A lack of com­mon sen­sor

Herald Sun - Motoring - - Readers Write -

I ama re­tired elec­tronic en­gi­neer and I worry about ve­hi­cle speed be­ing mea­sured by in-road sen­sors (trans­duc­ers), be­cause there will be an er­ror fac­tor in­volved. Trans­duc­ers are prox­im­ity sen­sors de­signed to work in one di­men­sion only, in this case hor­i­zon­tally. They have been com­monly used throughout in­dus­try for decades, usu­ally as lumps or in­den­ta­tions on spin­ning rollers as they pass a fixed trans­ducer coil. But, as the roller bear­ing wears, the trans­ducer be­comes in­ac­cu­rate, be­cause an­other di­men­sion is added. The prob­lem with us­ing them in roads is that cars have ad­di­tional ver­ti­cal move­ment from their sus­pen­sion, which will change the trig­ger point for the trans­ducer. So the ideal speed trans­ducer would be a dead-flat road for ve­hi­cles with no sus­pen­sion move­ment. This may help ex­plain why some free­way speed cam­eras are al­ways in dis­pute. It is in­ter­est­ing that the over­head speed dis­plays on sev­eral free­ways are usu­ally out of ser­vice, so how bad are they?

Bar­ney Rum­ble, email You raise a very in­ter­est­ing point, and one we had not con­sid­ered. Per­haps other read­ers have more to add. PUL­SAR FAD­ING I own a 2005 Nis­san Pul­sar N16 which is ap­proach­ing 100,000km. The man­ual says the tim­ing belt needs to be changed but my lo­cal garage says they don’t have a tim­ing belt. Is this cor­rect?

KenLong­bot­tom, email The cam belt is prob­a­bly the most im­por­tant ser­vice item in any car, be­cause if it fails the engine is likely to dis­in­te­grate when valves hit pis­tons. Get it changed. Buy the parts from a Nis­san dealer if nec­es­sary and give them to your me­chanic. MOV­ING THE PEO­PLE I have been told you might be able to help me as I am­look­ing at buy­ing a peo­ple mover for a small busi­ness I have started. I amwant­ing to spend around $8000 and I like the look of the Holden Zafira 2003. What do you think about this, or do you have any oth­ers you would rec­om­mend?

Si­mon Main, email The Zafira is fine. More like a baby wagon than a peo­ple mover, which is why it was not a big hit in Aus­tralia. If you need some­thing big­ger, the best value is a Kia Carnival. THE i30 HAS IT I saw the new Hyundai i30 and was look­ing at the Hyundai web­site where I saw that the Elantra has the same 1.8-litre engine, with the same 110kW/178Nm. Is this the same car with a new body? And a sec­ond ques­tion, what do you think of base model Veloster 1.6 litre?

Maria Salsa, email The i30 is com­pletely new and the chas­sis is not re­lated to the Elantra. The Veloster is a fun lit­tle car and great value. AMG-WHIZZ I have a 2007 BMW535i four­door sedan and our lease is up. We are look­ing at the Mercedes-Benz C63 AMG. Could you let me know what you think about it as a fam­ily car?

Gab­byFar­ru­gia, email The C63 is a rip­per car. Def­i­nitely a step up from a 535 and some­thing that you will re­ally en­joy. But not as big in the cabin as a 5 Se­ries. NUM­BERS­GAME I am­look­ing to buy a used Re­nault Me­gane RS 250 Cup Trophee with about 4000km on the clock, but I have been in­formed that the RS 265 is now avail­able in Aus­tralia. Is it worth spend­ing the ex­tra money to pur­chase the 265 or stick with the 250?

Michael Bal­liro, email Save the money and go with the 250. The 265 is all at the top end and oth­er­wise the cars are pretty much iden­ti­cal.

Sign of the times: Over­head speed dis­plays

may be hit and miss

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