|
I know some people have provided evidence of their cars not having DFCO, and they are probably right.
When you let off the gas pedal, the engine vacuum skyrockets to almost a perfect vacuum. In my Echo it comes close to 26 inches of vacuum. At 30 inches (depending on atmospheric pressure) you have a perfect vacuum. Think outer space.
With virtually no air getting into the cylinders (very close to none) you do not have enough air to compress and create enough pressure for decent combustion.
If there is any fuel available under those circumstances, that fuel will end up in the exhaust and the catalytic converter. It could create a nice kaboom in the exhaust, as well as very high unburned hydrocarbons which fails emissions tests and requirements.
DFCO is an easy way to eliminate the nasty consequences of fuel that has passed through the engine without combustion. Just eliminate the fuel.
Now all that being said, I believe there may be some emissions systems that do allow some fuel to be introduced (a very small amount). If so there has to be some air bypass to allow the fuel to burn in the converter, but it makes much more sense to me that the best solution is to just shut off the fuel altogether.
regards
Mech
|