O/T Compression ratio and supercharging, also efi pumps

[dzorde at erggroup.com]

Dave, its a Fiat 903cc, 4cyl, bore/stroke=65.6mmx69mm, 5 port alloy head, max
power rpm=8000.  did some measurements last night.  Chamber volume=21cc, deck
height=0.889mm, headgasket=66.7mmx1.6mm (uncompressed).  In this configuration I
can only bring compression back to around 8.8:1 (9.5:1 std), and I guess with a
compressed head gasket this will be closer to 8.9:1.  As I'm not ready to get
into any machine work I'll take the chance and see how it goes at this
compression, if I have to water inject it as well so be it.  I just need to get
the car running well enough for me to start on the fuel injection side of
things.  Although this will be a dedicated race car it would be nice to just run
on 96 leaded, but if I have to mix Toluene in it and bring it up I can do that,
or i can just run avgas (which according to CAMS is 106 octane in OZ).

Anyway for something completely different and efi related, a thread a while ago
was boosting fuel pump voltage for increased flow.  Well I may have a very
simple solution for those interested.  Found this by pure accident.  2 weeks ago
my fuel pump was very noisy and the frequency of the noise was going up and down
and the car was running excessively rich (4km/litre).  Anyway it turned out the
alternator was pumping out 16.5V sometimes dropping back to 14V as it should.
Problem turned out to be a dodgy connection where the wire for the charge light
plugs on.

Now it would seem that floating this connection caused the alternator to
increase output voltage, so maybe a simple switch in line disconnecting this pin
when you need that extra fuel pressure.  Any explanation ?

Dan  dzorde at erggroup.com


Keep Me Posted.  What is CID?  Qty Cyl? Bore size?  Alum Head?  RPM at max
Pwr?  All and more contribute, but found 8:1 lowest practical.  May need to
mix race fuel 30% for over 12 psi tho.

<snip>

TurboDave