The Bosch VP systems allow a two stage injection. This along with the introduction of DI helped VW TDi become the best by far at the time! - in terms of economy and power. NOP 1 (nozzle opening pressure) is set to establish the combustion, NOP 2 then flows the majority of the fuel for the overall duty cycle. NOP 1 (nozzle opening pressure) and NOP 2 I can allow the injector to delivery fuel as it is needed. How should NOP1 & NOP2 presures be set in relation to nozzle size and expected power? Does anyone know the science behind this?....I'm interested!
All i know is that the pilot injection is to start the ignition process, so that when the primary jet comes in, it doesnt jolt the piston as much, so making the engine more fuel efficant and quieter, or so i understand it. With age for some reason the pilot injection lessons or disapears, so tge engine gets louder. Im not sure how they set the pilot injection on larger/performance nozzle setup, but i assume it is the same as the std nozzles.
There probably wasn't much mathematical science behind this from new, more of a try it and see approach, which for the home user would prove expensive. When your an OEM and have lots of dyno's engineers and test beds it was acheivable.
When i get my nozzles fitted and balanced they shoukd setup the pre burst too. Kerma tdi say they do this as a matter of course when they do nozzle upgrades, shame thier across the pond.
They have to set both pressures when done properly, Im sure united diesel in this country will do it too.
click here 28 each injector if you supply your own nozzles plus 12 return postage...124 plus the cost of your chosen nozzles, ouchy! I am very tempted to just fit my bosio nozzles to the spare set of injectors, fit them, see how it runs, check cylinder balancing, trim iq accordingly and go from there...
