my engine is starting tonight .....I know the breakin procedures...but what if I buy 3 oil changes and go drive for 10 hours changing the oil every 500 miles????

Does that hurt it )))

I know, stupid questions come with stupid answeres....but seriously how many miles can I put on the car a day without hurting it for the breakin period?

 

One of the big keys to proper break on a rotary in is multiple engine speeds as opposed to fixed engine speeds for long distances.

So the last thing you would want to do is drive for 10 hours at the same speed, say cruiseing at 60 MPH for 500 miles. That would be bad. It should be varied from dead stops, to 25 MPH to 65-70 MPH, so all speeds are hit equally.

If you could do that, I don't see any reason that you couldn't drive 1000 miles, change the oil and drive another 3000 miles.

 

I have heard the "varying speed" and "no constant rpm" thing on and off for a while now, but no one has ever presented an engineering standpoint reason why this is. IF the engine is rotating at all then all surfaces are moving, oil is being distributed just teh same, etc.

ALso, explain how some high-end shops dyno-breakin their rebuilds for the equivalent of a few hundred miles before installation? I guess they set the dyno up to vary speeds as well?

I have done quite a few rebuilds now and have broken in a few on long trips with no noticeable difference to the other methods described above, except that it happens quicker. Perhaps this breakin might have some mreit for a NEW engine, new bearings and housings, but I see no real use for it on a regular rebuild.

I would be interested to hear opinions from those who may know why this is said to be a rule...

 

I've never really seen how the breakin could be that crucial to a rotary anyway .. all that has to break in is the seals to the housings. It's like like piston engines where its crucial to vary engine speeds to properly seat piston rings.

Since they only have to breakin to the housings and not have to seat properly, I dont see how apex seals would really care as to what speed the engine is going at. As long as its not high rpms that are going to JAM them into the housings.

 

Hey Kevin,

I am sure that the intial break in (what happens in the first 5 or so start/stop cycles) is more important, as the same applies for Tires and brakes... In which case it would be related to how the gaskets seal/seat and hot/cold temp cycles.

I personally think it is less important on rebuilt motors than on brand new, because the housings and rotors generally have already experienced the heat cycling.

But, it is my understanding (and I may be mistaken) that many high end builders that customers have specified a broken-in motor do run the dyno speeds from low bog/idle all the way up to redline.

But I have only rebuilt a couple of motors, unlike you, so my experience may not be as in depth as yours on this.

But something else that should be considered, is that break in is done for long term engine life. It would be instresting to see the number of FC or FD models that the owners followed the factory proscribed break-in (as I outlined in my first reply to this thread) and what life they got from their motors.

So based on that, IMO: that if the motor hasn't traveled 100K miles since its last rebuild, it would be almost impossible to say if the break in was needed or even correct.