Switching from 60% to 50% question...

[LeeWininger]

Looking to streamline our operation a bit and only run one fuel. Currently running CMB .45 Evos on 60%. Would anything other than needle setting need to be adjusted, like head clearance or pipe length, for optimal performance on 50%?


The other option would be switching the kids' RTRs to 60% from 50%, but not sure the Super Tigres would tolerate it for long.....

 

[Wasted wages]

I personally wouldn't go to 60% in the RTR's...
the ST's won't last long...
in fact, unless you are running for records, I would use 40-50% in everything. Big motors tolerate it better, and I don't see that much performance advantage versus plug consumption and parts breakage....
but that's just my .02

 

[Danny King]

Unless you are extremely fined-tuned to 60 you will not see much diff at all.

 

[Wasted wages]

Plus your needles will get super critical with higher nitro...my .21 rigger can go from too lean to too rich within 3 clicks on 65%...

 

[Tom Foley]

I noticed an immediate loss in torque , prop pulling ability when I went to 50 % . I had to run backcut props so I switched right back . Boat has twin .91's .

 

[Al Hobbs]

You probably will not have a ton of difference. Typically, you will adjust the needle, lengthen the pipe and go down on prop size; any or all to find the best result..

It is easier to find a needle the lower your nitro content, but you do give up some power and speed.

 

[bermudadude]

Big motors tolerate it better, and I don't see that much performance advantage versus plug consumption and parts breakage....
but that's just my .02
[/QUOTE]


actually the opposite is true. small engines run better on high nitro.
large engines it doesnt make much difference.

i started with k&b and 25% and had read the same but as i got into other stuff and felt the power and reliability increase with higher nitro i cant go back.

low nitro like 25% tends to over heat things but crazy water cooling can fix that .

21's and 45's even some 67's are just sad on less than 50.
also when u go up on nitro u go down on oil and that helps allot . also when u go down in size go down in oil
most people jetting problems with high nitro are because they didnt do anything to "fix" the engine. they come from a factory that tests on 0-5% . the stock needles are trash for 50+% carbs are useually too small too .
if ur not head hunting and just havin fun with the kids then a 45 with 50% is fine

 

[Wasted wages]

I should have clarified....

big motors tolerate 40-50% nitro better and I don't see that much performance advantage on 60 % versus plug consumption and parts breakage....
but that's just my .02

Yup.... the little motors run better on higher nitro...

 

[Tom Foley]

I should have clarified....

big motors tolerate 40-50% nitro better and I don't see that much performance advantage on 60 % versus plug consumption and parts breakage....
but that's just my .02

Yup.... the little motors run better on higher nitro...

I tell you these VAC .91s on 60 % with .011" - .012 " head clearance scream on 60 % ! Flow at 40 - 42 0n Boris double pump meter , 289 or 99 Odonnell and they are happy !!