4kq Timing belt/clearance

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <955.290T1213T12533554@borre.mail.telia.com> "John Torset" writes:

> >Supposedly, the 2.22l non-turbo engines can be hand-turned without the belt on.
> >I find this odd, because the 2.22l turbo engines can't - they interfere even
> >at 0 rpm.
> >
> >Whether or not this rumour is true, the engine _definitely interferes at
> >high rpm - and guess when your belt is most likely to break?
> 
> 
> This sounds a little strange.
> 
> On my old 200 Turbo 5 cyl you could turn the camshaft without the valves hits the piston
> and on an normal 5E engine the valves will hit the pistons.

Yes, this can be done even on an interference engine.  It's entirely possible 
for the crank to be in a position where none of the pistons are close enough to 
the valves to interfere.  It won't work if any of the cylinders are at TDC, 
obviously.  What will _never_ work on an interference engine is turning the 
crank. 

> Turbocharged engines have lower compression rates the an nonTC engine so that the maximum
> compression pressure/temperature, spesialy the temperature, are about the same at full
> load for both engines. This is to prevent knocking.

Compare MB (turbo) and JS (non-turbo) compressions.

The turbos avoid knocking via very aggressive control of ignition advance.

-- 
 Phil Payne
 Committee Member, UK Audi [ur-]quattro Owners Club