According to this motorcycle page, the best way to break in a 4-stroke engine is to methodically run it hard. I'm not sure if he's suggesting to do the same thing for car engines. His explanation:

(read the page for more specifics)

I'm curious... anyone think this technique makes sense? I'm assuming it does not apply to rotaries since they do not have pistons... or am I wrong?

 

RG thinks it has merit in the rotary. I don't buy it myself.

 

Does anyone have some sort of idea what the factory do with the newly assembled Renesis? For how long and how hard is it run in the factory? I've never seen anyone post anything about that........

 

Don't lose sight of the fact that you need to 'Break In' the transmission gears, and in the case of cars the rear diff gears, as well as the engine.....if not more so.

 

So why not do the high revving while out of gear? Or does the engine need a load in order to seat the seals properly (rotary or otherwise)?

 

Ive often heard 'drive it like you stole it' from day one, I dont buy it, I followed racing beats break in, but even if I hadnt read that, I would have gone at least 1k miles of easy drivng, stop and go, vary rpm and use low rpm, then change the oil and slowly work up to high load/high rpm driving and long time high rpm use, over a few hundred miles.

 

I have a friend that works for BMW in Oxford and they give new engines a good quick thrashing then check them and ship them out. I think this is only the higher end BMW's. I would think they do it to make sure they don't make any bad noises more then smoothing some rings

 

Alot of people support conventional break-in method but I have to ask, why? What makes you think it is any better to do this? Who ever started this technique? No one can ever answer this. It is just what they know and have always been told so they blindly support this method. Different is scary. A clutch and brakes are exceptions as these actually do need break-in. Even then the important part of bedding them in is the heat cycling of them together. The best way to break-in your brakes is also to use them very hard then let them cool. We know your bearings never break in so that's not an important part of break-in. If your bearings ever touch, you have problems. Do the seals need to "seat" or do they really just need to heat cycle? Each seal does not "seat" per se as that would imply a different shape for each seal in the housing and it doesn't work that way especially in a rotary where multiple seals constantly cross the same area. In a piston engine if your cylinder walls break in at slightly different shapes all around, the seals will generally break in to match as there is always only the same seal that crosses the same area back and forth only. We use multiple seals and they also move over a larger distance. The surfaces should stay flat and so should the seals. Hopefully they came this way when the engine was built. They will initially wear themselves "flat" to match out the imperfections in the housings or seals but that doesn't take as long as most think as it is such a small amount of material. The important part of a break-in in an engine is heat cycling of all of the parts together. After they have been heat cycled 4 or 5 times, it's basically done. If you've done it right your seals should be done matching each other by then too as this takes place right after the engine is first started and for the first few miles. This increased initial wear gets less and less, rapidly as the engine keeps running and after a while we start considering this "wear". If you want your seals to grind in to the same shape as the surface it is mating to the most important thing to do is to get them heat cycled so they don't warp. That's the biggest issue. After the engine has warmed up to operating temperature by idling for a while just help them out by keeping the engine at a load level that adds pressure to them to fully bed them in. How many engines on the road right now are running in cars that were floored right off of the dealership lot? Tons! Do they run good? Yep. I know lots of them. There shouldn't be any more failures of these engines vs those that are broken in slowly. The big reliability issue is with engines that aren't taken well care of in terms of oil changes. It's not those that get driven hard at first vs those babied. Typically the engines that are babied at first are also owned by those who do change their oil and are careful about overheating. That would be the only reason you'd see them as any more reliable. You will still inevitibly see some metal powder in your newly drained oil as there will always be a little wear-in material left behind in a new engine. This doesn't matter if it's broken in hard or easy. It's still there. Makes you wonder how one way is better if they both leave the same evidence. I'm a fan of changing the oil and filter after 20 miles on a new engine. Obviously this is easiest on an engine you just built yourself. You will find most of your break-in material in this oil change. For a new car, drive it home and immediately change the oil. Do not wait for the dealer service interval to arrive at 3000 or where ever miles. Then change the oil and filter again at 500 miles. Then again at 1000 miles. As I said, there will always be a little material in the oil at first but it rapidly decreases with added mileage. It's more important to the longevity of your engine that you get these out of the oil system as fast as you can. so the 2 biggest issues with the break in period are multiple heat cycles of all the parts together and removing the contaminants from the oil as quickly as possible. Remember it's these contaminants that can get between the seals and cause contact like fine grit sandpaper. The person who broke their engine in hard but changed the oil frequently, ok even easy break in with frequent oil changes, did themselves a favor over the person who waiting until the first scheduled oil change interval and they ultimately did far less harm to the engine.

Since we are mostly concerned with rotaries here some people may or may not be familiar with premixing of 2 stroke oil in their gas to lubricate the seals rather than relying on the oil metering system. Anyone who has ever rebuilt these engines can tell you that a premixed engine always looks newer inside longer than those that haven't been premixed due soley to the fact that the seals get a more even distribution of oil to them. Yes they still wear but it is generally slower. Wonder why? If there is a thin film of oil between sliding surfaces as there should be, what's touching that can wear away? If this is the case, what breaks-in? What's the difference between breaking in and wearing out? Think about that one for a while.

 

and now some evidence... i talked to my cousin who is an evo/240sx/honda tuner...
and his preferred method of break in is to run the engine up to redline.. but very slowly...

hes gotten stock civics that are 10-15hp more on the dyno using this break in vs normal break in civics... like stock civics that can beat out civics with intake/exhaust..

this is the way he explained it to me

so its like.. when getting on the freeway.. just pick a gear.. and go up and up and up very very very slowly until you redline... then back off.. rinse and repeat...

basically the idea is the same as when you sand a piece of wood... when its rough... you want to use a heavy grit sand paper and take off the roughness...and you put some amount of pressure on the sand paper but then.. when it smoothens out.. you switch to a lighter grit sand paper.. and lighten the pressure/load... you also increase speed of sanding strokes to get really really smooth wood....

the idea is the same with the engine... the inside is already bored pretty smooth.. and tolerances are tight... so you just want to get a really really smooth tight finish on it...

by reving high... you are basically stroking the metal fast.... and by increasing rpm very slowly... you are only putting a small load on the engine....

so this is like sanding lightly just to polish it up...

iono if that explanation would convince people... made sense to me as i'm a machinist and have worked with wood projects as well...

but if not.. the dyno never lies

for rotary... i don't know if this would apply... they have some sorta coating to aid in break-in... what it actually does.. i have no idea... but the way rotary moves... i don't see much use of breakin... besides just not putting too much load on it... like racing beat suggests...

a bigger load i would think might grind metal particles and other material harder into the chamber......

 

I like to take all the recommendations and throw them together.

You end up with...

1) Change the oil early. (Proven through UOA's at its effectiveness)
2) Vary the rpm's (No cruise control, flex through the entire rev range)
3) No hard stops or starts. (Smooth, Even, Gradual are the names of the game)

I followed a method similar to gerael, got right on the highway after buying my 6, and just shifted gears and slowly went up and down, people must of thought I was crazy...then I did as RG suggested and changed the oil when I got home, and put in fresh stock oil.

Here's two UOA's comparing the differences in wear metals between a normal UOA, and a brand new car with low miles.



Note the massive increase in wear metals vs a standard oil change interval. If you convert the 7k interval to 1k...

Thats about 12x more iron wear, 100x more copper wear, and 26x more silicon then a normal oil change interval.

 

Whether or not you believe in the hard break-in or the soft break-in method, at the very least change your oil often when the engine is new. After 20 miles, 500 miles, 1000 miles, then off to the regular change interval. Always change the filter with the oil. At least use this guide as a minimum rgardless of how you drive it when new. Your engine will last longer without this crap getting between the seals acting as an abrasive. Get it out of there.

 

Crossbow, I know you posted over on Mazda6Club about how Caddillac has published their new method of breaking in engines. Like you said, run the engine all the way up, but no hard starts etc. I wonder if the same would be true for a rotary?