tuj

I recently read an article about the controversial practice of running an engine hard during break-in. The theory is that by running it hard, the rings get ground correctly by the hone on the cylinders, and that the normal slow break-in wears this honing off without wearing the rings correctly.

I tend to agree with this philosophy for piston engines, but I was wondering what the take of some of the rotary guru's on here was regarding this practice? I would think it might help on the side-seals and corner seals, but I'm not so sure about the apex seals. Thoughts?

rotarygod

I agree with the run hard breakin. Let's face it, at the speeds the engine turns, those wimpy little springs under the seals aren't what is holding them to the walls of the combustion chamber. It is the inertia of the seals but more importantly the pressure of the gasses within the engine. At low loads and low speeds, we don't have as much of either. The seals aren't really wearing in as quickly. Any small irregularites are also more likely to be skipped over by the seals too. Running it hard at first holds pressure against the walls and allows the seals to break in very quickly and evenly. The 1st 20 miles of a new engines life are the most critical ones. None of this matters what type of engine it is.

People like to say that you are also breaking in the bearings. Untrue completely. If your oil is doing it's job properly, there is never any metal to metal contact in bearings. It can't really break in if it never touches anything. The only time you ever see evidence of metal to metal contact within bearings is when the oil system fails or when a car has been sitting a long time without being started and the oil has drained out of the engine. Any markings you see are not from breaking in but rather another source.

Breaking in an engine in this manner will result in a better sealing engine that makes mroe power. Several auto manufacturers rev their engines up to redline immediately after they warm up on the first startup. Race teams do this as well. They don't do it because they get rebuilt every so often. They do it because it makes more power and that plus reliability are what is needed to win a race. Time between rebuilds is irrelevant.

Slow gentle breakin periods that are recommended are the worst way to break in an engine. Ponder this, if something is done wrong once, and then the same thing is done wrong again and again until it becomes common practice and widely accepted, when does this wrong become right? The fact is that wrong never becomes right but rather the perception of what is wrong and right changes.

Here's how to properly break in a new engine. The very first time it is started let it warm up to normal opperating temperatures. You don't want to floor it immediately after it starts up as some oil has flowed off of the bearings and you need time for it to recirculate. Once at warm up temperature, drive hard! take it up through the gears at full throttle several times. Drive the engine hard for about the first 20 miles. Then change the oil and the filter. Yes after only 20 miles. The hard break in on the seals (not the bearings) has left some metal shavings in the system that need to be removed. Only mineral based oils should be used during breakin. Drive the rest of the first 500 miles as you normally would the car. At 500 miles change the oil and filter again. At this point you can switch to synthetics if you want to. I run them in my rotaries. I don't care what the manual says. Results say more than words in a book. Over half of your break in was done in the first 20 miles and the other half was done in the next 500 or so miles. That's it. No need to baby the car around. You'll most likely make less power in the long run this way. This is a very different way of thinking but it works.

Nubo

I don't understand what the problem is in breaking it in more slowly. Won't the pieces eventually mate just as well? If pieces aren't mating, they wear each other down. Once they've worn each other down, they're mated. To me it sounds like something that is inevitable. I can't see how it's avoided by either slow or fast breakin?

I've heard the advice about waiting to switch to synthetic oil until after the breaking period before too. People claim "it's too slippery so the parts never break in". I don't get it; doesn't that just mean it's "like new" for a longer period? What's the harm in that? Or is there some disfigurement that occurs that can't be recovered from?

tuj

Well the idea is that you want the seals/rings to wear in quickly, before the hone wears off of the cylinder/housing. If its run slow, the wear may not be enough to wear into the ring, but may be enough to wear off the hone, afterwhich no significant wear (of the good kind) will occur on the rings. The argument against synthetic is that its actually too good of a lubricant and prevents this initial wear-in that is being encouraged by running the engine hard. Synthetic can be used once wear-in has occured. This would be basically 20 miles or so, but to be safe, you can wait until 1500 or so (according to mototune).

I guess an analogy (perhaps poor) would be clamping a small piece of wood onto a drill and spinning it, then just barely pressing it against a piece of sandpaper on the table. If you run the drill at low rpms, the wood will not wear as much and will instead just wear down the sandpaper. If you run it at high rpms, the wood will wear more. Basically there is a certain amount of energy needed to wear off the imperfections in the seals/rings, and if this energy is not achieved, the imperfections may just skip along without wearing enough to get true fit. In fact, some of the newer turbines have their exhaust wheels designed to machine themselves into the housing during their first run.

My concern was whether or not this applied to rotaries, which Rotarygod, in his infinite wisdom, say it does. The next question would be, does Mazda do anything like this when they build the engines?

TeamRX8

iTrader: (25)

the Mazda rotary race engine break-in procedure is

use mineral oil, not synthetic
idle for 45 minutes after initial startup
drive 60 miles at a steady 5000 rpm
drive 60 miles at a steady 6000 rpm
drive 60 miles at a steady 7000 rpm
drive 60 miles at a steady 8000 rpm
drive 60 miles at a steady 8500 rpm
change oil, break-in is complete

of course you need to stop for fuel several times

Racing Beat lists a procedure on their website, they take the factory break-in procedure and stretch it out to 2000 miles, not sure I'm buying it ...

G8rboy

I don't either... it's something like <4000rpm for that duration, which I can't imagine. I respect the hell out of RB, but that procedure seems way overboard, and a recipe for carbon buildup. I've read about the hard break-in theory for a while from sport bike owners, and many of them swear by it... but I wasn't sure how that piston ring analogy would translate to the rotary. Since the piston comes to a stop at it's apex, a slight ridge forms, which you don't want to have happen during a mild break-in. In essense drive it during break-in like you plan on driving it the rest of it's life. Since our seals are in a continual rotary motion, I don't know how much of that theory applies.

midlife crisis

4 K is what mine runs on the interstate all day long. Always 20 MPG.

G8rboy

We're talking about break-in procedures...