Originally Posted by
Gargleblaster
3. How come that car engines haven't had a leaning mechanism ? The same engines are running in Amsterdam (height: 0ft) and Madrid (height: many ft :-)!
Better carb designs do. The SU and Stromberg carbs have a decent degree of mixture control, automatically adapting mixture in response to inlet manifold vacuum (i.e. air density).
My TR7 ran beautifully at sea level in Dover and at the top of the Stelvio pass in Italy (10,000 feet or so) - all done automatically by a pair of SU carbs with a basic design that is nearly 100 years old. That car had a Dolomite Sprint engine and 140bhp from 2 litres - and despite being a modified engine, the standard carbs could adjust automatically.
Perhaps a better question would be:
"Why in this day and age don't aero engines have automatic mixture control?"
Re: Icing:
Many carb equipped cars have water or electrically heated inlet manifolds - and even if they don't, the engine bay is usually warm enough to prevent icing thanks to heat from the radiator and/or exhaust manifold.
Re: Power:
Power (for a given cylinder/head/inlet/exhaust design) is, to all intents and purposes a factor of capacity and RPM - so the low RPM of a big aero engine means that they are never going to produce the same power as a faster revving car engine of the same size. BHP/litre on a VW flat four leaves Lycoming in the shade - thanks to the extra RPM for the most part.