[s-cars] Question about compression ratios and tuning

[M Pederson]

See previous re: dynamic CR.  Do your ABY/ADU and AAN all have the same
cam(s)?  Same boost profiles?  

Maybe one of these variable might explain the advance levels, and or suggest
that at the edge of the envelope, one might want to have their chips "set"
for the peculiarities, even on a mass production line, of the inevitable
variation that probably occurs from motor to motor, head casting to head
casting.

What do motor builders consider a "reasonable" or acceptable variation in
head cylinder volume ~> hence CR from cylinder to cylinder in the same
motor?

Mike

> -----Original Message-----
> From: Mihnea Cotet [mailto:mik at info.fundp.ac.be]
 
> Pistons and head combustion chambers are actually the same between 3B,
> AAN,
> ABY and ADU. The only difference in CR between an ADU and an AAN/ABY is
> the
> head gasket, the metal item is thicker and lowers CR by about .3:1. How do
> I know? The knock limits aren't at the same advance levels on a full
> RS2-equipped ABY than on an ADU. Just a few degrees, but that's enough to
> mess things up for those who do "generic" chips.
> 
> HTH,
> 
> Mihnea
>