Our me­chan­i­cal en­gi­neer is here to help the av­er­age mo­torist in Sin­ga­pore with his se­ries of the­matic Q&A ar­ti­cles.

Torque (Singapore) - - CONTENTS -

Our me­chan­i­cal en­gi­neer is here to help the av­er­age mo­torist in Sin­ga­pore with his se­ries of the­matic Q&A ar­ti­cles.

TTHIS is­sue’s ques­tion-an­dan­swer ar­ti­cle in our on­go­ing Torque Shop se­ries is about turbo petrol en­gines. Most tur­bocharg­ers used to be found un­der the bon­nets of high-per­for­mance cars, from Euro rock­ets to Evos, but th­ese days, every­thing from hum­ble lit­tle runabouts to rum­bling V8 mon­sters can have a turbo in the en­gine room. I drive a tur­bocharged Euro­pean car. Can I fill it up with 92-oc­tane fuel? This is an im­por­tant piece of in­for­ma­tion which you must ex­tract from the owner’s man­ual. The min­i­mum oc­tane rat­ing re­quire­ment is also usu­ally printed on a sticker on the in­side of the fuel filler flap.

In gen­eral, most tur­bocharged en­gines, whether Euro­pean or oth­er­wise, re­quire at least 95-oc­tane fuel.

Us­ing a lower oc­tane rat­ing than is rec­om­mended will re­duce both per­for­mance and ef­fi­ciency. How­ever, us­ing a higher than min­i­mum oc­tane rat­ing will not have any ad­verse ef­fect. I drive a Nis­san Qashqai 1.2 Turbo. Is it nec­es­sary to let the en­gine idle for sev­eral min­utes be­fore switch­ing the ig­ni­tion off? Tur­bocharged en­gines do need to cool down be­fore they are turned off.

But in nearly all driv­ing con­di­tions, the en­gine does not reach tem­per­a­tures


that re­quire a de­lib­er­ate cool­ing-down pe­riod.

How­ever, if you take your Qashqai to a race­track and drive hard for two or three laps, you should give it an­other lap at a mod­er­ate pace, fol­lowed by a pe­riod of idling, to re­store nor­mal en­gine oil tem­per­a­ture. Switch­ing off when the en­gine is very hot stops the cir­cu­la­tion of oil. The layer of oil around the tur­bocharger bear­ings stops flow­ing and lit­er­ally gets “burnt”. The black sludge that forms is sim­i­lar to what you find on a burnt fry­ing pan. That is not good for any en­gine.

In all other sit­u­a­tions, even sus­tained high-speed cruis­ing on Malaysian high­ways, there is in­evitably a pe­riod of low-speed driv­ing be­fore park­ing the car or switch­ing off the en­gine.

That is suf­fi­cient for the en­gine oil to cool to a level that will not dam­age the tur­bocharger bear­ings.

Also, al­ways en­sure that you are us­ing the rec­om­mended grade and vis­cos­ity of en­gine oil for your tur­bocharged car. At my turbo sa­loon’s last rou­tine ser­vic­ing, the work­shop re­placed the air fil­ter. Is the re­place­ment re­ally nec­es­sary? As its name in­di­cates, the air fil­ter in the en­gine com­part­ment serves to fil­ter the air that is drawn into the en­gine.

It is im­por­tant that air en­ter­ing the com­bus­tion cham­bers is clean, not only to max­imise the oxy­gen con­tent, but also to pre­vent any abra­sive in­fil­tra­tion that could have an im­pact on the cylin­der walls.

There are plenty of minute air­borne par­ti­cles and soot in the air, and the fil­ter stops th­ese for­eign par­ti­cles from en­ter­ing the in­take man­i­fold and hence the com­bus­tion cham­bers.

Over time, the fil­ter gets choked, and while it may con­tinue to stop dust flow­ing in, the spa­ces that al­low clean air to en­ter will be­come re­stricted.

A dirty air fil­ter can cause loss of power and an in­crease in fuel con­sump­tion.

Air fil­ters are rel­a­tively in­ex­pen­sive (usu­ally cost­ing less than $200) and it would be ad­vis­able to re­place them at least ev­ery 25,000 kilo­me­tres.

You could also clean the fil­ter with a vac­uum cleaner. If your air fil­ter is the wash­able type, you can wash it with an air-fil­ter de­ter­gent that you can buy from ac­ces­sory shops.

Most orig­i­nal air fil­ters are not wash­able, but there are wash­able re­place­ment fil­ters which cost a lit­tle more.

Use the rec­om­mended grade and vis­cos­ity of en­gine lube for your tur­bocharged ve­hi­cle.

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