Au­toStop saves money while you idle

Winnipeg Free Press - Section F - - AUTOS - JIM KERR

WE all like to save money, and be­ing able to drive far­ther on a tank of fuel is a very vis­i­ble way of sav­ing money.

With fill-ups now cost­ing in the $60 range for econ­omy cars and well over $100 for larger trucks and SUV’s, sav­ing five per cent on fuel costs starts to make a sig­nif­i­cant dif­fer­ence. That is what the Au­toStop fea­ture can po­ten­tially do for you.

Au­toStop is a fea­ture or pro­gram that au­to­mat­i­cally turns off the ve­hi­cle’s gaso­line en­gine af­ter a short pe­riod when you’re sit­ting at idle. As soon as you’re ready to move, the en­gine starts again.

The Au­toStop fea­ture may seem like it wouldn’t save a lot of fuel, but a study by the U.S. Trea­sury Depart­ment es­ti­mates com­muters en­counter an aver­age of 10 to 15 red lights on a typ­i­cal 30-kilo­me­tre com­mute, which can add up to 15 min­utes or more of idle time. And we all know that an idling ve­hi­cle gets zero for fuel econ­omy, so turn­ing off the en­gine can max­i­mize fuel use.

Only a cou­ple years ago, Au­toStop was limited to hy­brid ve­hi­cles, but now al­most all new ve­hi­cles on the mar­ket have Au­toStop. To pro­vide this fea­ture, the man­u­fac­tur­ers had to work with sev­eral ve­hi­cle sys­tems and com­po­nents.

Let’s com­pare Au­toStop in a hy­brid ve­hi­cle ver­sus a con­ven­tional gas en­gine. In the hy­brid ve­hi­cle, the gaso­line en­gine is turned off by the en­gine com­puter and restarted by the hy­brid sys­tem elec­tric mo­tor. This is a silent and smooth oper­a­tion.

In con­ven­tional ve­hi­cles, the en­gine com­puter still turns off the en­gine, but the reg­u­lar starter mo­tor is used to restart it. The starter mo­tor has to op­er­ate much more of­ten, so the man­u­fac­tur­ers had to build a starter mo­tor that would han­dle the re­peated star­tups over sev­eral years of oper­a­tion. This was rel­a­tively easy com­pared with ev­ery­thing else in­volved,

For the Au­toStop fea­ture to op­er­ate, safety must be en­sured. In au­to­mat­ic­trans­mis­sion ve­hi­cles, an elec­tric-mo­tor-driven pump was typ­i­cally added to the trans­mis­sion so the trans­mis­sion would stay in gear when the gas en­gine stopped run­ning. Brake sys­tems needed to be mod­i­fied so there would still be power-brake oper­a­tion with­out the gas en­gine run­ning.

On some ve­hi­cles, this meant in­stalling a big­ger brake vac­uum booster so there was more re­serve. Oth­ers use elec­tric as­sist, and many of the ve­hi­cles use a hill-hold fea­ture that keeps the wheel brakes ap­plied at a stop un­til ei­ther the ve­hi­cle starts to move or the brake pedal has been re­leased for a cou­ple sec­onds. Power steer­ing also needed changes. Elec­tric power steer­ing has be­come com­mon, and this al­lows power steer­ing at all times when the key is on.

Other con­cerns were with pas­sen­ger com­fort. The gaso­line en­gine is used to pro­duce in­te­rior heat and win­dow de­frost. It wouldn’t do to have the en­gine turn off when the pas­sen­ger com­part­ment is still cold, so it is de­signed to stay run­ning un­til in­te­rior tem­per­a­tures have reached the de­sired level. The same goes for air-con­di­tion­ing oper­a­tion. A pas­sen­ger com­part­ment can quickly be­come hot and muggy if the A/C is turned off.

Most A/C com­pres­sors are belt­driven by the gas en­gine, so in these mod­els, the en­gine will stay run­ning or restart if the in­te­rior tem­per­a­ture starts to rise too much. A few cars now use elec­tri­cally driven A/C com­pres­sors, so the gas en­gine can be turned off more of the time.

Be­cause of the need to in­te­grate pas­sen­ger-com­part­ment tem­per­a­tures to the Au­toStop fea­ture, most ve­hi­cles now use au­to­matic cli­mate con­trols, where a com­puter senses the in­te­rior tem­per­a­ture and sends sig­nals to the en­gine com­puter when it’s OK to op­er­ate the Au­toStop fea­ture.

As for driver oper­a­tion, it is vir­tu­ally seam­less. I’ve per­son­ally driven many Au­toStop-equipped ve­hi­cles and only oc­ca­sion­ally have I ex­pe­ri­enced any rough­ness — and this has oc­curred when the com­puter is stop­ping the en­gine just as I go to move again.

Switches and in­puts on the ped­als, cli­mate con­trol and pow­er­train tell the com­puter to turn off the en­gine when the ve­hi­cle is stopped and idling. As soon as you re­lease the brake pedal or start to en­gage the clutch (if a man­ual trans­mis­sion), the com­puter will restart the en­gine. It starts smoothly, qui­etly and in many cases al­most un­no­tice­ably. Jim Kerr is a me­chanic, in­struc­tor of au­to­mo­tive tech­nol­ogy, free­lance jour­nal­ist and mem­ber of the Au­to­mo­bile Jour­nal­ists’ As­so­ci­a­tion of Canada.

Au­toStop is a fea­ture or pro­gram that au­to­mat­i­cally turns off the ve­hi­cle’s en­gine

af­ter a short pe­riod when you’re sit­ting at idle.

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