There is more than one reason ( how I see it ) for blocking cold air to the radiator.
Now I'm talking Denver Winter, and the top half of the U.S. is where people need to worry about this.

#1 Get the engine warmer faster. Yes there is a regular thermostat. But every little bit helps. Not shoving 40mph, 50mph, 75 MPH zero degree air into the grille can only help.

#2 Run the engine at slightly warmer temp. We really need warmer air going into the engine also, but I'm still working on that! Warmer air means more gasoline vaporizes or atomizes or whatever. You know what I mean. Liquid gas won't burn. (scientific fact) Only gas vapors burn. Warmer intake would help more, but running the engine slightly warmer all the time means more complete combustion, less pollution, and more bang for your buck!

#3 Keep the engine warmer longer, so you get EV more often, and for longer stretches. This is the BIG benefit for blocking the raditor. The FEH will NOT enter EV mode if the water temperature is below 59'F ( 140'F ) and it will not EVER stay in EV mode below 51'C ( 125'F).

The catalyst needs to stay hot to not pollute. But this operates in the 800'F to 1200'F range. It is difficult NOT to melt a sensor at this temperature. The temperature condition of the catalyst is INFERRED by A) the water temp. and B) the air intake temp. In EV mode, there is no air intake. The water temperature, and the water temperature cool down rate is used to calculate ( infer ) the catalyst cool down rate. When the water has cooled to a certain level ( like 51'C ) is it inferred that the catalyst has also cooled below a certain point.

Hence, the BIG benefit to the radiator block is to TRAP heat... and keep the water warmer longer, so you may drive in EV longer, and more often.

Over the highway, I would expect the benefit to be slight... and in danger of an overheat if you drive hard (fast) on days over about 50'F.

Driving in the city would be fine, because each EV only shut down is an automatic cool down for the car.

I only advocate use of a radiator block for people who do mostly stop and go city driving, and have daytime highs below 50'F.

Hope that helps! I'd really like to know your individual results.
FWIW... I have ALL my radiator blocked, and went into EV mode after 5 minutes from a cold soak at 30'F. Which is the same 5 minutes it takes at 75'F without the radiator block. At zero 'F to -5'F I could not get EV mode, even with the raditor blocked. Probably the air-intake was too cold, and or the battery was frozen!


Cheers!
-John

 

So I've tested my first configuration. That envolved recording the Engine Coolant temperature at several points along my 1.6 mile trip to work. I have now done this for as delivered, and config 1.

I have only the center portion of the lower air intake covered for this round of testing. My conclusion is that there is no advantage over this distance with this configuration.

I'm on to round two where I cover up the bulk of the lower air intake. We'll see how this one goes. I'll post another note after I've had another week of driving it to work.

Right now I am only looking at Coolant Temp as my benchmark. After I have results from this round of testing I might try again resetting the MPG estimate each morning and using that data as my results.

 

I applaud your patience and attention to detail.
However, Winter may be over before you finish testing, and we (all) want to know the result to use this year!

For the record... I went from nothing, to full blockage, both top and bottom.
I've never had an overheat, but I drive gentle.

If you have only a 1.6 mile commute, how many minutes does that take?

Again, the benifit for me was, a 5 minute warm-up in 30'F temperatures, vs. a 10 minute warm-up in similar temperatures. WITH FULL BLOCKAGE.

It does not surprise me you have seen no difference.... yet...
The 1.6 miles is really too short of a test if you ask me.
More benifit will come with extended driving.

 

Yes, I've thought about that too, and I probably should have started out blocking more, but I also want something that is driveable during warmer (60 degree) weather. This is because I won't be the only one driving the vehicle, and because the temperatures don't seem to stay cold around here (Boston).

If I were the only one driving, I'd probably do the same.

It takes about 5 minutes. There are several stops along the way, and the time can vary quite a bit. That's another variable I haven't really accounted for, but you can see it in my data. There is a jump between two datapoints, but the slope of the rest of the data doesn't change.

Yes, and for that reason I would like a longer commute. But that's the only reason!

 

I find that shoe leather works great for improving my FE. Not by covering the radiator, though. Eliminate the short trips.

The recent discussions about losing the EV mode and autostop in cold weather are interesting, though. I live in N CO. and drive Berthoud Pass frequently in the winter. I've been wondering if a hybrid could stay in EV mode going down the Winter Park side. It descends steeply enough to keep the battery charged, but it is frequently sub zero F over there.

 

Gary, I am a little jealous. I have an 05 FEH with 4WD. I've had it since this past August. The highest MPG I've seen in my FEH over a tank was 32.0. I mostly get around 30 mpg with my overall driving. I have noticed when it is cold outside here (Wash DC area) it drops down to around 27 mpg. I would love to be able to get the range you've been getting. On my FEH, it says the range is 435 miles. However, the most I've been able to get out of a tank of gas was 360 miles. I have a hour long commute just to get to work.

Rich

 

I'm stunned! I was considering and Escape, but the gas mileage you folks are talking about is not much better than I get with my current car (Mercedes e320). I regularly get 32mpg, at 75mph, in cold weather, hauling my spouse/dog/junk. In town, over the past 30 days the mileage has been 21 mpg, and that's with the a/c blowing and my relatively heavy foot.

 

Kinda comparing apples and oranges since the MB is a luxury CAR and the Escape is an SUV.

What would the E320 get for gas mileage off-road? How is it in snow and mud?

The mileage hown in my signature below reflect mixed city/highway driving over the last year for the '05 and 8 months for the '06. Much of that is cold weather driving.

If you like the luxury car, keep it. If you want a fuel efficient, practical SUV, consider the Hybrid Escape. I doubt the two are interchangeable.....

JMO of course.

 

Also, 32 MPG for the Escape Hybrid is from a lot of Highway driving, where it is only about 10% better than an equal size gas only vehicle.

Where this baby shines is under 40 MPH and in heavy city stop and go.

Compare my 45-50 MPG City in my 4,000lb hybrid to your Mecedes 21 MPG and the
Ford Escape Hybrid is more than twice as light on gas.

Since most people do about 50/50 city/highway... the numbers stay in the mid-30's for attentive drivers.

 

Another aspect to think about is that summertime MPGs, and the AWD. Having AWD and getting 35 MPGs is a pretty big difference as well. Not to mention how many miles you can go between fill-ups.