Just an idea I had, don't know if it would do any good or not. I know one of the warm up things to the FEH and MMH is that the cat has to be at a certain operating temperature. Would it hurt to insulate it so that it doesn't lose it's heat so fast? Maybe just for the winter months?

I am amazed at some of your knowledge on here so I'm sure this may have been discussed or tried.

Thanks in advance, Jay.

 

Well, I found the answer myself in the SG thread....

I have not yet found a relationship with catalyst temperature.
I have had EV with catalyst temperature of 755'F.
Catalyst is over 1000'F within 30 seconds from a cold start.
Catalyst value cools about 1'F per second when the engine is off, no matter the ambient temp

So water temp is the main one to allow EV charge.

 

So far I've had good luck with blocking the radiator. Temperatures here are now in low 30s and I have not lost a whole MPG yet.

 

I'm sure someone here knows the real answer, but I always thought the emissions control system kept engine temperature up at a high level and did not try to control a specific catalyst temperature. One feature the Prius has that the FEH apparently doesn't is a thermos type storage container for coolant that keeps some coolant at higher temperature overnight to allow quicker engine heatup after a start.

 

You are correct that the FEH has no thermos bottle.
Does the Prius really keep itself warm overnight?
Or is that just to keep heat available to the passengers when you drive in EV mode? Or maybe during QUICK stops to the market.

 

I read about this in a Prius shop manual some time ago. If I recall correctly, the purpose was to bring the temperature of the engine up faster to allow it to go into EV mode sooner. I'm not sure what the volume of the container is but it supposedly keeps temperature for 24 hours. Maybe a Prius lurker can fill us in.

 

The Prius hot watter bottle feeds stored coolant into the intake side of the cylinder head. This is part of their strategy to reduce the cold-start emissions that account for so much of an engine's total emissions.

Running a lean mixture lowers emissions, but a cold engine needs a rich mixture to run well. Pre-warming the intake side helps the Prius run leaner when cold without affecting performance.

BTW: Toyoya says it can keep the fluid above 85°F for almost three days

 

Does that mean you won't find an engine block heater on a Prius?

I'm still thinking the MASS ( volume, whatever ) has got to be pretty small.
Still, sounds better than nothing at all!

P.S.
Oh, and I'm pretty sure the FEH takes the ambient air temp, intake air temp, and the cylinder head temp into account and GUESSES or infers what the CAT temp is.
I'm 99% sure this is all there is to it. I was told by Ford there is not CAT Temp. sensor, and it is just an inferred value.

So you really need to keep the engine hot, and intake air if possible.
The actual catalytic converter I don't think needs to be messed with.