Quote:
Originally Posted by cRiPpLe_rOoStEr
A hotter air intake would eventually require more gasoline to keep its charge cool enough to prevent knocking...
With a colder intake, a smaller amount of gasoline evaporates. Considering the modern engines fitted with EFI, they set a lower AFR exactly to keep the engine at its standard operating temperatures. Notice it in a rainy day, the fuel consumption usually goes down due to the colder air with more moisture on it
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I think my question is what's the dewpoint for gasoline in air? Let's say you're going for a stoichiometric AFR. What temperature would the air have to be in order to assorb all that gasoline?
You can vaporize as much gasoline as it will boil. But just like a tea kettle that's on the stove, once the steam (vapor) hits the cooler air it forms liquid droplets (the white "steam" that you can see coming out of the whistle). If the air saturates with gasoline the same thing will happen, much of the vapor will transition back into liquid droplets, which you could have gotten the same effect with a good fuel injection nozzle.
The air will have to have a minimum temperature in order to contain purely vaporized gasoline. Any cooler and you get droplets. But how hot would it have to be? Adding more gasoline to cool the intake charge wouldn't help efficiency at this point.
In other words, you boil gasoline in a vaporizer to get gasoline vapor
>but the air is too cool to keep that gasoline as a vapor, so it turns back into droplets, which should defeat the purpose of vaporizing the gasoline in the first place,
>so now you have to heat up the air too so it can hold more vapor without saturating and causing gasoline to condensate back into liquid,
>But now you have a hot dry charge of stoichiometric air and gasoline vapor that causes detonation, knock and maybe even other such problems.
>So the solution is to add more gasoline, which now puts us at a rich AFR, which wouldn't lower the intake charge temperature because no more gasoline can now evaporate because we are at the dew point already, but at least it will evaporate during combustion and hopefully cool the combustion process enough to prevent detonation.