The Premier's Limo: 2004 Toyota Prius "winter beater" ecomodding thread

[MetroMPG]

Oh, and just for fun, this weekend I also timed how long it takes to remove the tail: Under 2 minutes. I think it was actually around 1:30, but that doesn't include relocating the license plate from the tail back onto the car.

That will also be in the video.

Reinstallation takes a bit longer -- partly because it's easier to peel off duct tape from the seams than it is to put it back on again, and partly because it's more fiddly getting the bottom surface to meet up with the undertray without it getting hung up.

[MetroMPG]

Yesterday someone in a commercial pickup truck seemed to be following a bit too closely / aggressively... then I noticed he had his phone out and I assume he was taking pics or video.

His video will likely be online well before mine.

[MetroMPG]

House cleaning:



Here are the numbers for why I decided the air dam didn't help.

I did AAA-BBB coastdown testing, using a phone to capture video of the speedometer so I could get a precise time measurement later at home on how quickly the speed dropped.

Methodology: I thoroughly warmed up the car with a ~25 minute highway drive. On the test road, ran it up to ~96-97 km/h (~55 mph), shifted to N at the same point each time, then coasted down to 40 km/h (~25 mph). The start point for timing was 95 km/h.

95-40 km/h coastdown runs, 3 with the air dam on, 3 with it off:

A1 (on): 75.93 s
A2 (on): 75.67 s
A3 (on): 77.67 s
A avg: 76.42 s
A stdev: 1.09

B1 (off): 78.07 s
B2 (off): 78.20 s
B3 (off): 78.43 s
B avg: 78.23 s
B stdev: 0.18

Difference: 1.81 s

[California98Civic]

A discussion question: is this because the underside has a bellypan that has been optimized and therefore the airdam is only adding frontal area, increasing CdA?

[MetroMPG]

Another discussion question:

Further complicating things, the airdam coastdown testing was done with the tail ON, as well as the other usual mods (grille block, passenger mirror delete, driver's mirror folded, wheel discs, rear skirts, rear wiper delete). But minus the rear 1/2 undertray that I added later.

Would the results have been different on an otherwise naked Prius?

[MetroMPG]

Fortunately, it's just the little 12 volt one.

As far as I can tell, it's the original battery too.

I knew it was weak when I got the car: it has thrown an error code a few times which indirectly points to a weak 12v. Also, I had to jump start it once this winter because I hadn't driven it in about 2 weeks. Resting voltage is low, too (12.5).

Of course, it's not a regular 12v battery -- it's a special sealed Prius 12v battery that lives in the hatchback area, with a valve/overflow vent to the outside.

And it's over $200 to replace after taxes in Canuckistan.

Fortunately, it's got very close dimensions to a regular utility 12v battery (eg. lawn tractor), and some owners take that replacement route. I did that today. Capacity is going to be a bit less, and it doesn't have the overflow, but it's $65 instead of $200. I'm OK with that.

[Daox]

My father in law did that with his 06 Prius just last winter. Its been going fine so far.

[MetroMPG]

I did take the car for a spin after putting in the battery and noticed another thing right away: the coolant/thermos pump runs quieter -- it often runs off the 12v, and it must like the higher voltage.

And I didn't see the probably-battery-related error message, but I usually only see that if the car has been sitting for a week or so.

Also, my MPG is amazingly up 25%!

Just kidding!

[redpoint5]

I just received a LiFePO4 battery that I'll be installing in the Prius. It set me back $124, but at least it's cheaper than the OEM. It only has a 20 Ah capacity compared to about 40 on the OEM.

[MetroMPG]

Which will be completely fine, as long as you remember to turn the power fully on so the DC-DC is keeping voltage up when you're parked or listening to the radio or something.

I got in the habit of doing that to make sure my old 12v didn't get depleted.