10 minutes is always my target run time. The last two motors (NR p5xst and the NR +4) had no trouble reaching this goal. Of course I do run PTM modded engines. Mods are not always for raw power but can include efficiency.
Things you can do include:
Good motor/pipe combo - I am a big NR fan
Proper plug and Tune. Brand of Fuel can also alter runtimes. I run Byrons Gen2 30%.
Trigger finger - I would reduce the EPA on the throttle. This was a tip that I got from a Pro driver and immediately showed results on the track. I usually only let my carb open up 40-50%. I usually set this according to the "Big Jump" on the track I am running. Also try to pay attention to how you execute the trigger. Try using a quick rolling verse just squeeze it.
Drivetrain - Make sure the drivetrain is as smooth as it can be. Diffs, bearings, brakes, mesh. anything that would increase drag or resistance.
Smaller insert - This can tame down the low end power and increase fuel economy. If a track is real loose this can help on the bottom end with wheel spin. The more wheel spin you are experiencing the more fuel wasted.
Personally I do not run any extra filters or extened fuel line.
Thats all I can think of ATM. If the engine is still tight then over time your fuel economy will increase with proper tunning.
Rumor has it the NR +4 is capable of around 13 min. runtime. I have not experience that yet but is a goal I am working on.
Good Luck
