generic A4 questions

Grant Lenahan glenahan at
Mon Feb 5 20:16:26 EST 2007

Most of the below may be true, but are not the germain points.

1.) oil may be under pressure, but may not flow freely into the 
smallest of bearing openings.

2.) More importantly, at low temperatures, if gaps already exist in a 
film of oil, its a weak spot and the partial film may tear under 
pressure (shear)

3.) Most importantly, and rarely understood, and clearly stated in my 
original, by the way, the parts dont fit until warm.  Bearing 
tolerances; piston/ring/cylinder tolerances and every other tolerance 
is OFF.  In general they are TOO BIG. Think about this.  I dont have 
time to do a physics course in an email;, btu lots of bad things will 
happen when parts have big gaps.

Its not an "on" "off" thing where anyone can say "i did X and it didn't 
blow up".  But the chances of wear are far greater under cold 
conditions than under warm ones.

To huh's point, I would guess, but cannot prove, that even after 2 min 
things are far better off.

On Feb 5, 2007, at 2:14 PM, Huw Powell wrote:

>> yeah i'm not too sure what bad can [will?] come of redlining a cold
>> motor. if it's been running for a minute or 2 there ought to be
>> sufficient oil in the engine.
> There'd better be oil - under those conditions, the oil pressure gauge
> is pegged at 5 bar.  Hard to imagine "5w" isn't getting where it needs
> to be.  But at that time, I am not seeing motion on either coolant or
> oil temp gauges.  That comes a couple of miles up the road.
>> i did read recently in bike mag that one of the motogp mechanics
>> recommended gentle warmup because the rush of cold radiator juice when
>> the tstat opens into a prematurely hot motor is, like, bad or
>> something?
> Interesting, sort of.  But coolant thermostats aren't "on/off" 
> switches,
> they open gradually.  Also, at least with our engines, the "cold" juice
> from the radiator hits the t-stat before entering the engine, so if it
> is "too cold" only a little will get through at a time.
> -- 
> Huw Powell
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