The cold season is upon us, nipping any attempt to get good or even average FE in the bud at every cold start.
When it is freezing and I start my car and walk around it I can smell the unburnt fuel from the exhaust. Such a waste, but what to do?
What about electrically heating the intake air?
It needs to be electric; the exhaust manifiold is still cold too at first.
If I can heat the intake air by maybe 10 to 20 degrees Celsius, just until the engine is lukewarm, it will aid the combustion producing more heat, it will reduce pumping loss by being less dense, burn cleaner, rev lower, etc.
Investing a few hundred Watt to make an engine that consumes over 10 kiloWatt worth of fuel run maybe 5% more efficiently would make sense.
This has been lingering in my mind for a while. I believed it would not make economical sense but promised myself to do the math to prove it does not make sense.
So I just did the math, helped by the data in
Wikipedia's earth atmosphere article.
And much to my surprise it seems possible after all.
Here goes:
Take a typical 2 liter engine running stationary at 1200 RPM at 50% load. I focus on low revs/low load because that's where the combustion is worst in the cold.
Each cylinder would have 600 intake cycles at half atmosphere per minute, so it uses 600 liter of air (atm) per minute, or 10 per second.
It takes just over a kJ to heat a kilo of air by one degree Celsius.
The air density at sea level at temperatures just below freezing is about 1.4 kg per cubic meter or 14 gram per 10 liter.
So we would need just over 14 Watt to heat the intake air by one degree Celsius on this engine. A 140W heater could raise it by 10 degrees, 280W would do 20 degrees. For that 2 liter engine; mine is smaller and could do with less.
This is something I'd like to try out, if only I knew how to do it.
First of all, what heater? Camping and caravaning shops sell 12V 150W blow driers, that could be something; maybe it could even just fit the intake pipe. There are ceramic heaters, Peltier elements, you name it.
Then where to put it? I'd like it behind the air filter, as I don't want to waste time and energy heating that up. But then it has to be small enough to fit in between the filter and the throttle house. It needs thermal protection, don't want to melt the OEM stuff around there.