Not sure if this has been posted or not before, but a good read from PCA regarding Porsche's philosophy on the 4000 rpm advisement.

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New Engine Break-in Conundrum

By Ken Koop
The Yellowstone Region (Old Faithful Newsletter)

Since I was a young boy, I have always wondered why it takes so long to break-in a new engine–especially those built by Porsche. Most people driving new cars also do not fully understand the real reason for the break-in period. Are you one of them? A good friend of mine just picked up his brand new 911 Turbo and complained about the break-in period taking so long (2,000 miles, not exceeding 4,000 RPM). We have talked about this issue many times over the past few years, always coming up with many scenarios of why such a long break-in period is required. However, we have never agreed on a reasonable answer. Well, you are about to find out the reason Porsche requires the break-in period it has today. The answer comes directly from the engineers at Porsche.

I was on a recent Porsche factory tour and was watching an engine being built and dyno tested. Each engine is built by a single person on a moving production line. Porsche feels that they can obtain better quality control with one person building an individual engine from start to finish. In addition, each engine builder can assemble every type of production engine that Porsche produces and every gasoline engine is still built at the Stuttgart factory. It takes 2-3 ½ hours to assemble each engine, depending on the type. Afterwards, the completed engines are either used in the cars produced at the Zuffenhausen factory or are boxed up and shipped to Leipzig (for the Cayenne and Panamera) or off to Finland (for the Boxster and Cayman).

Before all of the parts are assembled for a particular engine; the pistons, connecting rods and valves are individually weighed and grouped together using similar weights to optimize performance. They are put onto a cart that moves along the assembly line with each engine block. This cart contains every part required to assemble that particular engine which includes each washer, nut, bolt, bearing etc… As a result, if any part is left in the cart at the end of the assembly line, then—Houston, we have a problem!At the end of the assembly line, the engine is filled with Mobil 1 Synthetic Oil. Each engine is then dry run (without fuel), pressure tested and checked for leaks. Every car coming off the production line is also run on a rolling road dyno. This enables all cars and engines to be tested at highway speed before they leave the factory.

Some of the engines are also randomly selected to be tested on a dyno stand before they are installed into the car. The assembly plant has 5 dyno rooms located directly off the production line. The day I was on the tour, there were around 40 engines lined up on dollies. Some of these engines were in the process of being tested for quality control purposes. Once the engine is bolted onto the dyno, warm water is circulated throughout the engine to bring it up to temperature. The operator then starts the engine and checks for the correct pressures and temperature before the actual test begins. Engine speed is then increased in RPM steps to about 80% of its red line (the engine’s maximum RPM). The entire engine run takes around 30 minutes. Since each engine type (Turbo, GT3, Boxster or Carrera…) has a different red line, all of the data is recorded and analyzed after the test is completed.After the engine is turned off, the engine is again checked for seal leaks and its actual HP is compared to its advertised HP. To pass final inspection, the engine has to develop, at a minimum, 100% of what its advertised HP rating is. Also, the engine cannot produce more than 5% over that same advertised rating. If the engine falls out of those parameters, the engine is rejected and then torn down to determine why it did not deliver the anticipated HP.

When the test was completed, a Porsche engineer came over to review the results. I couldn’t resist asking the question that I had been searching to find an answer to for all these years. I asked “why does Porsche feel it is safe for a new engine to run at nearly full throttle in the factory, while the customer must keep the engine speed to no more than 4,000 RPM for a 2,000 mile break-in period?” I thought that was a logical question and if I do say so myself-well stated!

The engineer replied, “Herr Koop, you do not understand (that I already knew). When we do our engine test, the metals inside the engine never reach the temperatures they would when driven on the street since the test session is fairly short. In other words, the bearings, pistons and cylinders never get a chance to thermally expand to their maximum. Therefore, there is little wear on the moving components. But when you drive a car on the street, the engine parts expand considerably more because of the heat being generated from the engine running for an extended period of time. No matter how tight the tolerances are, there is always a slight amount of expansion in the material. The moving parts can wear quickly if exposed to excessive heat and not always in a uniform way. We also constantly vary the speed and allow the engine to run at both high and low RPM’s”.

“Porsche wants the engine to break-in slowly, which means it needs to maintain a lower operating temperature (below 4,000 RPM) and to allow all parts to adjust (wear-in) within their own thermal expansion parameters. This is also the reason why Porsche wants the owner to vary the RPM throughout the break-in period; therefore the engine doesn’t get use to one operating temperature range”.

“Porsche has been using Mobil 1 Oil since the early 90’s. With its superior lubricating properties, it takes many miles of driving (without getting the engine too hot) before the components actually seat (or break-in). Porsche’s own tests reveal that after 2,000 miles have been driven, all of the moving parts have had a chance to wear into their adjacent surfaces and then an increase in engine RPM is permissible.” I replied, “JA DAS SOUNDS GUT, when you explain it that way, it makes a lot of sense.” I thought to myself “You Dummkopf, why didn’t you think of that”.

The engineer commented that there were many other moving parts other than the engine that needed break-in as well. Wheel bearings, constant velocity joints, tires, brakes and transmission were just some of the other components that were mentioned.

So breaking it down into layman’s terminology, it all comes down to; higher RPM equates to more heat, which leads to greater expansion. For a new engine, that can mean uneven wear on certain parts if excessive heat is allowed to build up. In Porsche’s opinion, the thermal expansion of different parts and various materials need time to adjust to one another. Porsche’s time frame for that to occur is calculated to be 2,000 miles, with the heat restriction being 4,000 RPM. So simple; who woulda thunk.

Many experienced Porsche engine builders and experts on the Flat-6 engine state that the peak power of a Porsche engine is developed around the 20,000 mile mark. This coincides with the principle of what the Porsche engineer was telling me; “Break it in correctly and the engine will last longer and perform better”.

It only took me 45 years to find out the real answer to this puzzling question. After I returned home, I explained this to my friend. As for our ongoing debate, we now feel a solution to this riddle has finally been reached. Neither one of us had the answer to this complex question totally figured out, but we were on the right path! I am finally able to resolve another one of my life’s unanswered mysteries and now it’s been crossed off the list. I hope this helps explain one of your unanswered questions in the car world as well.

 

Good read. I like it. Have always done it.

A good follow-up question by Herr Koop would have been, "Why does Europe have a different break-in procedure than the USA?".

 

So short higher RPM bursts are OK?

 

One additional question I would have asked is "Why do I only have to adhere to the break in period for 1860 miles if I live in a country that is on the metric system?"

 

Or no break-in period at all, in many countries.

The article has been around awhile. It explains nothing, as far as I'm concerned. What the Porsche engineer says makes no sense in light of the differences in break-in guidelines between markets.

 

And Internet opinions are so much more authoritative?

 

I assume part of it has to do with Porsche (and others) protecting themselves based on product liability and consumer protection laws in various jurisdictions around the globe. Hard to imagine the lawyers aren't involved in just about everything these days.

 

I don't have any actual knowledge of the subject, but unlike the anonymous Porsche "engineer" (read: somebody who was walking around with a clipboard and speaking German at the time the journalist was visiting) I'll admit it.

 

Well, I don't have any metallurgical engineering credentials either. But since I intend to keep my cars for a while and don't rebuild the engines after each race season, I see no harm in either breaking the car in for the length of time in the manual or changing the oil more often than indicated! On the other hand, if i planned to get a new one often, I would not worry about either.

On the third hand, I am way beyond the break in period but I recall being astounded at the performance when I was trying to stay below 4000 RPM. That is ticket bait in a 991 in 5th 6th or 7th. I do admit that it was all less tempting without PSE.

 

No breaking period at all required here, never had a issue on any of my Porsches.

 

The reply from the Porsche sales executive "Take it to the track from the showroom, its Porsche..."

 

Advice given to me, by the oldest guy at Porsche Centre South Africa (longest standing employee, has filled every position below CEO), was similar to the above, he only noted that I should avoid using launch control in the first 1000km

 

Correctamundo.

I am a little surprised though that an engineer would conflate and confuse the distinctions between throttle, load, temperature and RPM. For example, a quick blip of the throttle in neutral can red-line in a fraction of a second, generating little heat, while full throttle depending on gear and load might not get the engine even to 4k RPM, yet generate an immense heat load. Throw in ambient temp and its easy to see that if the goal is what the engineer claims (which is of course bunk, but go with it for the sake of argument) then the operating instructions would need to indicate "avoid hills and hot weather for 4k miles".

If break-in really were needed- and for the reasons indicated- then all operating manuals would instruct drivers thus. The simple fact that none do ought to be reason enough to doubt the whole break-in canard.

When it comes to break-in, Porsche has all the reason it needs to maintain the party line: product liability. Just as ladders come with warnings not to stand as high as you can, Porsches come with warnings not to drive as fast as you can. Filter all the fluff and illogic, that's all that's left.

 

This is the way I see it: If I can afford these things in the first place, I can afford to have them fixed should something go wrong as a result of my driving habits. Es ist alles gut!

 

Boy, I can't!