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Old 3rd May 2019, 20:20   #21
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I drive a lot of nearly new rental new rental cars. They fall into the category of not run in carefully. I find that in general the engines are alot more free revving and loose than private cars of similar low mileage that have been used more gently. Thrashed from day one and free revving is fun to drive, but I'd buy the gently used ones every time for the long term - less wear imo.

“The flame that burns Twice as bright burns half as long.” Lao Tzu, Te Tao Ching
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Old 3rd May 2019, 21:12   #22
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Quote:
Originally Posted by COLVERT View Post
Sorry----but I don't quite understand the 30/40 years.

Could you please give a bit more info.------Thanks in advance.
Should say '30/40 years ago'
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Old 3rd May 2019, 21:29   #23
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Originally Posted by bl52krz View Post
I tell you what, you run your engine in fast, and I will run mine in correctly, gentle and no more than 1500/2000 rpm for the first 500 miles, and then gentle acceleration for the next 500/1000 miles upto two thirds engine speed. Do not let the engine labour in to low a gear because of oil pressure being low.And mine will still be going when yours has either seized up or worn out.
what a strange reply, you seem angry with the "tell you what" bit. I'm not suggesting running it in fast, I was asking about it.


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Old 4th May 2019, 09:12   #24
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“The flame that burns Twice as bright burns half as long.” Lao Tzu, Te Tao Ching

And requoted by Eldon Tyrell.


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Old 4th May 2019, 09:18   #25
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Quote:
Originally Posted by COLVERT View Post
However----If an engine is tight somewhere the friction will generate a local hot spot.

Mineral oils break down at a lower temperature than synthetics giving you the possibility of metal to metal contact.-----

Personally I would always use semi or full synthetic oil.---

This is never going to occur in a modern engine. The machining tolerances are very low.
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Old 4th May 2019, 12:39   #26
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These makes for interesting reading (albeit that they are about motorcycle engines):

http://www.ashonbikes.com/content/running

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

As I'm very unlikely to be buying anything even close to having a new engine in the near future it's all just "background information" for me.

Andy.
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Old 4th May 2019, 20:57   #27
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Quote:
Originally Posted by mss View Post
This is never going to occur in a modern engine. The machining tolerances are very low.
I guess you mean precise ??

Years ago when I was working I designed some Air-Gauging machines.

They would work down to an accuracy of 0.0005 and better.

They would gauge several holes at the same time in items such as gear boxes and engines.

Each gauge was connected to a hopper containing the various items to fit into each hole. The information would trip the appropriate hopper and out would come all the items to fit all of the holes.

However all these machined parts had a plus and minus manufacturing tolerance. Thus you could comparatively loose and tight fits depending on which end of this tolerance the components were ejected.

Precision machining in those day is virtually the same as todays.--
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Old 4th May 2019, 21:15   #28
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Quote:
Originally Posted by AndyN01 View Post
These makes for interesting reading (albeit that they are about motorcycle engines):

http://www.ashonbikes.com/content/running

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

As I'm very unlikely to be buying anything even close to having a new engine in the near future it's all just "background information" for me.

Andy.
Just one thing to remember about bike running in being OK at 500 miles. Bike engines run at almost twice the speed of car engines for the same road speed. My own Honda CB 1,000 runs at almost exactly double the engine speed of my R75 at all speeds in top gear.

My point here being that the slower revs of the car engine means a 1,000 miles might be nearer running in distance for a car engine.
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Old 5th May 2019, 07:27   #29
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Quote:
Originally Posted by COLVERT View Post
I guess you mean precise ??

Years ago when I was working I designed some Air-Gauging machines.

They would work down to an accuracy of 0.0005 and better.

They would gauge several holes at the same time in items such as gear boxes and engines.

Each gauge was connected to a hopper containing the various items to fit into each hole. The information would trip the appropriate hopper and out would come all the items to fit all of the holes.

However all these machined parts had a plus and minus manufacturing tolerance. Thus you could comparatively loose and tight fits depending on which end of this tolerance the components were ejected.

Precision machining in those day is virtually the same as todays.--
No - I actually mean low tolerances as in a a low number after the +/-. This is correct terminology.

You seem to be mixing up tolerance, precision and accuracy!

Refs. for your perusal

https://www.keyence.com/ss/products/...sic/tolerance/

https://labwrite.ncsu.edu/Experiment...yprecision.htm
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Old 5th May 2019, 08:46   #30
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I remember building a modified mini engine many moons ago, uprated cam, etc.

Once built, run in for 500 miles at no more than 3000rpm, and always change gear at 3000rpm as well. Then oil change, then continue running in by increasing the revs by 500rpm for 100 miles (so, 3500 for 100, then 4000 for 100 etc.) right up to the rev limit of 8000 - was balanced so could easily take more but my ears couldn't.

It was a brilliant engine and did many many miles without issue.

When we purchased the new MG ZS just over a year ago, we were told to drive it at no more than 4000rpm for 1000 miles, and not to labour the engine - which is thankfully, quite hard to do in an auto.
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