▁that ▁there ▁is ▁a ▁short ▁injection ▁delay ▁when ▁inject ing ▁b iod ies el . ▁This ▁injection ▁delay ▁was ▁attributed ▁to ▁the ▁greater ▁vis cos ity ▁of ▁B iod ies el . ▁It ▁was ▁noted ▁that ▁the ▁higher ▁vis cos ity ▁and ▁the ▁greater ▁cet ane ▁rating ▁of ▁b iod ies el ▁over ▁traditional ▁pet rod ies el ▁lead ▁to ▁poor ▁atom ization , ▁as ▁well ▁as ▁mixture ▁pen etr ation ▁with ▁air ▁during ▁the ▁ign ition ▁delay ▁period . ▁Another ▁study ▁noted ▁that ▁this ▁ign ition ▁delay ▁may ▁aid ▁in ▁a ▁decrease ▁of ▁NO x ▁emission . ▁ ▁Em issions ▁Em issions ▁are ▁inher ent ▁to ▁the ▁comb ust ion ▁of ▁dies el ▁fu els ▁that ▁are ▁reg ulated ▁by ▁the ▁U . S . ▁Environment al ▁Prote ction ▁Agency ▁( E . P . A .). ▁As ▁these ▁em issions ▁are ▁a ▁by product ▁of ▁the ▁comb ust ion ▁process , ▁in ▁order ▁to ▁ensure ▁E . P . A . ▁comp liance ▁a ▁fuel ▁system ▁must ▁be ▁capable ▁of ▁cont rolling ▁the ▁comb ust ion ▁of ▁fu els ▁as ▁well ▁as ▁the ▁mit ig ation ▁of ▁em issions . ▁There ▁are ▁a ▁number ▁of ▁new ▁techn ologies ▁being ▁ph ased ▁in ▁to ▁control ▁the ▁production ▁of ▁dies el ▁em issions . ▁The ▁exhaust ▁gas ▁rec ir cul ation ▁system , ▁E . G . R ., ▁and ▁the ▁dies el ▁partic ulate ▁filter , ▁D . P . F ., ▁are ▁both ▁designed ▁to ▁mit ig ate ▁the ▁production ▁of