engine and drivetrain Rebuild is done, need tips on engine break in

[chuncomunco]

Anyone have any tips on how to break in a motor?

[Pinepig]

My last motor I went with what this guys says, I'm a believer.

http://www.mototuneusa.com/break_in_secrets.htm

[TobyB]

Yup, I tried that too-

worked great on the truck,

but the 2002 engine with Deves rings still burns oil.

In defence of the procedure, it's an older head, too,

so who knows where the oil's coming from!

t

[BillWilliams]

(nt)

[JohnN]

couple years ago:------------------------------

Date: Mon, 18 Dec 2000 21:33:42 -0800 (PST)

From: John Bolhuis

Subject: [uuc] New engine break in recommendations (long)

>

Chris and I were mailing back and forth. Does anyone have a good

link or a procedure they feel is good for new engines? I kind of have

my foot in my mouth. I don't want to steer him the wrong path...

>

Looking into the wayback files, I pulled this post from the Saturn

list from way back in late 1994. It may be the only break-in post

I've seen that has reasons for its actions. Whether or not you agree

with them, or whether or not BMW engines deserve the same treament,

well maybe that will generate some more gearhead-related discussion

here, which we could use. As for Ben Sloss, I left his name & address

attached, but I have no idea if he's still at that address.

Remember, if you reply to this message, EDIT & TRIM! (and run

through the spell checker for good measure)

Ben's guide to 4-stroke engine break-in:

The Practice. For the first 100 miles, only take short trips of <15

minutes. Do not rev above about 3500 rpm. Use full throttle in short

(2-3 second) bursts at low rpms (say 2500) - 5th gear on the freeway

is ideal for this. Do not do more than one full-throttle burst in the

same 2-minute period. Avoid driving for more than 2-3 minutes at the

same rpm - if you are on the freeway, vary your speed and alternate

between 5th and 4th gears.

>From 100-500 miles, increase the peak RPM you reach by 200 rpm each

time you drive the car (but don't go higher than redline). Do not rev

to your new peak under heavy throttle; instead, let the engine drift

up to the rpm under light load. For instance, pulling away from a

stoplight, leave the engine in first and accelerate lightly until you

reach the desired RPM, then shift. Continue the full-throttle-burst

procedure. Do not rev the engine high under full throttle, and do not

do either the peak-revving or the full-throttle procedure more often

than once a minute. Avoid driving for more than 5 minutes at any one

rpm - again, alternating between two adjacent gears and varying your

speed will work.

You will notice that each time you reach a new peak rpm, the engine

will be quite loud at that rpm, but after a few runs up it will quiet

down. This is a sign that the break-in is proceeding well. You will

want to have revved the engine to 6500(5500) rpm a few times by the

time you reach 500 miles. At that point I recommend you change the

oil, as most of the metal wear and contaminants from break-in are

released in the first 500 miles.

>From 500-3000 miles (the extended break-in) you can operate your

engine fairly normally. Most of the work is done. You should still

run the engine at higher RPMs on a regular basis (assuming you don't

in the normal course of driving ;-) ) and you should avoid prolonged

high-speed/high-stress operation, like racing or cruising at 110 mph.

I personally change the oil after 1500 miles since it will be dirtier

at that point that it would be after 3000 miles of post-break-in

operation, but it isn't critical. Be sure to change it at 3000 miles,

however. Although there is some difference of opinion on what KIND of

oil to use during break-in, the general consensus is to use normal

(non-synthetic) oil of the recommended weight (5- or 10-30).

>From 3000 miles onward, your engine is considered broken in. It will

probably continue to "loosen up" a bit over the next 3000-6000 miles,

so look for a small increase in gas mileage. Other than that, your

engine is now be ready for a long and productive life. Enjoy!

***** BEGIN TECHNICAL SECTION ***** [some of this is what I remember

from articles I have read and discussions. I cannot vouch for the

complete accuracy of what follows, but I believe it to be essentially

correct. If you *must* flame me, please do so in private unless you

think I've made a mistake which everyone need to know about to avoid

doing something unpleasant to their car]

The Theory. The primary goals of engine break-in are: 1) achieving a

good seal between the piston rings and cylinder walls, and 2) allowing

the engine to operate correctly throughout its RPM range. The major

enemy during the break-in period is localized heat buildup, mainly in

bearing surfaces (most notably the crankshaft bearings).

Initial state: When the engine is machined at the factory, many

wearing surfaces (places where parts rub against each other - cylinder

walls, bearings, etc) are purposely machined more roughly than they

could be. The reason for this is that it allows the engine to

complete the machining/polishing as it operates, thus allowing for the

individual variations inherent in any manufacturing process. This

wearing process, when complete, produces parts which will fit together

with very tight tolerances. However, the process also involves a

great deal of friction, which in turn means a great deal of heat. As

metal parts heat, they expand slightly. If the expansion goes beyond

a certain point, the parts will tend to bind with and/or score each

other. This must be avoided.

[To put this in plain english, the parts which rub against each other

are left a bit rough, and as the engine runs the parts will scrape

against each other until they wear down a bit and have a proper fit.

While they're still in the process of scraping, they can get very hot;

if they get too hot, they will damage each other in a permanent way.]

Since this sort of heat buildup is very localized, it will not show up

on the engine temperature gauge. Therefore, it is important to

operate the engine in such a way that the heat buildup will not reach

a dangerous level. More on this later.

Stress and Variation: Although the engine parts are metal and, as a

rule, quite rigid, they are still subject to slight deformation when

stress is applied. The largest stress in a piston engine is that

produced by reciprocating parts. The forces involved increase with

the square of the RPM. Any deformation will necessarily involve a

change in some tolerances inside the engine. Thus, in order for the

engine to operate properly over a range of RPMs, it is important that

it be exercised over this range during the break-in process so that

the wearing parts will experience the range of tolerances they will be

subjected to during normal (post-break-in) operation. Further, for

the wearing surfaces of reciprocating parts (most notably the piston

ring/ cylinder wall interface) operation at a single RPM for an

extended period of time will cause the machining process to progress

significantly further within the confines of the part's range of

travel without progressing at the point just outside that range, thus

building up a small ridge of metal just above the point of maximum

excursion.

[in order for your engine to run well from 1000 to redline, you need

to operate it at all those rpms while it is breaking in. If you

don't, the parts won't be used to working at the rpms you neglected,

and they won't work as well at those speeds]

Piston Ring Sealing: The seal between the piston ring and the cylinder

wall is crucial to getting good economy and performance from the

engine. A bad seal will allow more blow-by, reducing the amount of

power the engine can produce with each power stroke and thus reducing

both its horsepower and fuel economy, as well as allowing combustion

gasses to get into the crankcase and contaminate the oil AND allowing

oil to get into the combustion chamber and be burned, producing the

characteristic blue-smoke-from-the-tailpipe syndrome (note that oil

can also get into the combustion chamber via the valve stem guides,

but that's not something we can do much about during break-in). The

key to getting a good piston ring seal is high combustion chamber

pressures. Embarrassingly, I don't know why (can someone fill me

in?). High combustion chamber pressure is produced under hard

acceleration; also, the lower the RPM the longer that pressure is

maintained during each power stroke. SO - to get a good piston ring

seal, hard acceleration at low RPMs will give the best results.

Since hard acceleration also produces more heat and more stress

(leading to friction and still MORE heat), it should only be used in

brief bursts, followed by a couple of minutes of "normal" low-stress

operation to allow the heated parts to cool down.

Localized Heat Buildup:

As previously mentioned, wearing parts will produce inordinate

amounts of heat as they polish each other. This produces local points

of intense heat inside the engine, with temperatures far higher than

the engine as a whole (which shows up on the temperature gauge) or

even of the surrounding parts. The most susceptable points in an

engine for this kind of heat buildup are the crankshaft bearings,

which must withstand enormous stress and pressure. If the bearings

are allowed to get too hot, they will expand to the point of scoring

each other or (*gulp*) binding, producing a spun bearing. During the

initial stages of engine break-in, there is no satisfactory way of

keeping these bearings cool during even mild engine operation except

to turn the engine off after every 10-15 minutes of operation and

allow the bearings to cool down.

The theory I have outlined about should now be sufficient to explain

the "practice" section of the break-in instructions. For the first

100 miles, keep the rpms low and the trips short to minimize the

stresses and heat buildup in the bearings, and use short full-throttle

bursts to seal the piston rings. From 100-500 miles, gradually

increase the RPMs to allow the wearing surfaces to correctly mate, and

continue using full-throttle bursts to ensure ring sealing. Use

cooling periods (the 1-minute rule) to minimize the heat buildup

produced by the high RPM operation and the full throttle bursts. At

500 miles, change the oil to flush out all the metal particles

produced by the wearing process.

I hope everyone finds this information useful. If you have comments

which are of general interest, please post them - if you just want to

flame me for making a mistake, please email me so that we don't make

everyone endure a huge firestorm. I should also note that I practice

what I preach - at 7000 miles my CBR is more powerful than anyone

else's I have ridden and its oil is clean after 2000 miles of

operation, while my Saturn SL2 at 10,000 miles is getting 29 mpg

overall and consumes no oil at all.

Ben Sloss Database Kernel Hacker Email: ben@versant.com

Quote: 'It's all fun and games until someone gets paid.'

Transportation: '83 CB650SC (straight roads) '93 CBR 900RR (twisty roads)

'93 Saturn SL-2 (wet roads) '91 XR 250L (no roads)

[peteinjp]

Yup, I tried that too-

worked great on the truck,

but the 2002 engine with Deves rings still burns oil.

In defence of the procedure, it's an older head, too,

so who knows where the oil's coming from!

t

Well I used deves and I drove it really carefully for the first 1500cm. then i gradually raised the rpms to 6500 or so in the next 1000cm. Then I varied the rpms from 4800 to 6500 for the next 60 or so km's. And my deves seated just fine. At 1500 km's I showed excellent compression across all 4. At 5000 km's it was exactly the same and it is still the same at 30,000km's. So the rings are fine. Time will tell about the big/small end bearings etc. but it sounds fine.

I just looked over my 1600's owners manual and I think if I were to have a little more self control I might just go with what the factory recommended. But in this case I'd consult the maker of the rings and pistons.

[meyekel]

i had a loop that i would do around my house that has a decent size/grade hill for accelerating under load and then would drive back around for a cool down. i repeated this each day increasing the rpm's by about 200-300.

Mike

[JayKehoe]

I used regular, cheap oil for the first 500. In Northern Ca. , it is easy to find roads that have ups and downs and curves, so that you are not lulled into spending too long at one RPM level. That is the CURSE, lol. You need a varied RPM drive and you must not exceed recommended lower red line until the break -in is accomplished. A flat expressway would be a mistake to use. Your constant change of gears, and speeds could create a problem, no less let you remain too long at one setting. Let the topography of back roads and hills help you to do it right, and to even enjoy the process. Drain the oil and change the filter after the 500. Follow other archived suggestions for the next phase. Good luck, and remain vigilent on the RPMs.

[SHEN]

Keep it under 4k for the frst 1200 miles then have fun.