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Re: ENGINE NUMBER - Now High compression

To: <mgs@autox.team.net>
Subject: Re: ENGINE NUMBER - Now High compression
From: "Neil Cotty" <neilc@tradesrv.com.au>
Date: Mon, 5 Jul 1999 18:38:00 +1000
Hans,

> 1 What would the compression be?

Compression ratio of 8.8:1. Cylinder pressure around 160psi.

> 2 Does this high compression has advantages or disadvantages

Depends on the fuel you have available in your country. If it's of a
sufficient octane you can get more power with a higher compression motor and
properly adjusted ignition timing. If you have a HC motor and low octane
fuel in your area you can experience pinging - minor detonation. You can
retard the ignition timing to get around that but it sort of defeats the
purpose of the HC motor. I think the owners manual states that the unit
should be run on what, 99+ octane is that right people? I guess that used to
be available in the home market in the 60's. I gather the fuel
crisis/emissions drive etc culminated in the introduction of the L(ow)C
units - but as far as I know, these were mainly for the US market. Their
compression ratio was 8.0:1. I have an 18GJ motor which is a California only
car but it's also got a HC motor. It had the first smog gear installed - as
seen on the later cars. I guess this motor was somewhat of a test bed for
the later smog equipped cars. It runs fine on 96ish octane, leaded petrol
like we get in Australia. The distributor is also interesting, it has a
recommended setting of 20 degrees BTDC at 1000rpm(!).

Speaking of that, what would I have in there? - a 10 degree (total
centrifugal) advance, where the std is 20? Paul's website appears to be down
so I can't check!!! :) I wonder what the reasoning for that was....? A lot
of advance at idle to reduce emissions?!?

Cheers,
Neil.


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