Hi We are having a race here on the weekend were we are allowed to use 30% fuel we usually run 16% i was just wondering what i need to do to the engine to get the right performance out of it, when going from 16 to 30% fuel? (e.g re tuning, adding shims etc)

The engine is a JP FX12 Mod .12
The fuel is synthetic

honestly i've always run on 25% nitro....

i think there should be no problem changin nitro% ...but still u have to retune and maybe colder plugs

and don't forget more nitro means less lubricants....so better stay on the rich side a bit

a lot of magazines and hobbyists would say you would need to do a short break in period for your engine to "adjust" to the higher nitro content.

you may do that if you wish but just remember the important thing is that you will need to run your settings slightly richer than your current setting for higher nitro.

btw, higher nitro % does not mean less % in lubrication.

hello

what happens if you go from 20% to 16% in nitro ?

i have always run my engine on th esame fuel, would it hurt the engine changing to a lower nitro content for 1 race meet ??

There is a possibility that you will have to add a head shim, but you will have to determine that for yourself. This is for the guy going to 30%. Try emailing JP and ask them. They have always replied to questions very quickly.

I would add .2 head shim, # 7 plug (RB) & richen the top 1/8 of a turn. Use the first tank of fuel to tune & moniter temps. You will find that it will run cooler on 30% than 16%. Tune for performance & dont try & tune to get the same running temp you are used to on 16%. This is what I would do, other people may do it different with good results also.