[Vwdiesel] Turbo 1.6 diesel Fox

[LBaird119 at aol.com]

In a message dated 2/4/2012 9:45:11 A.M. Pacific Standard Time,  
mark at shepher.fsnet.co.uk writes:

Additionally, I  fail to see why an extra 100 psi, for example  at no fuel 
injection, gained from compression lowering, would be anything  more than 
100psi at 1200psi, or whatever combustion takes us to; indeed I  assume 
that 
it is less than that due to higher heat transfers.
Some  Googling required I think...





Theory is less pumping losses.  
>From what I've read  on the subject, anything over the 16:1 to 19:1 
range, increases pumping losses (to compress the extra ratio) with 
little or no gain in power output.  I remember that VW found, in the  1.5 
development that it was the most efficient at (don't recall which) 16: 1 or 
18:1 but went with 23:1 because of increased starting dependability.  
Apparently it was in an SAE paper on it but I haven't taken time to find 
again, where I read that.
 
  Many people think you need to lower compression on a diesel when 
you boost, or raise the boost levels.  I have yet to read anything by 
any experts that backs this up.  One would think... But most of that 
thinking comes from gas engine tech where you drop compression to 
prevent detonation, which is moot anymore with knock sensor equipped 
fuel injection, where you simply burn more fuel and retard the ignition a 
bit rather than lower the CR to where the car is unsafe to drive before 
boost hits!
    Loren