Fuel Heating System for better combustion.. ???


There are a half-dozen U.S. patents dating from the 1970's until the '90's that address the theory that by pre-heating the incoming fuel the combustion will be more complete. --- Gasoline (a power fluid) must be vaporized before it will burn.

The idea behind localized pre-heating is to present the raw fuel in a hot state so it will vaporize quicker in the short time it has before it is contained in the closed chamber. Researcher Ford Motor Company presented this at a SAE International Congress in Detroit on 24 Feb 1986.

They found "Engine tests with gasoline show the ability of the test configuratioin to evaporate all part throttle fuel flow before it enters the intake manifold". Results ... show the ability of local heating to reduce A/F excursions on the 1.6 L. engine by 80% over the ambient temperature range of 0/sup P/F. shoed the elimination of cyclinder to cylinder A/F maldistribution." ---

Does anyone have more information on this theory, does it really work, and if so why has it not been adapted by today's manufacturers? --- A friend of mine suggests how inexpensive it is to run the fuel line thru the coolant radiator before it goes into the induction system. ---Richard

Hi,

In aviation and the old days of regular carburators, there were problems caused by the cooling of gasoline that could cause carburator icing. Even today, all carburator equipped aviation engines have a separate air heating system to counter the potentially engine stopping and safety risk of ice in the intake manifold. But two design features mitigate that problem today, fuel injection and manifold coolant loops.

Fuel injection basicly 'mixes' the fuel and air at the very warm air intake valves. The electronic fuel injectors also run pretty hot and use the fuel to dump their heat.

Also, some intake manifolds today have a coolant loop but I can't find any evidence in the NHW11. On the NHW11 Prius, there are a pair of coolant hoses that connect to the throttle body. But I'm not convenced this makes much sense other than to avoid potential ice from venturi cooling since gasoline is injected further down, at the air intake ports.

There is one NHW20 Prius owner who pre-heats his intake air but a second owner was not able to replicate any improvement. I would be interested in reading any experimental results that demonstrate an advantage but I think there are better places to apply heat.

Bob Wilson

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