[alfa] Re: Compresion Ratio modification

[C2slayman@xxxxxxx]

Hi Gwynne,

Date: Tue, 08 Jun 2004 14:20:39 -0400
From: "Gwynne W. Spencer" <gwynnes1@domain.elided>
Subject: [alfa] Compresion Ratio modification

If one has a 2000 GTV engine with 10.4:1 pistons, SPICA injection and has 
problems with knock / detonation - is there a reasonable way to lower the 
CR with some form of special head gasket - I calculate that I would need to 
add about 0.8 mm or 0.032" in space between the head and the block to get 
it down to 9.5.

Thicker headgasket on an all-aluminum Alfa engine?  Yikes!  The thought of it 
makes me break out in a cold sweat!  But seriously, the Digest Advertisers 
would know if one is available.  If not, there are simpler alternatives to 
addressing the knocking problem (assuming you are already running a high octane).

Actaully, 10:4:1 doesn't sound that outrageos on the Alfa designed 
compression chamber.  I remember the '74 Spider manual bragging about being able to use 
low octane on a relatively high compression ratio.  (What was it, 10:1 back in 
'74?  I forget.)

1)  Make sure your cooling system is up to snuff (ie radiator core is clean). 
 You want a good high flow of coolant across the head to prevent hotspots.  
Run a 50/50 mix or less.  Water is a better heat conductor than glycol.  So 
running too much antifreeze actually reduces the effectiveness of the cooling 
system.

2)  Run the next cooler range on your sparkplugs.  The Lodge style 
recommended by Alfa might be better than the regular style plug as supressing knocking.  
I don't know. 

3) Fiddle a little with the ignition timing.  Sometimes too advanced a spark 
creates an uneven flame front.  (I'm not sure if any aftermarket knock sensors 
exist that would temporarily retard the spark.  In theory it's easy, I just 
haven't seen any product.  I think you would have to buy the entire integrated 
ignition system with the knock sensor built in.  That could be expensive.)

4)  Richen the mixture of the SPICA.  If you are on the lean side, this will 
cause pinging.

5) Octane boosters help, but they are expensive.

6) A water injection system is VERY effective.  But they tend to be 
expensive.  Especially if they have the feedback controls to detect RPM and vacuum.

Any experience with this kind of problem out there?

In an old fashioned solid block engine, one might just add an extra head 
gasket, but with the Alfa wet sleeve setup, do not know if this is a 
feasible solution - would guess NO.

Gwynne Spencer
Cheers,
Charlie
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided