The big bang the­ory

Herald Sun - Motoring - - Ask Smithy -

BLASTED PEST Re­cently, when I tried to start my 1998 Toy­ota Land­cruiser Prado on LPG, there was a large ex­plo­sion and the air box was blown apart. I have since learnt that this is not un­com­mon for ve­hi­cles fit­ted with LPG sys­tems and the con­di­tion of spark plugs and leads is crit­i­cal. These were re­placed only 12,000km and 20,000km ago. Hav­ing also re­placed the air box, what can I do to pre­vent this hap­pen­ing again?

Peter Mann, e-mail.

The ex­plo­sion is a re­sult of the air and LPG mix­ture in the in­take man­i­fold ig­nit­ing, most likely set off by a stray spark. Change the plugs and plug leads again. They are the usual cause of this prob­lem.

RID­ING HIGH I read some time ago that you should in­flate your

tyres 3 to 4psi above the pres­sures rec­om­mended by the ve­hi­cle man­u­fac­turer, as they spec­ify a lower fig­ure to give a softer ride. Do you agree?

James John­son, e-mail.

The tyre pres­sure that is spec­i­fied by the car­maker is one that gives the best blend of han­dling, brak­ing, ride com­fort and tyre life. In other words, it’s a bit of a com­pro­mise. By set­ting the tyre pres­sure a few psi above the rec­om­mended pres­sure you can usu­ally im­prove the tyre life, fuel econ­omy and the han­dling— but at the same time, you’ll make the ride less com­fort­able.

IT’SNOGAS I rec­om­mend any­one think­ing of con­vert­ing his or her car to LPG to think again. I con­verted a 2003 VY Com­modore V6 to LPG af­ter be­ing told by my dealer not to, and have had noth­ing but trou­ble ever since. I’m now run­ning on petrol and don’t have a prob­lem, but I’m a few thou­sand dol­lars down the drain. I say stick with petrol; our cars were not de­signed to run on LPG.

Pa­trick de Zilwa

It is un­for­tu­nate that you have had a bad ex­pe­ri­ence with LPG, be­cause your car is one that con­verts well and thou­sands of mo­torists have done it. But it is worth­while talk­ing to sev­eral con­vert­ers and own­ers who have made the switch to get their first-hand ex­pe­ri­ence of any trou­bles they might have had.

SPEEDO CHECK

I have noted that the speed in­di­cated on my GPS dif­fers by as much as 4km/h from that show­ing on the speedo of my car, and it is al­ways less. I have read that this is nor­mal. Which one is cor­rect?

John, e-mail

I can’t say ei­ther is

‘‘ cor­rect’’ but the speed shown on the GPS is prob­a­bly the more ac­cu­rate one.

Boom­times: APrado LPG con­ver­sion has­madeit a blast for all the wrong rea­sons

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