It's also the head material, aluminium on the Porsche and cast iron on the
Healey. I believe aluminium conducts the heat away better than cast iron.
Mike Brooks
'56 BN2
Milano
Italy
Date: Thu, 15 Feb 2007 18:58:22 +1300
From:
"Michael Salter" <msalter@precisionsportscar.com>
Subject: RE: compression
Ratios
Paul,
My guess would be a combination of combustion chamber design and
electronic controls. Basically the ignition is retarded at times when
the full
induction charge would normally result in detonation i.e. full
throttle at low
RPM and then is advanced when the induction efficiency
drops off.
Michael
In
New Zealand
- -----Original Message-----
From: owner-healeys@autox.team.net
[mailto:owner-healeys@autox.team.net]
On Behalf Of PG
Sent: February 15, 2007
3:13 PM
To: 'Healeys'
Subject: compression Ratios
List, hear is some food
to dwell on:
I was reading some articles last evening and a question popped
to mind.
Why is it that the Porsche 2007 911S has a compression ratio of
11:8 to
1
and yet does not have detonation whereas an older English motor with
compression of 10:5 to 1 has issues?
Is it that the advertised compression
numbers are "static" compression
and
because of valve timing, in particular,
the closing of the inlet valve,
that
the dynamic compression on the Porsche
might be substantially less than
the
11:8 to 1.
Also, could it be
combustion chamber design, better cooling etc etc.
Any thoughts
Regards,
Paul
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