General Information

The two stroke setting means that the firmware will inject the calculated amount of injector time in every stroke. Putting it off means that the injector time will be divided by 2. This will cause the tuning graphs to be twice as high. The advantage is that the graphs tune more easily and adjustments is 50% finer resolution. Especially for large injectors. A drawback is that 25 milliseconds maximum fueling is easily reached during accelerator pump function and might cause problems at tuning flat spots during blip conditions.

Another feature is the duel injector system. It can be tuned with a ratio adjustment or separate graph system which is discussed in this article. Note that the secondary injectors are compensated, on all the graphs except the lambda control. Also during cranking the secondary’s is not pulsed. During acceleration they will be pulsed even if the main graph for them is at zero.

Determining if coils are on the correct plugs.

Due to the duel spark plug system it is sometimes confusing to understand why some leads can be faulty. The rotary engine allows the leading plugs to be fired in wasted spark configuration. The reason is that the non-combustion rotor is still covering the leading plug with burned gas from the previous stroke. The trailing plug however is situated in the upcoming chamber when the other plug is fired, so it will ignite the fuel in the intake. Spitronics uses a different setup for the 3 coil wasted spark Leading coil pack. You connect both leading drivers on to the same wasted spark coil. Then it is Important to set the software to wasted spark as the firmware will then reduce charge time at high RPM to ensure that charge time does not overlap and that there is enough discharge time between charges. See the setting below.

Note: Should the “Wasted Spark Coil Per cylinder” be selected then the software will change it to Wasted Spark Coil Pack.

NOTE: Always use a colder spark plug on the trailing and one size warmer on the leading for instance NGK B10EG on trailing and NGK B9EG on the leading. This will help with detonation that can be caused by a warmer plug on the trailing do to heat glow on the intake cycle

To make sure that coils are setup in the right position, disconnect the drivers from the trailing coils. It is not good practice to pull off HT leads and let them spark in dry air. Reason is high voltage feedback may damage coil drivers. Now start the engine. There may be a 5% power loss but it should start easy and rev up smoothly. Get the timing light out and make sure timing is according to specs. Now disconnect the leading coils and reconnect the trailing coils. In the software set the maximum trailing degrees to zero as below. This will ensure that the trailing degrees fire the same time as the leading plugs. Now insert the trailing plugs onto their plugs. Again start the engine. If they are correct then the engine should start and rev up smoothly. There should be a power difference but no misfires. If they are incorrect there should be misfires in the intake manifold. Swop them around and try again.

Timing light degrees.

Due to 1 spark per revolution the normal timing light that does not have a 2 stroke setting will have an error in its reading. The degrees on the timing light will be double that of the actual degrees. If the timing light is on 20, it is 10 actual. If you use the wasted spark option, there are 2 pulses per revolution and the degrees will be quadrupled on the timing light. If the timing light is on 40, it is 10 actual. Best way in these conditions is to set the timing light to zero degrees and work on the degrees on the engine pulley.

Determine Maximum injector time.

This is important because at high revs there is only a certain amount of time to inject fuel. This time may not be exceeded as the engine will leaned out. You may argue, that at lower RPM’s you can go higher duty cycle with the primaries, but the problem is that this is not matrix and the switch over point is hard to determine. This time is calculated as follows.

Injection Time = 85% * 60 / Max RPM

= 51 / 8000

= 0.006375

Or 6.375 milliseconds

85% is recommended max duty cycle of an injector.

Max in this example is 8000 RPM

To tune this unit set the Micro fuel setting on graph. There are 2 graphs available for the dual injectors. Red is for primaries and blue is for secondary’s. First adjust the secondary’s to 0 right through the scale. Then at 3000 RPM adjust the primaries from light load to full load until the max time is reached. In this case 6.3 milliseconds. Make a note of the load where max injector time is reached. About 0.84 bar. Then make the rest of the graph flat at the same value.

Now take a load just smaller than max like 0.75 bar. and look at the air fuel ratio. Lift the secondary’s graph in totals till you see that the A/F ratio becomes richer. Decrease just enough till it is back to what it was. This offset will eliminate the dead band of the secondary injectors which will help to make the transition as smooth as possible.

Now you may increase the load and tune the secondary injectors to maintain the correct A/F ratio. Note that the secondary’s may also not increase the max injection time.

Lastly taper the injection time to the left off to eliminate pulse on the secondary injectors. Note the taper off is on the left where the primaries stopped working.

Multiple Throttles

A rotary engine normally has poor vacuum signal due to the small window that their air is sucked into the rotor. The vacuum signal is at its lowest pressure about 90° ATDC. Spitronics has developed a way to read the vacuum signal during this suction period. The time that the signal is read is adjustable in the same degree intervals as there are pulses from the crank sensor.

If you use the 36-1 gear it means you can adjust it in 10° resolutions. Start with 9 teeth which is 90° after TDC. This is entered in the Map Teeth block.

If you have the 24+TDC dizzy then it has only 30° resolutions. Here you need to first adjust TDC to be on one of the tooth so that you can get to 90° which is 3 teeth.

See the section on calibrating timing on the 24+TDC Dizzy.

Now connect the map sensor only on the throttle of Rotor 1 as in the sketch below.

Put the Throttle Selection on Dual for Multiple throttles.

You may now start the engine and get it to idle. Once it idles look at the Fuel Graph Top Map. The map bar should show a fairly good vacuum.

Now you can adjust the map teeth higher and lower while looking at the bar. Adjust it on a value where you get the best vacuum to the left side. Throttles do tend to create a flat spot due to the fact that it is only read when 1 rotor has vacuum. So you may need to adjust the accelerator pumps slightly. Refer to the ACC Pump adjusting in the manual.

Calibrating timing on the 24+TDC Dizzy.

Put the crank teeth on 1 and Timing Sensor on 0.

Now put the max timings on 0 as a Rotary can start and idle on zero degrees.

Put your timing light on zero degrees and use the TDC mark on the engine. Remember timing lights show double the degrees on a rotary with 4 coils because it is 2 stroke. If you have the wasted spark coil setup, then the timing light shows 4 times more degrees than actual engine degrees. If you make the light zero and use the engine marks, then you are 1 to 1 and more accurate. Now turn the dizzy till the light shows the mark is on TDC. Lock the dizzy.

As a test to make sure your trailing and leading coils is in the correct place do the following. Put the trailing degrees on 10°.

Put the trailing graph on 10°.

Now look with the timing light on 0 degrees. Leading coils (bottom plugs) will be on TDC and the trailing coils (top plugs) will be on 10° after TDC.