Vauxhall Astra Remap

Vauxhall replaced the Astra J with the K in 2015, and the two respond differently to the same work. The J, sold here from late 2009, carried the Isuzu-derived 1.7 CDTi, the 2.0 CDTi 165, the 1.4 Turbo and the 1.6 SIDI Turbo petrols and the 280PS VXR, and it picked up the 1.6 CDTi Whisper Diesel late in its own life as the 1.7's replacement. The K kept that 1.6 CDTi, added a 1.0 three-cylinder and a new 1.4 turbo four in place of the J's earlier one, and from around 2019 the facelift brought PSA-derived 1.2 petrol and 1.5 diesel units.

Plate years get you most of the way there. Broadly, a 59 to 15 plate is a J and a 65 to 71 plate a K, with one large exception: the Astra J GTC three-door carried on alongside the K until 2018, so a 16 or 17 plate GTC is still a J. A 22 plate onward is the Stellantis-based Astra L. The generation matters because Vauxhall claimed a saving of up to around 200kg on some K variants, so the same torque figure is moving less car. A 2015 registration is the awkward one, because build month decides it and the two take different files.

The 1.7 CDTi is an Isuzu-derived unit that Vauxhall used for a long time, and it shows its age. It is coarser, it is unhappier on short journeys, and by now the EGR valve and cooler on most of them have carboned up at least once. We will still map a healthy 1.7, but we are deliberately cautious with it and would rather under-promise on a tired example than sell a headline number. If the injectors are still the originals at high mileage, that is the conversation to have first. Injector correction values read on a road test tell you more about whether £220 is well spent than any brochure figure does.

The 1.6 CDTi that replaced it, sold as the Whisper Diesel, is a genuinely better engine and the better candidate. The 136bhp version runs 320Nm as standard and takes 380Nm at Stage 1, and because that torque arrives low down it fills in exactly where an Astra is normally short, pulling from about 1,500 to 2,500rpm in fourth or fifth. Telegraph Hill northbound on the A380 is the local test: a standard 136 typically wants fourth about two thirds of the way up, and in our experience a Stage 1 car will hold fifth. It starts out quieter than the 1.7 and it stays that way afterwards.

The A14NET 1.4 Turbo in the Astra J and the 1.4 Turbo 150 in the K share a badge and not a great deal else. The K car runs 245Nm as standard and roughly 290Nm at Stage 1, and it is doing that in a noticeably lighter body, so the mid-range change between about 2,000 and 4,000rpm genuinely alters how the car drives. The J's A14NET starts from a lower base and gains proportionally more on paper while hauling more weight, so it ends up feeling livelier rather than quick. On an A14NET we also want the cam cover breather and the plastic coolant outlet looked at, because both are well-documented weak points and both spoil the idle quality of an otherwise good map.

Which of the two is worth £220 is a fair question, and the answer differs. A K 1.4 Turbo 150 that sees the A38 and A380 regularly is a sound spend. A J 1.4 Turbo doing school runs and town miles is not, because you will not see the fuel back and the car is not light enough to feel transformed by 45Nm. The 1.6 SIDI Turbo and the VXR are a different case again: they put respectable power through the front wheels, and worn front tyres on a wet Devon lane will find the traction limit long before the engine does.

Astras went to fleets and to Motability in enormous numbers, so the used population splits neatly in two. One is the ex-rep 2.0 CDTi with 140,000 motorway miles on it. The other is the ex-Motability car with 45,000 miles, a full main-dealer history and a life made up of three-mile journeys. Owners assume the first is the risk. In our experience it is usually the second, because it is the one whose DPF has spent years part-loaded and part-regenerated and whose EGR has never been hot enough for long enough to keep itself clean. On an Astra, journey length tells you far more than the odometer does.

That is why the diagnostic here is a paid service and not a free health check thrown in to win the job. On an Astra it earns its money: DPF differential pressure and the stored regeneration history on a K, injector correction values on a high-mileage 1.7, boost and EGR readings, and a road test with the window down listening for M32 bearing noise. If the real complaint is a limp mode, a warning light, or a regeneration the car never finishes, a remap will not fix it and can hide it for a while, which is worse than leaving it alone.

Where the filter itself is the problem, that is an off-vehicle job. DPF cleaning starts at £210 at our Totnes workshop, with Devon-wide collection and return, or from £230 by post if you are further afield. We clean filters off the car in the workshop only, so there is no mobile option for that part of the work. The remap is the part we can bring to you.

The M32 six-speed manual fitted behind a lot of the higher-torque Astras has a well-documented bearing weakness, and the test is not subtle once you know what to listen for. The whine changes pitch when you change gear at the same road speed, it is usually loudest in fifth and sixth, and it fades away when you coast in neutral. If yours does that, adding 60Nm is not the right next move, and we would rather send you to a gearbox specialist first than take the booking. A healthy M32 is not a fragile thing, and plenty of Astras have already had the uprated bearing kit fitted. If yours has, tell us, because it changes the answer.

The clutch is something to plan around rather than worry about separately, because on an Astra it comes out with the gearbox. If the M32 needs bearings, the clutch is very nearly free labour and should be done while the box is on the bench. The reverse is the expensive mistake: paying for a clutch on its own while the gearbox is already whining means paying that labour twice inside a year. On automatic cars, the six-speed torque converter Vauxhall fitted is not in the class of the eight-speeds used in larger rear-drive cars, so on a high-mileage auto we keep the torque request conservative rather than chase the headline figure, and we say so when we quote.

This is the question people actually want answered, so here is the arithmetic rather than a slogan. A 1.6 CDTi covering 20,000 miles a year at roughly 55mpg gets through about 1,650 litres. Lift that to roughly 60mpg and it uses about 1,515, so the saving is in the region of 140 litres over the year, which depending on the pump price is broadly in the region of the £220. Do that sort of mileage and it should pay for itself inside the first year or so, assuming you get the gain and do not spend all of it on the throttle. The ecoFLEX cars are where the economy gain tends to be most real, because their taller gearing already has them lugging low down and the extra torque lands in that hole.

Cover 7,000 town miles a year in a 1.4 Turbo and it is not going to pay for itself in fuel, and we would not pretend otherwise. A remap also rarely adds anything to what an Astra is worth when you sell it, and some buyers will be put off by it. On a car with a slipping clutch, a loaded DPF or no service history, the same £220 does more good spent on the fault. Where it makes real sense is a sound, well-serviced diesel you intend to keep for another few years. Stage 1 starts at £220, and the original file is always backed up so the car can be returned to standard.

Insurance is the cost people forget, and on an Astra it swings hard depending on which one you own. A 1.6 CDTi sits in a modest group and a declared Stage 1 map is usually a small adjustment to the premium. The 1.6 SIDI Turbo, and the VXR in particular, are rated far higher before anyone mentions modifications, and that is where a declared map can change the number materially. Get a quote for the modified car before you book, not after. Our Stage 1 maps leave the DPF, EGR and emissions hardware in place so the car MOTs as normal, and we do not remove emissions equipment from road cars for anyone.