Engine Break-in

Originally Posted by jwarcd

The engine isn't the only thing that needs to be broken-in. The reason for the 100mph limit is to allow the differential to time break-in. A new differential will run very hot under load.

I'm sure this is what they are trying to gaurd against, the problem is that once again, good judgement can be better than a hard rule. Driving for 12 hours at 85mph is going to stress your new diff more than a short sprint to 120mph that lasts 5 min.

Cheers,
- VR

Originally Posted by phantom701

There is a couple of issues with the http://www.mototuneusa.com/break_in_secrets.htm article, it says do *NOT* use synthetic oil for break-in. .

I read somewhere that a lot of manufacturers put in a special blend of sinthetic oil for the new engine. Think of it as 'break-in' oil. And, you are not supposed to change your first oil early (before 15000 or when the light comes on) because this special blend is imperitive for the young engine's break-in. If you change your oil too early and put in the normal synthetic, then the engine will never break-in properly. I actually read this in a technical manual.

If you do ED, you'll quickly forget about break-in. I thought about it for all of 2 mins when pulling out of the BMW garage. As badly as I wanted to obey the break-in period, the autobahn just didn't let me. I have 14,200 miles so far and no problems, so far.

Originally Posted by solsurfr

If you do ED, you'll quickly forget about break-in. I thought about it for all of 2 mins when pulling out of the BMW garage. As badly as I wanted to obey the break-in period, the autobahn just didn't let me. I have 14,200 miles so far and no problems, so far.

If failure to follow break-in procedures is going to cause problems, wouldn't they be more likely to show up later rather than sooner?

Originally Posted by Bart001

If failure to follow break-in procedures is going to cause problems, wouldn't they be more likely to show up later rather than sooner?

Sure is possible but my thinking is that these cars are built to be driven and not pampered. The fact that you are on the autobahn and average speeds, at times, are above 90mph, it is simply impossible to hold back just cuz the manual says so. For me, it was such a thrill to drive over 100+mph for long stretches on the autobahn. If for any reason I have any major mechanical problems within the warranty period, I would attribute them to the quality control of the car rather than fast driving within the first 1000 miles. I'm no gearhead but I've heard arguments on both sides of the coin. Do a search for break-in period over at the ED forum and you'll find similar posts like mine. To each their own, I guess.

I would imagine that as long as you are gentle on the engine... shifting at lower rpm's, etc... that going over 100mph is not that big of a deal. Gentle acceleration during the break-in even to a higher rpm will be good enough that the engine will still last beyond 200k miles.

What the manual attempts to get you to do, but doesn't tell you why, is to limit the amount of heat applied to the various reciprocating/rotating components for any long period of time.

You have two opposite functions to perform at break-in:

1)Apply enough pressure to the piston rings (via high-load) to have them expand and match the cylinder bore (in fact, they both wear a bit and fit each other). This also applies to valve to valve-seat interfaces and all plain bearings.
2)Avoid excessive heat that would cause distortion that will prevent these parts from mating.

So how do we do this?
•Progressively take short bursts of acceleration higher and higher in the RPM range, followed by fully closed throttle deceleration.
•This accomplishes both requirements.
•The brief burst of acceleration loads the parts as required.
•The "closed throttle" deceleration relieves this pressure, and coats the moving parts with engine oil (not so much for lubrication, but to wash away the microscopic metal particles that your engine just "machined" during the acceleration phase.
•Oil is "drawn up" because, with the throttle closed, the combustion chamber is a very low pressure environment during the intake cycle as compared with the crankcase).
Understand, this is a two part process:
•The "closed throttle" part is every bit as important as the "open throttle" part. Full open throttle (2-3 seconds) followed by a completely shut throttle (3-5 second).
•Allow a few minutes between cycles for a thorough heat soak. Vary speed and gears (I usually start with second, and work my way up to fifth).
•Avoid any constant RPM.
•BMW advise not to exceed 4,500rpm or 160km/h for the first 2000 km.

Comments:
•BMW advise not to exceed 4,500rpm for the first 2000 km, for good reason, to prevent heat-seizures or cylinder scoring. This allows you to travel up to 160km/h in top gear, throttle on - throttle off, which is fine for breaking in and doesn't require too much throttle restraint.
•The main idea is to exercise the engine like you would a muscle. Build up slowly and don't do the same thing for too long. Yes, you want to keep engine revs down and increase gradually, but also you want to run a variety of engine and gearbox routines. Run City traffic for half an hour then country lanes for a couple of hours, then finish with maybe 15 minutes of mixed steady and fast motorway. Repeat until you've done the miles. Running motorways at 100 kph to do the distance will shorten engine life almost as much as not running-in at all.
•Here is an interesting statement from Jeremy Hall, a principal engineer in Honda's engine design department. He is quoted (page 61 of the July issue of Popular Science) as stating that the stress on an engine at 9,000 rpm is double that at 8,000 rpm. Something to think about as you wind your engine to redline.

Dave.

So what do you all say to somebody like me who is forced to take delivery of his car in LA then drive it to Seattle not more than two days later?

I'm going to try my best to put significant city mileage on it before I leave and on the interstate I will vary my RPM and vehicle speed but I don't know what else I can do here.

Originally Posted by Armen52

So what do you all say to somebody like me who is forced to take delivery of his car in LA then drive it to Seattle not more than two days later?

I'm going to try my best to put significant city mileage on it before I leave and on the interstate I will vary my RPM and vehicle speed but I don't know what else I can do here.

Take side roads and stop for food often?

Originally Posted by former

It's been awhile so it's hard to recall, but I believe the 3 series was keep it under a 100mph for the first 1000 miles or so and then also keep the revs below 4000-4500 for the same time limit.

I do vividly recall how hard it was to do as well. That baby just wants to keep on going and it is so much fun to let it run.

Enjoy your new ride.

-f

Easy solution: give to the wife for the first 1K.

What if you kinda go over to 5-6k rpm to avoid an accident at about 400-700 kms

no biggie?

Originally Posted by phantom701

One thing many of you keep on forgetting is that, BMW has a huge group of extremely smart engineers working on the engine. They probably know more about their engines than any armchair engineers.

Plus, BMW honors the warranty.