Down grade nitro ?
 

I have heard that if you ran 20% nitro in your engine you cant downgrade to say 5% or 10% but you can go up to 25 or 30% how much truth is in this ?

RE: Down grade nitro ?
 

There's no reason why you cannot run 10% if you've been running 30%. I have a Saito 72 that was always run on 30%. It now is used with 10%. It runs just fine

I'm sometimes opportunistic and run whatever fuel is the best deal. I swap back and forth between 10%, 15%, and 20% all the time with most of my engines.

RE: Down grade nitro ?
 

no truth. Urban myth

RE: Down grade nitro ?
 

The original wisdom applied to ABC type engines, where the piston and rod needed to bed in at temperature. If there ever was any truth to this, I don't think it applies to ringed 4-strokes.

RE: Down grade nitro ?
 

Actually it's more like the original myth started with ABC type engines :). Somehow everyone got onto this "you gotta run 'em HOT so all the bits will fit proper" which got someone to think that maybe lots of nitro would make them run hotter so the fits would wear in to suit. Then if you go to lower nitro it'll run cooler and the fits will change again and make it useless for the higher nitro. This doesn't happen but it makes a good story and eventually the story evolved into saying that as your ABC wears out you just go to lower and lower nitro levels so it runs cooler and cooler to keep the tight fits. But it's just a story.

In other words, to quote djlyon, "no truth. Urban myth" :D

RE: Down grade nitro ?
 

If this myth were a truth, then breaking in an ABC engine on glow then converting it to Diesel operation would be a very bad thing to do. But, converting an ABC engine to Diesel operation happens to be a very good thing to do.

RE: Down grade nitro ?
 

Roofer,


It is the other way around...

If an engine is designed to run on no-to-low nitro, having very high C/R (Rossi amd MVVS engines, for example) trying to run them on high nitro will result in anything from just running like a dog, to massive engine damage...

High nitro fuels require a lower C/R, so adding a head shim to a high compression engine will allow using more nitro.

Even if an engine is designed to run on 20-30% nitro, it will not run on 60%... You'll have to reduce the C/R even further.