@ I’ve just finished building a Mk5 van but there are a few things I need to tie up. It’s a 2007 model with a Z20LEH, steel rods, high flow inlet, intercooler, exhaust and a GT turbo and so on. It’s been mapped by a local lad and it’s struggling to make decent figures. In fact, it’s a total disappointment. It did 315bbhp and just didn’t seem to want to pull any harder and the lad pretty much shrugged his shoulders and said it was something that I’d done wrong. I’m gutted as I was hoping it’d crack 350bhp easily so any ideas on what to do? Cheers, Gavin.
AWe’d be inclined to agree with you, 315bhp is far below what a good Garrett based set up can produce so there is something amiss. First, we’d perhaps question the mapping skills. Given the relatively poor results, we’d pretty much expect any mapper worth his salt to be able to look at the data and advise where the issue lies so with little feedback, we’d recommend a trip to a reputable dyno and have the van checked over and fairly urgently as there could be some serious fuelling issues that could cause lasting damage. Said issues could be down to a hardware issue or indeed, the software which is why we always preach that cheap ‘custom’ map outfits should best be avoided.
Beyond this it would be pure speculation on our part but it’s worth considering factors such as the air flow meter, lambda sensor, the 2.5bar map sensor may be maxing out (a 3 bar one with appropriate ECU adjustment would be better suited) and the injectors may be too big and in turn creating a very rich mixture. There are simply too many factors for us to be able to provide a definitive answer but we’d certainly expect figures pushing towards 400bhp using a GT2871RS or similar. There are numerous Vauxhall tuners out there, a quick Google search will soon reveal those who are well respected so we’ll refrain from being specific but any will be able to diagnose, advise and hopefully round up those missing horses for you.