Roger posted this reply to my question on the MG website.
Simon
From: Roger Parker Tamworth roger.parker@virgin.net on 7/6/1999 20:08
It has always been the designers dream to have equal dimension exhaust
runners from the engine. In reality this probably never happens on a
production engine. Exceptions being the likes of Ferrari class cars where
each exhaust manifold resembles a birds nest of pipes to try and achieve the
ideal in the space available.
The reality of your dilema will not be anything other than perhaps a slight
alteration in the torque curve and perhaps a slight reduction of peak power
and the rpm that this is produced at. In other words it will not be worth
worrying over.
If you do manage to achieve a fit for both sides then the engine may well
produce a little more torque at slightly different rpm and the tope end
power may well be slightly higher, but probably the biggest difference will
be in the feel of the engine as with better exhaust breathing this will feel
sharper.
As an alternative to the SD1 manifoldss there is always the 4-2-1 manifold
set up used by later Range Rovers. These 4 into 2 cast iron headers then
joined a twin pipe tubular downpipe as is the case for the SD1, but here the
Range Rover has a problem with clearance and so the cast iron items are very
much tighter to the engine. These may well offer the opportunity to use the
4-2-1 ideal exhaust design for road torque.
Rog
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Simon Sparrow
Enterprise Network Architect
WANG NZ Ltd
simon.sparrow@wang.co.nz
Telephone: +64-4-382 0239
Facsimile: +64-4-385 6067
Mobile: 025 230 8048
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