Thanks, you might also want to check out a thread on EBHs at cleanmpg.com. Someone has been doing an analysis. For their hybrid (Mercury Marineer) 2.5 hours was optimal for pay back during summer'ish days. When they looked at $gas saved vs $electricy put in, they got a little over 7cents a day payback. While they could pre-heat longer, the additional cost of electricy offset the $ savings of gas. Since electricity isn't completly green, I'm pretty much going to go with similar effects. He plans to continue the analysis during the winter to optimize savings.

http://www.cleanmpg.com/forums/ford/...test-6140.html

 

Dear Mr. Kite,
We live in snow country (Truckee, CA) with a 2008 HiHy. We will be buying a block heater, and I'm wondering what type you ended up purchasing, and if you are happy with it. We picked up our '08 at the end of October. Our first two tanks were at 25mpg. Now that we've started using the heater, we're getting about 21mpg. Thanks for the mileage tips from your earlier postings.

 

Over the past two months, I have been experimenting with the use of reflective insulation as a radiator block and engine insulation to augment the effectiveness of the EBH.

Since early Mar, I have driven 2,100 mi, averaging 29.5 mpg, with temps averaging 40-45 F. I've also achieved my 2nd 500 mi tank. Prior to this time, my historical average for this temprature range was 26 - 27 mpg. In urban traffic (Philly), I was getting over 35 mpg.

Having just purchased a Davis Car Chip, I wanted to post some operating data, with and without the EBH.

Here is the cold start data without EBH (ECT = 32 F; air temp = 32 F)
Distance = 3.9 mi; time of trip 10 min; avg speed 23 miles per hour
Time to reach Mode 2 (104 F) = 3 min 08 s
Time to reach Mode 3 (173.4 F) = 7 min 34 s
Max Coolant temp: 176 F
Est mpg: 25
% of time ICE off (RPM = 0): 15.8%

I will post the same trip with EBH later today.

 

Here is the cold start data with 4 hr EBH (ECT = 115 F; air temp = 46 F)
Distance = 3.9 mi; time of trip 9 min; avg speed 26 miles per hour
Time to reach Mode 2 (104 F) = 0 min 00 s (vs. 3 min 08 s no EBH)
Time to reach Mode 3 (173.4 F) = 4 min 16 s (vs 7 min 34 s)
Max Coolant temp: 181.4 F (vs. 176 F)
Est mpg: 30 (vs 22 - better estimates)
% of time ICE off (RPM = 0): 20.1% (vs. 15.8%)
Avg engine RPM: 1022 (vs. 1087)

This trip was on typical WPA terrain - up and down hills. More level terrain should see even better performance with longer time in auto stop/stealth modes.

On a 21 mi. round trip with 3 stops, I calculated a 0.11 gal fuel savings, enough to offset the electrical usage.

 

Thank you for the information. Do you have a 2008 Highlander? If so, what kind of EBH did you get?
Thank you! dr

 

NP. I have a '07 HiHy (my trips are posted in the database).

Purchased EBH online fm Metro Toyota/Cleveland ($49 + shipping) - installed by my Toyota dealer ($118.50).
Type : # C0140-00644
Engine Block Heater
Model : Highlander Hybrid
Year(s) : 2007

Contact: Jesse Wright
Internet Parts Sales
Metro Toyota
Cleveland, Ohio
1.877.885.2900
www.metrotpn.com
parts@metrotoyota.com

Jesse can tell you if the EBH is compatible with '08 HiHys.

 

Thanks for posting your results.

I have the EBH as well along with a scangauge. I have my EBH on for around 2 hours. My engine temp is around 104 to 105 at startup. I have not tried having the EBH on for longer. Can you tell me when your max engine heating temp is reached by the EBH? Is it 4 hours? I know there is a point where the temp will level off. EBH is designed for a max temp much lower that operating temp of vehicle.
Also can you provide more detail and possibly pictures on the insulation methods used?

Thanks
Lenny

 

Lenny:

I have seen data posted elsewhere showing ECT temperature still increasing after 6 hr of EBH input.

The max temp gain can be estimated from the equation:

(T - Tenv) = Q/AU

where Q is EBH rating (about 570 W)
A = EB surface area (about 6 sq m.)
U = overall heat transfer coefficient (lumped natural convection and thermal radiation ~ 2.5 W/sq. m - K).

These estimates predict a max temperature gain of 38 K or around 68 F.

I see a pretty consistent 68 - 69 F temperature gain relative to outside temperature for a 4 hour cycle.

Temp vs time should follow an exponential decay:

T(t) - Tamb = 68 - exp (-t/to), where to is time constant (app. 1-1.2 hr)

You are going to see 85 - 95% of the benefit from 2 hr, and 95 - 98% from 4 hr.

Knowing the interaction between ECT and hybrid modes is definitely paying off. The car chip data lets me calculate % of time in stealth mode (RPM = 0 while miles per hour > 0). On this morning's trip of 17 mi, I was averaging a record-shattering 42.6 mpg. Not surprisingly, ICE was shut off while in motion 49.9% of the time. With the return trip at 36.5 mpg, I'm in terra incognita on this tank at 38.5 mpg.

Kudos to hypermilers like efusco for showing that 40 mpg on the HiHy is possible.

 

Here is my HiHy EBH Data w/ radiator block & reflective insulation

Delta T EBH time (hr)
===== =========
45.0 1.38
56.7 2.33
57.1 3.00
60.7 3.42
68.3 4.25
70.0 6.00

Max temp gain estimated to be ~73 F @ 9 hr.

A decent predictor for % Stealth / MPG for my 17.5 mi drive to work has been:

% Stealth = 0.5334 x Ln(ICE temp at startup) - 2.0561
MPG = 22 / (1 - % Stealth/100)

This predicts zero stealth when starting coolant temps are < 27 F.
Optimum EBH time appears to be around 3.3 hr (amb T 30 - 50 F),
but 2 hr appears to give 85 % of the net savings.

 

Subject's (link) vehicle was kept in a 75F garage...

We don't even heat our house to over 72F, (65F in setback mode) and while our garage is attached there is NO direct source of heat and the inbetween wall is heavily insulated.

"Link" is NOT a good source for comparitive information for block-heating vs not.