CAR­BON BUILD-UP

Car (South Africa) - - TECH -

Many man­u­fac­tur­ers are now em­ploy­ing di­rect-in­jec­tion petrol en­gines. While do­ing some re­search on this tech­nol­ogy, it ap­pears that, af­ter a few years, own­ers will en­counter some se­ri­ous is­sues due to car­bon build-up on the in­let valves. This will prob­a­bly hap­pen as soon as the war­ranty ex­pires and will not be a cheap re­pair. What re­course does the owner have, as this is essen­tially a de­sign flaw? FREDDIE VAN LEEUWEN Via email It’s an in­ter­est­ing ques­tion and we’re plan­ning a tech ar­ti­cle on the sub­ject for a fu­ture is­sue (also see page 114 for a hu­mor­ous in­sight).

With the in­tro­duc­tion of di­rect in­jec­tion, car­mak­ers and oil com­pa­nies have been work­ing to­gether to find a solution to the car­bon build-up on in­let valves. The fuel in port-in­jec­tion en­gines car­ries the nec­es­sary de­ter­gent prop­er­ties to keep the valves clean. The solution was an ad­di­tive for the oil de­signed to leak past the valve stem seals (in minute quan­ti­ties) to keep the in­take valves clean.

This has mostly solved the prob­lem but, wor­ry­ingly, car­bon build-up is still present in some en­gine de­signs. It may lead to a drop in en­gine per­for­mance and drive­abil­ity prob­lems but would rarely de­stroy an en­gine. We doubt man­u­fac­tur­ers would cover dam­age out­side war­ranty, though.

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