hi compressions: wasDIY_EFI Digest V1 #258

[RD Rick]

Somebody smart wrote:
>>Therefore another approach is to outrun the fuse,
>>which fast burn combustion chambers can do. Anyone notice how high 
the>>compression ratios of modern 4V engines (and even some 2V) are 
getting?

Talltom replied:
>Yes I have and I'm pissed! Would you say that is due to combustion 
chamber>design,>or to more precise tuning capability?

I have read that the big reason for four valves is to get the spark 
right in the center.  Flame front has much shorter distance to travel, 
meaning higher compression without detonation.  You could probably get 
the same effect with four spark plugs per cyl.   BTW, I believe 
detonation is what happens after spark but the mix explodes before the 
flame can travel far enough to get the whole mix burning.  Pre-ignition 
is another phenomenon in which hot parts or diesel effect ignite the 
mix before spark.
That's as I understand it.  Comments?

>While I've got your attention, have you seen the throttle valve the 
>later>vw's are using? It looks like anything else, but when you look 
>close the>blade fits into a recess machined into the bore, kind of 
>like a ball valve.
>To me it looks like this setup would alleviate the harsh throttle 
>opening at>the bottom end and allow full sail in an individual 
>cylinder basis. Whaddya think?

I think I'll take a look for myself.  What year VW?
RD