Why Run In?

[Carl]

One reason for starting the engine then getting it warm before thrshing it is that you have two different metals in the engine,Aluminium and iron,they both expand at different rates if the engine is driven hard from cold,so it is better to warm up your engine gradually.
That having been said,it is also better to drive the car straight away as the engine will get up to temperature quicker,and so will the oil.
I allway\'s keep to around 3000 rpm until the engine is warm because the oil filter has a by pass valve in it that can allow it to not be filtered if the Oil pressure get\'s to high which it will when cold as the viscosity is higher until warm.
Regards
Carl

[RemarkLima]

Old school of thought?

 My friend it\'s basic knowledge that new materials need time to work/bed in!  A most important factor among others on the subject.

 

Well metal work has changed a lot!

For example, I know it\'s a different kettle of fish but, the new Ford Transit. No run it period at all and first service at 12,000 miles!

Tolerances are so much tighter now, metals get worked and heat treated as part of the build process, nikasil, ceramics and other new alloys mean that you\'re not wearing a "rough" iron block into a rough iron piston ring. Plus synthetic oil are another world apart to the old monograde minerals, just read oilman\'s posts!

I know it\'s not a Ford Transit engine and essentially the design at origional manufacture is 15 years old but there\'s still some differences in these to the old iron block of yore.

All IMHO

[RemarkLima]

P.S. Don\'t get me wrong, I never give an engine any kind of throttle or revs until it\'s all up to temp, that\'s a decent amount of time after the water is up to temp as well!

Once it\'s warm however, the redline is, in theory, within the manufacturers tolerances

[Prof]

I can tell you one thing, it\'s been noted that there is a lot and I mean alot of people doing their own rebuilds now... this is worrying, I mean fair play, have a crack... but you won\'t get me ever buying a car that has had a homer done on it...
 
This again will only add to the unfortunate ever increasing bad rep of the Rotary engine and the Cars overall value! :3Confused
 
Rgds

I don\'t know about you chap, but when I take on the risk of doing a job of any kind on my house or my car, I take time to read about how to do it, I make sure I have the correct tools to do it, and then I take my time doing it.  Whether your doing central heating, house electrics or rebuilding an engine, there is nothing wrong with a \'home rebuild\' provided that care has been taken and no corners cut, and the correct materials are used.  The only thing you won\'t get is a warranty.
 
It\'s up to you whether you buy a car with an engine rebuilt by an amateur - but don\'t forget, some of our expert vendors started out as talented/gifted amateurs.
 
As to the purpose of this thread - it was to invite discussion - which it has done - I think it would be prudent to read the whole thread before posting up on it, and present your argument(s) in a clear form rather than just reactively.
 
Cheers,
 
Prof. :cheers

[MikeLMR]

it\'s alright saying metal work has changed a lot and new designs built in the factory using ALL new parts and very carfully matched parts from batches of 100\'000\'s of parts don\'t require as much of a running in regime

BUT .... step back a bit here and look at what we are talking about.  Mazda rotary engines

Engines that haven\'t changed vastly in design or material for 30 years and rebuilt engines that hardly ever have 100% new parts and even then it would have been a part selected from a batch of 1 of 1 (OK so some parts are catagorised for assembly tolerances as spares as well but you know what I am getting at ... it\'s not a factory assembly)

[antnicuk]

some good points here, Carl made a good point in his thread that it gives a good opportunity to ensure all other aspects of the car are working well with less chance of causing damage.  

One thing that needs differentiating,   letting your engine warm up and cool down properly is completely different to letting it run in for an excessive period.    I may not run an engine for more than a few hundred miles but i always let the car warm up and cool down and i run a decent coolant system and ensure my air temps are low and my oil is never too hot.   I also change my oil regularly.   As Jon mentioned, some people know more about rotaries and how they should be set up and run and what parameters are ideal and safe,

Some people who know a little less and are more likely to damage an engine they spent 2000 miles running in because they dont let it warm up or run it when its too hot and dont maintain it properly.

As for metals bedding in,  just think about how fast 4000 rpm is,  does a tip really know the difference between 4k rpm and 8 rpm, does a lot change in the engine between the two?   the tips are moving at one hell of a speed at what ever running revs they do, as do the bearings, its not like its run at 200 rpm for 50 hours to bed in.  If the engine is at running temp and you open it up i dont reckon the tips know any difference, same goes for boost.  


Trex, you dont even believe in water injection........  

[MikeLMR]

certain loads will go up "roughly" with a square law with relation to RPM so 4000-8000rpm would be 4 times the load.

[88GT-R]

Throw a spanner into this soup.... Bare in mind that the rotors are rotating at a 3rd of the rpm...

[Fish]

That having been said,it is also better to drive the car straight away as the engine will get up to temperature quicker,and so will the oil.
Regards
Carl

The other reason for this is, it brings the gearbox and diff oils up to temperature as well. So you\'re not giving them a hard time with cold oil when the rest of the car is warm.

Fish

PS. Nice to have a good technical type thread.

[antnicuk]

Throw a spanner into this soup.... Bare in mind that the rotors are rotating at a 3rd of the rpm...

i like it.......

Mike,   where is the load in a rotary engine,  its not like a boinger where the forces fight against each other..............  

i\'m no technician BTW

[MikeLMR]

I\'m not exactly sure but .... thinking alloud there is some eccentric movement so I guess there will be two loads from the rotors on the eccentric shaft at an angle to each other, both combining and causing a bending load on the shaft, then there are the reaction loads at both bearings. It\'s not an easy one to visualize ... I\'m not sure what loads the eccentrics will put on the shaft as well.
It gets more complicated as you start to think about how the rotors load the stationary gear etc. and I get a bit lost with what is happening.  It\'ll all be quite simple stuff but it\'s breaking it all down and understanding whats going on thats important.

100% rotary "engines" are easier  

[RemarkLima]

it\'s alright saying metal work has changed a lot and new designs built in the factory using ALL new parts and very carfully matched parts from batches of 100\'000\'s of parts don\'t require as much of a running in regime

BUT .... step back a bit here and look at what we are talking about.  Mazda rotary engines

Engines that haven\'t changed vastly in design or material for 30 years and rebuilt engines that hardly ever have 100% new parts and even then it would have been a part selected from a batch of 1 of 1 (OK so some parts are catagorised for assembly tolerances as spares as well but you know what I am getting at ... it\'s not a factory assembly)

True, however as we all know you can\'t just use a 13B from a FC and drop it into a FD (13B-REW) as they\'re different, I\'ve heard that the bearings in the REW are near full race spec.

And you get a decent choice of bearings when you order them, so should find something suitable. Also if you\'re serious then when replacing rotors go somewhere where you can weight a load of them and get a matching pair.

Really piston engines havn\'t changed in 100 years! It\'s just the materials and processes that have improved, along with oils and such like.

I\'m kind of playing devils advocate here, but also feel that 3000 miles is a massive run in period! Everything should be bedded in within 300 miles, ideally nothing should be touching as a nice film of oil is keeping it all apart

However when it comes to rebuild time, then I\'ll really know what side of the fence I fall into! Plus if the builder said run in for 3000 miles, I\'d do so.

[antnicuk]

I\'m not exactly sure but .... thinking alloud there is some eccentric movement so I guess there will be two loads from the rotors on the eccentric shaft at an angle to each other, both combining and causing a bending load on the shaft, then there are the reaction loads at both bearings. It\'s not an easy one to visualize ... I\'m not sure what loads the eccentrics will put on the shaft as well.
It gets more complicated as you start to think about how the rotors load the stationary gear etc. and I get a bit lost with what is happening.  It\'ll all be quite simple stuff but it\'s breaking it all down and understanding whats going on thats important.

100% rotary "engines" are easier  

Mike,

I have never changed the bearing in a rotor and never seen it done either, i\'m sure at some point one of the tuners have done it, but you dont often see worn out rotor bearings, so that load doesnt change from the original engine.

I think the higher mileage that the americans do wear the rotor bearings out but a lot less common in this country.

[MikeLMR]

another thing I was thinking is  cold-hot-cold cycles  these strike me as being the key things for bearings to bed into each other. How many miles does each engine warm up cool down cycle equal and how may cycles results in a properly run in engine? maybe this is where the run in mileages come from in an OEM\'s calculations ?

[kev-yorks]

Well this thread has had the desired effect a few people are thinking now.
As Tony alluded to how many rebuilds include new shafts and rotor bearings? new housings, plates possibly and seals then yes. So assuming the rebuild has required housings plates and seals the main friction area\'s we are bedding in are the apex seal to housing, side seals to plates and any shaft bearings that may of been changed. Shaft bearings are essentially the same as crank shaft bearings in a boinger with the same loads so can we assume that all the piston motor manufacturers that no longer require a run in are right? apex seals rely on the centrifugal forces to seal so it follows if you are reving harder during run in then they are sealing better so higher revs should aid bed in? which leave us the side corner seals are these the only reason we are running in?
Once again theres no rights or wrongs on this thread its purely a academic exercise to get the Grey matter working. Its up to each individual or builder to do his own thing.
Yes the rotary engine is old technology but so is a piston motor what is different is the evolution of the modern motor oil even mineral oils bear no comparison to what they where 10yrs ago let alone the advances with cracked mineral, semi and synthetic oils!:Hammer
Kevin