[Vwdiesel] Turbo 1.6 diesel Fox

[James Hansen]

Yeah, what he said.
I read the same paper, IIRC it was 18:1 was the most efficient
configuration, but not the best starting, which I recall as 23:1 too, so we
can't all be getting senile at once.
If it were me, I would try to "read" the piston tops before removing carbon,
then try to increase turbulence with dimples where the carbon is deposited
the most.  That in my armchair engineering estimation would be the best
rework for effort- to more fully burn the fuel while in the cylinder. We do
this with flat top pistons on the race car- and using rules legal methods
(no porting) attempt to increase the efficiency, or brake specific fuel
consumption. It's kind of a dark art, but does show results in gassers,
rather dramatic where you aren't allowed to reshape combustion chambers (as
if I know what to do with that anyway). You want to read some on that, look
up the writings of Jim Mcfarland, an engineer that writes a column on engine
tech for Circle Track. He's smart.
I'm thinking there is some room for gain there, since there is little we can
do with the non-existent combustion space on an indirect injected VW anyway.
-James

-----Original Message-----
From: vwdiesel-bounces at vwfans.com [mailto:vwdiesel-bounces at vwfans.com] On
Behalf Of LBaird119 at aol.com
Sent: February-04-12 11:53 AM
To: Vwdiesel at vwfans.com
Subject: Re: [Vwdiesel] Turbo 1.6 diesel Fox

 
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
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