Keep her above 4000rpm and she'll thank you for it every day.

[deliriousga]

I had read an article a couple of years ago in Panorama which was a reprint from the late 1970s that was about a man who bought a used Porsche 911 and the previous owner told him "whatever you do, keep her above 4000".

Before this, when I purchased my 928 it was making all of this clacking noise that was driving me nuts. I posted it on the 928 forums and one reply was "take her down the highway, warm her up and run the piss out of her, then keep her above 4000 when driving". He further explained that carbon builds and clogs things up if you drive it like other cars. Once that happens, you have to run it really hard to clean it out. Keeping her above 4000rpm while driving around town keeps the carbon from building up and helps the engine run better.

After several people agreed with his comments, I made this a habit and the only time that noise comes back is when the wife drives her (keeps it in the 2-3Krpm range) or when it's about 500 miles to the next oil change.

The reason I wanted to bring this up is there's a lot of scepticism out there about what some say is "running the engine so hard". I've had some say "I could never do that to my baby" and similar comments. Others are concerned with lower mileage. Well, I finally got confirmation from the Porsche factory folks on my last mountain run so I thought I would share.

We have mountain runs occasionally with Porsches, Ferraris, BMWs & even a guy in a Pantera that are a blast. Last time there was a guy in a Cayman S who is a Porsche engineer. He had the car from the factory to drive it in every day situations to see how it performs (quite nicely I might add). As the day went on, we stopped several times and would just chat for a few minutes to break the stress of driving so hard through the mountains. At one of the stops I had the pleasure of talking to him and asked what he does for Porsche. As it turned out, he is an engineer who helps to figure out the causes of problems in engines. He tears them down after a failure or if there is a persistent problem and examines everything about it.

After learning about what he does for Porsche, I asked what the most common problem is. His answer was "I go to court for Porsche all the time when people sue us because the engine is running poorly, making lots of noise, sputtering, etc. We take the engine apart and there is carbon built up all over the place causing all of the trouble." I asked him what causes the build up and he said "Most of the buyers are older since a Porsche is an expensive car. The problem is they bought a race car and drive it like they would a Jaguar or Cadillac. They don't drive the car hard enough to burn off the carbon so the engine clogs up and it runs like crap."

This seemed to confirm the rule I had learned earlier so I asked straight up "So is the keep her above 4000rpm rule a good way to keep the engine clean?" He said "Yes, you should keep the engine in the 4000rpm range and above to prevent carbon problems over time. If you look at all Porsche tachometers, 4000rpm is straight up to make it an easy reference point." I checked when I got home and sure enough the Boxster's tach has 4000rpm straight up too even though the tach goes to 1000rpm higher than the 928's tach.

So keep her above 4000 and she'll thank you for it every day.

[Adam]

Good deal...I make sure my tach needle sees at least 7,000+ rpm a couple of times every drive I take....once the engine is properly warmed up of course. I've not had one iota of trouble with the car period. People who buy Porsches for garage art and/or baby their cars are really missing out on some fun and the whole point of ownership.

[ohioboxster]

Interesting, I was just thinking to myself last night as I was driving home... My car is going to last forever.... because it never goes over 4k .

[blinkwatt]

I now have an excuse to drive at 100mph for my everyday driving,on the freeway of course.

[wild1poet2]

If he testifies this in court the rebuttal would be to pull out an owner's manual...me thinks.

I guess the implied reason would be there is incomplete combustion below 4,000 rpm. Or would it be another factor?

Originally Posted by wild1poet2

If he testifies this in court the rebuttal would be to pull out an owner's manual...me thinks.

I guess the implied reason would be there is incomplete combustion below 4,000 rpm. Or would it be another factor?

The owners manual does NOT discourage driving above 4,000 RPM. Except during the 2,000 mile break-in period.

[deliriousga]

Originally Posted by bmussatti

The owners manual does NOT discourage driving above 4,000 RPM. Except during the 2,000 mile break-in period.

Good point. I should have mentioned it's not a good idea to run her above 4000rpm if you're in the break-in period. My manual only says to stay under 4200rpm for the first 1000 miles. YMMV

[MNBoxster]

Originally Posted by wild1poet2

If he testifies this in court the rebuttal would be to pull out an owner's manual...me thinks.

I guess the implied reason would be there is incomplete combustion below 4,000 rpm. Or would it be another factor?

Hi,

There are lots of other factors. An engine never achieves complete combustion, if that were true, we'd never need emissions gear.

But, there is an RPM range in each engine where the combustion is most complete, and from the sound of it, it's in the 4k range for the M96 engine.

But other factors contributing to long life, maybe even the dominant factors, are that the Crankspeed dependent Oil and Coolant pumps (run off the crank-driven serpentine belt) may be in their most efficient range here as well.

All the engineer was speaking about was Carbon build-up, but a steady supply of Oil and Coolant will mean more to longevity than the buildup of a little Carbon. Carbon is softer than steel or aluminum and actually acts as a lubricant and sealant. You need some, but too much is a problem because it causes hotspots (retains heat) in the valvetrain and interferes with heat transfer to the head where the coolant can carry it away.

And, you need to put this into perspective. Incomplete combustion takes places at either end of the Tach. At some place north of 4k rpm, the piston doesn't remain at the top of the Compression Stroke long enough to combust all the fuel, even with an altered timing curve. This is why you often hear an exhaust popping on deceleration from a hard run, because unburnt fuel has accumulated in the exhaust and ignites there instead of in the cylinder where it's supposed to.

The interesting thing to me is that Porsche doesn't gear the Tiptronic or the Control Unit to shift at 4k rpm, I wonder why they wouldn't do that? And, the Tip cars generally have a more trouble-free life than the Manuals...

Happy Motoring!... Jim'99

[blue2000s]

Originally Posted by MNBoxster

Hi,

There are lots of other factors. An engine never achieves complete combustion, if that were true, we'd never need emissions gear.

But, there is an RPM range in each engine where the combustion is most complete, and from the sound of it, it's in the 4k range for the M96 engine.

But other factors contributing to long life, maybe even the dominant factors, are that the Crankspeed dependent Oil and Coolant pumps (run off the crank-driven serpentine belt) may be in their most efficient range here as well.

All the engineer was speaking about was Carbon build-up, but a steady supply of Oil and Coolant will mean more to longevity than the buildup of a little Carbon. Carbon is softer than steel or aluminum and actually acts as a lubricant and sealant. You need some, but too much is a problem because it causes hotspots (retains heat) in the valvetrain and interferes with heat transfer to the head where the coolant can carry it away.

And, you need to put this into perspective. Incomplete combustion takes places at either end of the Tach. At some place north of 4k rpm, the piston doesn't remain at the top of the Compression Stroke long enough to combust all the fuel, even with an altered timing curve. This is why you often hear an exhaust popping on deceleration from a hard run, because unburnt fuel has accumulated in the exhaust and ignites there instead of in the cylinder where it's supposed to.

The interesting thing to me is that Porsche doesn't gear the Tiptronic or the Control Unit to shift at 4k rpm, I wonder why they wouldn't do that? And, the Tip cars generally have a more trouble-free life than the Manuals...

Happy Motoring!... Jim'99

Carbon can also build up on the intake side. As fuel is exposed to a hot intake valve, it can solidify and build up. The build up within the ring seals is also partially irrespective of combustion. The faster engine speed gives the fuel less time to sit on hot surfaces as it is raced into the combustion chamber.

Also, don't forget about fuel quality and the presence of oil, which are also contributors.

[mquillen]

Although carbon build-up isn't good, I suspect another reason (perhaps the primary reason) for the advice to keep the revs up was the fact that all of the early Porsches were air cooled. Keeping the revs up meant airflow--lugging an aircooled engine is the fastest way to kill it.

[MNBoxster]

Originally Posted by mquillen

Although carbon build-up isn't good, I suspect another reason (perhaps the primary reason) for the advice to keep the revs up was the fact that all of the early Porsches were air cooled. Keeping the revs up meant airflow--lugging an aircooled engine is the fastest way to kill it.

Hi,

You make an excellent point!...

Happy Motoring!... Jim'99

[Bavarian Motorist]

Lol, not even CLOSE to a problem for me.


I beat the crap out of her! She loves me for it.

[teacher]

Though I know this is an old post, I wanted to ask anyone about how long they should keep their cars above 4000 rpm? Ten minutes? An hour? More?
Just curious!
Bill

[Paul]

If you're in top gear, until you get where you are going, just like in Germany.

[Paul]

Once it's good and warmed up, I always look for safe opportunities to floor it and shift above 6000. This happens every time I take it out.

[RandallNeighbour]

While keeping our engines above 4k does keep carbon from building up, it does wear the engine out sooner too. Brucelee stated this elsewhere on the forum a while back when asked this same question. Good logic.

I don't keep my motor above 4k at all times, that's for sure. But I do run it up to redline most every time I drive it though to blow out any cobwebs that might have accumulated in the car between drives

[Brucelee]

http://www.unofficialbmw.com/all/engine/all_redline_rpm_vs_reliability.html

[Topless]

Guys,
Didn't we do this whole engine load/rpm/excessive wear thing a couple of months ago??
http://www.986forum.com/forums/showthread.php?t=14724