Re: Compression questions

[mousetrap@juno.com]

>9.5-1 to 9.8-1 CR! Not bad eh? Now do the exhaust work, cam, intake, 
>knock sensor and P/P the head and you've got something like 11-1 CR 
>and about 145hp. 

Not to nit-picking but....  NO!

"exhaust work, cam, intake, knock sensor and P/P the head" will not
change the compression ratio.  They will help (with the exception of the
knock sensor) the engine breath better.  There are only two ways to
change the compression ratio.  You can increase the swept volume of the
cylinder by increasing the bore or the stroke.  Or, decrease the volume
of the combustion chamber by raising crown height (not in stock H2O VW),
milling the head, or installing the motorsports headgasket.

The knock sensor is generally used on an engine running 9:1 or higher
compression on pump gas.  The knock sensor allows the ignition to have a
very agressive advance curve without damaging the engine.  The KS is not
a requirement, but in a properly tuned system will allow the engine to
make more power than a non KS equipped car. 

Knock sensor conversions on early cars have fantastic results.  I ran the
ignition from an '87 GLI on  my '83 Jetta 1.7l @ 8.5:1 for a few weeks,
to test the wiring installation before doing a complete engine swap.  The
ignition works much like running a re-curved distributor, with lots more
mid-range torque.  Not enough to keep from completing the swap, though.

I like to keep my VW motors stock on the internal mechanicals.  Engine
swaps, sure.  Bolt-ons, no problem.  But nearly every bored, stroked,
monster motor that I have run across was short lived.  My Mk1 lives
happily with a G60 transplant, and nearly every bolt-on modifcation I
could build, fit, or buy.  It is approaching 180K miles, with the G60 in
place for about 90K.  No internal problems whatsoever.

Mike



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