HC absorber on the three way catalytic converter. That ought to raise the cold car emissions. Finally jacked it up and had a look.
HC absorber yes it was on the Classic and was used to capture the unburnt Hydro Carbons until the catalytic converter got up to temp and then introduced them into the converter. Think of it as a blanket of activated charcoal wrapped around the shell of the cat and the mouth of the converter has a valve that closes almost completely to divert the exhaust into the absorber and the HC is absorbed by the charcoal and when the cat gets going the O2 sensor tells the main computer to open the valve and when it does the exhaust entering the cat provides a slight negative pressue on the absorber and it releases the HC into the main stream of exhaust going into the cat. Does that make sense?
Re: HC absorber Yes but I'm confused re why the powers that be would make the decision not to include it on the 04. Is there any logical reason for that decision (other than cost, perhaps?)?
I think it is probably due to the flush of warm coolant that is stored in the "thermos" that is pumped into the cylinder head and that helps with the lowering of HC as compared to a true cold start.
Re: I think it is Just found this ( http://www.electrifyingtimes.com/prius_200..._westcoast.html ) The new gas motor is a 76HP, 1.5 16-valve DOHC liter Atkinson cycle engine. This new engine allows higher RPM (4500-5000) and it's claimed that a 3.6 mile range is possible without the engine turning on in the city. To optimize engine and emissions performance, the new Prius ueses an electric water pump and insulated hot water storage thermos ('HC absorber'). The intent is to ensure the engine is warm before the hybrid demands power from it. The claim is that the water storage system can maintain the water temperature above 85 degrees for 3 days.
I read somewhere that on startup the pump would circulate hot coolant (from the highly insulated thermos) around the cat and therefore was ready for the unburned hydrocabons right away.
Not the cat but thru the water jacket in the cylinder head. As the external temp of the cat is problaby in the order of a thousand degrees F. when it's at operating temp, it would evaporate the coolant almost instantly.
