1999-2009 [Subscribe to Daily Digest] |
Lou - Perhaps I've over stated it - I'm not worried about doing harm, I'm more concerned about keeping the engine next to perfect so it can go for the really long haul. I'm not an engine manufacturer, but I've spent a lot of time with tool and die and mold makers, and I've sweat trying to cope with brand new components, tools and molds that were ruined by improper heat treatment and strain relief.
The modern engine is certainly more carefully and thoughtfully manufactured than engines of not so long ago and is much more tolerant of being plunged right into the working world. However, ...
There's a lot more to properly breaking in an engine than merely worrying about the stray shavings that might not be caught by the oil filter. Precision machined parts drift out of shape and out of round - mind you I'm talking thousandths of an inch here - as they are heated up for the first/second/third times, and will stay out of shape if they are allowed to bake too long without going through cooling cycles. There is a whole science and industry of heat treaters who carefully manage the stress relief of machined parts by managing heat cycles.
New pistons, bearings, cranks, and other internal parts are full of stresses that are released as the part is heated, causing the part to change shape - maybe only a thou or two, but change shape none-the-less. If the heat level is sustained, the parts can permanently take on their new dimensions. If, however, the heat is cycled early enough, upon cooling the part returns back to the shape it started, and the level of the stress is reduced. The next heat cycle the amount of movement is less, and more of the stress is relieved. After several cycles, the stress is gone, and hopefully the part is the same shape it was when new.
Certainly all of the world's motor manufacturers are well aware of this phenomenon, and certainly today's modern engine plant heat treats and stress relieves critical components, greatly reducing the effect of sustained heating of a new engine. However, the mere bolting together of the parts and torqueing them down introduces new stresses, and these stresses are going to have their effect and are going to be dissipated over the first several hundred miles the car is driven.
For my money, on a new engine, it makes sense to be aware of this and to alter your behavior a little and give the engine the chance to settle in by not keeping it at running temperature for very long during the first critical miles.
posted by 63.13.1...
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.