Hey Guys and Gals,

I'm breaking in my engine right now and it's killing me. Every other second I wanna mash the Go-Pedal. I've been going out for late night cruises that have been averaging 100 miles every night just so I can hurry up and get this thing to 1,000 miles. Tonight I was driving and an M3 passed me. Just us two on the highway. I had to keep repeating to myself "There will be more M3s. There will be more M3s." I'm hoping to be done by Christmas but man is this frustrating!!! I crave boost!

Sorry, just had to vent that.

Now then, I'm following the "Keep it under 4,000 rpm and 5psi of boost technique...Changing the oil at 500 and then 1000 miles" method. After 1,000 I'm done.

What are some of your break in procedures?

 

There are alot of threads about this, mazdacomp says 300-500miles for proper break in some say 1k miles other say build the motor warm it up and its broken in.. I guess see what others have done and do what your gut tells you.

 

Totally depends on the builder...the parts replaced, and the condition of the parts reused. Usually 500-1000 miles is sufficient for most FD rebuilds. I have built engines for myself that I drove out of the garage WOT and never let off, and they break in fine too.

 

I dont feel sorry for you I did the 1k mile breakin except in 2 days....Those 2 days were the longest/worst of my life. I did about 600 without boost, then 450 with under 5 psi.

 

why would you wanna do that. That's not proper break in mileage.

 

Mine usually involves the following:

1) 500 mi below 4,000 rpm, then change oil
2) Another 1,000 mi below 6,000 rpm, change oil again
3) Let her rip, get another engine installed and then repeat.

I usually do step 1 in one long drive, step 2 in several shorter drives.

It won't be long before you're back at redline.

 

Bottom line is that they're gonna break eventually, I've broken in engines running them 1000 miles and never seeing boost, to staggering it every 500, to just letting it run for 5 minutes then going WOT. Quite frankly everyone and their mother is going to have an opinion on this but from my experience it doesn't really matter.

One engine lasted 6,000, another 30,000, and the other 62,000. All of these were professionally tunes, but the one that lasted 6,000 was the one I broken in the conventional 1,000 mile way.

 

Really, break is mainly about letting the seals seat to the rotorhousings. IF the housings were reused, then the seat time will be longer. OF course this can be measured with a compression check. So if you want to check the status of your breakin, do a compression check. Used housing engines will usually be around 95-105 after a few hours of run time, and after about 1000 miles will have increased to 115+. New housing engines usually start off at 105-110 and will increase to 125 after a few hundred miles.

IN my opinion, after your compression reaches 115 or so, you can pretty much do whatever you want with the engine, as that indicates a good seal and the seals are pretty much seated 100% by then...and it isnt going to get much better.

The only other consideration of breakin depends on whether or not your bearings were new or reused. Most builders reuse bearings as they generally don't wear too much, and if this is the case, then bearing wear/breakin is not a consideration during engine breakin. Bearings get broken in by rotation, heat, and heat cycling. This is part of the reason why the "change oil" stipulation is found on many breakin sheets, because as the glaze on the bearing is broken there will be some wear and fine particles will be washed away into the supply. Another part of the reason to change oil is that, no matter how clean and well prepped the parts are while apart, it is likely that some small particles of dust or whatever will find their way into the passages and crevices before/during assembly, so the oil supply will be ever so slightly tainted from the getgo, so the first and second oilchange is both for flushing purposes and a consideration for bearing wear.

 

I found this thread. No offense to them, but some of their break in routines seem kind of ridiculous.

https://www.rx7club.com/showthread.p...t=engine+break

 

Also, speaking of seals taking time to seat. Would it then be normal to see oil in the exhaust in the first few hundred miles of use before the seals have seated?

Thanks.

 

Not sure how relevant this is to rotaries but every piston engine myself or my father has broken in (many), has been taken to 1500-2000rpm for 20 minutes (I believe these figures are correct, it's been a while) immediatley after start up. This is out of gear of course. Then the oil is changed. Then 500 miles below say 5000rpm then change oil and you're good to go. Also almost everyone recommends dino juice when breaking in to help seat rings more quickly. Also it's very important if using moly coating rings since they cut down on friction just as the synthetic oil does.

Like I said little of this has relevance here but maybe the initial 20 minute thing would be good for rotaries? Maybe not, since our cylinders seal in such a radically different way.

I'm lucky, the engien and turbo I'm putting in tonight both hve just enough miles on them to be broken in but yet still fresh. Less than 3k on the turbo and around 1500 on the turbo (supposedly). Unfortunately I don't think I can make it out of my snow covered driveway with my half bald drag radials. The dry roads are only 30 feet away, it's painful.

 

No, seeing as the apex seals have nothing to do with sealing oil...that's the job of the oil control rings and irons. And there is no "breakin" on those parts, they either seal, or not, from day one. IF you're referring to an engine that's sit long enough to be cold since it last ran, and you looked into the exhaust ports, I would consider it normal to see a small puddle of oil at the bottom of each rotorhousing chamber...this is drain off from the OMP system and a little drains past the (stationary) oil control rings, and is responsible for the puff of smoke that is normal at startup.

 

people miss the fact that break-in has nothing to do with an arbitrary mileage number, it's all about HEAT CYCLING folks

therefore, take more short trips w/ plenty of on/off throttle...don't be afraid to get on the gas, moderately, just not WFO....you don't want to build too much heat into the engine too quickly or parts tend to "break down" instead of "breaking in" properly (i.e. overall longevity is compromised)

drag racers don't give a rip because they're going to rebuild after a few runs anyway, and they still get 95% of the power...small losses of compression don't effect power as much as you might think

 

Heat cycling has nothing to do with breakin in apex seals. IT is useful for strengthening bearings and e-shafts. Most of which get reused during rebuilds, therefore that is a moot point. The main thing being broken in, on most rebuilds, is apex seals versus rotorhousings. Put simply, the more passes a seal makes over the housing, the more it wears to match that housing, and the faster compression comes up. You can heat cycle an apex seal for 10 years and it will not seal any better against the housing than the day you installed it, if it hasnt made passes over the housing.

It is true that you do not want the apex seal to be forced against the housing by excess centrifugal force/high rpm, which is why a reasonable rpm limitation is usually mentioned. You want to let the seal slide across the housing and wear together on it's terms, not force it.

 

but I think it is also true that heat causes the parts to expand and "bed-in", including the seals, otherwise you could turn the engine over cold a few hundred thousand times and be "broke in"....I don't think so

 

The only things affecting how much tension the seal rubs the housings with are 1) centrifugal force from rpm, and 2) spring tension. Heat makes seals expand, but this wouldnt add any additional tension to account for anything...it only comes into play where the width of the seal versus the width of the seal slot is concerned, which is why you have to leave about 3 thousandths clearance...because the seal will expand about .5-1 thousandth when hot. But, when you consider that the seal routinely moves 1/8" in and out of it's groove, that .5-1 thousandth of an inch is meaningless on the height aspect.

And yes, IMO, you could rotate a cold engine (it would not stay cold due to friction, but would not reach full operating temperature because of lack of combustion) the equivalent number of turns, at the same general rpm, as if you had driven it 1000 miles, and you would get the same seal wear as if combustion were occuring.

 

we will agree to disagree

from overboost.com http://www.overboost.com/story.asp?id=1250 in regard to a piston engine in this context, but I believe the same principle applies

What specifically in a new engine needs to be broken in? The short answer is "everything." Many engine parts do not require a critical break-in process, but most of the major parts do: Camshaft, lifters, engine block, pistons and rings. The crankshaft and connecting rods don't really wear per se, but they do contain internal stresses as they roll off the assembly line. Heat cycling relieves the stresses over a short period of time, but also changes their shape, in turn affecting how a piston bears against its cylinder wall, how high it reaches at TDC, etc. Anyway, that's practically bordering on a nano approach to engine break-in, so we'll stick to the major points

 

Combustion pressure also pushes the seals (or rings) against the housings (or cylinders) This is why some people advocate break in which involves several hard runs.

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

 

very well.

 

That may be true of a piston engine design, but I dont believe it to be true to much of an extent in a rotary. The pressure, if anything, would tend to act to push the seal backwards into the rotor groove because both the rotor face and the seal tip are curved and 95% of the seal is hidden inside the rotor. There is no way the pressure can get underneath the seal and push it out, so it would either have a small or no effect, or it would push it in. It's the same reason we can pump atf or motor oil into our engines without fear of hydrolock...excess pressure will just cause the seal to be compressed into the groove and the pressure will go around. Of course this doesnt happen during combustion when there is extra rpm to help keep the seal seated against the housing.

 

So in other words, you could let it idle for 2 or more hours and it will wear to the housing just as well as it would driving 1000 miles?

 

No. Let's say your average rpm when driving is 3500 and with mixed city/highway driving you drive an average of 3/4 mile per minute. Using these rough estimates it takes you about 1300 minutes to break your engine in driving. During that time your engine has spun 4,666,000 times. Meaning each seal has passed over the housing 1.5 million times.

Now even if you idle your engine up to 1200rpm, it'd take you about 70 hours to match the number of rotations.

Also to be considered is that at the higher rpm of 3500, there is more tension on the apex seal, making it seat faster. Whereas at the low rpms near idle, there is very little seal tension...so in reality, idle is not a good way to break in the seals.

 

Your posts are great Landers!

I think the most coherent thing I have seen this thread is checking the status of your breakin with a compression tester

James