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Re: S4 20v vs S2 10v
On Tue, 7 Feb 1995, Eliot Lim wrote:
> i stand corrected. so, the high compression would be good for off-boost
> response (claims audi) and also higher efficiency (better fuel mileage).
> any other advantages? seems to me that a lower CR is better for
> high boost and high outputs. is that correct?
A lower CR would be better for "off boost" performance, meaning the time
before the turbo spools up. A few cars lately have been running *very*
low boost and maintaining the factory CR with very good results. EC did
an article about a VW (Golf?) that had a low-boost system, as well as a
Porsche 911 with a low boost system. It stands to reason that
maintaining the factory CR would make the car more reliable, and the
boost would become a less noticable "push" rather than a giant "rush"
when the boost comes up. It would not only be easier on the driveline,
but would make the car more tractable and utilize more of the available
hp. Reasoning: If the tires are smoking and the steering wheel is
writhing in your hands, you aren't going as fast as you think. It only
*seems* fast. If the boost is lower, the CR higher, the engine is more
manageable and more of the hp goes to the ground.
If you are running very high boost, a low CR is a must. This explains
the spacers for the head gask. in the VW kits.(which I am not quite sure
that I would trust) The spacer, or just running two headgaskets, raises
the head of the engine, thereby lowering the mechanical CR.
--So many variables...so little time...