We got our HH about a month ago, and we're loving it. But a friend asked me a question the other day I couldn't answer. I was telling him that it was a SULEV, and he asked how the emissions could be so much lower than a conventional vehicle getting <30 mpg. I know that part of it is that the gas engine doesn't have to work as hard because the electric motor gets it moving, but it doesn't seem like that could be a huge difference. Anyone know a more complete answer? Thanks!

 

The explanation I would apply from Prius is that the electric motors allow the gasoline engine to face a very controlled, predicatable load. This allows the engine to be held very tightly at the correct air/fuel raio. This allows the catalysts to do an optimum job.

Prius also goes to great lengths to get the catalysts up to operating temperatures as quickly as possible, but I'm not sure if the Highlander does it in the same way. Any catalyst-equipped vehicle is very much at its worst, pollution-wise, until that stuff gets up to about 660 oF.

In a conventional vehicle, the engine and catalyst have to deal with whatever load and fuel flow you throw at 'em. Rough life.

Didja notice there is no soot at the tailpipe outlet? There still won't be, in 5 years.

DAS