Nitro Engine Tuning
Engine tuning on 2 stroke engines is a bit of a black art, having many routes to achieve your goal.
Let’s start with basics: Exhaust timing raises power band on a 2 stroke engine, but with too high timing comes a loss of torque. With modern boat set ups and remote adjustable pipe movers, you have the best of both worlds being able to adjust pipe length whilst in motion and under load.
Induction timing is another critical part of a 2 stroke engine for power gains. Closing the timing later and/or opening earlier can increase power, but this has to be balanced with transfer port time and exhaust. For example, too high exhaust or late closing induction can cause engine bogging and the higher the tuning the more temperamental an engine can become. But when you get it right you can get more torque and rpm and bhp.
Torque is key in model boats as it allows you to swing bigger or higher pitch props. With high nitro content fuel, you can gain a lot of torque and can raise other timings for improved performance.
Head squish is also a power gain area, but too high a squish will result in power loss, but the engine may rev higher. If the cylinder head volume is not correct, this will cause detonation, (Visible pitting on the head and piston) and too low squish will cause a loss of performance. A correct volume head with high nitro and correct engine timings will give you a powerful motor.
High nitro content above 50% will sound like the engine has a misfire and it will be more critical to set up.
Lots of different people have ideas on tuning, but another critical part of power on a 2 stroke engine is the tuned pipe. Without this being correct you will not generate power or will not run right.
It’s all a balancing act to get the best boat performance – Pipe, fuel, gearing, props, engine mods.
Engine bogging can be seen quite often. Too high a timing of ports or the pipe being too short can cause this. Testing is the key to getting everything working together.
There are various engine tuning programs available for example Prestwich can supply one.
For tuning, typically you will need a Digital Vernier, Dremel with diamond burrs and polishing stones.