PORSCHE TECH­NI­CAL TOP­ICS

911 Porsche World - - Contents -

Tech­ni­cal prob­lems solved

A few months ago I de­scribed within these pages how 997 Car­rera owner Michael Frith ben­e­fited from an in­spec­tion of his car dur­ing an open day at the Dove House Mo­tor Com­pany, dur­ing which it was found that a re­place­ment battery had pre­vi­ously been in­stalled in such a way that it could have been vent­ing po­ten­tially dan­ger­ous fumes into the cabin air in­take. (The breather tube had not only been left off the new ac­cu­mu­la­tor, but also trapped and thus de­ci­sively squashed be­neath the cas­ing.)

I was re­minded of that while chat­ting more re­cently to Steve Mchale at JZM (jzm­porsche.com) about mod­ern DFI fuel in­jec­tors, and the re­sult­ing car­bon de­posits that can build up on the backs of the in­let valves in cars thus equipped. (See pages 72–76 of the June 2017 edi­tion.) In­evitably we started talk­ing about the as­ton­ish­ing com­plex­ity of all mod­ern Porsches – al­though Steve, to be fair, sees that more as a so­phis­ti­ca­tion that aids their main­te­nance and re­pair as much as I would view it as a pos­si­ble hin­drance – and then he proudly showed me the lat­est Porsche PIWIS III sys­tem testers that he and his tech­ni­cians are now us­ing. (Al­though they still have the older ma­chines, of course, for those cars that still need them.)

‘It was an­other sig­nif­i­cant in­vest­ment for us to make,’ he told me, ‘but if you are as se­ri­ous as we are about work­ing on any of the cars built after about 2008/2009 then you just have to have at least one of them. The ma­chines – and we have two – are linked in real time via the in­ter­net di­rectly to the fac­tory in Ger­many, and give us ac­cess not just to all of the car’s sys­tems and soft­ware, but also to every con­ceiv­able piece of tech­ni­cal in­for­ma­tion that you might need. Even to wiring di­a­grams that make fault­trac­ing as easy as fol­low­ing an Ord­nance Sur­vey map!’

The new ma­chines – each one about the size of a con­ven­tional lap­top PC, and able to con­nect wire­lessly to the car via Blue­tooth – make JZM one of the few spe­cial­ists able to ‘code’ new keys for the later ve­hi­cles, added Steve, and un­sur­pris­ingly that led us on to the cod­ing of their elec­tri­cal com­po­nents in gen­eral. Fit some­thing as seem­ingly straight­for­ward as a new head­lamp, for in­stance, and it will have to be en­abled to com­mu­ni­cate with the ve­hi­cle’s cen­tral sys­tem be­fore it will ac­tu­ally work. And if you think that is Porsche tak­ing the mickey, then con­sider this: you have to go through pre­cisely the same rig­ma­role with even an item as ba­sic as the battery.

‘To be fair, there is noth­ing phys­i­cally to stop you buy­ing an equiv­a­lent battery from what­ever source you like,’ said Steve. ‘And it will start and run the car with­out any prob­lem. But only the gen­uine Porsche item comes with the multi-digit num­ber that, when en­tered in the car’s mem­ory, al­lows the battery to “talk” to the main ECU, via the spe­cial con­nec­tion on the neg­a­tive lead, and with­out that there is no way of putting out the check light on the instrument panel. Fea­tures like the en­gine stop-start sys­tem will be dis­abled, too.’ Se­ri­ously? How long be­fore – ef­fec­tively as in the 991 al­ready, and to a sim­i­lar ex­tent in the Boxster and Cay­man – even the front-en­gined cars’ bon­nets are sealed shut at the fac­tory? You can see it com­ing, can’t you?

Un­sur­pris­ingly in light of their so­phis­ti­cated elec­tronic sys­tems, the lat­est Porsches re­quire even greater care than usual when work­ing on any as­pect of their elec­tri­cal sys­tems – and es­pe­cially when charg­ing a flat battery or us­ing a trickle charger. In this 991, for in­stance, the de­vice should be con­nected to the battery pos­i­tive lead/ter­mi­nal and an M8 screw threaded into this hole in the ad­ja­cent left-hand strut tower (ar­rowed). You might need a suit­able tap gen­tly to clean out the threads first, sug­gests JZM’S Steve Mchale. To jump-start this car, how­ever (and that is rec­om­mended only in cases of dire emer­gency), con­nect your pos­i­tive lead to the battery pos­i­tive ter­mi­nal, but then – and in this or­der – your neg­a­tive lead to the point pro­vided next to the right-hand strut mount (right)

JZM’S two new PIWIS III ma­chines, one of which is shown here in the safe hands of pro­pri­etor Steve Mchale (above), nat­u­rally re­quire a full un­der­stand­ing of their method­ol­ogy and many fea­tures, but in a way make the stag­ger­ing com­plex­ity of the later cars (al­most!) as easy to deal with as up­dat­ing your iphone. Op­er­a­tion is via key­board and/or touch­screen and sty­lus, and the ma­chine con­nects to the car via ei­ther a ca­ble or this wire­less de­vice plugged in to the ded­i­cated port un­der the fas­cia (right)

Mod­ern Porsches – that is to say those built after about 2008/2009 – have this ad­di­tional con­nec­tion (above) to their battery earth leads. Es­sen­tially it al­lows the car’s charg­ing sys­tem very pre­cisely to mon­i­tor the con­di­tion and out­put of the ac­cu­mu­la­tor, and even to dis­able in­di­vid­ual sys­tems that are not deemed safety-crit­i­cal if it de­tects the volt­age fall­ing be­low a cer­tain level – the en­gine stop-start fea­ture, for in­stance. It can also al­low rapid charg­ing by the ve­hi­cle’s own al­ter­na­tor, briefly push­ing up to 17 volts into the battery. Cru­cially, how­ever, it will func­tion only with a gen­uine Porsche battery, whose unique code num­ber has been pro­grammed into the car’s mem­ory via a so-called sys­tem tester

JZM’S tech­ni­cians al­ways con­nect a ‘buf­fer’ to the battery ter­mi­nals when car­ry­ing out any elec­tri­cal work – es­sen­tially a highly so­phis­ti­cated charger, in this case made by Bosch – and this is es­sen­tial when the car is hooked up to the sys­tem tester. The ig­ni­tion will be switched on, and many of the car’s con­sumer units in op­er­a­tion – and you cer­tainly don’t want any elec­tri­cal short­fall when tack­ling some­thing as crit­i­cal as cod­ing new sub-assem­blies

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