Engine break-in info

[MustGoFaster]

This was posted on 3SI.org a while ago and the subject just came up over here, so I though of it. Seems like good info to me.

http://www.3si.org/forum/f35/how-lon...ml#post4958377
Copied just in case:

Originally Posted by MaxTrouble

My work at the British Internal Combustion Engine Research Institute (BICERI); researching wear and life expectancies of engines for major manufacturers might help people decide the procedure they chose for break in/run in. The research found one of the most important factors for maximum engine life/reliability was the process of work hardening. This is similar to shot peening rods for example to relieve the stress in the material and increase the strength due to plastic deformation in the crystals of the material.

It was found that during various run in/break in procedures the most effective procedures are the ones that promote the highest degree of work hardening in materials of the engine, while regulating the loads produced before maximum hardness was achieved.

Most people correctly assume that modern manufacturing techniques and machining processes do indeed reduce the discrepancies in tolerances found in older engine manufacture/machining techniques, and so bedding in/wearing in of these parts is not a primary concern for modern engines. However with modern engines producing more power than ever before (this is especially applicable to modified forced induction engines), work hardening of the parts is essential for engine longevity.

During the research it was found that engines run hard (no break in/run in) from assembly, showed marked bearing wear compared to engines that had been subjected to controlled loads and revs during their initial break in period.

While cams, followers, pitons/rings, bores and other ferrous based metal components where found to differ only slightly in character during various break in procedures (including running hard without concern for break in); softer materials such as composite bearings were found to vary greatly dependant on the break in procedure used.

The procedure for testing each engine was to run each identical (ascertained by hand inspection and assembly of the engine to manufacturers blueprints) engine on a computer controlled engine Dyno, to a pre-programmed simulation of the various pre approved (by the manufacturer using previous test results) procedures. These included no break in at all; break in at no more than 33%, 45%, 55% and 75% of engine rpm for specific mileage periods, and the same as the later but with throttle restrictions.

Each engine was stripped down at every specified service interval and all components were measured and tested for hardness, surface properties (visually observed under a microscope) wear and surface deformation. These results were then logged and eventually compared to the results of the initial tests done before starting each engine for the first time. The components were then reassembled, and the engines were serviced according to the prescribed schedule before starting the next phase of the simulation.

This continued until each engine had reached the end of its respective break in period. At this time all the engines were run on the same simulation (based on pre recorded data from actual road driving conditions) without deviation; following the manufacturer’s service periods. After a period specified by the manufacturer (200000 miles was considered an acceptable life expectancy without major failure), all the engines were then run to destruction on the same simulation. The purpose of this was to determine the practical effect of each procedure on the engines final service life.

What became immediately apparent during the research was that engines run hard from the off developed greater wear/distortion effects on the soft metal surfaces (big ends/mains etc); than the engines allowed to work harden under moderate loads/revs. No major differences were found in the metallurgy, surface properties or hardness of the pistons/rings/bores of the engines run hard from start up or the ones run at 45%, 55% and 75% rpm at the final inspection before the destruction cycle. However the engines run with throttle restrictions saw a marked difference in the spot hardness and sealing faces of the rings and bores, which was attributed to the reduced load applied to the engine preventing satisfactory bedding of the rings and the bypass of combustion gasses past the rings. This had caused localised overheating and contamination of the bores, pistons and rings. All the engine run hard without concern for break in, suffered eventual failure most experiencing big end failure, while all other engines showed varying failures (including big end) from turbo failure to cam drive component failure, but in all cases the failure period of the lowest mileage broken in engine, was significantly higher than that the best non broken in engine. In total 200 engines were used for the research, all of which were turbocharged Saab engines.

In conclusion it was recommended that the most effective overall procedure to recommend to purchasers was a 45% rpm restriction over a mileage of 500 miles, with (and this is probably the most important part) the highest possible frequency of cold to hot running conditions, i.e. stop start driving over moderate distances long enough to allow the engine to completely attain full running temperature and completely cool before restarting. Large throttle openings during this period were found to be highly effective at setting the rings and generating enough forces in the engine to achieve the best material properties (note this is generalised for all components) from the work hardening process.

There were lots of other factors considered during the research like electronics and ancillary component wear/life expectancy etc, but the most relevant information gained for the person deciding on a break in procedure, was the effect of load and deterioration of the tolerances/surface finish of the soft metal components. Engines run with high loads on new components saw a marked deterioration of soft metal components over engines that were run at moderate loads 45% rpm limitations until maximum hardening had occurred (400-500 miles). It was also found that engine run for a further 500 miles with a restricted (75%) rpm limit saw a marked increase in the time to final destruction beyond 200000 miles.

If you are still with me after all that…

I am not saying this is the only way to break in a new engine; this is simply a summary of the findings from the research carried out to determine the effects of different procedures on one manufacturer’s engines.

From this I would surmise the research would show that for our cars, an rpm limit of around 3250 for the first 500 miles, broken into journeys of around 20-50 miles; followed by an rpm limit of 5400 rpm for a further 500 miles again with short journeys, during this period high throttle openings should be used and most importantly a cycle of allowing the engine to fully cool after attaining full operating temperature, will achieve the best all round break in results.

So go and visit lots of friends who live 20-50 miles apart giving it plenty of right foot up to 45% throttle, spend a few hours with each, and you will have improved your social life, and run your engine in while showing off your car to all your mates.

There was lots of other data and research carried out at the same time but essentially this is the most relevant to this post.




Russ

[scheides]

Wow, excellent post!

[Super Bleeder!!]

Very cool. Im glad i took it super easy breaking in my motor.

[goodhart]

That's crazy, thats pretty much the same thing I did with my new engine and it has been great. Danny and Shane at DB told me no more than 4k RPM and NO BOOST for the first 1k miles. The first 500 or so I never went over about 1/2 throttle, and the last 500 I started to slowly get into it a little more but still no boost until Shane tuned it for me. I guess it was the perfect break-in recipe!

[MustGoFaster]

Well, I actually think there's a typo in that second to last paragraph. He says 45% throttle, but think he meant RPM. If you go back and read the paragraph before it He says 3250 RPM, wich is just a little over 45%, but he also says "during this period high throttle openings should be used". I wouldn't consider 45% high throttle.

In an engine, the forces that HP/TQ apply to the components pails in comparison to the forces of accelerating and decelerating the rods an pistons at high RPM. By limiting the RPM you eliminate those forces, by using high throttle you put the cylinder pressure behind the rings to press them onto the cylinder walls before they develop the glaze and are no longer "abrasive" to the rings. That's just my interpretation based on the above quote and this one:

"However the engines run with throttle restrictions saw a marked difference in the spot hardness and sealing faces of the rings and bores, which was attributed to the reduced load applied to the engine preventing satisfactory bedding of the rings and the bypass of combustion gasses past the rings. This had caused localised overheating and contamination of the bores, pistons and rings."

Basically I get high throttle(seat the rings with cylinder pressure), low RPM(keep forces low) and heat cycles (work hardening).

[1QUICK4]

Meh, let 'er buck

[niterydr]

Originally Posted by 1QUICK4

Meh, let 'er buck

My thoughts exactly for most applications. If I am building a race engine, it won't make it to 200k without being torn down anyway.

But this is a very informative post, good work Ryan!

[MustGoFaster]

Originally Posted by niterydr

My thoughts exactly for most applications. If I am building a race engine, it won't make it to 200k without being torn down anyway.

That and take into account that you might be using forged rods and pistons (stronger components) or used rods (already heat cycled a billionty times) Let'er buck is probably a decent bet.

[niterydr]

Originally Posted by MustGoFaster

That and take into account that you might be using forged rods and pistons (stronger components) or used rods (already heat cycled a billionty times) Let'er buck is probably a decent bet.

You beat my ninja edit of good post .

[Pushit2.0]

Its good to see it all done up in a lab and whatnot, but for the most part the average joe is not going to have his motor last 200,000miles without something happening. But if you buy a new car and want it to last forever, now you know what to do. I think we had ~5miles on my engine before it was over 500awhp and 9500rpm right?

~John

[niterydr]

Originally Posted by Pushit2.0

Its good to see it all done up in a lab and whatnot, but for the most part the average joe is not going to have his motor last 200,000miles without something happening. But if you buy a new car and want it to last forever, now you know what to do. I think we had ~5miles on my engine before it was over 500awhp and 9500rpm right?

~John

I think we held out till 10 to actually let it rip all the way up, but I remember doing "vacumn pulls" well over 300awhp .