Cold-start driv­ing

Car Mechanics (UK) - - Help! -

I would like your ad­vice about cor­re­spon­dence between my­self and the Ssangyong Mo­tor Com­pany re­gard­ing my Tivoli. I do not ex­pect you to com­ment di­rectly on our dis­pute but merely to of­fer your opin­ion re­gard­ing the typ­i­cal per­for­mance char­ac­ter­is­tics of mod­ern, petrol-en­gined, cat­alytic con­verter-equipped, au­to­matic trans­mis­sion ve­hi­cles.

Ac­cord­ing to Ssangyong, it is a nor­mal char­ac­ter­is­tic of these ve­hi­cles to rou­tinely ‘hang’ in first gear from a cold en­gine start for the first few hun­dred yards – and, on at least two oc­ca­sions, for al­most quar­ter-of-a-mile – to al­low the cat­alytic con­verter to quickly at­tain the op­er­at­ing tem­per­a­ture re­quired to com­ply with emis­sion reg­u­la­tions. They say this hap­pens across a range of sim­i­lar ve­hi­cles pro­duced by other ve­hi­cle man­u­fac­tur­ers. Neil Pitcher

The mod­ern au­to­matic gear­box is a very com­plex unit and uses in­for­ma­tion de­rived from the en­gine ECU and sen­sors, as well as the in­for­ma­tion from its own ECU unit and sen­sors. If a prob­lem oc­curs, it will in most cases il­lu­mi­nate the warn­ing light for ei­ther the en­gine or gear­box sys­tem. With such an in­te­grated con­trol sys­tem, it is true that the gearchange is con­trolled to min­imise the warm-up time of both the en­gine and cat­a­lyst to the great­est ef­fect. One of the re­sults of this is that the gearchange is de­layed.

It is dif­fi­cult to com­ment on your par­tic­u­lar ve­hi­cle with­out ex­am­in­ing it, but one of the fac­tors to con­sider is the speed at which the ve­hi­cle is trav­el­ling be­fore the change takes place. If you are re­stricted to mi­nor roads for the first quar­ter-mile, it is likely the gearchange would be de­layed to this ex­tent. On the other hand, if you are mov­ing off and trav­el­ling onto a dual car­riage­way, it would be ex­pected for the gear­box to change up through the gears a lit­tle more quickly. The gearchange can also be af­fected by your driv­ing style, and re­leas­ing the ac­cel­er­a­tor slightly can of­ten in­duce the gear se­lec­tion ear­lier.

You do not men­tion if this is a new ve­hi­cle or one that has been used for some time. If the ve­hi­cle is not new, it would be ad­vis­able to check the con­di­tion of the tem­per­a­ture sen­sors, to en­sure the cor­rect data is be­ing trans­mit­ted to the con­trol units.

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