2001 S in a porsche technical document.

"In operation, the engine control unit operates timing pistons in the intake
camshaft chain tensioners. When the engine reaches 1,200 rpm, the control unit
signals the piston to rotate the intake camshafts by 12.5 degrees. When the
engine reaches 5,120 rpm, the pistons return the camshafts to their normal
positions. The control unit will delay VarioCam until 1,480 rpm if the engine oil
temperature exceeds 266 degrees Fahrenheit (130 degrees Celsius)."

So it looks like the engagement window isn't at 3k, at least not for the 3.2. Interestingly enough, however, the next paragraph says:

"The Boxster S shares its twin-resonance air induction system with the 911
Carrera. The system acts as a “resonance supercharger,” allowing the engine to
draw from higher velocity airflow at certain engine speeds. A crossover pipe
connects the individual air collector/resonance chambers for each cylinder bank.
A flap in the pipe remains closed from idle to about 3,100 rpm. When it opens,
each cylinder bank can draw from airflow “excited” by the resonance created by
alternating induction between all six cylinders. In essence, “dual resonance”
creates two induction paths for each cylinder. Below 3,000 rpm, the cylinders
draw air from a “short” path. From 3,000 rpm to about 5,100 rpm – when the
resonance flap opens – the cylinders draw from a long intake path, which boosts
torque. Above 5,100 rpm, the flap again closes to allow the cylinders to draw
intake air from a shorter intake path to boost horsepower at higher engine speeds"

Total shot in the dark, but I woudn't be that surprised if the vibration when hovering around 3k had at least something to do with the intake paths constantly changing between the long and short paths and the fluctuation of torque it would create.

Source:
http://press.porsche.com/archive/products/press_kits/press_kits_2001/PDF/Boxster_S_in_Depth.pdf p.13

[Uwe]

My 2000 S has the same issue, very faint on acceleration and cruising, sometimes not noticeable, but very pronounced while decelerating when the rpm's swipe through the 3000+- range.
Ive got nothing productive to add, other than seems to be a more common problem than I thought. The engine in my car has been replaced during prior ownership, with a 2002 S-engine. Maybe they didnt do the flywheel at that time. Receipts show clutch components, but no flywheel.
Are there visible clues if a dual mass flywheel has gone past it's lifespan?

[JFP in PA]

Originally Posted by Uwe

My 2000 S has the same issue, very faint on acceleration and cruising, sometimes not noticeable, but very pronounced while decelerating when the rpm's swipe through the 3000+- range.
Ive got nothing productive to add, other than seems to be a more common problem than I thought. The engine in my car has been replaced during prior ownership, with a 2002 S-engine. Maybe they didnt do the flywheel at that time. Receipts show clutch components, but no flywheel.
Are there visible clues if a dual mass flywheel has gone past it's lifespan?

No, unless is is really beat up. The correct way to test dual mass flywheels is to use the twist recovery method outlined in a factory TSB.

[tcoradeschi]

Originally Posted by Uwe

My 2000 S has the same issue, very faint on acceleration and cruising, sometimes not noticeable, but very pronounced while decelerating when the rpm's swipe through the 3000+- range.
Ive got nothing productive to add, other than seems to be a more common problem than I thought. The engine in my car has been replaced during prior ownership, with a 2002 S-engine. Maybe they didnt do the flywheel at that time. Receipts show clutch components, but no flywheel.
Are there visible clues if a dual mass flywheel has gone past it's lifespan?

My 03 base Boxster has done it for the last 160k miles and I assume it did so for 20k before I bought it. It’s very minor and something I have long ago tuned it out, unless I am looking for it.