Hi James, you wrote:
[...]
> There were a couple of propblems with the artical that I spotted, these
> conclusions I made are from memory. He jetted the single carburetter
> two his tubular exhaust system, but he did not mention wether he did the
> same with the dules, especialy running on 90's un-leaded.
My understanding was that the needle was changed on the single carb
to make it more compatible with the 1500cc motor. As you point out
the effect (on MPG) of changing the exhaust system was not mentioned.
The HP comparison data taken on the dynamometer was done with the
same exhaust system in conjunction with both carb setups I believe.
> The inlett
> manifold for the 1300 was a thiner bore than the 1500, more than likely
> any gain in low down power was due to that, as opposed to just one
> carburetter.
The smaller bore of the single carb manifold was cited as being a
likely factor for increasing low RPM torque. Unfortunately with this
type of comparison test it is impossible to separte the effects of
the manifold from those of the carb(s). I found it interesting that
the 1300 Dolomite manifold is almost identical to ZS manifold on
US model Spits.
> The arguments for fitting single carburetters and why they
> are more echonomical failed to convince me, I was proved correct when he
> failed to get the estamated economy.
I don't think he was attempting to convince anyone that they should fit
the single carb. He has just been experimenting with different ways to
reduce running costs of a Spitfire. When driving a Spit 20K miles a
year
(at UK petrol prices) any gain is worth consideration IMHO. As was
mentioned, the MPG increase gained from a single carb fell short of
expectations, but was measurable.
It was pointed out that changing one's driving habits is the biggest
factor in MPG return, but we're talking about Spitfires. The FunPer
Gallon must also be included in the analysis :-)
--
Bob Sykes
"Sometimes one pays most for the things one gets for nothing."
--Albert Einstein
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