Intake air preheating question

Heated air in summer would be inefficient.

Cold air in winter will cause carb icing (inside the throat). This can even happen when temp is ~10C, especially in damp weather.

Speedy Jim

Thanks. I thought so, but was not sure if too hot intake air would cause more problems than just inefficiency.

And will increase risk of pinging.

As well as intake manifold icing, right below the carb

This is very true.

Jan

Besides innefficiency (you loose 1-2 hp), it will overheat the carb in hot weather, and the fuel will boil when you turn the engine off. The bubbles from the fuel will cause the bowl to overflow and flood the engine. This allready happens in very hot weather, and feeding the carb with hot air constantlly, will make things worse. You could manually disconnect the heated air hose in hot days, and leave it for the winter.

Bill, '67 Bug.

Thanks. I thought so, but was not sure if too hot intake air would cause more problems than just inefficiency.

Anyone ever modded the carb heat to be manual, accessible from the cabin? I'd be inerested to hear how anyone's done it. Do a little throttle back to 1500 and carb heat on before I pull into the driveway. Anyone?

-Chip

'56 ghia, '66 beetle

I think VW took are of this when they introduced the thermostatically controlled airflap on the plastic1303 air cleaner. As the engine heats up the vacuum operated flap closes the hot air feed pipe to let in cooler air from outside. Cable operated engine lid louvres would be good though!

--Steve