OEM Initial engine break-in procedure.

[Retracnic]

Greetings,

I would like to know the initial engine break-in procedure used by major automobile manufacturers or their suppliers.

I am intimately aware of the procedures employed by race and performance engine builders. What I am looking for is what do the big guys (Toyota, GM, Honda etc) do to break-in an engine before it leaves the factory.

Any help would be appreciated in this matter

Regards,

Bryan Carter

PS – I know what the owner's manual says...

 

[DOHCPower]

Maybe theres more heat generated at a little bit higher RPM and thats helps the break in process.

 

[patprimmer]

Maybe there is more oil flying around and lubricating the cam.

I am sure 2000 rpm is not appropriate for all engines. It is the benchmark rpm for typical American V8 car engines.

I doubt there is much demand for hotrod cams for big diesels.

It might be better to say run at 2 to 3 times standard idle with no load to break in the cam, then short bursts from idle to half maximum speed, then progressively increasing rpm for short duration full load runs with short rests between to stop localised overheating. The indicator of how long this takes will be the reduction in blow by.

It really does depend largely on many factors like compression ratio, ring materials, ring dimensions, bore accuracy, bore surface finish, bore material, bore stability, piston speed, cylinder pressure, piston to bore clearance, ring grove clearance etc etc

Regards

eng-tips, by professional engineers for professional engineers
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[kenre]

Many of the big Diesels i rebuilt, mainly Cummins, have roller lifters. rolling is certainly easier than sliding friction. Alot less chance of Galling.

Pat, i agree with your comment on having more oil flying around at higher than idle RPM.

Ken

 

[NormPeterson]

I don't think I've ever done a cam break-in at a constant rpm. Varied, between ~2000 and 2500 or so. It's been explained to me in terms of varying the oil spray patterns that you do not want to maintain a steady rpm.

My offhand thoughts behind why 2000 or a little higher is used for performance cams is to reduce the loading as the follower goes over the nose. You get to use the cam's negative acceleration to your benefit this time - instead of worrying about floating the rest of the valvetrain clear of all contact with the cam you're using a very mild case of this to overcome just a portion of the spring load. Valve train inertia will use up more of the spring force at any given position if you let the cam profile accelerate linearly out from under the follower faster, and more rpm helps this. Perhaps 2000 rpm or so provides a good balance between decreased loads over the nose and increased loads on the opening flank. And/or maybe it represents a good compromise between minimizing camshaft lobe wear and wear elsewhere within the engine (bearings, rings, journals, etc.).

If I'm not mistaken, the recommendation for breaking in double and triple spring cams is to use only one of the springs; obviously another means of reducing loads over the nose.

Norm

 

[drwebb]

SAE has published many papers on engine break-in, although the actual OEM procedures may be semi-proprietary. Here is a current reference:

2004-01-2917 (SP-1894) "Effect of Break-In and Operating Conditions on Piston Ring and Cylinder Bore Wear in Spark-Ignition Engines"

 

[icrman]

The old Cat D342, D353 etc. All had flat tappets. (Non Roller) At break in the engine is idled for the typical 5 or so minute warm up period till a load is applied.

 

[ivymike]

im sure that is where all the high spots are worn down on the cylinder wall to enable a good seal.

What, no changes at the ring/groove interfaces?

Did you mean sealing gas in, or oil out, or both? Do the peaks on a plateau-honed cylinder liner really have any lasting effect on sealing? Does the answer depend on what you meant by "sealing?" Is gas-sealing so detrimentally affected by the presence of "initial peaks" on the liner that a customer would notice any sort of performance degradation while waiting for them to wear off?

 

[GregLocock]

Well, here's a puzzle.

As demonstrated above I'm a bit of an agnostic when it comes to running in, but, I am frequently told that the fuel consumption in cars improves rapidly over the first few thousand kilometres.

So, what's wearing in? Maybe it's the trans or the diff?

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[patprimmer]

Maybe ring tension relaxes a bit, maybe piston skirt clearance opens up a bit as the very tips of the high spots on the bore are worn, and as the pistons wear a bit.

Ring tension can be reduced by the rings taking set in the compressed position, wear in the bore, wear in the rings and wear in the ring groves.

Gear boxes and final drive gears probably contribute more in my opinion, especially crown wheel and pinion.

On my engines, the blow by reduces considerably within a minute or so of power runs.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[kenre]

On my engines, the blow by reduces considerably within a minute or so of power runs.

For blow by to reduce, something must change somwhere, and the ring/cylinder wall seal and to a minor extent ring/ring groove is it.
I would say its a form of lapping, so the parts mate together to live a long and happy life!

Ken

 

[evelrod]

Well, I get to take a practical look at this ring thing next week...new rings and bearings for old Rusty Booger...for the Laguna Seca race in Oct. I'll take a leak down after assembly, after initial warm up and, after the dyno runs. I'll post them here later, maybe in a couple weeks.

Rod

 

[ivymike]

the fuel consumption in cars improves rapidly over the first few thousand kilometres

Are you sure that reductions in mechanical friction are to blame (if you halved mechanical friction, what fuel econ benefit would you expect to see)? Could the performance of the fuel injectors, or some other part of the combustion system, be changing as well?

All of the "soft" bearings within the engine will change shape slightly during this initial period, and the bearing clearances will increase (some more than others) - this may account for a fraction of the friction reduction (hydrodynamic rather than mechanical).

blow by reduces considerably within a minute or so of power runs

By blow-by, do you mean the flow rate of all gases from the crankcase, or just the visible portion (many people refer only to the visible portion)?

When you say power runs, are you refering to only the initial few minutes that the engine runs near full power output, or every subsequent run at high power as well? Blow-by should drop temporarily every time the engine returns from high power to a lower setting, due to gap shrinkage (ring thermal expansion relative to bore) and piston clearance reduction (piston expansion). It should "grow back" as the piston and rings cool. Is this consistent with what you've observed, or are you talking about a permanant change?

Ring tension can be reduced by:
1) rings taking set in the compressed position people often refer to this happening, but at Tmax<250degC I can't see much tempering happening in steel rings. I've also never noticed a significant change in tension between new and slightly-used rings.
2) wear in the bore yes, this does happen, but in a 100mm bore you'd need ~0.75mm of wear (diametral) to give you a ~5% change in ring tension - so I'm guessing this effect is pretty slight
3) wear in the rings ignoring the change in cross-section, you'd again need about 0.75mm of wear to get 5% change in tension (with that much wear, you couldn't ignore the change in x-sec, but the real initial wear is more like 0.005mm and is limited to a portion of the ring face)
wear in the ring grooves Sorry, I have no idea whatsoever how groove wear can affect ring fitted tension. Wouldn't the ring fitted tension be the same even if the piston was entirely absent, and the ring was just sitting (properly oriented) by itself in the bore?


I'll take a leak down after assembly, after initial warm up and, after the dyno runs. I'll post them here later, maybe in a couple weeks. Do you lube the rings or bore during assembly (might make a big difference in the results)? I know that many people "clock" the rings in the bore when they're building an engine, believing that this reduces blow-by. I would agree that this may slightly improve sealing on initial startup, but after that the ring gaps go wherever they please, negating the effect. Anyone have any comments on that? Is clocking the gaps important for initial startup, because compression would otherwise be too low? Is the lack of a somewhat-evenly-spread oil film on the cylinder wall the missing ingredient for initial compression?

 

[patprimmer]

I am talking about visible blow by and a permanent effect.

In my observations, the rings fit closer to the piston, or hang further out of the groves with the piston removed after the engine has done a few passes. The rings are easier to compress and refit to the bores as well on a slightly used engine.

Re grove wear vs tension. OK I was grasping at straws there.

No matter what the reason, engines do turn easier by hand after they have been run.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[ivymike]

Is the effect you observe only on the first power run, or does the blow-by progressively decline with each subsequent power run, until you no longer have visible blow-by?

...Or is it the case that after every power run, you have a certain amount of visible mixture coming from the crankcase, and as the engine continues to run and cool the visible fraction declines, but then at the end of the next power run the cycle repeats?

I would also note that visible blow-by may not be a useful indicator of "ring seal" at all, since it doesn't necessarily correlate to the amount of gas passing the rings. In some select situations the two can be related (if, for example, the concentration and size distribution of oil droplets in the crankcase were relatively constant, and breather performance was not influenced by total blow-by volume, and piston temperature was constant, and cooling jet flow was constant, then I would expect that more gas flow means more visible stuff, and vice-versa. In other cases, more gas flow means less opportunity for droplets to clump together into a visible size. It can also happen that visible CCV constituents are most closely related to piston temperature and cooling jet flow, with next-to-no relationship to blow-by gas flow. Changing ring-groove clearances, perhaps due to wear, can also affect the size of droplets in the blow-by stream, making them more or less visible, without having a big effect on total gas flow, as can carbon and "gunk" accumulation at key locations on the pistons).

In any case, it has been my experience that blow-by (total, measured with a flow meter in a big duct) and oil consumption of an engine vary somewhat during the first 50 hours of running (or so), then tend to level out for a while, before heading off in whatever direction they eventually drift in (usually for the worse). There is usually an initial period of "rapid" change (although the magnitude of the change is generally pretty small compared to the magnitude of the parameters in question - 10% or less), after which changes happen at a much slower rate. Running at higher cylinder pressures would tend to make the "rapid change" period shorter, by a bit, than it would be if lighter load was used. There is a measurable change in bore surface finish, and the peaks do get smoother. The tops of the "plateaus" become more like plateaus and less like pincushions. I doubt that gas flow past the ring faces changes much as a result of these bore surface finish changes - the peaks aren't THAT big, and they should be pretty "mooshy" when the gas-loaded ring rubs across them. The ring and groove flanks both become smoother during this period as well, and regions where loads are concentrated tend to get "rubbed down" a bit - I would tend to attribute gas sealing improvements to better ring-groove contact and reduced groove runout. Then there's the accumulation of oil in the inter-ring volumes and in the backs of the grooves, which also likely helps to reduce gas flow past the rings.

 

[patprimmer]

It progressively improves over the first few runs. The runs increase in duration and RPM from say 3 seconds at full load at med RPM to a final full power run for 8 or 10 seconds. The level of improvement tapers off until improvements are not detectable by eye. The RPM level and duration are increased according to the amount of blow by noticed. The engine is slowed to a no load fast idle for a minute or so between runs

My method is purely subjective using the only tools I have for this, which are my eyes.

I have no means to measure cylinder pressures, nor internal temperatures. I do monitor oil and coolant temperatures to make sure they are "normal" but normal probably covers 85 to 110 deg C.
for coolant and 90 to 120 deg C for oil.


Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[evelrod]

Isaac, I think your 'overthinking' the problem. It's pretty straightforward from a practical point of view. If all the demensions are in spec, ie, no bore distortion/taper and proper piston specs then, no it probably makes little difference in the long run wheather you 'clock' the rings on installation or not. That is not to say I don't do it, rather mechanically, out of habit. My ring gaps are ~0.014" cold and, again, no I have not done a leak down on a cylinder with gaps alligned (to be honest, I probably won't either) Anyway, it'll have enough compression to start as static is 14:1 on the Mini and 15:1 on the Lotus.
At one time in my life I succombed to the 'drag racer mentality' and pushed the pistons in dry or on one particular 394 Hemi, used a fine 'jewelers rouge'...not these days. Now I liberally oil the cylinder AND the piston/rings before assembly. The new piston never runs on a dry cylinder and I have seen no unusual anything in the last twenty or thirty engines save a broken ring on a street Ford Fiesta 15 years ago.
[Another, sorta related question to explore...Why do I still run my engines in on paraffin based lube instead of just going to synthetic to start? The OEM's that use syn don't bother?]

"wear in the ring grooves Sorry, I have no idea whatsoever how groove wear can affect ring fitted tension. Wouldn't the ring fitted tension be the same even if the piston was entirely absent, and the ring was just sitting (properly oriented) by itself in the bore?"

Firstly (or lastly), ring tension is ring tension until the fire is lit...then, especially on Dykes or drilled pistons, the tension increases, a lot.
Secondly(or firstly) from my experience, when the ring groves begin to exceed a certain wear limit, expecially the top ring, blowby increases dramatically. I see it as a result of "ring flutter" whereby the ring no longer makes a square, perpendicular fit to the cyl. I come by this opinion from some tests I was privy to on some 'dykes ringed' versus 1/16" versus 1mm versus zero gap top ringed Cosworth pistons in a Lotus Twincam 1594cc engine many years ago (sorry, I don't recall the specifics of each type. I do recall that the Dykes and 1mm were about the same.) I have a set of JE's with 1mm's (for that 10,000rpm "one of these days" engine) and a set of Venolia's with Deves 1/16" for the vintage engine (run in quickly and last a long time). One BIG difference in ring type is overall bore clearance...the smaller the ring the more critical the fit.

Sorry this post got a little longer than I had intended.

Rod

 

[GregLocock]

Well, it had to happen one day. Rod is Wrong, or at least, not completely accurate. We still use running-in oil for our first fill, in production, and pay more for it than the normal stuff.

But, I think it might be a bit special since our darling customers tend to skip or delay the first (1000 mile) service, so it has to stand up to regular use as well.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[ivymike]

especially on Dykes or drilled pistons, the tension increases, a lot. ... sure, but I'd call that radial pressure, not ring tension. That's what I was referring to when I mentioned "gas-loaded" rings.

 

[evelrod]

Awww, shucks. I was on a 65 year run, too.----- Oh, wait! The way I read it, Greg...since I still use Castrol to run in my engines and then switch to Mobil 1...doesn't that mean RIR?

Rod

 

[evelrod]

Your correct, Isaac. I should have said that in relation to ring tension, radial pressure remains the same until the fire is lit, etc. My tongue was over my eye tooth and I couldn't see what I was typing. I knew what I ment.

Rod