Just for your information gents, as many of you will know we spent countless hours developing our dpf removal kits. I can confirm that on the e90 330d 231hp and 335d 286hp models that fitting the downpipe to a stock car with no software modifications results in a loss of power, not to mention outrageous turbocharger behaviour.
The reason this happens is simple, the reduction in backpressure causes the boost to reach its set limiter much earlier and as power on the diesel vehicles is controlled by injection two things happen here to protect the vehicle... the car will adjust the vanes very slightly(or wastegate depending on model) and reduce injection to limit the boost pressure... A direct result of this is a loss of power.
The DPF flows reasonably well when not blocked but the bigger issue is exhaust gas temperatures... as these particular models have the DPF bolted straight to the turbo, the heatsoak causes EGT's to climb...this has a direct affect on turbo and charge air temperatures.
The engine management system has injection limiters based on exhaust gas temps, intake air temps, backpressure levels etc... limited injection = limited power :-)
I hope you don't mind my input but having invested 500hours plus of dyno time on these models, perhaps this can take some of the guesswork out of it. I'm happy to provide any information that you feel may be helpful.
Last edited by ecotuneuk; 12-09-2012 at 06:43 AM.