Re: S4 20v vs S2 10v

[Eliot Lim <eliot@u.washington.edu>]

On Mon, 6 Feb 1995, Robert D. Houk wrote:

> (I suspect it also means you can charge five times as much for a tune-up
> since you have five times as many coils to tune, right?)

for sure, but do coils get routinely replaced?  labor to replace
spark plugs will probably be more..

>    my understanding is that the 9.3 compression on the S4 is for
>    off-boost response.. once the turbo spools up, CR is really quite a
>    meaningless number, because 2 bars of boost is 2 bars of boost,
>    regardless of what the geometric dimensions of the engine are.  i.e. 2
>    bars in a 9.3 compression engine is equally likely to detonate as 2
>    bars in a 7.8 engine, all other things being equal.. no?
> 
> Um, I don't think so. 7:1 compression of 2 bars is 14 bars, while 10:1
> compression of 2 bars is 20 bars of pressure. 

ok, so "boost pressure" as we know is induction pressure then..

> At 20:1 you can dispense with ignition altogether (you have a
> diesel engine). 

hmm the S4 has a 9.3 compression and 2.15 bars would make it
19.995!!

i wonder how they keep this baby from blowing its brains?

how about the 1987 formula 1 cars that ran 4 bars of boost..  i think
they had compression ratios of 6.5 or thereabouts.. which means 26:1
???

> Now if you had direct injection . . .

how about sequential injection that the S4 uses?  how does that
affect things vs. simple CIS?


eliot