Events10 things you need to know about rotary tuning
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10 things you need to know about rotary tuning
by Admin Thu Jul 04, 2024 2:02 pm
10 things you need to know about rotary tuning
1. A rotary has half the available processing time of a piston engine. It means you have to inject the required amount of fuel and charge the ignition coil in half the time (approx 10 milliseconds at 6000rpm) compared to an equivalent piston engine. It’s important to check that your ECU is capable of interfacing with the factory Mazda crank angle sensor, supports staged injection, allows you to tune the end of injection angle and ignition split angle as well as supporting the rotary engine cycle itself.
2. Remember that as the revs climb the demand on your fuel and ignition system increase. Make sure your fuel/ignition system is capable of providing enough spark and fuel to the engine at high rpm. Your fuel/ignition system needs to be bigger/more powerful than on an equivalent piston engine as it needs to provide the same amount of fuel/spark in half the time.
3. Running lean and engine misfire are the enemies of a rotary engine – avoid them at all costs.
4. Rotary engines use two spark plugs per rotor, a leading and a trailing spark plug. The leading plug (mounted lower in the rotor housing housing) ignites up to 95% of the air/fuel mixture providing most of the power. Trailing plug (mounted above the leading plug) fires 10-15 degrees after the leading plug and completes the combustion providing a more uniform flame front across the rotor face.
5. Ignition Split Timing is the angle the trailing plug fires after the leading plug. The lower the split timing the more chance of engine damage. Typically, setting your entire split map at 10 degrees will yield good results with the least chance of engine damage.
6. Remember that your rotary ignition map won’t look like its piston engine equivalent. Don’t chase the power by adding ignition timing as the rpm increases. The timing should only increase a few degrees across the whole rev range.
7. Diagnosing ignition problems on rotaries is difficult as a misfire is not clearly audible. A quick way of diagnosing an ignition problem is by disabling the trailing spark plug by unplugging its ignition module and putting the engine under load. If there is a problem with the leading plug, a run on a dyno will reveal an ignition misfire.
8. Most rotary engines like to idle at at Air/Fuel ratio of 13.5 – 14:1. As the engine approaches atmospheric pressure, target A/F ratio of around 11:1 is recommended. On boost, your A/F ratio should be around 10.5:1.*
9. Most rotary engines should be happy with an injection angle of 270 degrees under cruising conditions and 330 degrees at the rev limit.
10. Don’t lose power at the top end of your RPM range. Providing everything attached to the engine is sized correctly and working properly, your power curve should come up to full power and hold close to this power until the rev limit. If the power starts dropping before max RPM check your injection angle.
1. A rotary has half the available processing time of a piston engine. It means you have to inject the required amount of fuel and charge the ignition coil in half the time (approx 10 milliseconds at 6000rpm) compared to an equivalent piston engine. It’s important to check that your ECU is capable of interfacing with the factory Mazda crank angle sensor, supports staged injection, allows you to tune the end of injection angle and ignition split angle as well as supporting the rotary engine cycle itself.
2. Remember that as the revs climb the demand on your fuel and ignition system increase. Make sure your fuel/ignition system is capable of providing enough spark and fuel to the engine at high rpm. Your fuel/ignition system needs to be bigger/more powerful than on an equivalent piston engine as it needs to provide the same amount of fuel/spark in half the time.
3. Running lean and engine misfire are the enemies of a rotary engine – avoid them at all costs.
4. Rotary engines use two spark plugs per rotor, a leading and a trailing spark plug. The leading plug (mounted lower in the rotor housing housing) ignites up to 95% of the air/fuel mixture providing most of the power. Trailing plug (mounted above the leading plug) fires 10-15 degrees after the leading plug and completes the combustion providing a more uniform flame front across the rotor face.
5. Ignition Split Timing is the angle the trailing plug fires after the leading plug. The lower the split timing the more chance of engine damage. Typically, setting your entire split map at 10 degrees will yield good results with the least chance of engine damage.
6. Remember that your rotary ignition map won’t look like its piston engine equivalent. Don’t chase the power by adding ignition timing as the rpm increases. The timing should only increase a few degrees across the whole rev range.
7. Diagnosing ignition problems on rotaries is difficult as a misfire is not clearly audible. A quick way of diagnosing an ignition problem is by disabling the trailing spark plug by unplugging its ignition module and putting the engine under load. If there is a problem with the leading plug, a run on a dyno will reveal an ignition misfire.
8. Most rotary engines like to idle at at Air/Fuel ratio of 13.5 – 14:1. As the engine approaches atmospheric pressure, target A/F ratio of around 11:1 is recommended. On boost, your A/F ratio should be around 10.5:1.*
9. Most rotary engines should be happy with an injection angle of 270 degrees under cruising conditions and 330 degrees at the rev limit.
10. Don’t lose power at the top end of your RPM range. Providing everything attached to the engine is sized correctly and working properly, your power curve should come up to full power and hold close to this power until the rev limit. If the power starts dropping before max RPM check your injection angle.
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