I think that since the incoming air (during relatively high power/RPM
operation) spends very little time in the manifold, it will not
really heat up all that much.
I think the heated manifold has two main benefits:
1: Warming up cold air during idle (when the airflow is low).
2: Most important, reducing the tendency of the vaporized petrol
to condense on the manifold walls during cold weather and/or idle
operating conditions.
But if you don't drive the car much in the winter, you might never
notice the lack of the heated manifold...
Doug Braun
'72 Spit
At 09:54 AM 2/1/01 , Richard B Gosling wrote:
>Kevin,
>
>The original design had coolant running (from the top of the thermostat
> housing) through a conduit in the inlet manifold. The idea was to heat the
> incoming air, to reduce the need for the choke. This never really made much
> sense to me, as you only need the choke when the engine is cold, when the
> manifold heater won't do any heating; once the manifold has heated up from
> this coolant conduit, the engine is hot and you don't need the choke anyway.
> Moreover, hot air is less dense, so if you suck a given amount of hot air
>into
> your engine you are sucking in fewer molecules, so you have less power - this
> is why turbo- and super-charged engines use intercoolers, to cool the air
> before it enters the engine. The whole thing seems daft to me, but I have
> never got around to seeing what happens if I bypass the manifold coolant
>pipe.
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