I'm not going to think of this as riding a bicycle, because the amount of torque I can apply at 50 RPM is much greater than the torque I can apply at 200 RPM. If I could apply the same torque at 200 RPM, I'd be stressing my knees just as much, if not more.

And my reference about the 1500 RPM max torque was a BMW 135i which is a turbo charged gas engine. Imagine how "lugged" that car will be all the time. How foolish of them to let the car have any torque below 4000 RPM.

Regarding the cooling, you are burning less fuel at lower RPM and getting more mechanical work per volume of gas burned, so you need less cooling.

At 800 RPM you might be lugging the engine. At 1500 RPM, I don't see how that qualifies with an engine capable of variable timing.

I think you're points are mainly academic. In truth, at idle (700rpm) the Boxster 2.5 is producing only 27HP and 22 Ft.lbs., it's right there in the owners manual. And it doesn't get much better until you're waay north of 2500rpm. Not much to push a 3,000lb. car.

But, there's a practical experiment you can do. Start your car and try to idle (or up to 2500rpm) in 5th or 6th from a standing start. You'll soon learn how possible it is to 'lug' the engine, that is if it doesn't simply stall out first. Why? Because the load exceeds the power of the engine at that rpm level.

Yes the timing is variable, but only within limits, same with the fuel delivery. You're gonna get knock, ping, detonation. You will be putting a greater load on the engine than the power it can provide at that rpm level to overcome that load - you'll be operating outside it's powerband - in other words, lugging it!

:cheers:

Nobody is suggesting that it is wise to drive at idle in a high gear. Plenty of people seem to think 2k to 3k is, and that's simply false.

If I had to keep my car above 2800rpm most of the time, I would never use 4th or 5th with my Tip. I understand to not lug the engine down, but rolling down the road at 2200-2800rpm is not going to destroy an engine. If I need the extra boost, I drop down a gear or two to pass or climb a hill and run the revs into the 4000-5000 range. But once I'm done, I drop back to crusing range.

Is this wrong?

Heres a question: Which way uses more gas, keeping it below 2800 or above. It seems like youd have to press the pedal more when you are in a lower range to get it moving than when you have the RPMs high but it also seems youd waste more gas keeping em high?

You get great gas mileage keeping the revs low and driving smoothly (no herky jerky braking or throttle). I just spent the whole weekend driving it like uhh a Porsche. I'd say my gas mileage took a good 35% hit, at least. Keeping it above 3K requires a great deal more downshifting than I realized. Need to brush up on my heel and toe shifting! LOL

Einstein used to like to do thought experiments. Lets do one with this.

Driver A sets out for cross counrtry trip, 3500 miles on the Interstates. To make this fun, he simply gets in, drives at 75 MPH and about 3000 RPMs.

Now, Driver B is sure that this low RPM crap is for the birds. He knows his car should be meant to be driven faster, at higher RPMs.. Anything less that 6500 RPMs will ruin his race intended Boxster, even though it is a stock Box. Hey, Porsche is a racing company right?

So, off he goes. Now, in this experment, there are NO speed limits, so he can run at 6500 RPM the whole way. He can use any gear he wants, so he choose to cruise in sixth grear, which maybe nets him about 140 MPH????

Anyway, off they go.

Now, who gets there first? Well, if both engines hold up, clearly driver B if he choose to go faster than 75 MPH.

Now, whose motor was STRESSED more? which car's oil ran hotter during the entire trip? Which motor would have worn more, even if we can't measure it right now? Which oil is still fresh as a daisy after 3500 miles.

What do you think?

Porsches are made to be driven at 6500 rpms all day long. And they do so in Germany everyday of the year.

The car will last longer than most of us have left, so enjoy it.

Actually I never said they woudn't. The assertion made here is that they will NOT drive all day long at say 3000 RPMs and that the 6500 level results in less engine wear and risk of IMS implosion.

Nope. This is the way to better gas mileage and reduced wear on your car.

Well, just to add a little more fact to the mix, here is what Porsche says about engine operation and gear shift points from the '99 owners manual:

"The specified maximum rpm figures should not be exceeded when shifting down, exceeding the safe operating limit can result in damamge to the engine.

For smooth shifting, observe observe the following shift points (applies to standard gear ratios only):

Maximum downshifting points

• 5th to 4th ... 120mph/193km/h or 5100rpm
  4th to 3rd ... 84mph/135 km/h or 4700rpm
  3rd to 2nd ... 56mph/90 km/h or 4400rpm
  2nd to 1st ... 35mph/56 km/h or 4000rpm

Minimum upshifting points

• 1st to 2nd ... 15mph/24 km/h or 3000rpm
  2nd to 3rd ... 25mph/40 km/h or 2900rpm
  3rd to 4th ... 40mph/64 km/h or 3100rpm
  4th to 5th ... 45mph/72km/h or 2500rpm"

Now it seems to me, by strictly observing this, you'll be in the 'disputed' range and not lugging the engine.

:cheers:

Interesting...I don't think I've ever downshifted to 1st from 2nd.

Good stuff. thanks.\

Could we change the title of this thread to "uninformed opinions maquerading as facts about IMS failures"?

Lugging and almost stalling an engine are not the same thing! Wear to cylinder walls, main bearings, piston rings, etc. does not cause IMS failure therefore arguments that state that high RPM causes wear miss the point.

There was one post early on that tried to give a reasonable (although theoretically only) explanation that links low RPM, variocam and additional force to the IMS that sounded like a good argument for staying on the high side of the variocam switch over point. But that is just a promising theory. Jake Raby's anecdotal evidence that one seriously beaten engine has not had IMS failure supports the theory but certainly does not prove it.

I like the idea of driving your car the way you want and not worrying about IMS. If it blows up then either warranty fixes it, you sell the hulk, or pay Jake. Simple and stress free solution.

^ actually you'd be surprised how many people were unaware of the pitfalls of driving at low RPMs in the wrong conditions. I've been on this forum and others for years and the possibility of this type of driving being linked to IMS failure is seldom if ever discussed unless you follow a more technical forum like Renntech.

I don't think you'll ever prove anything when it comes to these engines... like whether 10K oil change intervals are worse than 7K or letting your oil come up to temp will lead to a longer running engine. There are doubts about everything including Porsche's most recommended oil. Doesn't mean it shouldn't be considered.

This is why I quit commuting in my Boxster (that's what I use the Fit for). I found myself starting to thinking about gas mileage, tire wear, brake wear, etc. That's the last stuff I want to worry about when I drive my Boxster.

If reasonable but spirited driving helps keep my IMS healthy, all the better. If it doesn't, and my IMS blows anyway, despite regular maintenance, then I'll deal with it then.

BTW, the great part about my Fit is that I can drive it flat-out on my commute and nobody around me can tell! And it still gets over 30 mpg when I'm thrashing it.

^ Yeah I rented a Prius once. Drove from Orlando to Miami never going slower than 90 mph. I was passing Corvettes and Mustangs who were saving gas in the middle lane...oh the irony. When I arrived at my destination I managed 30+mpg.

agreed, saving less than a grand a year on gas by short shifting and keeping the revs low really looks silly in light of possibly causing a $8,000 emergency engine transplant.

IMO Porsches are toys, enjoy them or get rid of them. Many days the best part of my day is the 30 minute commute in each direction. That's why I drive at least one of my Porsches year round. This year it was the 3.6, what a blast when I floor it.

I must admit, however that since this is the most powerful Porsche I've owned, I cannot floor it from a dead stop unless I use second gear from a stop, since the acceleration in first is not manageable even with traction control, 265x18 tires and a LSD.

I'm currently looking for a 3.8 X51 for my 01 2.7.......

^You can do that with an 00-02? I thought the electronics made it tough?

Man if me engine ever went, I'd certainly consider that. 381HP? Eat those Carreras for lunch.

EDIT:
"Hans Hoffman, Ruf’s technical guru in Dallas, advises anyone with a pre-2005 Boxster contemplating a 3.8S conversion that the main wiring buss for the ECU is completely different, and they are better off trading up to a later model Boxster"

If it can be done on a 98, it can be done even easier on a 01 since it already has Can bus and eGas. My 98 is running a 7.8 motronic.

I like your 18" 5 spoke wheels, tell me more and where to find a set.....

Ruf is not needed to do these conversions, there are much less expensive options out there:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=120386821494&sspagenam e=STRK%3AMEWAX%3AIT&viewitem=

I think that was a 986forum.com car

The Ebay username sounds a lot like the forum username.


My 18" 5 spokers are factory. Stole them for a song from Ernie's Alloys back in '05.
I think I paid what the Italian replicas go for now. Wheeldynamics.com carry the 30# replicas. I think the price is $1100 now. Was $800 at one point before the Euro took off.

I'm also thinking about picking up a set of 997 Turbo replica wheels for Summer use. I'll need rear spacers though which I'm not crazy about.

Some of the information we have gathered is related to shockloading the IMS sees as the transmission of loads from the variocam is sent upstream to the IMS through the timing chains.

The IMS bearings do not have very much longitudinal thrust capability and these shock loads place a lot of shock on these bearing, a portion of that is thrust.

Don't quote me on any of this, as lots of questions are still unanswered and I am working hard to prove whats occurring as the engine is running with the variocam engaging/disengaging continually.

Thats all I am willing to state now and I reserve the right to change this based on future findings.

Jake,
Just in your experience to date, which cars have you noticed the highest number of IMS failures 97-99, 00-02 or 03-04?

IMS?? These issues generally occur post 99, the pre- 99 engines are more prone to cylinder failures.

After 99 the IMS syndrome is random through all models, none are more or less prone to it.

Jake,

At appoximately what RPM does the VarioCam engage and disengage on a 3.2?

Thanks,

Rick

I had much the same question and thought...

Attempting to translate Jake's most recent statement into my own words, variocam action is shockloading the IMS and a primary suspect in causing IMS failure.

I don't know exactly how Variocam works, but I assume it does its magic as RPMs increase and probably not in a linear but probably more of a logarithmic function. Higher RPMs mean more Variocam effect...

If I have all this right, then my logic tells me that for daily, around town, stop n go driving, one would have a better chance of avoiding an IMS failure by following the recommendation of the owners manual to use 3K rpm for an upshift point for every gear. I would also assume that conservative, smooth acceleration between shifts would lessen loads as well. Hmmm....

I'd also think that you'd be asking for engine failure by trying to accelerate hard with the transmission in 4th, 5th or 6th gear at 30 MPH or less. Same goes for a tip in manual mode...

That would be the day I use 3k rpm as my shift point...might as well just drive my Grand Cherokee instead.

Just warm it up and floor it almost to redline, I've been doing this to every Porsche I've owned since 1974 without any engine problems.

My 01 has almost 20,000 stage 1 revs and after 75,000 miles it still uses no oil.

My only confusion when reading all these posts is that everyone praises the car for being both a daily driver and high performing vehcle and I agree with that but if the rpm level is so sensetive I think less people would praise it around town, unless they all have tips?

its not there are all too many failures out there I just think what this thread is trying to say that is IF there is a failure its in car that hasnt been pushed at all and is kept at very low revs.

Something doesn't add up

1. TIP is not known for IMS failures. TIP usually keeps car at Very Very low RPM's, usually around 1500-2000 RPM's. If we take a driver that doesn't push the car.. it will never go above 4K PRM
-- This is very different from:
2. Driving a manual transmission under 2800 RPM = trouble

Logically.. to avoid IMS failures.. you should start in 2nd and rarely get to 2800RPM.. to simulate TIP.... (and of course don't push hard in low rpms)

am I missing something?

Sasha

I drive a manual by sound more than watching the RPMs....if it feels the engine is ready, I shift. If I'm getting on it, I wind out the gears more, if I am driving casually I shift through the gears quicker and soem times around 2k, if downshifting around a turn, sometimes at 1700