Mommy, where does engine vacuum come from?

[Martin]

What in the hell is a carburator?

If the fuel boiled it would be gas, not atomized as a vapor.

who would have thought this newfangled fuel injection would catch on

I copied this from <!-- w --><a class="postlink" href="http://www.factorypro.com">www.factorypro.com</a><!-- w -->

The stuff is actually useful when you're trying to diagnose old cars or even newer bikes like my 2000 Honda CBR


To begin with, only gasoline vapor will burn, so fuel must change its state from a liquid to a gas at some point or the
engine won't run.

To do this it must absorb enough heat to boil.

" Boil the gasoline, now I know this guy's a dufus"!

"For the sake of argument how the hell can I boil gasoline when it's below freezing and icicles hanging off my nose?"

"Them carburetors may be magic but they ain't that magic!"

The answer is reduced pressure. What we call "vacuum".

Water boils at a lower temperature on a mountain top than it does at sea level because there's less atmospheric pressure
bearing down on it, right?

So the vacuum in the carburetor's venturi and intake manifold do the same thing only better, causing the gasoline to boil
and fuel vaporization to occur when very little heat is present.


The boiling point is reduced so that the fine atomized droplets that are sprayed into the intake stream vaporize from the \
latent heat in the air, no matter how little that might be. Within reason.

We do know about carb icing, right?

Of course, until the engine has warmed itself up, only a small part of the available gasoline actually turns to vapor, which
is why we need the choke to cut down on the air.