Prius Mods part 3.3 – DEFA SafeStart WarmUp cable installation

The engine block heater installation went remarkably well.  Compared to the installation of the Toyota Canada EBH from the top, which could involve removal of the wipers, windscreen tray, various brackets, lots of wiring and some skin, the DEFA installation from the bottom is a breeze.  (There is a way of installing the Toyota EBH from the bottom, but the top-down method seems to be the most popular.)  If my previous post didn’t convey the ease with which one may slide under a car, remove those pesky plastic push-pins holding the undertray and pop something onto the rear of the engine block, then please re-read; you’ve obviously missed the message.  Or the irony.

Which way for the cable?

Since the Toyota EBH is towards the top, it makes sense to route the cable up and to the left.  (By convention, “left” is when viewed from the rear of the car.  So an Australian car is Right-Hand Drive and an American or European car is Left-Hand Drive.) The cable terminates in a simple earthed plug, which is coiled up against the wing when not in use.

So, do I snake through the high voltage lines and exhaust manifold from the left (right in this picture) or dice with A/C and brake lines on the right (left in this picture)?

Since the DEFA EBH will fit about a dozen cars with similar engines, the instructions don’t specify a single route for the connector cable.  The instructions merely warn to keep the connector cable away from Air Conditioning and brake lines.  Taking that somewhat literally, I tried to find a path to the left of the engine, the opposite side to the A/C and Brake lines.  If I could only get under the exhaust manifold and support the cable far from it, I should be right from there.

Adding to the fun is that the cable has a large, weatherproof socket at one end; read, non-detachable socket at one end.  So I started by feeding it through the grille first and then back to the EBH (somehow).  There was a nice gap in the foam surround on the left of the radiator too.  I reached up from the fog lamp access flap to direct the cable up.  But there was just too much cabling from there and no real sight-lines and since my pearl-catcher on a stick was missing, there was no easy way to feed the cable down to the rear of the block.  I spent an hour or more trying various permutations of origin, fastener and route but none seemed to work.  The one that seemed to be out of contention was from the right-hand side on account of the A/C lines attached to the front of the radiator.  Getting late, I tidied up and waited for another day.

Bonus: I found the fog lamp adjustment screws and turned them so that the light actually goes in front of the car instead of below it!

DEFA socket test fitting in the bottom grille. The left-hand side seemed to be the best option at first.  Would have been a nice spot, I thought.  Then I thought, “why are all those pebbles jammed under the grille?”

New day, fresh start.  (Or should that be SafeStart?)

Next day I decided to fit the cable no matter what, even if it was a temporary fix accessed by opening the bonnet (hood).  I could play around on top of the engine as long as I wanted and only needed to pull apart the bottom for the relatively easy part of plugged the cable into the EBH once the route was determined.

Here’s where the belt-less engine design goes from merely being a technological wonder to become a really nice idea.  The right-hand side of the engine has a good 120mm of clearance between it and the inner wing.  The DEFA instructions that warned of not touching the A/C lines were actually telling me which route to take.

Back under the block and looking from many angles, the amount of space to play in became obvious.  Without a 3D model to work with you don’t realise that there’s a good armful of space.  Yes, there’s a steering column (RHD car) and the crank pulley (belt-less) to contend with, but they are far away.  I fed the cable down from the engine mount… and suddenly discovered the ideal earth mount close to the negative battery charging terminal. (There are no other holes or bolts small enough to attach the earth wire at the bottom of the engine.) From underneath I attached the cable to the EBH and checked the clearance.  HEAPS! There’s a clear run from the bottom with a lot of space between it and the A/C and brake lines.  What was I worrying about?

Looking up: View from the right-hand side of the block upwards, shows a lot of space for the cable. Bonnet (red) is in the bottom right and crank pulley (belt-less, remember) is in the bottom left.
Looking down: Lots of space. A/C lines run horizontally on the right (left of picture) avoiding the cable by a wide margin. Engine mount at bottom of picture.
The final, temporary fitting. Cable zip-tied to engine mount, earth lead attached near negative battery charging terminal (bottom right). Cable looped around coolant bottle and zip-tied for some degree of fastening. Dreaded A/C lines (centre) appear close, but are clear.

The final, temporary fitting is not ideal, but it works.  I have to open the bonnet to access the plug, but at least it is out of the weather.

Plug-in test

I used my Watts Clever power meter to check the power, which sat on 328W, slightly over the 300W specification and current was 1.37A at 240V (P=IV).

Temperature test

Since the Prius does not have a temperature gauge, I have to use my Garmin 2460 LT with ecoroute HD, which takes some 10-20 seconds for the gauge to display.  After 30 minutes, engine warmed from estimated 15°c to 30°c.  (The engine was running for about 10 seconds and read 32°c when the gauge appeared.)  Subsequent tests show a change from about 6°c to over 30°c in just under 2 hours.  I am yet to test from cold for the maximum 3 hours (the temperature does not rise after that) to see how hot the engine block can get.

So, why did I bother again?

The benefit on these cold mornings is that I can start-stop at the top of my hill and can use the heater earlier.  The difference in fuel consumption can’t be quantified without an OBDCII data logger tracking every variable.  A back of the envelop calculation suggests that 20¢ of electricity (3 hours) could save 15¢ of fuel (at Australia’s high electricity and fuel prices), which at face value seems silly.  But that simple maths doesn’t account for reduced emissions, less wear, easier start-stop, quick heater response and quick acceleration response.  Confirmation bias might skew my thinking of how quickly I’ll pay the AUD 280 back, so I shouldn’t comment… except to say that for the Saturday morning run to drop off Chikako at work and then to the dog park here’s the difference between a warm engine (30°c) and a cold one (10°c):

  • Before: 19.3km Cons: 3.8l/100km Avg: 40km/h (74.3 mpg(Imp) 62.2 mpg(US) 26.32 km/l)
  • After: 19.1km Cons: 3.1l/100km Avg: 42km/h (91.1 mpg(Imp) 76.2 mpg(US) 32.3km/l)

Any worries?

Removed what appeared to be several kilograms of debris, rocks, pebbles, grass, leaves and broken glass from the undertrays. Might look into the crash history of the car.

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2 thoughts on “Prius Mods part 3.3 – DEFA SafeStart WarmUp cable installation

  1. I want to thank you for your excellent work. Especially about how to install defa engine heater. I followed your text and installed defa heater to my -10 Prius. Greetings from Finland!

    WBR Mikko

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