mtruex

i was reading this article about a rossi pirahna 21 engine, there is a high nitro and low nitro head button that comes with it..im interested in the difference in them if anyone knows or has experience with this engine..ive been having a problem with my os vzm doing exactly what he talks about in the artice with the low nitro head..glow plugs looking new and shiny but elements broken with 60 % nitro.. heres the link. http://findarticles.com/p/articles/m...02/ai_n9211520

ryan_t888

Run a cold plug when using high nitro.

Ryan

mtruex

i am.....

ryan_t888

Have you tried adding shims to lower compression for higher nitro?

Ryan

jetpack

My Feedback: (1)

A low-nitro head has more compression, and if you use 60% nitro it will pound out the element. Blowing out new elements is one of the signals when the compression ratio is too high in any configuration.

As you go up with nitro you go down in compression and your letting the nitro make the power, not the compression. You begin to "blow" fuel through the motor in more of a pin-wheel fashion letting the higher rpm's do the work - same power with less of a piston load through less compression and more violent fuel. This is what also causes a less sensitive needle as you go up in nitro.

rageman

It sounds like there is a power limit beyond which you can not go with an engine. Increase power with more nitro but have to simultaneously reduce power by reducing the compression ratio to allow the use of the higher % nitro. I think the term is " Catch 22"?

Does anyone know the proper path to obtain a sum total gain in hp in this secenario?

Or am I reading this all wrong?

Dan S

its not that your losing power with less compression, its that the higher nitro requires les compression to detonate, if you keep your compression to high you will have pre-detonation.

Dan.