Originally Posted by
invrtd
7 min is unheard of where I race. I am running 032 header and 9886 and only getting about 4:45. And most other racers are only getting about 5min. But I am running on a large track. I know the 9886 is a gas hog. Will have to do some testing with 2015 when I get back home with maybe an OS 70mm header. Will also test OS 70mm header with 2060 since I have that pipe too. I am running HB GT with OS XZ-b engine right now. Will be moving to GT specific engine when I get back and thinking the R21 is a good option since I don't run GT all the time. I did read on OS web page the newest OS GT engine got the new 22E carb that is advertised to get better run time.
Long track with sustained full throttle use and a high rpm setup will use more fuel than tracks with shorter straights. Perhaps look into changing your gear ratios to smaller spurs if you can when you test with the 2060 and OS header. It will shift the power band lower than the 41032 / 9886 combo. (kinder on the rod too!). This will make more difference to fuel economy than the carb. The engine and pipe dictate how much fuel it needs.