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Reman engine break in?


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I recently had my engine in my 03 996 replaced by Porsche. How do I break in the engine? Some say follow the new car break in instructions in the manual. The service manager at the dealer said drive it normally with no red line. Some say drive it hard, some say do an oil change at 400 miles to remove metal particles. Any opinions here? Thanks,

Neil :help: eil

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Proper breakin must be done in the first 100 -200 miles and below is the proper procedure:

1. Always bring engine to FULL operating temperature before high revs.

2. Drive trhe car easy for the first 10 miles or so, varying the rpm's from 2,000 - 5,000.

3. Then, start bringing the engine up to maximum rpm's and letting the the engine bring the revs back down by coating in gear.

4. Repeat several times, in order to create maximum heat in the cylinders.

5. Drive around at lower RMP's for seveal more miles, remembering to vary the speed of the engine every couple of miles.

6. Repeat number 3, 4 and 5.

7. Park car and let the engine cool down overnight.

8. Repeat all the above 2 more times.

Your engine is now fully broken in correctly and should be driven hard from here on.

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Proper breakin must be done in the first 100 -200 miles and below is the proper procedure:

1. Always bring engine to FULL operating temperature before high revs.

2. Drive trhe car easy for the first 10 miles or so, varying the rpm's from 2,000 - 5,000.

3. Then, start bringing the engine up to maximum rpm's and letting the the engine bring the revs back down by coating in gear.

4. Repeat several times, in order to create maximum heat in the cylinders.

5. Drive around at lower RMP's for seveal more miles, remembering to vary the speed of the engine every couple of miles.

6. Repeat number 3, 4 and 5.

7. Park car and let the engine cool down overnight.

8. Repeat all the above 2 more times.

Your engine is now fully broken in correctly and should be driven hard from here on.

While I do not have a problem with the above, I think that you should do this for more than 3 cycles. Minimally a 1000 miles, 2000 is better, frustrating as it may be. Also I would keep revs below 4200 and when you do start redlining the car do not sustain redline, redline the motor, then back off for a few minutes, repeat. Do the redline cycle for a couple of hundred miles.

Step 5 is really important. Do not go for a 200 mile cruise on the interstate when the motor is new and put the cruise control on. Every five minutes or so shift to another gear.

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Proper breakin must be done in the first 100 -200 miles and below is the proper procedure:

1. Always bring engine to FULL operating temperature before high revs.

2. Drive trhe car easy for the first 10 miles or so, varying the rpm's from 2,000 - 5,000.

3. Then, start bringing the engine up to maximum rpm's and letting the the engine bring the revs back down by coating in gear.

4. Repeat several times, in order to create maximum heat in the cylinders.

5. Drive around at lower RMP's for seveal more miles, remembering to vary the speed of the engine every couple of miles.

6. Repeat number 3, 4 and 5.

7. Park car and let the engine cool down overnight.

8. Repeat all the above 2 more times.

Your engine is now fully broken in correctly and should be driven hard from here on.

While I do not have a problem with the above, I think that you should do this for more than 3 cycles. Minimally a 1000 miles, 2000 is better, frustrating as it may be. Also I would keep revs below 4200 and when you do start redlining the car do not sustain redline, redline the motor, then back off for a few minutes, repeat. Do the redline cycle for a couple of hundred miles.

Step 5 is really important. Do not go for a 200 mile cruise on the interstate when the motor is new and put the cruise control on. Every five minutes or so shift to another gear.

If you don't do step 3, then you will not properly hone the cylinders round as you will not go through the entire heat range. This is the most important step other than warming up the engine. You must create as much pressure and heat in the cylynders during break in.

Edited by 1999Porsche911
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If you don't do step 3, then you will not properly hone the cylinders round as you will not go through the entire heat range. This is the most important step other than warming up the engine. You must create as much pressure and heat in the cylynders during break in.

That is contrary to porsche recommendation.

I think it is more important to run the engine "gently" for the first 1000 miles, then start the higher level break in.

To each there own.

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If you don't do step 3, then you will not properly hone the cylinders round as you will not go through the entire heat range. This is the most important step other than warming up the engine. You must create as much pressure and heat in the cylinders during break in.

That is contrary to porsche recommendation.

I think it is more important to run the engine "gently" for the first 1000 miles, then start the higher level break in.

To each there own.

It is wrong to simply assume that just because Porsche makes a recommendaton that it is in fact correct. This is quite obvious when you look at all the reoccurring problems Porsche engines have had over the years. I have NEVER had a car burn or loose any oil EVER. I have always broken in the engines as described above. I have had 5 cars go over 180,000 miles and one car is still going with 273,000 miles on the original engine and no oil is lost between 5,000 mile oil changes. I know so many people that burn oil and they have followed the manufacturer's breakin recommendations. I have rebuilt numerous engines and you can clearly see the physical defferences (especially the cylinder bore) of a car that has been babied and one that is aggressively broken in. The single most obvious problem was the cylinder being out of round on the babied engine. This is the cause of many flatsix engines oil consumption. It takes very little distortion in the bore to allow oil to seep past the rings.

Until I see a problem and until ANYONE can specifically show ANY sound reason for not breaking it in this way, then I don't expect to change a procedure that has worked for more than 30 years. The is no reason given to follow Porsche's recommendation, but many reasons to follow mine.

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Just in case anybody is interested. Take an aircraft engine ( they generally are flat 4 or flat 6 engines and aircooled) and read the Manual. They will tell you to run the engine HARD for 30-40 hours ( and vary the rpm regularly) to make sure the rings are seating properly. If you don't you may glase the jugs which results in increased oil consumption AND reduction in power ( blow-by). If / when that happens, you have to take the cylinder(s) off, hone them etc and break the engine in again. Oh yes, and there is special oil too( mineral oil without scavenging additives for the first 50 hours or until the oil consumption stabilizes).

Cheers

HarryR

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Just in case anybody is interested. Take an aircraft engine ( they generally are flat 4 or flat 6 engines and aircooled) and read the Manual. They will tell you to run the engine HARD for 30-40 hours ( and vary the rpm regularly) to make sure the rings are seating properly. If you don't you may glase the jugs which results in increased oil consumption AND reduction in power ( blow-by). If / when that happens, you have to take the cylinder(s) off, hone them etc and break the engine in again. Oh yes, and there is special oil too( mineral oil without scavenging additives for the first 50 hours or until the oil consumption stabilizes).

Cheers

HarryR

But that makes too much sense. Too many on this board are convinced that Porsche knows all the answers so no matter how much proof you show the, they have to do it the PORSCHE way. I wonder if Porsche has a subsidiary that manuafactures oil? Anyway, some people will always follow the crowd.

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OK, it might be useful to shed some light on the technical background of break-in:

As most people correctly understand, the main objective of engine break-in (as opposed to breaking in the gearbox, brakes, and so forth) is making sure that the piston rings fully seal all around the bore.

In a 996 engine, there are 3 rings per cylinder:

1) The top one is called a compression ring and seals against the combustion pressure.

2) The secondary compression ring seals against the combustion pressure but also serves as an oil scraper ring. It has a different shape from the top ring and is slightly tapered (1/2 - 1 degree). It also works by slightly twisting.

3) The oil control ring performs the bulk of the oil retainment. It has a completely different design with typically two rails and a spacer.

The oil control ring performs its sealing function solely because of it spring tension, i.e. the pressure with which it is pressed against the cylinder wall.

The top two rings are aided by the combustion pressure, which gets behind the rings and presses them against the bore. It is because of this pressure that the compression rings seal.

If there is insufficient combustion pressure, the top two rings are not pressed against the cylinder wall and break-in takes a long time. This is why cruising down the highway in 6th gear at 60 mph to break in the engine is not such a good idea.

Great, so I’m gonna take it to the redline straight away!

Err … no. The problem is that high revs mean a lot of heat and high piston temperature, because per unit of time you have many combustions. The main way the piston sheds this heat is via its piston rings to the cylinder, because the rest of the piston is not in contact with the bore. During break-in, the piston rings are not fully seated against the bore and this makes the heat transfer from the piston to the actual cylinder much harder. Therefore, the piston can overheat, and piston rings can get stuck in the piston grooves. Not so good.

Also, high revs don’t mean high combustion pressure! Combustion pressure is highest where the engine has its maximum torque (around 4500rpm), and not its maximum power. Therefore, going over 4500rpm does not improve the bedding-in process of the piston rings, all it does is increase the heat (and temperature) because of the increased number of combustions per minute.

This is precisely why car manufacturers recommend varying revs and engine load during break-in: You want some load on the engine to assist break-in, but you don’t want high revs for a longer period of time, because of the heat transfer issue.

Finally, because of its different design, seating of the oil control ring is not aided by combustion pressure and engine load. It just takes time.

Yes, I used to work as an automotive engineer for Mercedes-Benz. I’ve got a B.Sc. and an M.Sc. in Mechanical Engineering from the University of Stuttgart and a PhD from Cambridge. ;)

Cheers,

Uwe

Edited by umn
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If there is insufficient combustion pressure, the top two rings are not pressed against the cylinder wall and break-in takes a long time. This is why cruising down the highway in 6th gear at 60 mph to break in the engine is not such a good idea.

It is not that it takes a long time, it makes the cylinder bore oblong. The cylinder reaaches it final shape and honing in the first 100 miles of engine operation, If you do not properly hone them using the equalized pressure of the rings against them during that time, you have increased you chances of both oil seepage and compression loss. Once the cylinders are properly honed by the rings, there will be minimal wear on the cylinder from the rings for the life of the engine. All wear will continue to be even and will promote maximum compression and oil sealing.

Also, the heat in the cylinder is removed 1/3 by coolant/oil, 1/3 by exhaust and 1/3 is used for the power.

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It is not that it takes a long time, it makes the cylinder bore oblong.  The cylinder reaaches it final shape and honing in the first 100 miles of engine operation,

...

No, on a LOKASIL or NIKASIL coated cylinder there is no measurable wear during break-in. It certainly does not make it oblong. If it did, you'd have a major problem, because NIKASIL coatings are only around 0.05mm thick.

In fact, the whole idea of using a silicon-based coating is to make sure it is harder than the piston ring, so it is the piston ring that wears.

Cheers,

Uwe

Edited by umn
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It is not that it takes a long time, it makes the cylinder bore oblong.  The cylinder reaaches it final shape and honing in the first 100 miles of engine operation,

...

No, on a LOKASIL or NIKASIL coated cylinder there is no measurable wear during break-in. It certainly does not make it oblong. If it did, you'd have a major problem, because NIKASIL coatings are only around 0.05mm thick.

In fact, the whole idea of using a silicon-based coating is to make sure it is harder than the piston ring, so it is the piston ring that wears.

Cheers,

Uwe

This sounds right to me. In my honda, which has a hardened aluminum block, when I had the head off at 150K miles, there was no appreciable wear in the cylinder. Popping the pistons out and putting them back in was a piece of cake. The honing also went very easily. I think that in the old days of cast iron blocks uneven cylinder wear was a problem. These days it isn't.

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