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minimum RPM's vs gear selection

 
Old 12-25-2004, 01:12 AM
  #16  
Phil
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Originally Posted by 1999Porsche911
It is my belief and my experience that there is NO NEED to baby any engine during the so called "break in period". Over the years you have heard people say things like "you have to properly seat the valves and the rings and the pistons", etc. etc. Believe me, It's as if all these componants have just been thrown in the block and its the new owner's responsibility to get them to fit properly. If these things were not properly seated, fitted, installed, etc, your engine would immediatley come to a stop.

All materials used in the engine are properly machined and hardend prior to assembly and further driving of the car will not change that. It appears that some people think that an engine is assembled with parts that are ALMOST a proper fit and need final fitting during the operation of the engine. I wonder if these same people break in their new tires the first 3,000 miles to make them rounder?

I have rebuilt many engines, and believe me, if the componants are not built and installed with tight tolerances, even a low rev of the engine will throw them through th block or intake. On the topic a varying the speed....why? What happens to the engine when you drive for awhile at 5,000 rpm and then drop to 3,000 rpm? What happens if you simply drive at 4,000 rpm all day long? The same thing happens at all speeds. The engiine operates as it is designed. Oil continues to lubricate and the engine coninues to maintain a constant temperature. So once again, what changes, other than engine speed, by decreasing the revs once in awhile? Absolutely nothing. All moving parts are constantly lubricated by either water, oil, grease or fuel no matter what speed the engine is at.

In my opinion, the only requirment to increasing the life of a properly maintained engine is to let it get to full operating temperature before the abuse begins.

I have read that many Porsche owners have taken the first 3,000 miles to break in their new toys, yet they only drive the car 2,000 miles a year. What a waste of the first 1 1/2 years of ownership of such a nice car.

Drive the car and enjoy it. But if you insist on following the recommendations of Porsche for the break in period, make sure you use only Porsche Oil, Porsche coolant, Porsche replacement parts and you'll also have to eliminate all the non Porsche mods that so many of us have. There may also be a recommendation to use official Porsche air in the tires too.

Why is it that many will disgard the recommnedation from Porsche that only genuine Porsche parts be used, yet they use an after market oil filter or air filter? I mean if Porsche recommends something, it must be critical that we follow it, isn't it?

I think as we become more knowledgeable about something and develope an understatnding of its function, we grow more confident in making modifications. Those of you who insist on following the breakin period need to get a better understanding of the working of a combustion engine.

IMHO.
I for one only use......"porsche air" in my tires...there is nothing better. Have you tried Porsche air?

I do wonder.....when will you be manufacturing a supercharger....or for that matter a car?
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Old 12-26-2004, 01:53 AM
  #17  
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1999,

I completely disagree, as do many professional engine builders and mechanics I know personally. No offense intended, but I wouldn't want to own a car you drove off the showroom floor.

Question for you: If nothing changes within an engine during the first few thousand miles, then how do you explain the well-documented fact that cars are quicker and faster after they have accumulated several thousand miles? Many of the car mags' long-term test cars are quicker after 30K miles than when new. Also, it is widely known (and personal experience confirms this) that cars get better mpg after they have several thousand miles on them than when they are brand new. Clearly, things change within the engine during the engine's early life (as well as in its later life), and how an engine is treated during the break-in period influences this.

Regarding your "averaging" of 3K and 5K rpm to get 4K rpm and your suggestion that they are equivalent: the forces, loads and temps within an engine are different at each of those revs, and at all other engine speeds. Running an engine at 3K revs for 30 minutes followed by 5K for 30 minutes does not expose the engine to the same set of circumstances (loads, forces, temps, etc.) that running it at 4K for an hour would.

BTW, Porsche obviously gains financially by recommending use of their replacement parts. What does Porsche (and other manufacturers) have to gain by recommending a break-in process and period?
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Old 12-26-2004, 02:37 AM
  #18  
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I've known some gearheads that drove there engines hard, right out of the box, and to this day, claim it is one of the strongest running machines they own.
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Old 12-26-2004, 10:27 AM
  #19  
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The reason a car will get better gas mileage when it gets more miles on it is because the engine and drivetrain become looser decreasing the resistance while drriving. The wheel bearings, valves, pistons, etc take less force to move and therefore the car can move quicker with the same amount of force and the MPG will increase.
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Old 12-26-2004, 11:52 AM
  #20  
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Then, same reason as you said, would it be better to slowly and cautiously make those fractions to be smoothened out over time rather?

Anyway, whenever I buy a new car, break in period only lasts a week. So, for me, I always stick to break in rule.
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Old 12-26-2004, 03:12 PM
  #21  
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--------------------------------------------------------------------------------

Then, same reason as you said, would it be better to slowly and cautiously make those fractions to be smoothened out over time rather?

Anyway, whenever I buy a new car, break in period only lasts a week. So, for me, I always stick to break in rule.


Yeah and I guess if you use that logic, the breakin period nevers ends as all moving parts and their mating parts continue to wear forever. So maybe we all should keep our Porsches below 3,000 rpm for the first 100,000 miles. But what about the next 200,000 miles?

I would like someone to give me a single fact that a specific time period or mileage mark makes an engine "broken in" and what specifically is "broken in". If it's 2,000 miles, why not 1,995 miles?
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Old 12-26-2004, 11:54 PM
  #22  
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As I understand it and in very basic terms, different engine revs and loads result in a wide variety of bearing loads, piston/ring loads against cylinders, and temperatures among the various parts. As the various metal surfaces undergo these heat and load cycles, they change subtly and "bed in," and that a more durable wearing surface is the result.

I doubt that there is a magical change b/w 1995 miles and 2000 miles, but the point is that the way an engine is driven over the first few thousand miles (not at exactly 2000 or 1898.2 miles) makes a difference. Also, the bedding-in process is completed in those first few thousand miles, so there is no need to baby the car for the first 100K. Also, following the break-in period occupies only a very small portion of one's time and miles with the car (usually). It seems to me a very small price to pay to take good care of it. While sometimes frustrating, I also enjoy this to a point -- it's sort of like a right of passage to go through with a new car or engine.

Again I ask: while Porsche clearly gains by recommending use of its replacement parts, what does Porsche gain by advising a break-in period? Nothing, as far as I can tell, so why advise it unless there is a benefit to the car?
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Old 12-27-2004, 03:19 AM
  #23  
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If you do a Google search & check some manufacturer's websites, you'll find that whether it's automobile, motorcycle, airplane or boat engine makers, there seems to be unanimous support for a prescribed break in process & period. Heck, ebben ar rezidint inginear JimBob wood ahgree.
Of course, maybe all the engine makers' engineers (& JimBob) are wrong & 1999Porsche911 will direct us to some authoritative published support for his position. Until then, I'll stick with the recs from the folks who designed & built my engine.
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Old 12-27-2004, 07:10 AM
  #24  
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I took delivery new 7 years and 3 days ago. Because I don't possess even a miniscule fraction of Porsche and others' collective R&D, I did the break-in exactly as the manual suggests.

I would love to know the long term maintenance history of this guy's TT, just getting his oil warmed up 13 miles from delivery at the factory:

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Old 12-27-2004, 07:50 AM
  #25  
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Hey Chicago - wouldn't treat a dog the way you appear to treat your Porsche engine. Ever had an engine rebuilt and seen the care taken to bed everything in? Fortunately it seems the majority of the guys do take care.

Gear changing is all about not labouring the engine - can change at 2000 rpm if all that's happening is a long cool cruise - look at the way Tiptronic changes; adjusts to driving style - hard driving goes to near red line, gentle driving changes much, much earlier.

PJC
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