In sub-freezing temperatures, about 90%. I use 2 pieces of cardboard that would cover the entire radiator, and then overlap them to cover a certain amout that I can change with different temperatures. The temperature gauge usually stays in the normal range, with the Hot Air Mod, it just seems to get there quicker, especially on cold mornings.

 

thanks. wow- its almost like removing the radiator from the system!

 

I believe blocking the radiator does not effect the speed of engine coolant temp increment.
The thermostat is shut off until about 180 F and a radiator does nothing until then.
The radiator is still cold.

Ken@Japan

 

Even in the closed position, there is still coolant circulation to the radiator, it's just at a greatly reduced rate. I don't know what the HCH's calibration is, but the general rule of thumb is that in the closed position, it still flows about 10% to the radiator. As such, it would still have a small effect how much of the radiator is blocked even when the thermostat is in the closed position.

 

On the '04, there is no way to kill the A/C compressor during defrost, as the hack doesn't work. All it does is allow the driver to turn the indicator light on or off in defrost, not the compressor clutch itself.

Of course, the dealer knows nothing...

Matt

 

Move to Hawaii.

 

Maybe you could get one of those engine block heaters that they use in Canada and Alaska. The HCH engine is going to rev until the fluids are hot enough. It happens here in San Diego even if the temp is only in the 50s or 60s in the morning. I get 10-20 mpg on the first mile or so, no matter what.

 

Call me irresponsible, but it's winter here in the high country and it's just impossible to worry about serious hits to the FE. I've got studs on, the roads are either packed snow or slush, and the trips over the mountain passes are usually in 3-6 inches of snow. It takes forever to warm up, I don't want the tires overinflated 'cause I need all the contact with the road I can get, etc., etc. But it's still possible to keep the ECO light on a lot of the time, and I know I'm getting much better mpg than in my past cars which were much less comfortable, especially in these conditions. The HAH is handling these conditions quite well for 2WD. No complaints. MPG with studs on clear roads is just 1-2 below non-studded tires.

Still, one can obsess about FE in any conditions, and I'd appreciate any winter FE tips.

One last thought. Congrats and thanks to all the civilized, thoughtful and helpful folks who contribute here. The tone is refreshing compared to so much of what's on the web. It's a pleasure to know 'ya.

 

Yesterday afternoon I finally put in some cardboard and completely covered the radiator. Currently the mornings are at 35F - just above freezing. The coolant temperature warmed up in one mile - not two and remained at it's normal operating temperature on the way to work.

 

...and that is what is most important. Obsessing is a personal decision. We're all still better off regadless.