why so many "break-in" opnions?
05-23-07, 01:44 AM
#28
Passing life by
I agree and that includes the use of any wearable internal. To much of follow the leader around here.
05-23-07, 09:45 AM
#29
Engine, Not Motor
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On the flip side, people have been rebuilding Mazda rotary engines with used bearings, for what, 50 years now? And not had issues. 
Like many things in engine building, it's a matter of opinion. I tend to use new bearings almost all the time, but I've also reused bearings and not had problems. One nice thing about old, factory installed bearings is that they will hardly ever spin. Putting in new bearings increases the chances that they will spin drastically. And inexperienced builders can easily screw up the pressing of new bearings...
Like many things in engine building, it's a matter of opinion. I tend to use new bearings almost all the time, but I've also reused bearings and not had problems. One nice thing about old, factory installed bearings is that they will hardly ever spin. Putting in new bearings increases the chances that they will spin drastically. And inexperienced builders can easily screw up the pressing of new bearings...
05-23-07, 10:10 AM
#31
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Seems like a reasonable breaking procedure. One issue is that 90% of the time when I'm breaking in an engine, it's on a fresh standalone. So it's very difficult to judge power increases since the car is basically untuned anyway. Some people are insane about their breakins, making the whole thing last 10K. Personally I can't stand that...I think I had 2KM on the engine in my turbo-NA car before it went WOT... 
05-23-07, 03:33 PM
#33
Passing life by
There not actually bearings that is just what we call them. However they should not touch if the bearing comes in contact with the crank then the oil is not doing its job plain and simple.
05-23-07, 04:41 PM
#35
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The oil film keeps the eccentric from actually touching the bearing surface. If the e-shaft touches the bearing at any resonable RPM, even for a short time, the bearing will most likely spin. You'll also get chunks of it ripped off...I have some pictures around here of what happens when too thin an oil is run, combined with lack of oil pressure that caused a shaft to briefly touch a bearing...not pretty. I'll see if I can post them when I get home...
05-23-07, 05:06 PM
#36
People, this is basic engineering, in the most comon engineering principles this is contact, regardless of what your friction modifier is, for friction to be present you are calculating CONTACT.
I have a degree in mechanical engineering, please dont try to tell me nonsense that is in opposition to all commonly accepted engineering principles and methods. Hell this stuff EVERYONE learns in 12 grade physics.
It IS contact, else your calculated friction would be zero or would be accepted as zero.
When the engineers calculate bearing load analysis it is accepted that the one object is loading on the other via a bearing, a friction modifying film inbetween does not eliminate the load, it modifies the friction.
I have a degree in mechanical engineering, please dont try to tell me nonsense that is in opposition to all commonly accepted engineering principles and methods. Hell this stuff EVERYONE learns in 12 grade physics.
It IS contact, else your calculated friction would be zero or would be accepted as zero.
When the engineers calculate bearing load analysis it is accepted that the one object is loading on the other via a bearing, a friction modifying film inbetween does not eliminate the load, it modifies the friction.
Last edited by RockLobster; 05-23-07 at 05:12 PM.
05-23-07, 06:59 PM
#38
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People, this is basic engineering, in the most comon engineering principles this is contact, regardless of what your friction modifier is, for friction to be present you are calculating CONTACT.
I have a degree in mechanical engineering, please dont try to tell me nonsense that is in opposition to all commonly accepted engineering principles and methods. Hell this stuff EVERYONE learns in 12 grade physics.
It IS contact, else your calculated friction would be zero or would be accepted as zero.
When the engineers calculate bearing load analysis it is accepted that the one object is loading on the other via a bearing, a friction modifying film inbetween does not eliminate the load, it modifies the friction.
I have a degree in mechanical engineering, please dont try to tell me nonsense that is in opposition to all commonly accepted engineering principles and methods. Hell this stuff EVERYONE learns in 12 grade physics.
It IS contact, else your calculated friction would be zero or would be accepted as zero.
When the engineers calculate bearing load analysis it is accepted that the one object is loading on the other via a bearing, a friction modifying film inbetween does not eliminate the load, it modifies the friction.
05-23-07, 07:44 PM
#39
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ok guys, the discussion is about break in options
Someone said something about too much follow the leader around here and several people in the past have told me not to break in a rotary the way I mentioned before but could never give me any good reasons why. So other than the possability of maybe spinning a bearing easier why else might an engine builder not want to do it in that basic procedure?
We do have different break in procedures at our shop for different engine specs and calculations but all of them are close to the outline I mentioned, so what might someone do different for lets say a:
Daily driver
Street performance engine
Road coarse race engine
Drag race
N/A or Turbo engine
Bridgeported??
etc...
Someone said something about too much follow the leader around here and several people in the past have told me not to break in a rotary the way I mentioned before but could never give me any good reasons why. So other than the possability of maybe spinning a bearing easier why else might an engine builder not want to do it in that basic procedure?
We do have different break in procedures at our shop for different engine specs and calculations but all of them are close to the outline I mentioned, so what might someone do different for lets say a:
Daily driver
Street performance engine
Road coarse race engine
Drag race
N/A or Turbo engine
Bridgeported??
etc...
05-24-07, 09:55 AM
#41
Engine, Not Motor
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It IS contact, else your calculated friction would be zero or would be accepted as zero.
When the engineers calculate bearing load analysis it is accepted that the one object is loading on the other via a bearing, a friction modifying film inbetween does not eliminate the load, it modifies the friction.
When the engineers calculate bearing load analysis it is accepted that the one object is loading on the other via a bearing, a friction modifying film inbetween does not eliminate the load, it modifies the friction.
) but under no normal circumstances should the eccentric shaft come in physical contact with the bearing surface. If it touches, even for a brief moment, the bearing will be severely damaged. There is an oil film between the two which prevents direct contact.The shaft rides on an oil film, not the bearing. However this is expressed in engineering terms, that's how it works. If the shaft rode on the bearing, there would be no room for the oil film except within the pores of the metal and wear would occur extremely quickly.
05-30-07, 09:48 AM
#42
If you technically consider contact full molecular direct interaction between the two solid metals then, YES, there should not be contact.
I guess my point is, it is really dangerous to think of it that way or to describe it that way to a non technical person. They might think as long as there is oil there is no possibility of wear or failure.
Oil is a friction modifier, albiet a staunchly critical one to have an engine run successfully for even one second. But you still have load, wear, and heat development from contact between the two parts. It is better to think about it that way than to fall into the line of thinking that oil is a magical substance that eliminates all loading forces and friction. Which a non-technical person might gather from the statement "There should be no contact between the bearing and the xxxx"
I guess my point is, it is really dangerous to think of it that way or to describe it that way to a non technical person. They might think as long as there is oil there is no possibility of wear or failure.
Oil is a friction modifier, albiet a staunchly critical one to have an engine run successfully for even one second. But you still have load, wear, and heat development from contact between the two parts. It is better to think about it that way than to fall into the line of thinking that oil is a magical substance that eliminates all loading forces and friction. Which a non-technical person might gather from the statement "There should be no contact between the bearing and the xxxx"
05-30-07, 10:11 AM
#43
if it has new rotor housings with new apex seals? then you just drive it away. i think maybee after a couple miles your good.
after a rebuild with used housings? if it makes good compression from the get go, then you can drive it like normal, but nothing to heavy after a couple hundred miles like 500 or so imho.
thats what road trips are for. go on a road trip and after you come back, youll be dandy.
after a rebuild with used housings? if it makes good compression from the get go, then you can drive it like normal, but nothing to heavy after a couple hundred miles like 500 or so imho.
thats what road trips are for. go on a road trip and after you come back, youll be dandy.
05-30-07, 04:01 PM
#44
i was wondering why so many people prefer to break in there 7's so differently? if there suppost to be one single way? or is it application specific? right now i have almost exactly 500 miles on my 87t2 with ceramic housings, and i havent taken it past 3k or boosted yet. was aiming for a reliable DD that could be auto X'd occasionaly. any suggestions?
You have 500 miles on your new engine? That's about the right time to change the oil and oil filter to get rid of all those wear particles floating around from break-in. It isn't strictly necessary, but it's nice to do. Use mineral oil again, then change it after 3,000 miles. Your car should be broken in after that. It might actually be 2,000 or 2,500 miles, but I'm too lazy to go check the first scheduled oil change in my RX-7's owners manual (it's different from the normal 7500 mile interval). In the mean time, drive gently like you've been doing.
In other words, the lazy man's way of driving it easy for a while and using cheap oil works fine.
Last edited by ericgrau; 05-30-07 at 04:09 PM.
05-31-07, 11:01 AM
#45
if anyone said this already i am sorry..didnt have time to read all...
1st question is quite simple really.....break in will depend on clearance, materials of seals etc, type of durability needed, were used parts and bearing used, or brand new stuff, ........ and of course every builder likes to be specific about their preference....
The way I have done it is if its new stuff or harder seals..i would run my car with a hugh fan in front for about a hour on first start up..check for leaks and oil pressure and all the important pre run checks....( tires on and tight)
Then i would take it out and run it very gentle not exceeding 3500 rpm....for about 4 hours.....then i will increase to 4500 for about a hour......then 5000 for about half....then a couple nice pulls ( not MAX pulls) then back to shop....change oil and filter.......then back to track and run it hard for a few laps.....thencheck over and its done
Of course this is a PP race car , but once i do this my car runs all year competitivly.....with out much problems............of course this is carbon seals etc....that is why i said in the beggining it depends on a few variables
hope this helps
1st question is quite simple really.....break in will depend on clearance, materials of seals etc, type of durability needed, were used parts and bearing used, or brand new stuff, ........ and of course every builder likes to be specific about their preference....
The way I have done it is if its new stuff or harder seals..i would run my car with a hugh fan in front for about a hour on first start up..check for leaks and oil pressure and all the important pre run checks....( tires on and tight)
Then i would take it out and run it very gentle not exceeding 3500 rpm....for about 4 hours.....then i will increase to 4500 for about a hour......then 5000 for about half....then a couple nice pulls ( not MAX pulls) then back to shop....change oil and filter.......then back to track and run it hard for a few laps.....thencheck over and its done
Of course this is a PP race car , but once i do this my car runs all year competitivly.....with out much problems............of course this is carbon seals etc....that is why i said in the beggining it depends on a few variables
hope this helps
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