DIESEL DO NICELY

Performance Vauxhall - - QUESTIONS & ANSWERS -

@ I’ve just bought a Astra Mk5 CDTi 150bhp with the X-Pack, black leather in­te­rior, two lady own­ers, it’s re­ally fast and can keep up with new VXRs. How do you get it up to 240bhp like 888 diesels? Michael

AGood choice of car and they have loads of po­ten­tial, plus are still ca­pa­ble of re­turn­ing ex­cel­lent MPG fig­ures and re­li­a­bil­ity if looked af­ter. It could be ar­gued that the de­ci­sion to bor­row th­ese lumps off the Ital­ians was one of Vaux­halls best de­ci­sions. They do go well, how­ever a new VXR would make it look very silly in­deed so we’ll opt for the de­fault “he wasn’t try­ing” re­sponse as the new VXR is a very quick car. To put it in to per­spec­tive, the CDTi will hit 60 in 8.4secs, the new VXR will do it in 5.9secs. The CDTi will do 130mph flat out, the VXR is 155mph on pa­per and re­puted to be good for 160 and more… it’s one of the quick­est in its class.

Tak­ing a CDTi to 240bhp like the 888 diesels is also a bit far-fetched. For a start the 888 CDTi was 200bhp, not 240bhp and get­ting a diesel to 240bhp, whilst pos­si­ble, is nei­ther cheap nor easy. A remap, in­ter­cooler, ex­haust, hy­brid turbo and even at that you may just crack 200bhp. There was al­ways talk of re­designed man­i­folds and such like but ul­ti­mately, the M32 boxes aren’t too keen on the huge torque fig­ures such mod­i­fi­ca­tions bring. Many have tried and some have re­move the O2 sen­sor so that it runs rich and it will bang. I have tried this and still no pop­ping or bang­ing. I don’t re­ally want spend loads on it as it’s had too much money on it al­ready. Thanks in ad­vance. PS the O2 sen­sor is now back in. Steven. suc­ceeded but get­ting 240bhp from the CDTi unit is not an easy task. A re­li­able 180bhp to 200bhp along with chas­sis and brake up­grades would be the bet­ter pack­age. That said, a new VXR would still tear it a new one… and that’s be­fore any­body men­tions tun­ing pack­ages.

ANot quite sure where to start with this one to be hon­est… yes, some cars will nat­u­rally pop and bang, and with highly tuned, ag­gres­sively mapped cars it comes with the ter­ri­tory. There are a few rea­sons why a car will do it but it’s more com­monly at­trib­uted to un­burnt fuel, valve over­lap, map­ping and an un­si­lenced ex­haust sys­tem. Some big power en­gines will pop and bang as they will be fu­elling heav­ily at the top end to match but thus can’t back the fu­elling off enough on closed throt­tle, so tend to ‘bang’ as the ex­cess fuel ex­its the cham­bers through the hot man­i­fold. It sounds in­cred­i­ble on your Wortec equipped Monaro VXR or highly strung XE on throt­tle bod­ies.

How­ever, on a 1.6 Astra… less in­cred­i­ble and the fact some generic maps are of­fered that ac­tu­ally over­fuel the car on pur­pose, purely to try and im­press Chantelle out­side Maccy D’s, is a bit wor­ry­ing. Dis­con­nect­ing X, Y or Z is a ter­ri­ble idea… not only will the fuel econ­omy suf­fer, but un­burnt fuel burns cat­a­lysts, gums up the fuel sys­tem and also re­duces power. It’s right up there with fake brake discs as far as good ideas are con­cerned so we don’t con­done such an­tics and would in­stead sug­gest money is spent else­where. Nor­mally as­pi­rated, small ca­pac­ity en­gines that were de­signed for re­li­a­bil­ity and econ­omy need not pop and bang.

Want ‘pops and bangs ‘ from a small ca­pac­ity N/A en­gine... look else­where

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