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3rd May 2019, 20:20 | #21 |
Gets stuck in
MG ZT Join Date: Apr 2018
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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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3rd May 2019, 21:12 | #22 |
This is my second home
MG ZT-T 190 Join Date: Jun 2009
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Should say '30/40 years ago'
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3rd May 2019, 21:29 | #23 | |
This is my second home
Rover 75 Saloon & Tourer Join Date: Sep 2012
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Quote:
macafee2 |
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4th May 2019, 09:12 | #24 |
This is my second home
Rover75 and Mreg Corsa. Join Date: Nov 2006
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4th May 2019, 09:18 | #25 | |
This is my second home
Rover 75CDT, Jaguar XF-S 3.0V6, V'xhall Omega V6 Estate, Twintop 1.8VVT, Astra Estate and Corsa 1.2 Join Date: Dec 2007
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Quote:
This is never going to occur in a modern engine. The machining tolerances are very low. |
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4th May 2019, 12:39 | #26 |
This is my second home
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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. |
4th May 2019, 20:57 | #27 | |
This is my second home
R75 Saloon. Join Date: Feb 2009
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Quote:
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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4th May 2019, 21:15 | #28 | |
This is my second home
R75 Saloon. Join Date: Feb 2009
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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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5th May 2019, 07:27 | #29 | |
This is my second home
Rover 75CDT, Jaguar XF-S 3.0V6, V'xhall Omega V6 Estate, Twintop 1.8VVT, Astra Estate and Corsa 1.2 Join Date: Dec 2007
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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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5th May 2019, 08:46 | #30 |
I really should get out more.......
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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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Richard. No longer a 75 owner as my tourer made it to the moon, and died on it's way back. But 1/4 million miles ain't bad. |
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