This car is a MB SL 500 with AMG 5.5liter supercharged engine conversion. V8, with dual-sparkplug per cylinder ignition and 3-valve heads.
In stock trim delivers over 500hp.
Primary trigger 60-2 configuration (VR).
Camsync: not needed
Ignition - for the 2 * 8 sparkplugs
Nothing is purchased yet, but I opted for 4 Bosch coil-packs. - good. Well, 1 2x2 coilpack and 2 3x2 coilpacks (if you have the 4 pin connector for the 3x2) would be more economical, less weight, and less work to mount.
A: Yesterday the owner already purchased 4 2x2 coil-packs so we have to go that way. PeepPaadam
Real wasted spark
Since there are two sparkplugs per cylinder, we could go "full sequential", but that is not a good idea after all => remember that wasted spark automagically uses 90% of the coil energy in the cylinder (full of unburnt air) to be fired. The other cyl, containing exhaust gases (and ions) has much lower resistance so only wastes appr 10% of the energy (in the "series connection" wasted spark circuit).
So if you try to "improve" and drive a given cylinder's 2 sparkplugs by (the 2 outputs of) one coil, you only get considerable reduced energy, 5/9 of what you would get with wasted spark ! Avoid this ! With wasted spark, you get better spark energy.
Wasted spark arrangement also improves reliability through redundancy (if one coil, coilpack powerline, driver, or connection or fuse breaks), than both cylinders serviced by the given (failing) coil are still ignited through the other sparkplug. For the best redundancy, make sure that for any given cylinder, the 2 sparkplugs are serviced from coils from different coilpacks.
specify the Firing order: change cylx below according to real firing order to get a practical example mapping. Timeline table:
- cyl1
- ignch1 from coilpack1
- ignch0 from coilpack2
- cylx
- ignch3 from coilpack1
- ignch2 from coilpack3
- cylx
- ignch5 from coilpack3
- ignch4 from coilpack2
- cylx
- ignch7 from coilpack3
- ignch6 from coilpack2
We assumed that coilpack1 is 2x2 type, coilpack2 and coilpack3 are 3x2. Note that the first 4 and second 4 is exactly the same ignch and coilpack, only the cylx differs:
- cylx (the pair of cyl1, 360 crankdegrees away)
- ignch1 from coilpack1
- ignch0 from coilpack2
- cylx
- ignch3 from coilpack1
- ignch2 from coilpack3
- cylx
- ignch5 from coilpack3
- ignch4 from coilpack2
- cylx
- ignch7 from coilpack3
- ignch6 from coilpack2
With the above, enable ign_dualout and use h[2] ign_sequnce like:
- ign_dualout=72
- ignchmax=07
- h[2]=70 50 30 10 70 50 30 10
Note that logically there is only 4 output-pulses to control (the other 4 is timed the same way). Eg, the 4 stepper outputs would be a good choice to drive (2 each) a total 8 active wasted spark coils (if active coils were chosen... the Bosch motorsport coils are passive).
With passive coils, it is strongly counterrecommended to drive 2 coils from 1 IGBT (to prevent overloading of the) power ign. output, so the ign_dualout option must be configured to drive 2 outputs simultaneously. This has to be considered during mapping... the above example was made with this in mind.
Drive by Wire Throttle
Engine features also drive-by-wire throttle that has separate little motor and could be controlled independently (TPS for VEMS anyway) but owner decided to got mechanical throttle. We'll see, maybe we'll experiment with the MB DBV setup also since it don't need any outside assistance.
The throttle valve for supercharger boost control operates from 12V, and uses high current (max 10A). We'd like to control it from VEMS. Since all ignition and injector putputs are in use, a separate hi-power FET output (with flyback diode inside ECU) is needed => request +1 10A FET-output with flyback in the order note (done).
Shiftcut
Engine has gearbox overload protection which means that before every gearshift the gearbox sends a signal to ECU to reduce timing to 5degrees BTDC for 400mS in order to save gearbox from stress. This is called "shiftcut", a standard feature, and implemented through an analog mcp3208 input channel (you have free analog input => fine). Normally shiftcut is configured for cutting ignition (can also be fuelcut).
[engine, gearbox and supercharger system .doc]
[http://porsche-foorum.ee/album/albums/userpics/10026/drossel.doc
Supercharger throttle control schematic .doc]