Anyone know how to force an AutoStop in Winter

[Steve C]

Hello all;
I live in Canada and as you may be aware it gets a little cool here during the winter months.
I have noticed over the last couple of years that my fuel consumption goes from 3.5L/100km in the summer to 4.2L/100km in the winter. I associate the bulk of this difference to the fact that Auto-Stop will not function when the tempurature drops to approx 5c or lower. (I have confirmed this milage drop by getting similar fuel consumption results leaving A/C on -thus disabling the auto-stop during the summer).

I am trying to find a way to force the Auto-Stop feature to continue to shut off the engine when the car comes to a stop regardless of the outside tempurature.

I think that the Honda engineers must be afraid of a little cold weather... Hey Honda, if a driver can handle no air conditioning during an Auto-Stop, they can likely handle no heat during an Auto-Stop!!!
Us Canadians are a hardly lot!

Anyone have a fix, thoughts, insights?

[Yves M.]

Set the temperature control to Off. Then the auto-stop will work.

You'll need a hat and gloves. And if you use it too long, you'll have ice in the inside windows or you need to stop breathing all the while

[Steve C]

Hi Yves;
Thanks for the reply.
Are you serious about tuning temp control to off?

I was hoping that the solution would not be to have to start flicking
climate control buttons off and on each time I come to a red light!!!

[ElectricTroy]

Use the ignition key. I've done that sometimes if my engine refuses to shut off.

Hi Steve C.:

___Given you live up in Canada and I am sure you are experiencing temperatures far cooler then most folks to the south already; Auto-stop is not always advantageous. Our little beauties blocks lose heat like you wouldn’t believe and even 30 seconds worth of autostop might place your overall energy consumption higher then if you just let her idle. If you are driving a 5-speed, you have lean burn idle with maybe .2 oz. of fuel burn/minute if that helps you judge.

___Autostop itself is supposed to disappear below 40 Degrees F. Complete speculation here but I highly doubt Honda decided that was the temperature to disable that function because of defrosting the wind screen. I can almost bet they were measuring the ICE’s FE through autostop events in varying temps and found that on average, 40 degrees was close to the break even point between FE savings and dropping block temps which needs to be re-warmed at the expense of fuel economy after the event.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:1q43zrw5]Waynegerdes@earthlink.net[/email:1q43zrw5]

[Steve C]

Thanks for the feedback Wayne;
You make some very interesting points. In my own testing I have discovered that leaving the engine running at stop lights (during the summer) increases my mileage from 3.5L to 4.0L/100km. The difference of .2L in the winter I am attributing to oil viscosity and other minor factors.
Since the cooler weather has hit, I decided to perform a test and turn off the ignition whenever I came to a stop. I did this for about 500km and found that my mileage dropped from 4.2L down to 3.7L/100km.
Thus my conclusion Auto-stop is one of the more signifcant contributing factors to fuel consumption rates.

As for the engine block cooling off during a stop light, I suspect that this may not be an issue until you are down to something like -30. I can't remember the values from my Thermodynamics class days anymore, but the thermal conductivity of aluminum, (and oil and antifreeze within the block) cannot transfer/dissipate heat energy quickly enough that it this would be a factor once the engine was up to operating temperature.

I keep hoping that Honda will let me in on a little secret to making auto-stop work at any temperature. Something like "hold down the Auto and Off button, open and close the glove compartment twice while singing I'm dreaming of a White Christmas".

[Guillermo]

Auto-stop is mostly to reduce pollution and does improve mileage in city driving with lots of traffic lights. But you must drive in 100% extreme stop and go city conditions with dozens of red lights daily for the mileage difference to be 20%!

[joecvt]

Hello Steve C,

I recently did a mod to do what you are suggesting. Although, I'm pretty
sure it will not Auto-Stop in extreme cold temps. There is a sensor in the
front bumper to measure the outside temp. Looking from the radiator
towards the inside of the front bumper, you will see it in the middle. You
can remove the sensor (without cutting any wires) to a warmer part of
the engine. I placed mine near the MAP sensor area (Under the right side
of the top engine plastic cover. The idea is to report the correct outside
temp when the engine is cold (overnight) and report a warmer temp once
the engine has warmed up so you will go into Auto-Stop more often.

JoeCVT - Just your average CVT owner

[Yves M.]

An other idea that could be investigated, would be to heat up the interior temp sensor (in the dash next to the steering) so that the system thinks the interior rempature is OK and there is no need to use the heater. Or some type of temporary bypass with a switch.

I remember reading somewhere that if the interior tempature is really above the dialed tempature, the Auto-stop works. Even under the about 40 F temp

[Insightful Trekker]

Too much auto stop in cold weather will cause the ICE to chill too much and go into cold enrichment ( Kinda opposite of Lean Burn ) and your overall MPG will be even lower.

Also the IMA batteries will need to limit auto stop if their too cold else severe damage can be done!

So "overriding" the designed parameters may not get you the MPG increase your hoping for and could cause IMA battery damage.

Try a manual override of the IMA cooling fans to INCREASE their draw from the *heated* cabin. There was a post from last Aug or Sept by an Insighter in Phoenix that simply added 2 common computer cooling fans blowing into the face of the intake duct and plugged them into the accessory power outlet. A good proof of concept mod.

Guess you'll have to "soften-up" a bit with a toasty warm car to drive in. <g>


With all that said and an ETM and Service manual in hand the ENGRDY line distributed to the gauge, heater function control panel and PCM is what your looking for. Applying 12v to this line is what enables the heater function control panel to override autostop based on full auto or econ settings. It will not override IMA battery thermal limit management so "hacking" this feature _should_ be safe.

You can add an auto stop "disable" switch but no unqualified enable. Which should be useful for the stop and go traffic auto stop annoyance problem.


Tried the 7 x 16" cardboard radiator block and a hot intake air mod to regain cold weather MPG?

HTH! :)