Nitroaddict

Am I right in stating that a decrease in head shims or an increase in compression ratio will increase torque because as the compression ratio goes higher the actual ignition timing occurs sooner. In my opinion, this is the same effect that happens with a colder plug except in the instance of a colder plug the ignition is slowed until a greater point of compression build occurs. however there is a point of diminishing returns where detonation occurs or engine temps can soar this is where a colder plug can also help. This sound right?

Consequently, I am assuming the same effect occurs when you increase the head clearence. top end is enhanced as the ignition timing is retarded and occurs later. generally a hotter plug is needed to advance the ignition cycle so the timing does not occur to late in the cycle as at this point you end up overleaning the engine to get it to rev properly and the engine life will suffer dramatically.

So what I am asking - Is that if reduced shimming is done in regards to low end torque, will there be pre-detonation at high RPM? Will shim tuning need to be re-evaluated from one track to another?

proptop

My Feedback: (8)

Well, not to get nit-picky but, it's either pre-ignition, or detonation...Sorry, just had to get that out of the way, because I see it (pre detonation)too many times scattered around @RCU...Friends of mine who run 1/8 on road say they pick the fuel (nitro %, in their case 40%)and shim the comp. higher till it starts blowin' plugs, then back off a little... Increased comp. will give more torque because (generally) the B.M.E.P. goes up. That's Brake Mean Effective Pressure that works on the piston. Same thing, basically, occurrs if you start combustion sooner. These guys have a whole bunch of engines, and several combinations available for each track, so if you want to tune close to perfection w/ 1 engine, then you're gonna have to do a change of shim(s) and/or plug heat range(s) for ea. track, and substantial weather change, and keep a log book of what works, and what doesn't. Otherwise, I'd say go for the closest to max. you can get till she starts eatin' plugs, then come back on the comp. a little. A different brand of fuel can effect ign. timing too, w/ the % of oil (more oil retards the combustion, slows the flame front) to the % of methanol, and nitro. Nitro is an Oxygen bearing compound, so that's annother story in itself. Yada yada yada...If you want to really get into it, I can prob. find some interesting stuff in my tech. mannuals (A.M.T.) about the theory of combustion, chamber design, etc. etc. etc.

Nitroaddict

thanks for the heads up - since i am just running a single engine, it does propose a small problem, although all the tracks i race at are in FL, so weather shouldnt come into play too much. Yeah, any other tech info would be appreciated