RX7 mazda wankel engine, running with leading-trailing ignition

Originally the trigger WAS 12+1 with two hall sensors. (primary trigger + sectrig)

Finally (2010-09-21) using 4 ign transformers, 2 leading and 2 trailing spark (1.1.81 firmware).

This car consumes a lot. Almost 20 liter / 100 km ! With trailing spark it runs smoother, with better throttle-response, and consumes somewhat less (nowhere near MembersPage/ShellEcoMarathonHungary :-).

The +12V power supply of the trailing spark ignition transformers can be switched with a relay, using misc output1. Mostly just to try the difference: a way to quickly disable trailing without opening the hood.


1. 45° ATDC The intake stroke is just beginning. The exhaust port has just closed, and on a stock or street ported engine, the intake port has been open for approximately 15°.

2. 90° ATDC The intake port is almost completely open, and the chamber is starting to expand at a fairly rapid rate.

3. 180° ATDC The intake port is all the way open, and has just passed the point of maximum flow. Maximum flow occurs at approximately 135° ATDC, which corresponds with the maximum rate of chamber volume increase.

4. BDC of the intake stroke. The intake chamber is now at its largest possible volume. The intake port is partially open, and the port is still flowing in the forward direction, even though the chamber is no longer increasing in volume. This is due to the inertia of the column of air flowing in the induction system. This effect is referred to as inertial supercharging, and is described in further detail in the airflow section of my webpage. This will also be addressed in a later article.

5. 45° ABDC The chamber has started to decrease in volume, and with the exception of a stock US model 12A, which has an intake port closing of 40° ATDC, the intake port is still partially open. At high rpm, the intake port is still flowing in the forward direction due to inertial supercharging. At low rpm, airflow in the port has reversed, and some of the intake charge is being squeezed back into the induction system by the pressure of the intake chamber which is decreasing in volume. This is the result of the low velocity in the induction system. This is a very important point to consider, as this alone affects the operating range of the engine more than any other factor.

6. 90° ABDC The intake port is completely closed, and air fuel mixture is being compressed.

7. 135° ABDC Same as #6.

8. 180° ABDC More of the same.

9. TDC of the compression stroke. The mixture is fully compressed, and ignition has started.

10. 90° ATDC The expansion cycle has started, and is already 45° past the point of maximum torque transfer to the eccentric shaft, which occurred at 45° ATDC.

11. 135° ATDC The expansion stroke continues, but the torque transferred to the output shaft is now down to about 35% of its peak.

12. 180° ATDC The exhaust port is still closed, and the torque transfer to the eccentric shaft is approximately 15% of its peak.

13. 225° ATDC At this point, the exhaust port has been open for approximately 30°, and exhaust flow is quite high.

14. BDC of the exhaust stroke. This is typically the point of maximum flow through the exhaust port. Even though the chamber volume is not decreasing at an appreciable rate, the chamber pressure is very high, and this is responsible for a large percentage of the total exhaust flow.

15. 90° ABDC The chamber volume is decreasing, and is 45° away from the point of maximum rate of decrease of the chamber volume.

16. 180° ABDC The exhaust chamber volume continues to decrease, and at approximately this point, a bridge ported, or peripheral ported engine will have started to open the intake port.

17. 225° ABDC The exhaust port is still open, and the chamber volume is decreasing at a relatively slow rate. At this point, a mildly bridge ported engine will have just opened the intake port.

18. TDC of the intake stroke. Here we are at the beginning, ready to start all over again. Note that the exhaust port is still open, but the intake port, for a non bridge ported engine has not opened yet.

Rotary trailing spark - see InputTrigger/RotaryTrigger

This feature needs firmware 1.1.77 or newer

Tested with the following config with c012 trigger (coil-type 12 primary trigger tooth with one camsync tooth):

Configured for 2 rotor. Must be set 4 cylinder.

With VemsTune (newer then 2010-05-18) you can simply config with configlet (vankel 2 rotor).

It contains the following configuration:

h[1]=00 80 06 80 00 00 00 00









( if the ECU used from a generated trigger signal from PC, you have to select double RPM )

2010-09-20 1.1.27 dump - car running with leading spark only

Most az autón csak a két leading van gyujtva, egy wasted spark trafóval. (in config ignch4 and ignch5 ??)

Felszereltem 4db coil on plug trafót, amit a helyes trailing időzítés beállításakor az első 4 gyujtáskimeneten vezérelve szeretnék használni.

Tested config on 1.1.81 (works, but knock have to disable):

(This is not ready to upload to car, need to check manually before)

testing config: